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