1. Unit 9 Central Nervous System, Spinal Nerves, and Cranial Nerves
Unit 9 Central Nervous System, Spinal Nerves, and Cranial Nerves

2. Objectives: Describe how the spinal cord is protected
Describe the structure of the spinal cord

3. Spinal Cord Structure: Protection and Coverings
Inside Vertebrae
Spinal meninges
Three layers of connective tissue
Dura mater
Arachnoid mater
Pia mater
Continuous with cranial meninges
Cerebrospinal fluid (CSF)

4. Spinal Meninges and Spaces (Outside to Inside)
Epidural space: Between vertebrae and dura mater
Dura mater-Tough, dense connective tissue
Extends to vertebra S2 (well beyond spinal cord)
Arachnoid mater: Resembles spider’s web
Extends into subarachnoid space
Subarachnoid space
CSF circulates in this space
Pia mater: Thin, delicate layer
Adheres to surface spinal cord (and brain)
Contains blood vessels

5. Spinal Meninges and Spaces
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6. Gross Anatomy of Spinal Cord
Extends from medulla of brain to L2 vertebra
Cauda equina (horse’s tail)
Extends inferior to end of spinal cord
Consists of roots of lumbar, sacral and coccygeal spinal nerves
Left and right halves partially separated by
Anterior median fissure and posterior median sulcus
Small central canal (filled with CSF) in middle
Enlargements: Cervical and Lumbar regions
Points of origins of nerves to upper and lower limbs

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8. Internal Structure of Spinal Cord
Gray matter forms “H” (“butterfly”)
Three horns on each side; sites of cell bodies
Posterior gray horns: contain sensory neurons
Anterior gray horns: contain somatic motor neurons
Lateral gray horn: contain autonomic motor neurons
White matter (surrounds gray “H”)
Consists of white columns
Posterior, Anterior, and Lateral columns
Contain tracts (bundles of axons)
Sensory tracts: ascending to brain
Motor tracts: descending from brain

9. Internal Structure of Spinal Cord
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10. Spinal Nerves 31 pairs Nerves attached to spinal cord by 2 roots
Named according to level of vertebra
C1-C8, T1-T12, L1-L5, S1-S5, 1 coccygeal
Emerge from spinal cord through intervertebral foramina
Nerves attached to spinal cord by 2 roots
Dorsal root: made of axons of sensory neurons
Dorsal root ganglion: swelling containing cell bodies of sensory neurons
Ventral root: composed of axons of motor neurons
Both somatic motor and autonomic motor

11. Objectives:
Describe the composition, coverings, and distribution of spinal nerves.

12. Spinal Nerve Composition
Are Mixed:
Formed from dorsal root (sensory) and ventral root (motor) root
Connective tissue coverings
Individual axons wrapped in endoneurium
Axons grouped in fascicles wrapped in perineurium
Outer covering = epineurium

13. Spinal Nerve Composition
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14. Distribution of Spinal Nerves
Spinal nerves branch after pass through intervertebral foramina
Some join with branches from neighboring nerves to form Plexuses
Nerve names relate to region innervated
Spinal nerves T2-T12 do not form plexuses
Called Intercostal nerves
Supply abdominal muscles, skin of chest and back, and muscles between ribs.

15. Plexuses Cervical plexus Brachial plexus
Supplies posterior head, neck, shoulders, and diaphragm
Important nerves: phrenic - diaphragm
Brachial plexus
Supplies upper limbs + some neck and shoulder muscles
Important nerves: radial, ulnar, axial - median to arm, forearm, hand

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Brachial Plexus
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17. Plexuses Lumbar plexus Sacral plexus
Supplies abdominal wall, external genitalia, and part of lower limbs
Important nerves: femoral (to anterior thigh: quads)
Sacral plexus
Supplies buttocks, perineum, and most of lower limbs
Important nerves: gluteal, sciatic (to posterior thigh and all of leg and foot)

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Lumbosacral Plexus
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Dermatome
An area of skin that the sensory nerve fibers of a particular spinal nerve innervate
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20. Objectives: Describe the functions of the spinal cord
Describe the components of a reflex arc

21. Spinal Cord Functions Pathways for nerve impulses within tracts
Ascending (sensory)
Descending (motor)
Reflexes: fast, involuntary sequences of actions in response to stimuli
Can be simple (withdrawal) or complex (learned sequence such as driving car)
Levels
Spinal (reflex arc): simple
Cranial: more complex

