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Chapter 14 The Central Nervous System

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1 Chapter 14 The Central Nervous System

2 Brain – Directional Terms and Landmarks
Rostral (toward the forehead) - Caudal (toward the cord) Major parts of the brain - cerebrum, cerebellum, brainstem


4 Cranial Meninges Dura mater -- outermost, tough membrane
outer periosteal layer against bone where separated from inner meningeal layer forms dural venous sinuses draining blood from brain supportive structures formed by meningeal dura mater falx cerebri, falx cerebelli and tentorium cerebelli NO epidural space (as in vertebral canal) Arachnoid mater is spider web filamentous layer Pia mater is a thin vascular layer adherent to contours of brain

5 Cranial Meninges

6 Dura and venous sinuses

7 Meningitis Inflammation of the meninges
Serious disease of infancy and childhood between 3 months and 2 years of age Bacterial and virus invasion of the CNS by way of the nose and throat pia mater and arachnoid are most likely to be affected Signs include high fever, stiff neck, drowsiness and intense headache and may progress to coma Diagnose by examining the CSF (spinal tap)

8 Longitudinal fissure separates 2 cerebral hemispheres.
gyri are the folds and sulci the grooves surface layer of gray matter is called cortex; deeper masses of gray matter are called nuclei bundles of axons (white matter) are called tracts

9 Brain Ventricular System

10 Ventricles and Cerebrospinal Fluid
Internal chambers within the CNS lateral ventricles found inside cerebral hemispheres third ventricle is single, thin, vertical space under corpus callosum (between thalami) cerebral aqueduct runs through midbrain fourth ventricle is small chamber between pons & cerebellum central canal runs down through spinal cord Lined with ependymal cells and containing choroid plexus of capillaries that produce CSF


12 Cerebrospinal Fluid Clear liquid fills ventricles and canals & bathes external surface of brain and spinal cord (in subarachnoid space) Functions buoyancy -- floats brain so it neutrally buoyant protection -- cushions from hitting inside of skull chemical stability -- rinses away wastes Escapes from 4th ventricle (through lateral and medial aperatures) to surround the brain Reabsorbed by arachnoid villi into venous sinus

13 Blood-Brain and Blood-CSF Barriers
Blood-brain barrier (BBB) is tightly joined endothelium (tight junctions) of brain capillaries (in brain tissue) Allows materials to pass thru cells NOT between them. permeable toH20, glucose and lipid-soluble materials (alcohol, O2, CO2, nicotine and anesthetics) Inflammation/damage to BBB may allow pathogens to enter Blood-CSF barrier at choroid plexus is ependymal cells joined by tight junctions circumventricular organs (CVOs)in 3rd & 4th ventricles at breaks in the barrier where blood has direct access to brain Allows for monitoring of glucose, pH, osmolarity & other variations Possible route of infection (HIV)

14 The Brain Hindbrain Midbrain (mesencephalon) Forebrain
Medulla oblongata (myelencephalon) Pons Cerebellum Midbrain (mesencephalon) Forebrain Diencephalon Thalamus Hypothalamus Epithalamus Cerebrum (telencephalon) (metencephalon)


16 Photo of Sagittal Section of Brain

17 Hindbrain: Medulla Oblongata
3 cm extension of spinal cord Ascending & descending nerve tracts Pyramids – corticospinal tracts (somatic motor) decussate Nuclei of sensory & motor cranial nerves (IX, X, XI, and XII) Cardiac center adjusts rate & force of heart beat Vasomotor center adjusts blood vessel diameter Respiratory centers control rate & depth of breathing Reflex centers for coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue & head

18 Pons Bulge in the brainstem, rostral to the medulla
Ascending sensory tracts Descending motor tracts “Relay center” cerebrum to cerebellum up to thalamus Nuclei concerned with sleep, hearing, balance, taste, eye movements, facial expression, facial sensation, respiration, swallowing, bladder control & posture cranial nerves V, VI, VII, and VIII

19 Cerebellum Right & left hemispheres connected by vermis
Parallel surface folds called folia are gray matter White matter (arbor vitae) visible in sagittal section Muscular coordination – motor control Spatial perception

