Gross Brain and Spinal Cord BLOCK 3 –

Gross Brain and Spinal Cord BLOCK 3 – 2011-12
Robert R. Terreberry, PhD Room 142 Ph

Layers of Scalp

Scalp Skin B O N E Connective Tissue Aponeurosis Loose CT Pericranium

Scalp A. Extends from the superior nuchal line posteriorly to the supraorbital margins anteriorly B. Laterally the scalp extends into the infratemporal fossae to the level of the zygomatic arches C. Classically defined as having five (5) layers 1. Skin 2. Connective tissue 3. Aponeurosis epicranialis 4. Loose connective tissue 5. Pericranium (periosteum)

Scalp cont… D. Skin E. Connective tissue (Dense)
1. Thin, especially in elderly persons 2. Contains many sweat and sebaceous glands and hair follicles 3. Abundant arterial supply, good venous and lymphatic drainage E. Connective tissue (Dense) 1. Thick, dense subcutaneous layer of connective tissue is richly vascularized and well innervated 2. Collagen and elastic fibers criss-cross in all directions attaching to the epicranial aponeurosis 3. Fat is enclosed in lobules between connective tissue fibers a. Amount of subcutaneous fat in scalp is relatively constant, varying little in emaciation or obesity Does decrease with advancing age

Scalp cont… F. Aponeurosis epicranialis (epicranial aponeurosis)
F. Aponeurosis epicranialis (epicranial aponeurosis) 1. Strong membranous sheet that covers the superior aspect of the calvaria a. Term galea aponeurotica is sometimes used to indicate its helmet-like nature b. Continuous laterally with the temporal fascia overlying the temporalis muscle 2. Serves as the membranous tendon of the fleshy bellies of the epicranius muscle 3. Epicranius muscle a. Two (2) occipital bellies (occipitalis muscle) b. Two (2) frontal bellies (frontalis muscle)

Frontalis Muscle Epicranial Aponeurosis Frontalis muscle
Arises from epicranial aponeurosis Inserts into skin and dense connective tissue layer near the eyebrows Note that frontalis has no bony attachments Innervated by temporal branch of the facial nerve (CN VII) Action is to pull scalp anteriorly and wrinkle skin on the forehead transversely

Occipitalis Muscle Epicranial Aponeurosis Occipitalis muscle
Arises from lateral 2/3 of superior nuchal line and mastoid part of the temporal bone Inserts into epicranial aponeurosis Innervated by posterior auricular branches of facial nerve (CN VII) Action is to pull scalp posteriorly and wrinkle skin on the back of the neck

Scalp cont… G. Loose connective tissue H. Pericranium (periosteum)
1. Consists of loose, areolar connective tissue a. Allows for free movement of the superficial 3 layers 2. Due to loose connective tissue, this layer has numerous potential spaces capable of allowing fluid to accumulate H. Pericranium (periosteum) 1. Dense layer of connective tissue firmly attached to the bones of the calvaria via Sharpey’s fibers

Innervation of Scalp and Face
Don’t memorize yet Innervated Anterior to external ears via all three branches of trigeminal nerve (CN V) Posterior to external ears via branches of C2 and C3 spinal nerves Extra notes: Sensory innervation of the scalp 1. Anterior to external ears via all three branches of trigeminal nerve a. V1 branches Supratrochlear nerve Supraorbital nerve b. V2 branches Zygomaticotemporal nerve c. V3 branches Auriculotemporal nerve 2. Posterior to external ears via branches of C2 and C3 spinal nerves a. C2 branches Lesser occipital nerve (ventral rami of C2, C3) Greater occipital nerve (dorsal ramus of C2) b. C3 branches 3rd occipital nerve (dorsal ramus of C3)

Blood Supply of Scalp & Face
Don’t memorize yet Know variety of sources and extremely robust Extra information: Blood supply to scalp 1. From external carotid artery system a. Occipital, posterior auricular and superficial temporal arteries 2. From internal carotid artery system a. Supratrochlear and supraorbital arteries off the ophthalmic artery 3. These arteries freely anastomose with one another in the subcutaneous connective tissue layer of the scalp (Layer 2) 4. Venous drainage via corresponding veins

Skull Views Superior – Norma verticalis Inferior – Norma basalis
Posterior – Norma occipitalis Anterior – Norma frontalis Lateral – Norma lateralis Skull is the most modified portion of the axial skeleton

Calvaria Calvaria 1. Consists of flat bones of the skull
a. Frontal b. Parietal c. Occipital 2. Each flat bone has an outer (external) table and an inner (internal) table of compact bone a. Between the two tables is cancellous (spongy) bone termed the diploë 3. Outer table is usually thicker and tough 4. Inner table is thinner, denser and more brittle 5. Removal of calvaria allows one to examine the internal aspects of the skull including the cranial fossae

Norma Verticalis Frontal bone Parietal bone Occipital bone
Coronal suture Sagittal suture Bregma Lambda Parietal foramen Parietal and frontal bones predominate view, with small part of occipital bone visible Coronal, sagittal and lambdoid sutures visible Bregma is point where coronal and sagittal sutures intersect Lambda is point where sagittal and lambdoid sutures intersect

Inner Calvaria Frontal bone Parietal bone Coronal suture
Sagittal suture Frontal sinus Groove for superior sagittal sinus Groove for middle meningeal artery Granular foveolae

Cranial Fossae Anterior Middle Posterior

Anterior Cranial Fossa
Orbital plate of frontal bone Cribriform plate of ethmoid bone Lesser wing of sphenoid bone Body of sphenoid CN I (olfactory nerve) runs through cribiform area  why you can loose sense of smell with trauma Floor formed by orbital plate of frontal bone, cribriform plate of ethmoid bone and the lesser wing and anterior part of the body of the sphenoid bone

Anterior Cranial Fossa
Crista galli of ethmoid bone Frontal sinus Anterior clinoid process Optic groove Optic canal CN I (olfactory nerve) runs through cribiform area  why you can loose sense of smell with trauma  runs through foramena of cribiform plate Frontal bone contributes to the anterior and lateral walls of this fossa Crista galli is a vertical projection of the ethmoid bone, serves as an attachment sight for falx cerebeli attach (splits brain) Foramen cecum is just anterior to the crista galli Anterior clinoid processes are posterior extensions of the lesser wings of the sphenoid bone Optic canal and a groove for the optic chiasm (chiasmatic sulcus) are also visible in this view

Middle Cranial Fossa Lesser wing of sphenoid bone
Anterior clinoid process Chiasmatic sulcus Petrous temporal Dorsum sellae of sphenoid bone Red outline represents middle cranial fossa a. Deeper and more extensive than anterior cranial fossa b. Bounded anteriorly by lesser wings of sphenoid bone, anterior clinoid processes and chiasmatic sulcus c. Bounded posteriorly by dorsum sellae of sphenoid bone and petrous temporal bone d. Bounded laterally by the squamous temporal, parietal and greater wings of the sphenoid bones Petrous = hardest bone in the skull; inner ear here

