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Contents of the Neurocranium, Part II

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1 Contents of the Neurocranium, Part II
The Brain, its Blood Supply and the Cranial Nerves

2 Embryology Central nervous system begins as neural tube
Anterior portion of neural tube differentiates into three primary divisions: Hindbrain Midbrain Forebrain Should be familiar with this. Recall CNS begins in neural tube, brain is an outgrowth of neural tube, three portions of this, bulges, posteriori is hind, then mid, then forebrain.

3 Embryology Lateral walls of the forebrain expand and protrude from both sides of the neural tube Median portion of forebrain is the diencephalon Lateral projections form the telencephalon Lateral walls of forebrain begin to bulge laterally, and this will form cerebrum, main portion of the brain, the median portion, part that stays here, is diencephalon, and the lateral that form cerebrum and cortex is telencephalon

4 Two primary axes of growth in the developing brain
Embryology Two primary axes of growth in the developing brain 1. Longitudinal flexion of anterior neural tube 2. Inferior spiral rotation of the telencephalon There are two primary axis of growth, longitudinal flexions, folded over on itself, several folds that occur in the neural tube to create structure of brain in adult. Other axis is a spiral rotation of the telencephalon, primarily posteriorly, so it grows forward and then around like a rams horn, if you look at structures in the brain, several have C shape because they follow that axis of growth, anteriorly then superiorly then around inferiorly.

5 Ventricles Lumen of neural tube becomes the CNS ventricular system
Shape of ventricular system reflects developmental deformation of neural tube What you're left with, because of that growth pattern, laterally then growing around posteriorly and inferiorly, left with a neural tube that expands into several places, these are the ventricles. See that the ventricles follow along in the pattern of rotation that goes down into the temporal lobe, and there are two, one in each hemisphere, result of bulging of telencephalon laterally. Midline of the neural tube is still a signal pathway, so the lateral ventricles feed into the third, expanded area of the neural tube as the diencephalon grew, then midbrain, has what is just a canal, cerebral aqueduct which goes into fourth then central canal of spinal cord

6 Ventricles Lateral ventricles Third ventricle Fourth ventricle
Anterior horn Body Posterior horn Inferior horn Third ventricle Interventricular foramen (of Monro) Cerebral aqueduct Fourth ventricle Lateral ventricles have anterior horn, anterior projection past interventricular foramen, main body, superior portion, inferior horn, and posterior horn which projects into occipital lobe

7 Hindbrain Cerebellum Motor coordination Cognitive functions
temporal coordination planning Hind brain first, first major structure you see is the large cerebellum, inferior view of the brain, cerebellum when you try to remove brain, if you didn’t cut Tentorium, then the cerebellum along with brain stem got torn and left behind, responsible of coordination of muscle movement, when you are walking down the street, ability to pick up a foot and put it in front of the other without thinking is motor patterns generated by cerebellum, isn't exclusively motor, large lateral portion is involved in similar cognition, timing of sequence of events, damage there, have a hard time putting a sequence of events into temporal order. Six steps along to getting to grocery store, cant do that.

8 Hindbrain Medulla Oblongata
Anatomical and physiological junction of brain and spinal cord Initiates respiration Regulates heart rate Origin of cranial nerves IX, X, XI, and XII Lies inferiorly to cerebellum, and anteriorly, anatomical and physiological junction of brain and spinal cord. Also regulates heart rate, nuclei run with cranial nerve 10, origins of cranial nerves 9 10 and 11, 12.

9 Hindbrain Pons Bridge between cerebellum and the rest of the brain
Origin of cranial nerves V, VI, VII, and VIII Large fat structure on anterior portion of brain stem, bridge between cerebellum and the rest of the brain, all the pathways, axons that go out to cerebellum and back to brain are transmitted through fiber tracts of pons, also CN nuclei in the pons, origins of cranial nerves

10 Midbrain Least differentiated primary brain division
Contains cerebral aqueduct Origin of cranial nerves III and IV (from dorsal surface) Just above the pons, just below diencephalon, that is midbrain, pretty small, least differentiated portion of neural tube. Diencephalon and telencephalon become greatly enlarged, hind because of cerebellum. Contains cerebral aqueduct, third ventricle to fourth, origin of cranial nerves 3 and 4, Trochlear nerve comes from posterior surface of the brain stem, starts back there and wraps around.