20 Midbrain, Cross Section
Cerebral aqueduct CN III and IV eye movement Substantia nigra sends inhibitory signals to basal nuclei & thalamus (degeneration leads to tremors and Parkinson disease)

21 Reticular Activating System
Clusters of gray matter scattered throughout pons, midbrain & medulla Regulate balance & posture relaying information from eyes & ears to cerebellum gaze centers allow you to track moving object Includes cardiac & vasomotor centers (medulla) Origin of descending analgesic pathways (block pain) Regulates sleep & conscious attention injury leads to irreversible coma

22 Diencephalon: Thalamus
Oval mass of gray matter protruding into lateral ventricle (part of diencephalon) Receives nearly all sensory information on its way to cerebral cortex integrate & directs information to appropriate area Interconnected to limbic system so involved in emotional & memory functions

23 Diencephalon: Hypothalamus
Walls & floor of 3rd ventricle Functions hormone secretion & pituitary ANS control thermoregulation (thermostat) food & water intake (hunger & satiety) sleep & circadian rhythms memory (mammillary bodies) emotional behavior

24 Diencephalon: Epithalamus
Pineal Gland Epithalamus consists of pineal gland (endocrine) and the habenula (connects limbic system to midbrain.

25 Cerebrum -- Gross Anatomy
Cerebral cortex is layer of gray matter with extensive folds to increase surface area ---- divided into lobes

26 Functions of Cerebrum Lobes
Frontal contains voluntary motor functions and areas for planning, mood, memory and social judgement Parietal contains areas for sensory reception & integration of sensory information Occipital is visual center of brain Temporal contains areas for hearing, smell, learning, memory, emotional behavior Insula is still little known (language?)

27 Tracts of Cerebral White Matter
Most of volume of cerebrum is white matter Myelinated fibers glia Types of tracts projection tracts extend vertically from brain to spinal cord forming internal capsule commissural tracts cross from one hemisphere to the other corpus callosum is wide band of white fiber tracts anterior & posterior commissures are pencil-lead sized association tracts connect lobes & gyri of each hemisphere to each other

28 Tracts of Cerebral White Matter

29 Cerebral Cortex Surface layer of gray matter -- 3 mm thick
Neocortex (six-layered tissue): (90% of cortex) newest part of the cortex (paleocortex & archicortex) layers vary in thickness in different regions of brain 2 types of cells stellate cells have dendrites projecting in all directions (local) pyramidal cells have an axon that passes out of the area into white matter

30 Basal Nuclei Masses of gray matter deep to cerebral cortex
Receive input from substantia nigra & motor cortex & send signals back to these regions Involved in motor control & inhibition of tremors

31 Limbic System Loop of cortical structures surrounding deep brain
Amygdala - important in emotions Hippocampus - important in memory Smell?

32 Cognition Cognition is mental processes such as awareness, perception, thinking, knowledge & memory 75% of brain is association areas where integration of sensory & motor information occurs Examples of effects of brain lesions parietal lobe -- contralateral neglect syndrome temporal lobe -- agnosia (inability to recognize objects) or prosopagnosia (inability to recognize faces) frontal lobe -- problems with personality (inability to plan & execute appropriate behavior)

33 Accidental Lobotomy of Phineas Gage
Accidental destruction of ventromedial region of both frontal lobes Personality change to an irreverent, profane and fitful person Neuroscientists believe planning, moral judgement, and emotional control are functions of the prefrontal cortex

34 Somesthetic Sensation
Somesthetic signals travel up gracile and cuneate fascicui and spinothalamic tracts of spinal cord Somatosensory area is postcentral gyrus

35 Sensory Homunculus Demonstrates that the area of the cortex dedicated to the sensations of various body parts is proportional to how sensitive that part of the body is.