22. Reflex Arc Sensory receptor: responds to stimulus
Sensory neuron: through dorsal root ganglion and root  posterior horn
Integrating center: single synapse between sensory and motor neurons
Motor neuron: from anterior horn  ventral root  spinal nerve 
Effector: muscle responds

23. Example of Reflex Arc: Patellar Reflex
Sensory receptor is stimulated by tap on patellar tendon
Sensory neuron: through dorsal root  spinal cord
Integrating center: single synapse in spinal cord
Motor neuron: through ventral root  spinal nerve  femoral nerve 
Effector: quads contract, extend leg

24. Example of Reflex Arc: Patellar Reflex
helps maintain posture
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Withdrawal Reflex
Protective
11-11
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26. Crossed-Extensor Reflex
Flexor muscles contract
Flexor muscles on opposite side inhibited
Extensor muscles on opposite side contract for balance
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27. Objectives: Discuss how the brain is protected and supplied with blood
Name the 4 major parts of the brain and explain the function of each part
Describe three somatic sensory and somatic motor pathways

28. Brain Development Three Major Vesicles Forebrain Midbrain Hindbrain
Forebrain (prosencephalon)
Anterior portion (telencephalon)
Cerebrum
Basal ganglia
Posterior portion (diencephalon)
Thalamus
Hypothalamus
Posterior pituitary
Pineal gland
11-17

29. Brain Development Midbrain (Mesencephalon) Midbrain
Hindbrain (Rhombencephalon)
Anterior portion (Metencephalon)
Cerebellum
Pons
Posterior portion (Myelencephalon)
Medulla oblongata
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30. Brain: 4 Major Parts Brain stem: continuous with spinal cord
(A) Medulla oblongata, (B) pons, (C) midbrain
Diencephalon: superior to brain stem
Thalamus, hypothalamus, and pineal gland
Cerebrum: largest part and most superior
Surface covered with gray matter: cortex
Deep to cortex is cerebral white matter
Cerebellum: posterior and inferior
Means “little brain”
Brain is protected by: Cranial meninges: dura mater, arachnoid mater, and pia mater

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Brain: Major Parts
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Brain: Major Parts
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33. (1) Brain Stem: (A) Medulla Oblongata
Most inferior part of brainstem
White matter connects spinal cord and other parts of brain
Contains vital nuclei
Cardiovascular center
Regulates heart rate, blood pressure
Medullary rhythmicity area
Adjusts respiratory rhythm
Other sensory and reflex motor areas
Cranial nerves VIII-XII attached here

34. (1) Brain Stem: (B) Pons Serves as a “bridge” Contains nuclei
Connects medulla to midbrain and above
Contains ascending and descending tracts
Connects left and right sides of cerebellum
Contains nuclei
Motor relays from cerebrum to cerebellum
Helps control breathing
Cranial nerves V-VIII attached here

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(1) Brain Stem
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36. (1) Brain Stem: (C) Midbrain
Connects pons to diencephalon
Large tracts: Cerebral peduncles
Nuclei:
Substantia nigra: related to Parkinson disease
Red nuclei: help coordinate movements
Origin of cranial nerves III and IV (control eye movements)
Superior colliculi: nuclei involved in
Scanning eye movements
Responses to visual stimuli
Inferior colliculi: responses to auditory input

37. (D) Reticular Formation
Netlike arrangement of gray and white matter
Contains ascending and descending tracts
Ascending part = reticular activating system (RAS)
Carries sensory pathways to cerebral cortex
Helps maintain consciousness
Helps induce sleep

38. (D) Reticular Formation
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39. (2) Diencephalon Thalamus: major sensory relay center
Also motor, autonomic, and consciousness functions
Hypothalamus: lies inferior to thalamus
Control of pituitary and hormone production
Works with ANS regulating many viscera
Involved with feelings and behavior patterns
Regulation of eating, drinking, fluid levels
Control of body temperature
Regulation of circadian rhythms, sleep, waking
Pineal gland: secretes melatonin
Controls sleep, biological clock

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(2) Diencephalon
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(2) Diencephalon
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42. (D) Types of Sleep Rapid Eye Movement (REM) Slow Wave
Some areas of brain active
Heart and respiratory rates irregular
Dreaming occurs
Slow Wave
Person is tired
Decreasing activity of reticular system
Restful
Dreamless
Reduced blood pressure and respiratory rate
Ranges from light to heavy
Alternates with REM sleep

43. (D) What If You Stopped Sleeping?