11 Midbrain Corpora Quadrigemina
Superior Colliculi Visual tracking Coordination of head turning & eye movements Inferior Colliculi Sound location Focusing attention to auditory stimuli Contains several small but important structures. Posterior portion, fourth ventricle cut away, looking into fourth ventricle posteriorly, back of brain stem. Four protrusions, corpora quadrigemina, superior colliculi and inferior. Superior colliculi involved in visual tracking and movements of eyes and head and neck, following object in space. Inferior colliculi have similar function but for auditory stimuli instead of visual. Hear a loud noise, turn to focus attention on it, using inferior colliculi, focusing attention on that sound source, for auditory mobilization.

12 Midbrain Substantia Nigra
Darkly pigmented (neuro-melanin) nucleus Produces dopamine Parkinson’s disease—destruction of the cells of the substantia nigra Brainstem cut away, revealing midbrain, central canal, two bands of darkly pigmented substance, this is substantia nigra, produces dopamine, important for movement, without it cant move muscles. Parkinson's destroys these cells, unregulated muscle movements, have a shake, dis-inhibition of basal ganglia

13 Midbrain Substantia Nigra
In 1982, 6 drug addicts in Santa Clara, CA manifested with Parkinson’s disease (oldest patient was 41 yrs. old) Each had injected synthetic heroin—MPPP (1-methyl-4-phenyl-4-propionpiperidine), an analog of meperidine (Demerol) The poorly synthesized designer drug contained a contaminant—MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine), which kills the cells of the substantia nigra Important for muscle control, movement, it can be damaged by Parkinson's but other ways too. 6 drug addicts has severe Parkinson's, and the oldest was 41, typically Parkinson's strikes older adults. If you don’t synthesize this correctly, create MPTP, which is a potent toxin for the cells of substantia nigra, selectively kills those cells.

14 Midbrain Cerebral Peduncles
Major fiber bundles connecting forebrain to hindbrain Contain descending axons of upper motor neurons from cortex Cerebral peduncles. Not critically important that you know this, two fiber pathways above the pons, see CN 3 and 4 right in front, major fiber bundle to connect upper motor cortex to connect to pons and medulla.

15 Diencephalon Thalamus
Potato-shaped structure Sensory relay for all afferents except olfaction Moving up the neural tube into the expanded area along midline, third ventricle, if we look inside third ventricle, space connecting left and right side, that is the massa intermedia, connecting the two thalamic bodies, thalamus is a structure shaped like a potato, looking from top down, sliced through top of brain, two bulges, the thalami, along midline is third ventricle. Connection not found in everyone, non functional. Thalamus is important for sensory information, relays all the sensory information from the peripheral sensory receptors, to the cortex of the brain. Also some functions involved in cognitive moves from associative portions of cortex connecting to thalami and basal ganglia, but know primary function, sensory relay for sensory input, exception is olfaction, input goes straight into cortex without passing thalamus. Part of the reason why olfaction has different sensory quality, also closely related to areas of brain involved in memory formation, smells can evoke strong memories more than visual information etc. Memories often associated with emotion.

16 Diencephalon Thalamus
Thalami form walls of 3rd ventricle Third ventricle, and that bulge with the massa intermedia, that is thalamus, forms the lateral walls of third ventricle.