Middle Cranial Fossa Squamous temporal bone Parietal bone
Greater wing of sphenoid bone

Middle Cranial Fossa Sella turcica (TS + HF+ DS) Tuberculum sellae
Hypophysial fossa Dorsum sellae Sella turcica (Latin for ‘Turkish saddle’) is prominent feature in this view Located between the anterior and posterior clinoid processes Composed of three parts Tuberculum sellae anteriorly Hypophysial fossa intermediately Dorsum sellae posteriorly Pitutary gland = hypophesis; lies in the hypophysial fossa. A sheet of tissue overlies it to keep it separate from the rest of the cranial fossa

Middle Cranial Fossa Foramen ovale Foramen spinosum Foramen lacerum
Numerous foramina are seen in the floor of the middle cranial fossa – referred to as the “crescent of foramina” as they appear in a crescent-shaped line from medial to lateral Superior orbital fissure Foramen rotundum Foramen ovale Foramen spinosum Foramen lacerum is posteromedial to the foramen ovale at the end of the carotid groove. It is filled with carlidge; internal carotid artery runs over the top of it, NOT through it (Netter is incorrect)

Middle Cranial Fossa Carotid groove Hiatus for greater petrosal nerve
Hiatus for lesser petrosal nerve Look in atlas when it come * Lateral to sella turcica is a shallow groove for the internal carotid artery Two small openings can be seen along the petrous temporal bone Hiatuses for the greater and lesser petrosal nerves Hiatus for lesser petrosal nerve is lateral and anterior to the hiatus for the greater petrosal nerve

Posterior Cranial Fossa
Basioccipital portion of occipital bone Petrous temporal Internal occipital crest Internal occipital protruberance Largest and deepest cranial fossa Bounded anteriorly by the body of the sphenoid and basioccipital portion of the occipital bone Bounded posteriorly by the occipital bone Bounded laterally by the petrous and mastoid parts of the temporal bone Internal occipital crest and protuberance can be seen on occipital bone posterior to foramen magnum Basioccipital portion of occipital bone = basilar part of the occipital bone Cerebellum sits in the posterior cranial fossa

Posterior Cranial Fossa
Foramen magnum Jugular foramen Internal acoustic meatus Hypoglossal canal Foramen magnum = largest foramen in the head, allows continuity with the spinal cord and the medulla Jugular foramen is at the junction between the occipital and petrous temporal bones Internal acoustic meatus = CN VII ( facial) and CN VIII (vestibulocochlear nerve) run through this Hypoglossal canal = hypoglossal nerve run through this (CN XII)

Meninges Dura mater Pachymeninx Outer Arachnoid Middle Leptomeninges
Pia Mater Inner 1. Three (3) connective tissue membranes envelop the brain and spinal cord a. Dura mater – tough b. Arachnoid – flimsy, like a spider web c. Pia mater - intimate on surface 2. Dura mater referred to as the pachymeninx 3. Arachnoid and pia mater together are referred to as the leptomeninges 4. All 3 layers derived from mesenchyme surrounding the neural tube

Meninges Cranial Dura Mater Spinal Dura Mater
Dura mater (Latin for ‘hard or tough mother’) = Outermost layer of meninges, adjacent to either the skull (cranial dura) or the vertebral column (spinal dura). Structure of cranial dura is different than spinal dura mater

Spinal Dura Epidural Space Subdural Space Dura Mater Loose CT Fat
Epidural venous plexus Spinal Dural matter/ dural sac/ dural sheeth = fibrous sheeth: Initially develops as two separate layers that remain separate in life Inner surface of vertebral column bones is lined by own periosteum (outer layer of spinal dura mater) Wide epidural space between the periosteum and dura exist and contains loose connective tissue, fat and the epidural venous plexus Separate dural membrane loosely encloses the spinal cord (inner layer of spinal dura mater) Subdural space = between dura and arachnoid. The arachnoid sits very close to the dura, so it is more of a potential space, and should not be very big at all. Can get subdural bleeds here Spinal dura mater is attached to the spinal cord via extensions of the pia mater called denticulate ligaments These pial extensions run from the pia mater to the dura at regular intervals between the dorsal and ventral rootlets of the spinal nerves

Spinal Dura Ends at S2 vertebral level Filum terminale externum  S2
Terminal end Spinal dura mater ends at the second sacral vertebra (S2) (NOT cord level): Inferior extension of spinal dura below S2 vertebra is called the filum terminale externum Spinal dura mater has collagenous bundles oriented longitudinally; an inner surface lined with squamous epithelium and has fewer elastic fibers than cranial dura mater Spinal dura mater is innervated by meningeal branches of spinal nerves proper that branch just prior to the branching of the dorsal and ventral rami

Cranial Dura Shiny stuff = dura matter
Embryologically cranial dura mater develops as two layers just like the spinal dura develops, but cranial dura mater layers will fuse to form a more-or-less continuous single layer of dura

Cranial Dura Endosteal layer Fused Cranial Dura Meningeal layer
Cranial dura consists of 2 layers of closely joined connective tissue with elongated fibroblasts Outer (endosteal) layer Inner (meningeal) layer

Cranial Dura Endosteal layer Meningeal layer Thick bundles of collagen
Cell rich Numerous blood vessels Meningeal layer Thinner than endosteal layer Inner layer smooth with squamous mesothelium Inner layer forms sheet-like extensions Outer (endosteal) layer adheres to the inner surfaces of the bones of the skull and functions as the periosteum of these bones This layer has thick bundles of collagen, is cell rich and contains numerous blood vessels Inner (meningeal) layer of cranial dura is thinner than the outer (endosteal) layer Fine fibers form an almost continuous sheet of tissue Inner surface of this layer is smooth and covered with a layer of squamous mesothelial cells At several sites in the cranial cavity the inner layer of cranial dura will fold on itself to form sheet-like protrusions call dural folds or reflections Due to the fact that the 2 layers of cranial dura mater are fused as one, there is virtually no epidural space in the normal individual Epidural bleeds will occur between the periosteal (?) layer of dura and the bones of the skull

Cranial Dura – Blood Supply
Anterior meningeal as. Off ethmoidal as. Middle meningeal a. Off maxillary artery Largest meningeal artery Posterior meningeal brs. Off vertebral /occipital as. Cranial dura mater receives its own blood supply from the meningeal arteries Meningeal arteries course in periosteal (?) layer of dura Meningeal arteries arise from several different sources to supply the cranial dura mater Dura of the anterior cranial fossa supplied by: Anterior meningeal branches of the anterior and posterior ethmoidal arteries (branches off ophthalmic artery) Meningeal branch off of the cavernous portion of the internal carotid artery Dura of the middle cranial fossa supplied by: Middle meningeal artery off the maxillary artery Largest meningeal artery Enters cranial cavity through the foramen spinosum Accessory meningeal artery off either the middle meningeal artery or the maxillary artery Will enter the cranial cavity via the foramen ovale Supplies the trigeminal ganglion, dura and bone in the region Dura of the posterior cranial fossa supplied by: Meningeal branches of the occipital artery Enter the cranial cavity through the jugular foramen and mastoid foramen Posterior meningeal branches of the vertebral artery Enter cranial cavity through foramen magnum