44. (3) Cerebrum: Structure
Cerebral cortex
Internal white mater
Deep gray nuclei
Surface folds of cerebral cortex: Gyri
Grooves between gyri: Sulci
Longitudinal fissure: divides cerebrum into left and right hemispheres
Hemispheres connected by Corpus collosum

45. (3) Cerebrum: Structure
Each hemisphere has 4 lobes
Frontal, parietal, temporal, occipital
Central sulcus separates frontal from parietal
Precentral gyrus anterior to sulcus: Primary Motor area
Postcentral gyrus: Primary Somatosensory area
Deep gray nuclei: Basal Ganglia
Globus pallidus, Putamen, Caudate nucleus

46. (3) Functions of Cerebrum
Interpretation
Storing memory
Retrieving memory
Reasoning
Center for intelligence and personality

47. (3) Limbic System
Ring of structures on inner border of cerebrum and floor of diencephalon
Called “emotional brain”: primary role in
Pain, pleasure, anger, affection and behavior
Involuntary activity related to survival
Important in memory development

48. (3) Limbic System Consists of Portions of Frontal lobe
Portions of Temporal lobe
Hypothalamus
Thalamus
Basal nuclei
Other deep nuclei

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(3) Limbic System
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(3) Cerebrum
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(3) Cerebrum
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52. (3) Functional Areas of Cerebral Cortex
Sensory areas receive input  perception
Motor areas  initiate movements
Associative areas  complex integration: memory, emotion, reasoning, judgment

53. (3) Sensory Areas Primary Somatosensory area: postcentral gyrus
Input includes: touch, proprioception, pain, itching, tickle, temperature
Primary Visual area: occipital lobe
Primary Auditory area: temporal lobe
Primary Gustatory (taste) area: base of postcentral gyrus
Primary Olfactory (smell) area: medial aspect of temporal lobe

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(3) Sensory Areas
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(3) Sensory Areas
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56. (3) Motor Areas Located anterior to central sulcus
Primary Motor area: precentral gyrus
Broca’s speech area
Interacts with premotor area and primary motor area to regulate breathing and speech muscles
Is in left hemisphere in 97% of persons

57. (3) Motor Areas Frontal Eye Field Above Broca’s area
Controls voluntary movements of eyes and eyelids
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58. (3) Association Areas
Adjacent to sensory and motor areas and connected via association tracts
Integrate and interpret information
Provide memory, reasoning, verbalization, judgment, emotions
Examples:
Somatosensory Association area
Posterior to primary somatosensory area
Integrates sensation: exact shape and texture of object compared with stored memories
Wernike’s area: left temporal, parietal lobes
Interprets meaning of speech: words  thoughts
Right hemisphere adds emotional content

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(3) Association Areas
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60. (3) Association Areas Frontal Lobe Concentrating Planning
Problem solving
Judging
Temporal Lobe
Remember visual scenes
Remember music
Remember complex patterns
Occipital Lobe
Combine visual images with other sensory experiences
Parietal Lobe
Understanding speech
Using words to express thought

61. (3) Cerebrum: Functional Areas
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62. (3) Lateralization
Brain controls opposite side of the body: all sensory and motor pathways cross in CNS
Left hemisphere important for spoken and written language, numerical and scientific skills, and reasoning
Right side more involved with spatial and pattern recognition and emotional content

63. (3) Hemisphere Dominance
In over 90% of population, left hemisphere is dominant
Non-dominant hemisphere
Nonverbal tasks
Motor tasks
Understanding and interpreting musical and visual patterns
Provides emotional and intuitive thought processes
Dominant hemisphere
Speech
Writing
Reading
Verbal skills
Analytical skills
Computational skills

64. (3) Memory Process for storing and retrieving information
Involves structural and functional changes
Involves association areas, parts of limbic system, and diencephalon
Skill memory also involves cerebellum and basal ganglia

65. (3) Memory Short Term Working memory Closed circuit
Circuit is stimulated over and over
When impulse flow stops, memory disappears
Long Term
Changes structure and function of neurons
Enhanced synaptic transmission

66. Electroencephalogram (EEG)
Brain Waves – Electrical signals of nerve impulses
EEG
Records wave generated by neurons close to the surface in the cerebral cortex
Detected by metal electrodes placed on forehead and scalp
Used to study normal brain functions such as changes that occur during sleep
Used to diagnosis variety of brain disorders
Epilepsy, tumors, metabolic abnormalities, sites of trauma, and degenerative diseases