17 Diencephalon Hypothalamus
4 g neural structure Connected to pituitary gland Regulates: Body temperature Hunger Thirst Sexual activity Goal-seeking behavior Endocrine functions Affective behavior Visceral motor system Immediately beneath is inferior protrusion, hypothalamus. Hypothalamus weighs 4 g, but has a lot of important functions. Connected to pituitary, has several nuclei in it which affect the pituitary gland in releasing different hormones. Hormonal activity directly originating from hypothalamus or regulated by it, by its connection. Goal-seeking, drive to do a particular task. Affective: emotional kinds of behavior

18 Telencephalon Basal Ganglia
Caudate nucleus Globus pallidus Putamen Modulate and integrate components of motor activity (and cognitive functions) System depends on dopamine— affected by Parkinson’s disease Moving to telencephalon, see that there is cortex on the outside of brain, white matter, beneath are gray matter structures. Cut horizontally, looking down on brain, two thalami forming walls of third ventricle, these gray matter structures are first portion of telencephalon, three structures, the basal ganglia. Remember that in the nervous system a nucleus is a collection of nerve cells, in the CNS, and a ganglion is a cluster of nerve cells in PNS. Not basal ganglia, but basal nuclei, technically. Caudate nucleus, globus pallidus, putamen. If you look at these, caudate in front and back, putamen on outside, and glubus pallidus is two layers deep to putamen. Caudate in green, following the ventricles, spiraling along, following developmental path. Putamen in blue, and glubus pallidus in red. This system modulates motor activity, also integrates motor activity, one of the things is that if you are walking up hill, force required in each step is modulated by the basal nuclei, ganglia. That is different from coordination with cerebellum, that’s involved in motor pattern, but modulating the motor behavior is the basal ganglia. This is not just motor behavior, like cerebellum, important connections in cognitive functions, especially from the anterior portions of the brain, the prefrontal cortex. Dependent on dopamine, substantia nigra is then part of this. Area affected in Parkinson's disease, removal of substantia nigra disinhibits the basal ganglia, normally have inhibitory function to control basal ganglia to control and maintain muscles. If you remove dopamine, its disinhibited and you get free motions.

19 Telencephalon Amygdala
Lies at tail of caudate nucleus but is not functionally part of the basal ganglia Involved in the control of rage, aggression and sexuality At tail of caudate, is amygdala, attached to basal ganglia, but not functionally part of it. Area of the brain involved in emotion, emotion relating to negative kinds of emotion, rage aggression, as well as positive emotions such as sexuality. One of the things that happens to monkeys where they take it out, get “cluver busy” syndrome, monkeys start mounting other monkeys, indiscriminately. . . Become very aggressive. . .

20 Telencephalon Hippocampus
Composed of three-layered cortex (archicortex) Fornix—major output pathway Involved in the formation of new episodic memories Deep structure, hippocampus, in the floor of lateral ventricle, inferior horn, bump structure here continues up posteriorly and superiorly and loops around. Hippocampus, proceeds anteriorly, in a C shaped loop. This is cortex, not nuclei like basal galglia, this is cortex, layered, distinct cellular layers, in this case only three layers, archicortex, old portion of the brain, if you follow evolution of brain tissue, see that as you progress, brain layers become more differentiated, if you look at less derived brains, see more archicortex, no neocortex. Attached to hippocampus, fornix, loping structure, left and right connected by a midline section that allows information to pass. Hippocampus is important for formation of new memories, episodic memories, not emotional memories which is amygdala, and not motor memories, like ability to walk. Kinds of memories here are like what happened yesterday or this morning, if you damage the hippocampus of fornix, or anterior mamillary bodies, then you get anterograde amnesia.