Cranial Dura - Innervation
The dura, unlike the brain and leptomeninges is sensitive to pain Several sources provide innervation to the cranial dura mater Dura of the anterior cranial fossa supplied by: Branches of anterior and posterior ethmoidal nerves (branches off nasociliary nerve from the ophthalmic division of the trigeminal nerve (V1)) Branches off maxillary (V2) and mandibular (V3) divisions of the trigeminal nerve Dura of the middle cranial fossa supplied by: Nervus spinosus which is a branch of V3 that reenters the middle cranial fossa through the foramen spinosum Nervus meningeus medius is a branch off V2 just prior to its exit through foramen ovale Dura of the posterior cranial fossa supplied by: Ascending branches of upper cervical (C2, C3) spinal nerves that enter the cranial cavity through the foramen magnum Branches of the vagus nerve have been described as providing sensory innervation to the posterior fossa Tentorium cerebelli is supplied by the tentorial nerve off of V1

Spinal Arachnoid Pia mater Arachnoid Dura mater Arachnoid:
1.Intermediate layer of spinal and cranial meninges 2.Thin, net-like avascular membrane that is transparent – resembles a spider’s web a.Arachnoid is attached to the inner surface of the dura – forming a potential subdural space b.Separated from pia mater by extensive subarachnoid space Where CSF lives 3.Main elements are interlacing collagenous bundles surrounded by fine elastic networks a.Small strands of collagen fibers extend from the arachnoid to the pia mater and are termed arachnoid trabeculae Trabeculae help to suspend the brain and spinal cord within the meninges

Spinal Arachnoid Ends at S2 vertebral level
Filum terminale externum  S2 Terminal end Spinal arachnoid ends at the level of the second sacral vertebra Inferior to S2 vertebra the arachnoid contributes to the filum terminale externum - This is just like dura matter

Cranial Arachnoid Similar to spinal arachnoid structurally
Does not extend into sulci or fissures Enlargements of subarachnoid space are termed cisterns

Spinal Pia Pia mater Arachnoid Dura mater
Pia mater (Latin for ‘tender mother’) Innermost layer of meninges, tightly adherent to the external surfaces of the brain and spinal cord, follows all sulci and fissures unlike the arachnoid and dura mater

Spinal Pia Ends at L1/L2 vertebral level Filum terminale internum
Conus Medullaris Ends at L1/L2 vertebral level Filum terminale internum conus medullaris Filum Terminale Internum Spinal pia mater ends at the level of the conus medullaris, L1/L2 intervertebral disc Inferior extension of spinal pia below the conus is called the filum terminale internum

Pia Mater Tightly adherent to surfaces of CNS
Follows sulci and fissures Highly avascular Spinal pia mater is firmer and less vascular than cranial pia mater Blood vessels traveling in the subarachnoid space are held to pia by strands of connective tissue As each vessel penetrates the surface of the brain, it is surrounded by a small pial-lined space – perivascular (Virchow-Robin) space whose function and importance has, and is still, been debated for decades

Cranial Pia Mater Invaginates to form tela choroidea
3rd ventricle 4th ventricle Forms choroid plexuses Lateral ventricles Cranial pia invaginates to form the tela choroidea of the third ventricle and the choroid plexuses of the lateral and third ventricles As it forms the roof of the fourth ventricle it helps to form the tela choroidea and choroid plexus of the fourth ventricle

Dural Folds (Reflections)
The inner (meningeal) layer of cranial dura mater is folded inwards as four (4) septa that partially divide the cranial cavity into freely communicating spaces 1. Falx cerebri 2. Falx cerebelli 3. Tentorium cerebelli 4. Diaphragma sella

Falx Cerebri 1. Strong, crescent-shaped vertical sheet of dura located in the interhemispheric (longitudinal) fissure between the cerebral hemispheres 2. Attached anteriorly to the crista galli of the ethmoid bone 3. Attached posteriorly to the tentorium cerebelli where it blends in the midline of the tentorium 4. Convex upper margin is attached to the internal cranial surface on each side of the median plane as far back as the internal occipital protuberance 5. Narrower anteriorly, broader posteriorly a. Anterior part is thin and may be fenestrated 6. Superior sagittal sinus runs along upper margin 7. Inferior margin is free and concave and contains the inferior sagittal sinus 8. The straight sinus is located along the point of attachment between the falx cerebri and tentorium cerebelli

Falx cerebelli 1. Small, crescent-shaped fold in the midline of the posterior cranial fossa 2. Attached to posterior part of the internal occipital crest of the occipital bone 3. Partially separates the lateral hemispheres of the cerebellum 4. Occipital sinus is located in margin attached along the internal occipital crest

Tentorium cerebelli 1. Crescent-shaped fold of dura located between the occipital lobes and the cerebellum a. Midline attachment of falx cerebri to superior aspect of tentorium draws the tentorium upwards 2. Concave anterior edge is free and between it and the dorsum sellae of the sphenoid bone is the tentorial incisure (notch) that allows the midbrain to pass superiorly 3. Posteriorly it is attached to the petrous portions of the temporal bones and the margins of the sulcus for the transverse sinuses in the occipital bone a. Transverse sinuses course along this posterior margin of the tentorium 4. Tentorium cerebelli defines supratentorial and infratentorial compartments of the cranial cavity a. Infratentorial compartment is commonly referred to as the posterior cranial fossa

Diaphragma sella 1. Roofs over the sella turcica of sphenoid bone
2. Small, circular layer of dura with a small central opening that transmits the infundibular stalk of the pituitary gland

Cranial Dural Folds Falx Cerebri Falx Cerebelli

Cranial Dural Folds Falx Cerebri Tentorium Cerebelli

Cranial Dural Folds

Cranial Dural Folds Falx Cerebri Falx Cerebelli

Cranial Dural Folds Hypophysis Diaphragma Sella Sphenoid Sinus Pons

Spinal Cord 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal
Extends from the foramen magnum to the level of L1/L2 intervertebral disc Continuous rostrally with the medulla of brainstem Inferior end is called the conus medullaris 31 segments, although surface does not demonstrate any obvious segmentation Segments defined by spinal nerve attachments 8 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segment

Spinal Cord Dorsolateral Sulcus Dorsointermediate Sulcus
Dorsal Median Sulcus (Dorsal, in situ)

