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Overview Brain Stem Cerebellum Diencephalon Cerebrum Cranial Nerves
Lecture 10: Brain & Cranial Nerves
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Brain Overview Brain Stem Cerebellum Diencephalon Cerebrum
Function Protection Blood Supply Cerebrospinal Fluid Brain Stem Cerebellum Diencephalon Cerebrum Cranial Nerves Brain Lecture 10: Brain & Cranial Nerves
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The Brain and Cranial Nerves
Sensations Memory Emotions Decision making Behavior
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Principal Parts of the Brain
Cerebrum Diencephalon Thalamus Hypothalamus Cerebellum Brainstem Medulla Pons Midbrain Cerebrum Diencephalon Brain Stem Cerebellum
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Protective Coverings of the Brain
Bone Periosteum Meninges same as around the spinal cord dura mater arachnoid mater pia mater Periosteum And Bone Dura Mater Arachnoid Mater Pia Mater
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Protective Coverings of the Brain
Dura mater extensions falx cerebri tentorium cerebelli falx cerebelli Falx cerebri Tentorium cerebelli Falx cerebelli
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Ependymal cells Blood Supply to Brain Capillary Arterial blood supply is branches from circle of Willis on base of brain Vessels on surface of brain----penetrate tissue Uses 20% of our bodies oxygen & glucose needs blood flow to an area increases with activity in that area deprivation of O2 for 4 min does permanent injury at that time, lysosome release enzymes Fluid O2 Elec. Glucose waste
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Blood Supply to Brain protects cells from some toxins and pathogens
Ependymal cells Blood Supply to Brain Capillary Blood-brain barrier (BBB) protects cells from some toxins and pathogens proteins & antibiotics can not pass but alcohol & anesthetics do tight junctions seal together epithelial cells, continuous basement membrane, astrocyte processes covering capillaries Fluid O2 Elec. Glucose waste
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Cerebrospinal Fluid (CSF)
ml (3-5oz) Clear liquid containing glucose, proteins, & ions Functions mechanical protection floats brain & softens impact with bony walls chemical protection optimal ionic concentrations for action potentials circulation nutrients and waste products to and from bloodstream
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Origin of CSF Choroid plexus = capillaries covered by ependymal cells
Lateral Ventricles Choroid plexus = capillaries covered by ependymal cells 2 lateral ventricles, one within each cerebral hemisphere roof of 3rd ventricle fourth ventricle Third Ventricles Fourth Ventricles
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Drainage of CSF from Ventricles
One median aperture & two lateral apertures allow CSF to exit from the interior of the brain Lateral aperture Median aperture
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Flow of Cerebrospinal Fluid
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Reabsorption of CSF Reabsorbed through arachnoid villi
grapelike clusters of arachnoid penetrate dural venous sinus 20 ml/hour reabsorption rate = same as production rate
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Continued production cause an increase in pressure --- hydrocephalus
Blockage of drainage of CSF (tumor, inflammation, developmental malformation, meningitis, hemorrhage or injury Continued production cause an increase in pressure --- hydrocephalus In newborn or fetus, the fontanels allow this internal pressure to cause expansion of the skull and damage to the brain tissue Neurosurgeon implants a drain shunting the CSF to the veins of the neck or the abdomen
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Brain Overview Brain Stem Cerebellum Diencephalon Cerebrum
Medulla Oblongata Pons Midbrain Reticular Formation Cerebellum Diencephalon Cerebrum Cranial Nerves Brain Lecture 10: Brain & Cranial Nerves
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Medulla Oblongata Continuation of spinal cord Ascending sensory tracts
Descending motor tracts Nuclei of 5 cranial nerves Cardiovascular center force & rate of heart beat diameter of blood vessels Respiratory center medullary rhythmicity area sets basic rhythm of breathing Information in & out of cerebellum Reflex centers for coughing, sneezing, swallowing etc Medulla
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Ventral Surface of Medulla Oblongata
Ventral surface bulge pyramids large motor tract decussation of most fibers left cortex controls right muscles Olive = olivary nucleus neurons send input to cerebellum proprioceptive signals gives precision to movements
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Dorsal Surface of Medulla Oblongata
Nucleus gracilis & nucleus cuneatus = sensory neurons relay information to thalamus on opposite side of brain 5 cranial nerves arise from medulla -- 8 thru 12 CN 7 CN 8 CN 9 CN 10 CN 11 CN 12 Nucleus gracilis Nucleus cutaneous
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Injury to the Medulla Hard blow to the back of the head may be fatal