21 Telencephalon Cerebrum
Major portion of cerebrum, large convoluted portion, most of what you're looking at is cerebrum. Have deep nuclear structures, have some old cortex in hippocampus white matter, and on exterior surface is neo cortex, or six layered cortex, on the outside surface of the brain with white matter axons deep to that. Cerebrum is the center of all that makes you human, sensory inputs and motor outputs and cognitive functions. Composed of six-layered neocortex and deep white matter Center of sensory input, motor output, and higher cognitive functions

22 Cerebrum Primary Fissures Longitudinal cerebral fissure
Cerebrum is folded. Lots of groove and bumps. Cortex is the functional part of brain that leads to higher mental cognitive functions, so in humans and great apes the animals that have high intelligence have a lot of cortex, but there is a limit on how big your head can get. Take cortex and fold it over on itself to get it in smaller area. Several folds in the brain, sulci, bumps are gyri, and the major folds of the brain, large fissure along middle, which is the longitudinal cerebral fissure, separation of the two halves of telencephalon as they grow out of the tube

23 Cerebrum Primary Fissures Lateral fissure Central sulcus
Lateral fissure, gap between the front part of brain and inferior temporal portion. This is a result of downward spiral of growth. Then large sulcus, central sulcus divides the frontal lobe from parietal lobe

24 Cerebrum Lobes Frontal Parietal Occipital Temporal
Not functional designations, anatomic. Some general correlations between functions and the areas of the lobes of the brain, but primarily functional areas are smaller than a lobe. Frontal lobe contains both motor cortex, involved in muscle movement, contains prefrontal cortex for cognition, olfactory cortex, associative cortex, term that applies to cognitive domains of the brain. Frontal lobe in red, in front of central sulcus and above lateral sulcus, parietal in blue, behind the central sulcus and above lateral sulcus, and then occipital, and temporal lobe separated from occipital lobe and parietal , inferior portion of brain. Named for the bones that overlie them.

25 Cerebrum Lobes Insula In addition ot those lobes, if you pry apart, there is a cortex deep, area of cortex left behind as the brain grows around. Bulge then protrusion of cortex around it, bulge buries this layer of cortex, insula, we don’t have information on what it does. Used to be viewed as vestige.

26 Cerebrum White Matter Corpus callosum— primary connection between left and right cerebral hemispheres White matter, axons myelinated, medial section of brain, see band of white matter, cut in half. This is a cut surface, this is the corpus callosum, connecting left hemisphere and right. All of the information that passes from one side to the other passes through the corpus callosum. Other smaller tracts like fornix, anterior and posterior commissure, but primary connection is corpus callosum

27 Cerebrum White Matter Internal capsule—primary pathway of fibers ascending to cortex from thalamus and descending from cortex to cerebral peduncles Cut beneath corpus callosum main body. Between the structures of diencephalon, is a band of white matter called internal capsule, primary pathway of fibers ascending into cortex and descending, through the cerebral peduncles, information that passes along motor pathways goes through here, see a lot of other white matter, but this is largely connection between different areas of cortex between same hemisphere.

28 Motor Cortex Primary motor cortex lies along the precentral gyrus in the frontal lobe Motor output projects to contralateral side Central sulcus here, motor cortex, primary, lies right in front of central sulcus on precentral gyrus, anterior to central sulcus. This is the start motor output, when you want to move a muscle, electrical impulse from the brain to that muscle originates here. Motor cortex fibers to muscles cross in the medulla to go to the contralateral sides, left hemisphere controls right side of the body.

29 Motor Output Pathways Voluntary movement—conducted to lower motor neurons via the pyramidal pathway Major output pathways. Band of the precentral gyrus, in red the fiber pathways coming out of motor cortex, down through internal capsule, through cerebral peduncles, pons medulla, then crossing. This is the pyramidal pathway, upper motor neurons connecting to lower.

30 Motor Output Pathways Balance, posture, limb coordination information conducted by numerous extrapyramidal pathways Also neurons in the cortex that pass through midbrain and connect to structures of midbrain like red nucleus, proceeding down through pons into spinal cord, these are extra pyramidal pathways, voluntary are pyramidal, other movements like balance, posture, those are extrapyramidal, several different minor pathways involved n each of these functions, only need to know pyramidal one though.