Cervical Segment C8 Dorsal Median Sulcus Dorsointermediate Sulcus
Dorsolateral Sulcus Ventrolateral Sulcus Surface does exhibit several grooves (sulci) Ventral (anterior) median fissure Anterior spinal artery located here Dorsal (posterior) median sulcus Less conspicuous than ventral median fissure Depression, not all the way through Dorsolateral sulcus Point of attachment of the dorsal rootlets Posterior spinal arteries located medial to these sulci Ventrolateral sulcus Point of attachment of the ventral rootlets Dorsointermediate sulcus Only seen at cervical and upper thoracic spinal levels (C1-T6) Ventral Median Fissure

Thoracic Segment T10 Dorsal Median Sulcus Dorsolateral Sulcus
Ventrolateral Sulcus Ventral Median Fissure No dorsal intermediate sulcus because below T6

Thoracic (T10) Dorsal Horn Lateral Horn Ventral Horn
Dorsal (posterior horn) Considered to be the sensory horn of the spinal cord Receives central processes of spinal ganglion (DRG) neurons Can send information to the brain (cerebrum for conscious processing, or cerebellum for subconscious processing) or to the ventral horn (for motor root reflexes) Ventral Horn

Thoracic Gray Matter (T10)
Lissauer’s Tract Substantia Gelatinosa Nucleus Proprius IML VH Clarke’s Nucleus Dorsal (Posterior) Horn Lissauer's tract (zone) (dorsolateral fasciculus) Superficial to substantia gelatinosa Consists of lightly myelinated or unmyelinated axonal fibers Substantia gelatinosa [Lamina II] Cell column of relatively small neurons General somatic afferent (GSA) neurons Body of dorsal horn (nucleus proprius) [Lamina III-IV] Cell column of larger cells Sometimes termed tract cells, projection neurons or secondary (second order) sensory neurons Typically associated with the transmission of sensory information to higher levels of the CNS Intermediate zone Intermediomedial nucleus Sensory cell column typically associated with general visceral afferents (GVA) Lateral horn (intermediolateral nucleus) Motor cell column containing general visceral efferent (GVE) (preganglionic autonomic) neurons In the thoracic and upper lumbar areas these neurons are preganglionic sympathetic neurons Forms the lateral horn of the spinal cord At sacral levels 2-4 these neurons are preganglionic parasympathetic neurons No obvious lateral horn found here even though these neurons are similarly located Clarke's nucleus (nucleus dorsalis) Cell column located only at C8-L2/3 spinal levels Located in medial aspect of the intermediate zone

Ventral (anterior) Horn
Figure: General somatotopy of the ventral horn Considered to be the motor horn of the spinal cord Large alpha () motorneurons, general somatic efferent (GSE), reside here Lamina IX and give rise to axons which comprise the ventral roots of the spinal cord Neurons are organized somatotopically and are divided into several groups (Fig) Also contains smaller gamma () motorneurons which innervate muscle spindles

Rexed's laminae In 1952, Bror Rexed, a Swedish neuroanatomist, devised a system for subdividing the spinal gray matter into layers or laminae, based upon differences in cytoarchitecture Scheme was initially developed for animal models, but is widely used in discussions of the human spinal cord Ten different laminae described for the human spinal cord Laminae I-VI = dorsal horn Lamina VII = intermediate gray matter Laminae VIII & IX = ventral horn (VIII = interneurons) (IX = alpha () motorneurons) Lamina X = midline area of gray matter around the central canal

White Matter White matter is made up primarily of neuronal axons, some of which are directed rostrally from neuronal cell bodies in the spinal cord gray matter or the dorsal root ganglia (DRG), while others have descended into the spinal cord from cell bodies in the cerebral cortex or brainstem nuclei

Funiculus Funiculus - composite bundles of tracts
Dorsal (posterior) funiculus or the “dorsal columns” Between the dorsal root entry zone (dorsolateral sulcus) and dorsomedian sulcus Composed of ascending tracts Lateral funiculus Between the dorsolateral and ventrolateral sulci Composed of both ascending and descending tracts Ventral (anterior) funiculus Between the ventrolateral sulcus and ventromedian fissure Also know: Anterior white commissure Area where some spinal-related axons decussate Both Anterior white commissure and funiculus are in the white matter

Cervical Enlargement (C8)
DREZ FC FG LCST STT 9 main pathways in the spinal cord: 1.Dorsal column system (acending pathway) a.System concerned with discriminative sensations and conscious proprioception b.Two separate tracts Fasciculus gracilis Fasciculus cuneatus c.Fasciculus gracilis (FG) Found at all levels of the spinal cord Located lateral to dorsomedian sulcus d. Fasciculus cuneatus (FC) Found only at T6 level and above Located lateral to fasciculus gracilis Separated from fasciculus gracilis by dorsointermediate sulcus 2.Spinothalamic tract (STT) (ascending pathway) a.System concerned with pain and temperature as well as crude touch b.Axons originate from neurons in the dorsal horn and intermediate gray and will decussate and form spinothalamic tract in the lateral funiculus, contralateral to their cells of origin c. Note that some authors refer to this pathway as the anterolateral system due to the fact that it actually has several distinct pathways in it, including the STT. For the sake of simplicity, we will call this the spinothalamic tract in the spinal cord only and you will see that the name of this pathway will change to the spinal lemniscus once we get into the brainstem. LCST = lateral corticospinal tract (descending pathway) a. Located in the lateral funiculus, dorsal to the ventral horn, medial to the spinocerebellar tracts See Terreberry’s notes for the others (McWhoter will get to exact tracts we need to memorize over time)