Cranial nerve malfunctions on same side as injury; loss of sensation or paralysis of throat or tongue; irregularities in breathing and heart rhythm
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White fiber tracts ascend and descend
Pons One inch long White fiber tracts ascend and descend Pneumotaxic & apneustic areas help control breathing Middle cerebellar peduncles carry sensory info to the cerebellum Cranial nerves 5 thru 7 Pons
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Extends from pons to diencephalon
Midbrain Third ventricle One inch in length Extends from pons to diencephalon Cerebral aqueduct connects 3rd ventricle above to 4th ventricle below Cerebral aqueduct Midbrain Fourth ventricle
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Midbrain in Section Cerebral peduncles Substantia nigra Red nucleus
clusters of motor & sensory fibers Substantia nigra helps controls subconscious muscle activity Dopamine Red nucleus rich blood supply & iron-containing pigment cortex & cerebellum coordinate muscular movements by sending information here from the cortex and cerebellum Red nucleus Substantia nigra Cerebral peduncles
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Dorsal Surface of Midbrain
Superior colliculi Corpora quadrigemina superior colliculi inferior colliculi coordinate eye movements with visual stimuli coordinate head movements with auditory stimuli Inferior colliculi
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Midbrain Superior, middle & inferior peduncles attach to brainstem
inferior carries sensory information from spinal cord middle carries sensory fibers from cerebral cortex & basal ganglia superior carries motor fibers that extend to motor control areas Superior peduncles Inferior peduncles
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Reticular Formation Scattered nuclei in medulla, pons & midbrain
Reticular activating system alerts cerebral cortex to sensory signals (sound of alarm, flash light, smoke or intruder) to awaken from sleep maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles Motor function is involvement with maintaining muscle tone Reticular formation
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Overview Brain Stem Cerebellum Diencephalon Cerebrum Cranial Nerves
Lecture 10: Brain & Cranial Nerves
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Cerebellum 2 cerebellar hemispheres and vermis (central area) Function
correct voluntary muscle contraction and posture based on sensory data from body about actual movements sense of equilibrium
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Cerebellum Transverse fissure between cerebellum & cerebrum
Cerebellar cortex (folia) & central nuclei are grey matter Arbor vitae = tree of life = white matter
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Brain Overview Brain Stem Cerebellum Diencephalon Cerebrum
Thalamus Hypothalamus Epithalamus Circumventricular Organs Cerebrum Cranial Nerves Brain Lecture 10: Brain & Cranial Nerves
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Diencephalon Surrounds 3rd Ventricle
Superior part of walls is thalamus Inferior part of walls & floor is hypothalamus Thalamus (enclosed in 3rd ventricle) Hypothalamus
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Thalamus (enclosed in 3rd ventricle)
1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate mass) Relay station for sensory information on way to cortex Crude perception of some sensations Thalamus (enclosed in 3rd ventricle)
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Thalamic Nuclei Nuclei have different roles
relays auditory and visual impulses, taste and somatic sensations receives impulses from cerebellum or basal ganglia anterior nucleus concerned with emotions, memory and acquisition of knowledge (cognition) Emotions Emotions, Alertness, Memory Emotions Auditory Integrates with other nuclei Visual Motor
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Connects to pituitary gland
Hypothalamus Dozen or so nuclei in 4 major regions mammillary bodies are relay station for olfactory reflexes infundibulum suspends the pituitary gland Major regulator of homeostasis receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood Smell Connects to pituitary gland Pituitary gland
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Functions of Hypothalamus
Controls and integrates activities of the ANS which regulates smooth, cardiac muscle and glands Synthesizes regulatory hormones that control the anterior pituitary Contains cell bodies of axons that end in posterior pituitary where they secrete hormones Regulates rage, aggression, pain, pleasure & arousal Feeding, thirst & satiety centers Controls body temperature Regulates daily patterns of sleep Smell Connects to pituitary gland Pituitary gland
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Epithalamus Pineal gland Habenular nuclei
endocrine gland the size of small pea secretes melatonin during darkness promotes sleepiness & sets biological clock Habenular nuclei emotional responses to odors Pineal gland Habenular nuclei
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Subthalamus & CVO Subthalamus small area just inferior to thalamus