31 Somatosensory Cortex Primary somatosensory cortex lies along the postcentral gyrus in the parietal lobe Representation of body is from contralateral side In addition to motor cortex, there is somatosensory cortex in parietal lobe, posterior to central sulcus, post central gyrus, and this is the area of the brain which receives touch information from the rest of the body. Touch information comes into the spinal cord, then in spinal cord or brain stem, crosses over to other sides into thalamus then up into cortex to end up in post central gyrus, primary somatosensory cortex. If you stimulate it during brain surgery, get sensation of touch in an area of brain adjacent to or involved in that part of body. Can do this because for brain surgery only need anesthesia for meninges and external parts, frequently put people under. . . Cut open their brain. . .then wake them up and stimulate their brain so you don’t take out anything important.

32 Somatosensory Cortex Sensory and motor cortices are arranged somatotocially, different areas of the body are in adjacent areas of brain. Start off with legs, then trunk, hands neck, face, those are proportional for motor cortex to motor control you have. Large areas of sensation for the hands and for muscles of the face, and also portion to sensory areas. Sensory information in the face, hands. Medial surface genitals, not much motor control but a lot of sensory. Somatosensory cortex (like motor cortex) is mapped somatotopically and proportionate to sensitivity, not size

33 Other Sensory Cortices
Visual cortex— occipital lobe Auditory cortex— superior portion of temporal lobe Rhinal (olfactory) cortex—anterior medial temporal lobe Gustatory (taste) cortex—inferior aspect of postcentral gyrus Motor cortex and somatosensory cortex, there are other primary sensory cortical areas. Visual cortex is in posterior portion of occipital, area of brain where visual information is processed, auditory lies on the superior edge of temporal lobe. Down here is insula, part of temporal is cut away to see auditory cortex. Rhinal is olfactory, and gustatory lies at the end of the somatosensory area, post central gyrus.

34 Language Areas Occur only in the left hemisphere of most people (96 % of right-handed individuals, 72% of left-handed individuals) Broca’s area—motor speech center, in frontal lobe Wernicke’s area—language interpretation center, in temporal & parietal lobes Lots of areas associated with other cognitive functions. Language areas occur in left hemisphere for right handed people. Primarily left hemisphere function. In the frontal lobe, area called broca’s area, motor center for speech and language. If you have damage there, not only difficult to talk but also difficult to write and get words out of your body. People who have damage to this area have halted, stuttering speech, difficult to speak. Wernicke’s area in posterior portion of temporal lobe, and inferior portion of parietal lobe, area for language interpretation, the ability to understand words that other people speak. Damage here have unusual speech aphasia, weird speech deficit where people string words together that don’t make sense. Don’t understand language, don’t understand that what you're saying doesn't make sense, blissful ignorance.

35 Cranial Nerves Olfactory Optic Occulomotor Trochlear Trigeminal
Abucens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal Accessory Hypoglossal reading through Then counting through on the picture waving the red point. . .

36 Cranial Nerves Exit from Neurocranium
I Cribriform plate Inferior surface of brain, CN exits from brain to sensory destination through cribriform plate

37 Cranial Nerves Exit from Neurocranium
II Optic canal

38 Cranial Nerves Exit from Neurocranium
3 comes from midbrain, 6 from the pons, and 4 from posterior midbrain and loops around. These all go through superior orbital fissure, cover this when you go through orbit. III, IV, VI Superior orbital fissure

39 Cranial Nerves Exit from Neurocranium
V1 Superior orbital fissue V2 Foramen rotundum V3 Foramen ovale Three parts, V1, ophthalmic division through superior orbital fissure. V2 maxillary division passes through foramen rotundum to come out to this area of face, then V3, mandibular through foramen ovale to inferior mandible. Three sensory, also a motor branch that goes with V3 portion. Be familiar with this from face.