Thoracic (T10) DREZ FG LCST STT Below T6 so no FC

The 9 main pathways of the spinal cord
9 main pathways in the spinal cord: 1.Dorsal column system (acending pathway) a.System concerned with discriminative sensations and conscious proprioception b.Two separate tracts Fasciculus gracilis - conveys info from legs (lower half) Fasciculus cuneatus -conveys information from arms (upper half) c.Fasciculus gracilis (FG) Found at all levels of the spinal cord Located lateral to dorsomedian sulcus d. Fasciculus cuneatus (FC) Found only at T6 level and above Located lateral to fasciculus gracilis Separated from fasciculus gracilis by dorsointermediate sulcus 2.Spinothalamic tract (STT) (ascending pathway) a.System concerned with pain and temperature as well as crude touch b.Axons originate from neurons in the dorsal horn and intermediate gray and will decussate and form spinothalamic tract in the lateral funiculus, contralateral to their cells of origin c. Note that some authors refer to this pathway as the anterolateral system due to the fact that it actually has several distinct pathways in it, including the STT. For the sake of simplicity, we will call this the spinothalamic tract in the spinal cord only and you will see that the name of this pathway will change to the spinal lemniscus once we get into the brainstem. 3.Spinocerebellar system a.System concerned with unconscious proprioception information to the cerebellum b. Lower half of the body Dorsal (posterior) spinocerebellar tract (DSCT) Location Axons of neurons of Clarke's nucleus (nucleus dorsalis) course in the dorsal lateral portion of lateral funiculus Ventral (anterior) spinocerebellar tract (VSCT) Axons of [spinal border] cells (located at the lateral perimeter of the spinal gray matter) decussate and ascend ventral to the DSCT in the lateral funiculus as the VSCT c. Upper half of body Rostral spinocerebellar tract Cuneocerebellar tract 4. LCST = lateral corticospinal tract (descending pathway) a. Located in the lateral funiculus, dorsal to the ventral horn, medial to the spinocerebellar tracts 5.Ventral (anterior) corticospinal tract (VCST or ACST) a. Located in medial-most area of the ventral funiculus 6. Rubrospinal tract (RST) a.Located just ventral to the lateral corticospinal tract in the lateral funiculus 7.Vestibulospinal tracts a.Lateral vestibulospinal tract (LVST) Located just ventral to the ventral horn in the ventral funiculus b.Medial vestibulospinal tract (MVST) Axons descend within a composite bundle called the medial longitudinal fasciculus (MLF) MLF is located in medial portion of the ventral funiculus 8.Reticulospinal tracts a. Medial reticulospinal tract (MRST) Located in the ventral funiculus, ventral to the lateral vestibulospinal tract b.Lateral reticulospinal tract (LRST) Located in lateral funiculus, lateral to the ventral horn, medial to the spinothalamic tract 9.Tectospinal tract (TST) a.Located within the ventral funiculus of the spinal cord, near the MLF Only descends through cervical levels

Medulla Ventral Medulla (Medulla oblongata)
Inferior segment of the brainstem -Continuous caudally with the spinal cord -Continuous rostrally with the pons Red lines indicate pontamedullary boundary (superior border) and inferior border of medulla with spinal cord Ventral

Medulla Olive Pyramid Ventral Median Fissure Pyramidal Decussation
Located on either side of the ventral median fissure Large descending fiber tract (corticospinal tract) Pyramidal decussation Gross landmark that is used to denote the spino-medullary junction – caudal (inferior) end of the medulla, rostral (superior) end of the spinal cord Represents a large number of fibers (80-90%) of the pyramids which decussate here before entering the spinal cord to become the lateral corticospinal tract Ventral

Medulla Post-olivary Sulcus Pre-olivary Sulcus Olive Pyramid Lateral
Large, oval swelling lateral to the pyramid Represents the inferior olivary nucleus Groove between olive and pyramid is called pre-olivary sulcus Groove dorsal to olive is called post-olivary sulcus Lateral

Medulla CN IX CN X CN XI CN XII Ventral
CN I and II do not have a direct attachment to the brain stem, but every other CN does. Cranial nerves attached to the medulla: CN IX (glossopharyngeal nerve) Attached to medulla dorsal to olive, in post-olivary sulcus, rostral to CN X CN X (vagus nerve) Attached to medulla dorsal to olive, in post-olivary sulcus, caudal to CN IX, rostral to CN XI CN XI (cranial portion of accessory nerve) Attached to medulla dorsal to olive, in post-olivary sulcus, caudal to CN X CN XII (hypoglossal nerve) Attached to medulla in pre-olivary sulcus

Medulla CN IX CN X CN XI CN XII Olive Ventrolateral

Medulla Rhomboid Fossa of 4th Ventricle Obex Gracile Tubercle
Cuneate Tubercle Dorsal surface anatomy Not normally visible due to presence of overlying cerebellum Closed part of medulla (caudal portion) Central canal persists here Gracile tubercle Elevation at rostral end of fasciculus gracilis, just off midline Corresponds to the location of the underlying nucleus gracilis Cuneate tubercle Elevation at rostral end of fasciculus cuneatus, lateral and slightly rostral to gracile tubercle Corresponds to the location of the underlying nucleus cuneatus Open part of medulla (rostral portion) Seen after cerebellum is removed Central canal opens into diamond-shaped depression – 4th ventricle Central canal opens into 4th ventricle at obex Caudal portion of 4th ventricle seen in medulla, rostral portion is in pons Floor of the 4th ventricle (rhomboid fossa) Diamond-shaped fossa Mid-portion is broad, narrows towards obex caudally and cerebral aqueduct rostrally Divided symmetrically by median sulcus Most caudal end of rhomboid fossa resembles a pen and thus is referred to as the calamus scriptorius The point of caudal junction of the walls of the 4th ventricle is the obex Immediately rostral to the obex on each side of the 4th ventricle is a slightly rounded eminence – area postrema A circumventricular organ where the blood-brain-barrier is lacking Monitors blood for toxins May initiate vomiting when stimulated Dorsal

Pons Ventral Middle segment of the brainstem
Continuous caudally with the medulla Continuous rostrally with the midbrain Ventral

Pons Basilar Pons Basilar Sulcus Ventral Basilar pons
Conspicuous, distinctive feature of the pons Large bulbous structure on ventral aspect of pons Consists of numerous fiber tracts and a set of nuclei Shallow groove (basilar sulcus) runs along length of basilar pons in midline Basilar artery courses in this sulcus Ventral

Pons CN V CN VI CN VII CN VIII Ventral
Cranial nerves attached to the pons: CN V (trigeminal nerve) Largest of the cranial nerves Attached to lateral aspect of pons, penetrates the middle cerebellar peduncle CN VI (abducens nerve) Attached to ventral pons at pontomedullary junction, just off the midline CN VII (facial nerve) Attached to caudal pons at pontomedullary junction, in the cerebellopontine angle slightly medial to CN VIII CN VIII (vestibulocochlear nerve) Attached to caudal pons at pontomedullary junction, in the cerebellopontine angle slightly lateral to CN VII Ventral

Pons CN VII CN V CN VIII CN VI Ventrolateral

Middle Cerebellar Peduncle
Pons Middle Cerebellar Peduncle CN V Lateral surface anatomy: Middle cerebellar peduncle (brachium pontis) Prominent feature is large bundle of fibers = crus cerebri Fibers originate in the pontine nuclei in basilar pons and project to the contralateral cerebellum Lateral

Pons Rhomboid Fossa of 4th Ventricle Facial Colliculus Dorsal
Not visible normally due to presence of overlying cerebellum Rostal portion of 4th ventricle seen in pons Floor of the 4th ventricle (rhomboid fossa) Diamond-shaped fossa Mid-portion is broad, narrows towards obex caudally and cerebral aqueduct rostrally Divided symmetrically by median sulcus Facial colliculus – “little floor”  Represents portion of the facial nerve system Slight swelling at inferior aspect of medial eminence Produced by motor fibers of facial nerve looping over abducens nucleus in dorsomedial pontine tegmentum Dorsal