36 Special Senses Organs of smell, vision, hearing & equilibrium project to specialized regions of the brain Locations taste is lower end of postcentral gyrus smell is medial temporal lobe & inferior frontal lobe vision is occipital lobe hearing is superior temporal lobe equilibrium is mainly the cerebellum, but to unknown areas of cerebral cortex via the thalamus

37 Sensory Association Areas
Association areas interpret sensory information Somesthetic association area (parietal lobe) position of limbs, location of touch or pain, and shape, weight & texture of an object Visual association area (occipital lobe) identify the things we see faces are recognized in temporal lobe Auditory association area (temporal lobe) remember the name of a piece of music or identify a person by his voice

38 Motor Control Intention to contract a muscle begins in motor association (premotor) area of frontal lobes Precentral gyrus (primary motor area) processes that order by sending signals to the spinal cord pyramidal cells called upper motor neurons supply muscles of contralateral side due to decussation Motor homunculus is proportional to number of muscle motor units in a region (fine control)

39 Motor Homunculus

40 Functional Regions of Cerebral Cortex

41 Language Includes reading, writing, speaking & understanding words
Wernicke’s area permits recognition of spoken & written language & creates plan of speech Broca’s area generates motor program for larynx, tongue, cheeks & lips transmits that to primary motor cortex for action

42 Language Centers

43 Lateralization of Cerebral Functions

44 Cerebral Lateralization
Left hemisphere is categorical hemisphere specialized for spoken & written language, sequential & analytical reasoning (math & science), analyze data in linear way Right hemisphere is representational hemisphere perceives information more holistically, perception of spatial relationships, pattern, comparison of special senses, imagination & insight, music and artistic skill

45 The Cranial Nerves 12 pair of nerves that arise from brain & exit through foramina leading to muscles, glands & sense organs in head & neck Input & output remains ipsilateral except CN II & IV

46 I. Olfactory Nerve Provides sense of smell
Damage causes impaired sense of smell

47 II. Optic Nerve Provides vision
Damage causes blindness in visual field

48 III. Oculomotor Nerve Provides some eye movement, opening of eyelid, constriction of pupil, focusing Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing & inability to move eye in certain directions

49 IV. Trochlear Nerve Provides eye movement
Damage causes double vision & inability to rotate eye inferolaterally

50 V. Trigeminal Nerve Main sensory nerve to face (touch, pain and temperature) and muscles of mastication Damage produces loss of sensation & impaired chewing

51 VI. Abducens Nerve Provides eye movement
Damage results in inability to rotate eye laterally & at rest eye rotates medially

52 VII. Facial Nerve Provides facial expressions, sense of taste on anterior 2/3’s of tongue, salivary glands and tear, nasal & palatine glands Damage produces sagging facial muscles & disturbed sense of taste (missing sweet & salty)

53 Branches of Facial Nerve
Clinical test: Test anterior 2/3’s of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, frown, raise eyebrows, etc.

54 VIII. Vestibulocochlear Nerve
Provides hearing & sense of balance Damage produces deafness, dizziness, nausea, loss of balance & nystagmus

55 IX. Glossopharyngeal Nerve
Provides control over swallowing, salivation, gagging, sensations (taste) from posterior 1/3 of tongue, control of BP and respiration Damage results in loss of bitter & sour taste & impaired swallowing

56 X. Vagus Nerve Provides swallowing, speech, regulation of viscera
Damage causes hoarseness or loss of voice, impaired swallowing & fatal if both are cut

57 XI. Accessory Nerve Provides swallowing, head, neck & shoulder movement Damage causes impaired head, neck & shoulder movement, head turns towards injured side

58 XII. Hypoglossal Nerve Provides tongue movements of speech, food manipulation & swallowing Damage results in inability to protrude tongue if both are damaged or deviation towards injured side & ipsilateral atrophy if one side is damaged

59 MNEMONICS I. Old Olfactory S Some II. Opie Optic S Say
III. Occasionally Oculomotor M Marry IV. Tries Trochlear M Money, V. Trigonometry Trigeminal B But VI. And Abducens M My VII. Feels Facial B Brother VIII. Very Vestibulocochlear S Says IX. Gloomy Glossopharyngeal B Big X Vague Vagus B Brains XI. And Accessory M Matters XII. Hypoactive Hypoglossal M Most

60 Innervation of muscles of eyeball movement
MNEMONICS 2 Innervation of muscles of eyeball movement LR6 (SO4) 3 Lateral Rectus (CN 6) Superior Oblique (CN 4) All others (CN 3) (superior, medial, inferior rectus and inferior oblique) I Nose, II Eyes (CN I. – olfactory; CN 2 – Optic)


62 PET Scans during a Language Task

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