40 Cranial Nerves Exit from Neurocranium
Come off of junction between the pons and the medulla. They exit through the internal auditory meatus, 8 is Vestibulocochlear so it goes to cochlea, and also vestibule for balance. C7 passes through there, goes past vestibule and cochlea and it makes a turn and exits to face. VII, VIII Internal auditory meatus

41 Cranial Nerves Exit from Neurocranium
IX, X, XI Jugular foramen 9 cut off here, passes through jugular foramen, large one is 10, through jugular foramen , and 11 comes from two parts. Spinal part from the spinal cord and passes up through foramen magnum and back out jugular foramen, and then portion coming out of brain stem itself, cranial portion, and it joins with spinal accessory portion briefly, then joins with vagus. 11 via 10, means cranial portion of 11 joins spinal portion then jumps to vagus. Motor portions of cranial all come from same nucleus.

42 Cranial Nerves Exit from Neurocranium
12 to tongue, exits through hypoglossal canal XII Hypoglossal Canal

43 Cranial Nerves Exit from Neurocranium
Counting and waving red pointer. Part of five goes through foramen rotundum and ovale and Supraorbital fissure Nerve that passes over pin A, easy when that nerve goes up through foramen magnum and out jugular foramen.

44 Blood Supply Vertebral arteries Internal carotid arteries
Provide ~30% of blood supply to brain Internal carotid arteries Provide ~70% of blood supply to brain Blood supply from vertebral arteries and internal carotid arteries. Vertebral arteries provide 30%, carotid is main supply

45 Circle of Willis Vertebral aa.  basilar a.  posterior cerebral aa.
Internal carotid a.  middle cerebral aa.  anterior cerebral aa. Posterior communicating arteries connect posterior cerebral aa. and internal carotid aa. Anterior communicating ARTERY (sing.) connect anterior cerebral arteries Vertebral arteries and the internal carotid arteries form a loop around the pituitary gland and the optic nerve junction, called optic chiasm, and this is the circle of Willis. Start with vertebral arteries joining to form basilar, which splits to left and right posterior cerebral, internal carotids give rise to middle cerebral and anterior cerebral, posterior cerebral and middle cerebral arteries are connected by posterior communicating arteries, then off of anterior cerebral arteries, one connection between, singular anterior communicating artery, forms loop, circle around pituitary. Anterior, middle and posterior branches are cerebral arteries supply blood to brain

46 Blood Supply Middle runs between the base of frontal lobe and portion of temporal out to lateral portion of brain. Anterior passes medially to the medial surface of the brain, then taken over by posterior cerebral artery, supplies medial portion of posterior, and inferior surface of temporal lobe

47 Blood Supply

48 Venous Drainage Blood from the cortex drains to surface veins that drain into the dural venous sinuses Veins on lateral surface of brain, draining through bridging veins into superior sagittal sinus

49 Venous Drainage Blood from the deep brain (thalamus, basal ganglia) drains into great cerebral vein (of Galen) before entering the straight sinus Blood from the lower brainstem drains through the foramen magnum into the vertebral venous plexus Veins from deep brain draining into the great vein of Galen into straight sinus, then medial portion of brain drains into the inferior sagittal sinus, and the areas of the lower brain stem drain through foramen magnum into venous plexus

50 Cerebrovascular Accident (CVA)
Ruptured aneurysm—failure of a localized defect in the elasticity of a vessel Arterial thrombus—blockage of an artery Embolism—clot from elsewhere in the body that lodges in a cerebral artery Hypertensive apoplexy—sudden effusion of blood into cerebral tissue due to rise in blood pressure AKA stroke. Several kinds. One is ruptured aneurism, bulge in a blood vessel, and this is a rupture, failure of the localized effect in the elasticity of the vessel, get a berry aneurism, bulge from the artery, then pops and spills blood into brain. Arterial thrombus, blockage of artery, Embolism is a different kind of blockage, clot from somewhere else. Frequently get a clot from femoral artery in the leg, then get logged in lungs or brain Then hypertensive apoplexy, just sudden rush of blood through the small capillaries of the ends of the cerebral arteries which results in blood being dumped into the brain as small arteries and capillaries rupture, caused by sudden rise in blood pressure

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