Midbrain Ventral Rostral segment of the brainstem
Continuous caudally with the pons Continuous rostrally with the diencephalon Ventral

Midbrain Interpeduncular Fossa CN III Crus Cerebri Ventral
Crus cerebri (cerebral peduncles) Prominent feature of ventral midbrain Massive bundle of descending fibers originating in cerebral cortex Medial third consists of corticopontine fibers Middle third consists of corticospinal and corticobulbar fibers Lateral third consists of corticopontine fibers Ventral

Interpeduncular Fossa
Midbrain CN III Interpeduncular Fossa Crus Cerebri Interpeduncular fossa Large space located between the crus cerebri Posterior perforated substance seen on surface of fossa Branches of posterior communicating artery penetrate the brain surface here, giving it a perforated appearance CN III (oculomotor nerve) Attached to ventral midbrain, courses through interpeduncular fossa Ventral

Midbrain Superior Colliculus Inferior Colliculus CN III Crus Cerebri
Lateral

Midbrain Superior Colliculus Inferior Colliculus CN IV Dorsal Tectum
Also called the corpora quadrigemina Consists of 4 small elevations (“little hills”) Pair of superior colliculi (singular is colliculus) Pair of inferior colliculi (singular is colliculus) Inferior brachium (brachium of inferior colliculus) Tract that consists of projections from the inferior colliculus to the medial geniculate nucleus of the thalamus (auditory) Superior brachium (brachium of superior colliculus) Small tract that consists of retinal ganglion cell axons that project to the superior colliculus and pretectal area (extra-geniculate projections of the visual system) CN IV (trochlear nerve) Attached to the midbrain on dorsal surface, just caudal to the inferior colliculus Only cranial nerve to exit the dorsal surface of brainstem Innervates superior oblique (in eye) Dorsal

Midbrain Superior Brachium Inferior Sup. Coll. Brachium Inf. Coll.
CN IV Dorsal

Cerebellum Mid-sagittal Midbrain Pons Medulla 4th Vent
The term cerebellum means “little brain”; however, while it seems relatively small, being only 10% of the total volume of the brain, it contains more than 1/2 of all the neurons in the CNS Also, if you were to fold it out, the cerebellum would be over a meter in length, due to its highly convoluted surface Lies dorsal (posterior) to the brainstem Covers all of the pons, most of the medulla, and some of the midbrain Overall function Equilibrium (maintenance of posture) and coordination of eye movements Maintenance of muscle tone Coordination, planning and initiation of voluntary (?) motor movements Surface is comprised of numerous transversely oriented folds - folia (singular is folium) Folia increase the surface area of the cerebellum Folia separated by shallow sulci or deep fissures Mid-sagittal

Cerebellum Folia – 3 anatomical and 3 functional areas Posterosuperior

Cerebellar Peduncles SCP MCP ICP Midbrain Pons Medulla
Inferior cerebellar peduncle (restiform body) Associated with spinal and inferior olive inputs primarily to the vermis and paravermal areas of the cerebellum Also associated with some efferents (?) – projections to vestibular nuclei and brainstem reticular formation Middle cerebellar peduncle (brachium pontis) Associated solely with pontocerebellar projections from the contralateral basilar pontine nuclei to the lateral hemispheres of the posterior lobe Superior cerebellar peduncle (brachium conjunctivum) Associated primarily with outputs from the deep cerebellar nuclei to the red nucleus and thalamus Also associated with some afferents (?) – ventral spinocerebellar tract will enter the cerebellum via this peduncle

Cerebellar Peduncles SCP MCP ICP Ventral

Cerebellum Anterior Lobe Posterior Lobe Posterosuperior PF
Cerebellum can be divided either in the sagittal or transverse plane Transverse (horizontal) subdivisions This scheme utilizes several distinct fissures (deep sulci) to demarcate 3 lobes oriented in the transverse plane Primary and posterolateral fissures Anterior lobe Located superior and anterior to the primary fissure Posterior lobe Located posterior to both the primary fissure and posterolateral fissure Largest lobe in this scheme Flocculonodular lobe (See next slide) Posterosuperior

Posterolateral Fissure
Cerebellum Anterior Lobe Primary Fissure Flocculonodular Lobe Posterior Lobe Posterolateral Fissure Flocculonodular lobe Located anterior to posterolateral fissure (3 parts) Nodulus is on midline Flocculi (singular is flocculus) located laterally (2 of them) Smallest lobe in this scheme Space below anterior lobe = 4th ventricle Mid-Sagittal

Cerebellum Anterior Lobe Posterior Lobe Flocculonodular Anterior Lobe

Cerebellum Vermis Paravermis Lateral Hemisphere
Sagittal (vertical) subdivision Vermis Midline region “Worm-like” appearance Lateral hemisphere One right and one left Lateral to vermis Bulk of cerebellum in this scheme

Cerebellar Cortex Granular layer (layering pattern  very organized)
1. 3 layers which are incredibly uniform throughout the cerebellar cortex 2. Receives all cerebellar afferents 3. Influences neurons in the deep cerebellar nuclei 4.Molecular layer a.Relatively cell free area b.Primarily contains axons, dendrites and small interneurons 5.Purkinje cell layer a.Contain approximately 15 million Purkinje cells in a single, continuous row, from folium to folium b.Only neurons of cerebellar cortex to project out of the cerebellar cortex (to the deep nuclei) 6.Granular layer a.Contains approximately 1011 granule cells – more cells than in both cerebral hemispheres combined b.Function as interneurons that excite Purkinje cells Each Purkinje cell may receive synaptic input from up to 100,000 granular cells

Deep Cerebellar Nuclei
Fastigial nucleus FGED Globose nucleus Emboliform nucleus Dentate nucleus Four of them on each side Remember “Feel Good Every Day” Note: You may see the term nucleus interpositus or interposed nucleus used when discussing the globose and emboliform nuclei, but this usage should not be used in describing the human deep cerebellar nuclei.