work with basal ganglia, cerebrum & cerebellum to control body movements Circumventricular organs in walls of 3rd & 4th ventricles monitor changes in blood chemistry because lack blood brain barrier (parts of hypothalamus, pineal & pituitary gland) sites of entry of HIV virus into brain (dementia)
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Brain Overview Brain Stem Cerebellum Diencephalon Cerebrum
Lobes White Matter Basal Ganglia Limbic System Function of Cortex Sensory Motor Association Lateralization Brain Waves Cranial Nerves Brain Lecture 10: Brain & Cranial Nerves
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Cerebrum (Cerebral Hemispheres)
Cerebral cortex is gray matter overlying white matter 2-4 mm thick containing billions of cells grew so quickly formed folds (gyri) and grooves (sulci or fissures) Gray matter White matter
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Cerebrum (Cerebral Hemispheres)
Longitudinal fissure Longitudinal fissure separates left & right cerebral hemispheres Corpus callosum is band of white matter connecting left and right cerebral hemispheres Corpus callosum
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Lobes and Fissures Frontal Parietal Occipital Temporal
Each hemisphere is subdivided into 4 lobes Frontal lobe Motor area Personality, behavior Emotions Memory Parietal lobe Somatosensory – skin and muscle Occipital lobe Vision Temporal lobe Hearing Smell Taste Frontal Parietal Occipital Temporal
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Lobes and Fissures Central sulcus (black)
precentral & postcentral gyrus Parieto-occipital sulcus (red) Lateral sulcus (yellow) Frontal Parietal Occipital Temporal
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Insula within Lateral Fissure
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Cerebral White Matter Association fibers between gyri in same hemisphere Commissural fibers from one hemisphere to other Projection fibers form descending & ascending tracts Association fibers Association fibers between gyri in same hemisphere Commissural fibers from one hemisphere to other Projection fibers form descending & ascending tracts Commisural fibers Projection fibers Lecture 10: Brain & Cranial Nerves
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Basal Ganglia Connections to red nucleus, substantia nigra & subthalamus Input & output with cerebral cortex, thalamus & hypothalamus Control large automatic movements of skeletal muscles Parkinson’s Disease Caudate Globus pallidus Putamen
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Limbic System Emotional brain
intense pleasure & intense pain Strong emotions increase efficiency of memory
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Brain Injuries Causes of damage
displacement or distortion of tissue at impact increased intracranial pressure infections free radical damage after ischemia Concussion---temporary loss of consciousness headache, drowsiness, confusion, lack of concentration Contusion--bruising of brain (less than 5 min unconsciousness but blood in CSF) Laceration--tearing of brain (fracture or bullet) increased intracranial pressure from hematoma
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Sensory Areas of Cerebral Cortex
Receive sensory information from the thalamus Primary somatosensory area = postcentral gyrus = 1,2,3 Primary visual area = 17 Primary auditory area = 41 & 42 Primary gustatory area = 43
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Motor Areas of Cerebral Cortex
Voluntary motor initiation Primary motor area = 4 = precentral gyrus controls voluntary contractions of skeletal muscles on other side Motor speech area = 44 = Broca’s area production of speech -- control of tongue & airway
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Association Areas of Cerebral Cortex
Somatosensory area = 5 & 7 (integrate & interpret) Visual association area = 18 & 19 (recognize & evaluate) Auditory association area(Wernicke’s) = 22(words become speech) Gnostic area = 5,7,39 & 40 (integrate all senses & respond) Premotor area = 6 (learned skilled movements such as typing) Frontal eye field =8 (scanning eye movements such as phone book)
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Aphasia Language areas are located in the left cerebral hemisphere of most people Inability to use or comprehend words = aphasia nonfluent aphasia = inability to properly form words know what want to say but can not speak damage to Broca’s speech area fluent aphasia = faulty understanding of spoken or written words faulty understanding of spoken or written words word deafness = an inability to understand spoken words word blindness = an inability to understand written words damage to common integrative area or auditory association area
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Hemispheric Lateralization
Functional specialization of each hemisphere more pronounced in men Females have larger connections between 2 sides Damage to left side produces aphasia Damage to same area on right side produces speech with little emotional inflection
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Electroencephalogram (EEG)