67. (4) Cerebellum
Location: posterior to medulla and pons, inferior to cerebrum
Attached to brain stem by cerebellar peduncles
Structure:
Two cerebellar hemispheres
Cerebellar cortex: gray matter
Tree-like appearance (seen in sagittal section) of white matter and gray nuclei

68. (4) Cerebellum Functions
Receives wide range of sensory input from muscles, joints, tendons, eyes, inner ears
Compares actual movements with intended ones
Helps produce smooth, coordinated movements
Helps execute skilled motor activities
Regulates posture and balance

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(4) Cerebellum
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70. Brain Blood Supply and Blood-Brain Barrier
Requires 20% of the body’s O2 supply
4 min lack  permanent damage
Requires continuous glucose supply
Protected by blood-brain barrier
Allows passage of lipid soluble materials: O2, CO2, alcohol, anesthetic agents
But controls entry of most harmful materials
Created by tight capillaries and astrocytes

71. Ventricles Within cerebral hemispheres and brain stem
Interconnected cavities
Within cerebral hemispheres and brain stem
Continuous with central canal of spinal cord
Filled with cerebrospinal fluid (csf)
2 Lateral ventricles
Third ventricle
Fourth ventricle
Cerebral aqueduct
11-4

72. Cerebrospinal Fluid (CSF)
Formed in the 4 ventricles of brain
by choroid plexuses
Specialized capillary networks (covered by ependymal cells) in walls of ventricles
Through filtration and secretion of blood plasma
Pathway
Through 4 ventricles  central canal of spinal cord and within subarachnoid space  around the brain
Reabsorbed through arachnoid villi into blood in superior sagittal sinus
Cushions brain and provides nutrients

73. Cerebrospinal Fluid (CSF)
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74. Objective:
Identify the 12 pairs of cranial nerves by name and number and give the functions of each

75. Cranial Nerves (Table 10.2)
Olfactory: special sensory—smell
Optic: special sensory—vision
Oculomotor: motor—control of eye movements
Trochlear: motor—control of eye movements
Trigeminal: mixed
General sensory: touch, pain, pressure, hot, cold in face
Motor: to muscles used for chewing

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Cranial Nerve V
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77. Cranial Nerves Abducens: motor—control of eye movements Facial: mixed
Special sensory (taste) from anterior of tongue
Motor to muscles of facial expression, tear glands, and some salivary glands
Vestibulocochlear: special sensory—ear

78. Cranial Nerves VI and VII
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79. Cranial Nerves Glossopharyngeal: mixed
Sensory for posterior of tongue, pharynx, and palate; blood pressure
Motor to pharyngeal muscles (swallowing), salivary gland (parotid)

80. Cranial Nerves Vagus: mixed (the major parasympathetic nerve)
Sensory from pharynx, ear, diaphragm, visceral organs in thoracic and abdominal cavities
Motor to palatal and pharyngeal muscles (swallowing and voice); to viscera in thoracic and abdominal cavities

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Cranial Nerve X
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82. Cranial Nerves
Accessory: motor to voluntary muscles including sternocleidomastoid and trapezius (move head, shoulders)
Hypoglossal: motor to tongue (swallowing and speech)

83. Objective:
Describe the effects of aging on the nervous system

84. Aging Rapid brain growth during first few years of life
Due to increase in size of neurons and proliferation of neuroglia
Increase in development of dendritic branches and synaptic contacts
From early adulthood through old age:
Decline in brain mass
Fewer synaptic contacts brain function
Some decrease in brain function

85. Life-Span Changes Over average lifetime, brain shrinks 10%
Most cell death occurs in temporal lobes
By age 90, frontal lobe has lost half its neurons
Decreased levels of neurotransmitters
Fading memory
Slowed responses and reflexes
Changes increase risk of falling
Sleep problems common

86. Clinical Application Concussion Cerebral Palsy
Cerebral Injuries and Abnormalities
Concussion
Brain jarred against cranium
Loss of consciousness
Temporary loss of memory
Mental cloudiness
Headache
Recovery usually complete
Cerebral Palsy
Motor impairment at birth
Caused by blocked cerebral blood vessels during development
Seizures
Learning disabilities
Cerebrovascular Accident
Stroke
Sudden interruption in blood flow
Brain tissues die

87. Brain Injury