Diencephalon Interventricular Foramen Posterior Commissure
Lamina Terminalis Interventricular Foramen Posterior Commissure 3rd Ventricle Diencephalon: Part of the cerebrum (forebrain) immediately rostral to the brainstem, continuous with the midbrain Cerebrum is the diencephalon plus the cerebral hemispheres Paired structure on either side of the 3rd ventricle Rostral extent is near the interventricular foramen (of Monro) and is formed by the lamina terminalis that forms the anterior boundary of the 3rd ventricle Caudally the diencephalon appears continuous with the midbrain Posterior commissure demarcates the junctional zone between the diencephalon and midbrain Mid-sagittal

Diencephalon Pineal Gland Mid-sagittal Thalamus MI Hypothalamus
Hypothalamic Sulcus Diencephalon divided into: 1. Thalamus (dorsal thalamus) a. Located dorsal to hypothalamus b. Egg-shaped nuclear complex c. Important relay center for all sensory information except olfaction d.70% of all brains contain a massa intermedia (inter-thalamic adhesion) which is a midline connection between the 2 thalami e. all senses except smell are relayed through the thalamus f. contains mostly gray matter 2. Hypothalamus a. Located ventral to the thalamus b. Separated from the thalamus by hypothalamic sulcus Very important regulator 3. Epithalamus a.Located along the superior aspect of the diencephalon b.Epithalamus consists of several structures including the: Pineal gland (epiphysis) Small, cone-shaped structure attached to roof of 3rd ventricle via the pineal stalk Parenchyma is formed by secretory cells (pinealocytes) and glial cells, but no neurons Pinealocytes secrete presumptive hormone melatonin Released in circadian fashion, high serum levels in dark phase of 24-hour light/dark cycle 4. Subthalamus a. Considered to be a transitional diencephalic zone that is ventral to the thalamus and lateral to the hypothalamus b. Contains an important nucleus that plays an important role in basal ganglia circuitry – subthalamic nucleus Dorsal surface anatomy of diencephalon 1. Cerebral hemispheres cover most of diencephalon 2. Pineal gland seen at posterior aspect of diencephalon, just dorsal to the superior colliculi Mid-sagittal

Diencephalon Mamillary Body Infundibulum Optic Chiasm Tuber Cinereum
Ventral surface anatomy of diencephalon 1. Hypothalamus forms ventral surface of brain at this level 2. Hypothalamic structures seen on ventral surface a. Mamillary (mammillary) body Round structures just rostral to midbrain Represents caudal extent of hypothalamus Important in motion b. Tuber cinereum Intermediate region of hypothalamus Swelling on surface of tuber cinereum is called the median eminence Infundibulum (stalk) of pituitary gland attaches to median eminence 3. Optic chiasm seen at rostral end of hypothalamus a. Formed by decussating fibers of the optic nerves b. Optic tracts extend posterolaterally from the optic chiasm to go to the thalamus Mid-sagittal

Diencephalon Optic Nerve Optic Chiasm Median Eminence Optic Tract
Ventral Mamillary Body

Interhemispheric Fissure
Cerebral Hemispheres Sulci Gyri Interhemispheric Fissure Cerebral cortex Consists of a thin sheet of gray matter external to white matter - cerebral cortex Cerebral cortex presents as a continuous series of folds and shallow grooves Folds are called gyri (singular is gyrus) Grooves are called sulci (singular is sulcus) Several sulci are quite deep and are called fissures Pattern of gyri and sulci is fairly constant, but there are variations from brain to brain and even from one hemisphere to the other in the same brain Small gyri with lots of folds  mental retardation Rats have no gyri so if you had less gyri or no gyri = intellegence of a rat Dorsal

Brodmann’s Areas In 1909, Korbinian Brodmann [a German neuropsychiatrist] divided the human cerebral cortex into 47 different areas, based upon differences in the cytoarchitecture (histology) of the cortex (Fig. 5) The numbers Brodmann proposed are still in use today Note that although Brodmann’s system has 47 areas, a system devised by von Economo in 1929 has 109 areas and a system devised by the Vogts in 1919 has more than 200 areas. Some neuroscientists think that there are many more than 200 areas.

Functional Designation
Select Cortical Areas Functional Designation Brodmann’s Anatomical Name Primary Motor Cortex Area 4 Precentral Gyrus Premotor Cortex Area 6 (lateral) Sup/Mid Frontal Gyri Frontal Eye Fields Area 8 Middle Frontal Gyrus Supplementary Motor Area Area 6 (medial) Sup. Frontal Gyrus Broca’s Area Areas 44 & 45 Inf. Frontal Gyrus Primary Somatosensory Cx Area 3,1,2 Postcentral Gyrus Unimodal SS Assoc. Cx Areas 5 & 7 Sup. Parietal Lobule Multimodal SS Assoc. Cx Primary Visual Cortex Area 17 Banks Calcarine Sul. Primary Auditory Cortex Areas 41 & 42 Transverse Temp. G. Wernicke’s Area Area 22 Surrounds 41 & 42 Will go though in due time

Cerebral Hemispheres Parietal Lobe Frontal Occipital Lobe Temporal
Each hemisphere is divided into lobes based on the location of certain gyri and sulci 4 classically defined lobes in each hemisphere Frontal lobe Parietal lobe Occipital lobe Temporal lobe Lateral – Right Hemisphere

Interhemispheric Fissure
Frontal Lobe Central Sulcus Interhemispheric Fissure Frontal Pole Skip for now Lateral Fissure

Frontal Lobe Central Sulcus Precentral Sulcus Superior Frontal Sulcus
Inferior Frontal Sulcus Lateral Fissure Skip for now

Frontal Lobe Precentral Gyrus Superior Frontal Gyrus
Middle Frontal Gyrus Inferior Frontal Gyrus Skip for now

Inferior Frontal Gyrus
Frontal Lobe Inferior Frontal Gyrus Pars Orbitalis Skip for now Pars Opercularis Pars Triangularis

Superior Frontal Gyrus
Frontal Lobe Central Sulcus Cingulate Sulcus Superior Frontal Gyrus Medial Skip for now

Frontal Lobe Olfactory Sulcus Olfactory Bulb Gyrus Rectus
Orbital Gyri Gyrus Rectus Olfactory Bulb Olfactory Tract Olfactory Sulcus Ventral Skip for now

Parietal Lobe Central Sulcus Preoccipital Notch Lateral Fissure
Skip for now

Parietal Lobe Postcentral Sulcus Intraparietal Sulcus Lateral Fissure
Skip for now Lateral Fissure Lateral

Parietal Lobe Postcentral Gyrus Superior Parietal Lobule
Inferior Parietal Lobule Skip for now Lateral Lateral Fissure

Superior Temporal Sulcus
Parietal Lobe Supramarginal Gyrus Lateral Angular Gyrus Superior Temporal Sulcus Skip for now Lateral Fissure

Parietal Lobe Central Sulcus Cingulate Sulcus Parieto-
Occipital Sulcus Medial Skip for now

Occipital Lobe Central Sulcus Occipital Pole Preoccipital Notch
Lateral Fissure Preoccipital Notch Occipital Pole Lateral Skip for now

Occipital Lobe Central Sulcus Parieto- Occipital Sulcus Occipital Pole
Calcarine Sulcus Medial Skip for now

Occipital Lobe Parieto- Occipital Sulcus Upper bank Calcarine Sulcus
Lower bank Medial Skip for now

Temporal Lobe Central Sulcus Lateral Fissure Preoccipital Notch
Skip for now Temporal Pole

Temporal Lobe Inferior Temporal Sulcus Lateral Fissure
Skip for now Superior Temporal Sulcus