Brain waves are millions of nerve action potentials in cerebral cortex diagnosis of brain disorders (epilepsy) brain death (absence of activity in 2 EEGs 24 hours apart) Alpha -- awake & resting Beta -- mental activity Theta -- emotional stress Delta -- deep sleep
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Overview Brain Stem Cerebellum Diencephalon Cerebrum Cranial Nerves
Lecture 10: Brain & Cranial Nerves
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Cranial Nerves Olfactory Optic Oculomotor Trochlear Trigeminal
Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory hypoglossal CN I CN II CN III CN IV CN V CN VI CN VII CN VIII CN IX CN X CN XI CN XII
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I -- Olfactory Nerve (S)
Extends from olfactory mucosa of nasal cavity to olfactory bulb Sense of smell Anosmia – loss of smell
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II -- Optic Nerve (S) Connects to retina supplying vision Defect in
Visual acuity Visual field Visual field defect Visual acuity defect
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III = Oculomotor Nerve (S/M)
Sensory: Proprioception – sense of position Motor: Levator palpebrae raises eyelid Ptosis – drooping of eyelid 4 extrinsic eye muscles Superior, medial, inferior, and inferior oblique 2 intrinsic eye muscles accomodation for near vision (changing shape of lens during reading) constriction of pupil Diplopia – double vision
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IV = Trochlear Nerve (M)
Sensory: Proprioception – sense of position Motor: Superior oblique eye muscle
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V = Trigeminal Nerve S/M)
Sensory: touch, pain, & temperature receptors of the face ophthalmic branch maxillary branch mandibular branch Motor: muscles of mastication Tic douloureux - severe, stabbing pain to one side of the face.
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VI = Abducens Nerve (S/M)
Sensory: Proprioception – sense of position Motor: Lateral rectus eye muscle
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VII = Facial Nerve (S/M)
Sensory: taste buds on anterior 2/3’s of tongue Motor: facial muscles salivary & nasal and oral mucous glands & tears Bell’s Palsy
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VIII = Vestibulocochlear Nerve (S/M)
Cochlear branch begins in medulla receptors in cochlea hearing if damaged deafness or tinnitus (ringing) is produced Vestibular branch begins in pons receptors in vestibular apparatus sense of balance vertigo (feeling of rotation) ataxia (lack of coordination)
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IX = Glossopharyngeal Nerve (S/M)
Sensory: Somatic sensations & taste on posterior 1/3 of tongue Motor: Stylopharyngeus m. (lifts throat during swallowing) Secretions of parotid gland
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X = Vagus Nerve (S/M) Sensory: Motor: Receives sensations from viscera
Controls cardiac muscle and smooth muscle of the viscera Controls secretion of digestive fluids Bradycardia
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XI = Spinal Accessory Nerve (S/M)
Cranial portion arises medulla skeletal mm of throat & soft palate Spinal portion arises cervical spinal cord sternocleidomastoid and trapezius mm.
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XII = Hypoglossal Nerve (S/M)
Sensory: Proprioception – sense of position Motor: Controls muscles of tongue during speech and swallowing Injury deviates tongue to injured side when protruded
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Aging & the Nervous System
Years 1 to 2 rapid increase in size due to increase in size of neurons, growth of neuroglia, myelination & development of dendritic branches Early adulthood until death brain weight declines until only 93% by age 80 number of synaptic contacts declines processing of information diminishes conduction velocity decreases voluntary motor movements slow down reflexes slow down
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Cerebrovascular Accident (CVA)
Third leading cause of death after heart attacks and cancer 2 types of strokes ischemic due to decreased blood flow hemorrhagic due to rupture of blood vessel Risk factors high blood pressure, high cholesterol, heart disease, diabetes, smoking, obesity, alcohol Tissue plasminogen activator (t-PA) used within 3 hours of onset will decrease permanent disability
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Transient Ischemic Attack (TIA)
Episode of temporary cerebral dysfunction Cause impaired blood flow to the brain Symptoms dizziness, slurred speech, numbness, paralysis on one side, double vision reach maximum intensity almost immediately persists for 5-10 minutes & leaves no deficits Treatment is aspirin or anticoagulants; artery bypass grafting or carotid endarterectomy
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Alzheimer Disease (AD)
Dementia = loss of reasoning, ability to read, write, talk, eat & walk Afflicts 11% of population over 65 Loss of neurons that release acetylcholine Plaques of abnormal proteins outside neurons Tangled protein filaments within neurons Risk factors -- head injury, heredity Beneficial effects of estrogen, vitamin E, ibuprofen & ginko biloba
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