Temporal Lobe Middle Temporal Gyrus Inferior Temporal Gyrus
Lateral Middle Temporal Gyrus Inferior Temporal Gyrus Lateral Fissure Skip for now Superior Temporal Gyrus

Temporal Lobe Superior Temporal Gyrus Transverse Temporal Gyri
of Heschl Skip for now Horizontal cut

Temporal Lobe Occipitotemporal Sulcus Collateral Sulcus Inferior
Skip for now

Temporal Lobe Inferior Temporal Gyrus Occipitotemporal Gyrus
Parahippocampal Gyrus Inferior Skip for now

Temporal Lobe Parahippocampal Gyrus Occipitotemporal Gyrus
Collateral Sulcus Medial Skip for now

Limbic Lobe Cingulate Gyrus Fornix Septum Pellucidum Uncus
Medial Septum Pellucidum Skip for now Uncus Parahippocampal Gyrus

Limbic Lobe Uncus Parahippocampal Gyrus Occipitotemporal Gyrus
Inferior Skip for now

Hippocampal Formation
Limbic Lobe Fornix Hippocampal Formation Inferior Skip for now

Insular Cortex Opercular Cortex Lateral Skip for now

Insular Cortex Lateral Skip for now

Insular Cortex Frontal/Parietal Opercular Cortex Insular Cortex
Coronal Cut Temporal Opercular Cortex Skip for now

Centrum Semiovale Horizontal cut White matter
Deep to the thin layer of cerebral cortex is the white matter of the cerebral hemisphere Sometimes referred to as the medullary region of the cerebral hemisphere More commonly referred to as the centrum semiovale Oval-shaped, common central mass of white matter that contains cortical commissural, association and projection fibers

Internal Capsule Corona Radiata Internal Capsule Putamen
Brings info to and from the cortex Even a small stroke in it can cause paralysis of half the body Internal capsule = Very large bundle of white matter interconnecting the cerebral cortex with subcortical structures Both cortical afferents and cortical efferents Upper extent is referred to as the corona radiata

Internal Capsule Anterior Limb Genu Posterior Limb Horizontal cut
Look for a big white V on it’s side = internal capsule (see blue lines) Divided into 3 parts: Anterior limb Between caudate nucleus and lentiform nucleus Posterior limb Between lentiform nucleus and thalamus Genu “Bend” or continuity between anterior and posterior limbs Anterior and posterior limbs seen on both coronal and horizontal brain sections Genu only seen clearly on horizontal brain sections Difficult to identify with certainty on coronal brain sections

Corpus Callosum B G S R Commissures
Fiber bundles which connect structures in one hemisphere with structures in the opposite hemisphere Corpus callosum Largest fiber bundle in the human brain million fibers Divided into 4 parts: 1. Rostrum Helps form rostral boundary of 3rd ventricle 2. Genu “Bend” which contains fibers which interconnect the frontal lobes Body Bulk of corpus callosum Contains fibers which interconnect the frontal and parietal lobes Splenium Most posterior portion Contains fibers which interconnect the temporal and occipital lobes

Deep Gray Matter There are large masses of gray matter (nuclei or nuclear complexes) located deep within each cerebral hemisphere Diencephalon Basal ganglia Amygdaloid complex

Deep Gray matter cont… Diencephalon
Thalamus and hypothalamus are located at the center of the cerebrum Basal ganglia Set of nuclei (gray matter) located deep within each hemisphere Caudate nucleus Putamen Globus pallidus Amygdaloid complex (amygdala) Nuclear complex deep to cortex of the uncus Anterior to hippocampal formation Part of the limbic system

Diencephalon Anterior Commissure Posterior Commissure 3rd Ventricle
Lamina Terminalis Anterior Commissure Posterior Commissure 3rd Ventricle Anterior commissure Located anterior to the hypothalamus, near the inferior extent of the rostrum of the corpus callosum Contains fibers which interconnect the temporal lobes Posterior commissure Small fiber bundle seen posterior to the thalamus Contains fibers which interconnect parts of the midbrain Important connections in some visual reflexes Mid-sagittal

Basal Ganglia Caudate Putamen Globus Pallidus Thalamus Horizontal cut
Gray matter basal ganglia: Set of nuclei (gray matter) located deep within each hemisphere Caudate nucleus Putamen Globus pallidus Very important for voluntary movement

Ventricular System Hollow core of developing neural tube will develop into a continuous series of ventricles in the adult brain  brain is hollow 1. All of the ventricles are lined with a continuous sheet of ependymal cells 2. Each major portion of the CNS contains a component of the ventricular system a. Cerebral hemispheres = lateral ventricles b. Diencephalon = third ventricle c. Midbrain = cerebral aqueduct (of Sylvius) d. Pons = fourth ventricle e. Medulla = fourth ventricle and central canal f. Spinal cord = central canal (inconstant)

Ependymal Cells Ciliated, cuboidal epithelium Lines ventricles of CNS
Discontinuous basal lamina allows for movement of material between CSF and brain rather easily

Ventricular System Lateral Ventricle Cerebral Aqueduct Third Ventricle
Fourth Ventricle The red area = where CSF is in ventricles (produced by ependymal cells) = coronoid plexus

Cerebral Blood Flow Central nervous system
2% of body by weight 15% of all cardiac output 20% of all O2 consumed Total brain blood volume every 5-7/min Loss of consciousness after 10 sec Necrosis after 4-5 min of hypoxia A. Metabolically the CNS is one of the most active systems in the body 1. CNS comprises just 2% of body by weight, but receives 15% of cardiac output and consumes 20% of body’s oxygen 2. Neurons have no significant ability to store oxygen or glucose B. Brief interruptions in blood flow can cause neurological or mental disturbances 1. Brain blood volume turns over 5-7 times/minute 2. Unconsciousness results if blood flow ceases for more than 10 seconds 3. Within 4-5 minutes of hypoxia, irreversible tissue damage begins C. Regulation of CNS blood flow 1. Blood flow to a region may increase or decrease in proportion to neural activity in that region a. This is utilized in PET and SPECT imaging studies 2. Regulation of cerebral circulation is primarily controlled by auto- regulation of the blood vessels themselves a. Vessels constrict (increasing vascular resistance) in response to increased blood pressure and dilate (decreasing vascular resistance) in response to decreased blood pressure b. Increased levels of CO2 in brain extracellular fluid causes vasodilation and increased blood flow and vice versa for low CO2 levels – vasoconstriction and decreased blood flow c. Local levels of K+, adenosine and pH function cooperatively to adjust blood flow in response to metabolic activity in the brain

Cerebral Blood Flow Arterial supply to brain and much of spinal cord derived from 2 sets of arteries Internal carotid arteries Anterior circulation - 80% of blood supply Vertebral arteries Posterior circulation - 20% of blood supply Linear extent of capillaries/Unit volume Gray matter > White matter Sensory, interneurons > Motor

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Gross Brain and Spinal Cord BLOCK 3 –

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