1. © 2015 Pearson Education, Inc.

2. Spinal Cord
Nervous tissue that extends from the foramen magnum of the skull to the first or second lumbar vertebra
Provides a two-way conduction pathway to and from the brain
31 pairs of spinal nerves arise from the spinal cord
Cauda equina  a collection of spinal nerves at the inferior end of the spinal cord

3. Cervical
spinal nerves
Cervical
enlargement C8
Dura and
arachnoid
mater
Thoracic
spinal nerves
Figure 7.20 (1 of 2)

4. Lumbar
enlargement
T12
End of
spinal cord
Cauda
equina
Lumbar
spinal nerves L5
End of
meningeal
coverings S1
Sacral
spinal nerves S5 S5 S5
Figure 7.20 (2 of 2)

5. Spinal Cord Anatomy Meninges cover the spinal cord
Spinal nerves leave at the level of each vertebrae
Dorsal root
Associated with the dorsal root ganglia, or collections of cell bodies outside the central nervous system
Ventral root
Portion of spinal cord containing axons

6. Figure 7.21 White matter Dorsal (posterior) horn of gray matter
Central canal
Dorsal root
ganglion
Lateral horn of
gray matter
Spinal nerve
Ventral (anterior)
horn of gray matter
Dorsal root of
spinal nerve
Ventral root
of spinal nerve
Pia mater
Arachnoid mater
Dura mater
Figure 7.21

7. Homeostatic Imbalance
Flaccid Paralysis
Occurs when there is damage to the dorsal root
Nerve impulses to not reach the muscles affected; thus, no voluntary movement of those muscles is possible
The muscles begin to atrophy because they are not longer being stimulated

8. Homeostatic Imbalance
Spastic Paralysis
Results if the spinal cord is transected (cut crosswise) or crushed
Affected muscles stay healthy because they are still stimulated by spinal reflex arcs and movement of those muscles still occur
Movements are involuntary
A loss of feeling occurs in the body areas below the point of cord destruction

9. Peripheral Nervous System (PNS)
Nerves and ganglia outside the central nervous system
Nerve  bundle of neuron fibers
Neuron fibers are bundled by connective tissue

10. PNS: Structure of a Nerve
Endoneurium surrounds each fiber
Groups of fibers are bound into fascicles by perineurium
Fascicles are bound together by epineurium

11. Axon
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Blood
vessels
Figure 7.23

12. PNS: Classification of Nerves
Mixed nerves
Both sensory and motor fibers
Sensory (afferent) nerves
Carry impulses toward the CNS
Motor (efferent) nerves
Carry impulses away from the CNS

13. PNS: Cranial Nerves
Twelve pairs of nerves that mostly serve the head and neck
Only the pair of vagus nerves extend to thoracic and abdominal cavities
Most are mixed nerves, but three are sensory only

14. PNS: Cranial Nerves Device
Oh – Olfactory
Oh – Optic
Oh – Oculomotor
To – Trochlear
Touch – Trigeminal
And – Abducens
Feel – Facial
Very – Vestibulocochlear
Green – Glossopharyngeal
Vegetables – Vagus
A – Accessory
H – Hypoglossal

15. PNS: Cranial Nerves I Olfactory nerve—sensory for smell
II Optic nerve—sensory for vision
III Oculomotor nerve—motor fibers to eye muscles
IV Trochlear—motor fiber to one eye muscle

16. PNS: Cranial Nerves
V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles
VI Abducens nerve—motor fibers to eye muscles
VII Facial nerve—sensory for taste; motor fibers to the face
VIII Vestibulocochlear nerve—sensory for balance and hearing

17. PNS: Cranial Nerves
IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx
X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera
XI Accessory nerve—motor fibers to neck and upper back
XII Hypoglossal nerve—motor fibers to tongue

18. Figure 7.24 III Oculomotor IV Trochlear VI Abducens I Olfactory
II Optic
V Trigeminal
V Trigeminal
VII Facial
Vestibular
branch
Cochlear
branch
VIII Vestibulocochlear
X Vagus
IX Glossopharyngeal
XII Hypoglossal
XI Accessory
Figure 7.24

19. PNS: Spinal Nerves
There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs
Formed by the combination of the ventral and dorsal roots of the spinal cord
Named for the region from which they arise

20. C1 2 3
Ventral rami form
cervical plexus
(C1 – C5)
Cervical
nerves 4 5 6 7
Ventral rami form
brachial plexus
(C5 – C8; T1) 8 T1 2 3 4 5
Thoracic
nerves 6 7
No plexus
formed
(intercostal
nerves)
(T1 – T12) 8 9 10
Lumbar
nerves 11 12
Sacral
nerves L1 2 3
Ventral rami form
lumbar plexus
(L1 – L4) 4 5 S1
Ventral rami form
sacral plexus
(L4 – L5; S1 – S4) 2 3 4
(a)
Figure 7.25a

21. PNS: Anatomy of Spinal Nerves
Spinal nerves divide soon after leaving the spinal cord
Ramus  branch of a spinal nerve; contains both motor and sensory fibers
Dorsal rami  serve the skin and muscles of the posterior trunk
Ventral rami  form a complex of networks (plexus) for the anterior

22. Dorsal root Dorsal ramus Dorsal root ganglion Spinal cord Ventral
Spinal nerve
(b)
Figure 7.25b

23. PNS: Spinal Nerve Plexuses
Plexus  networks of nerves serving motor and sensory needs of the limbs
Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions
Four plexuses:
Cervical
Brachial
Lumbar
Sacral

24. PNS: Spinal Nerve Plexuses
Cervical Plexus
Originates from ventral rami in C1 – C5
Important nerve is the phrenic nerve
Areas served:
Diaphragm
Shoulder and neck

25. PNS: Spinal Nerve Plexuses
Brachial Plexus
Originates from ventral rami in C5 – C8 and T1
Important nerves:
Axillary
Radial
Median
Musculocutaneous
Ulnar
Areas served: shoulder, arm, forearm, and hand

26. Axillary nerve Humerus Radial nerve Musculocutaneous nerve Ulna Radius
Ulnar nerve
Radial nerve
(superficial
branch)
Median nerve
(a) The major nerves
of the upper limb
Figure 7.26a

27. PNS: Spinal Nerve Plexuses
Lumbar Plexus
Originates from ventral rami in L1 through L4
Important nerves:
Femoral
Obturator
Areas served:
Lower abdomen
Anterior and medial thighs

28. Femoral Lateral femoral cutaneous Obturator Anterior femoral cutaneous
Saphenous
(b) Lumbar plexus,
anterior view
Figure 7.26b

29. PNS: Spinal Nerve Plexuses
Sacral Plexus
Originates from ventral rami in L4 – L5 and S1 – S4
Important nerves:
Sciatic
Superior and inferior gluteal
Areas served:
Lower trunk and posterior thigh
Lateral and posterior leg and foot
Gluteal muscles of hip area

30. (c) Sacral plexus, posterior view
Superior
gluteal
Inferior
gluteal
Sciatic
Posterior
femoral
cutaneous
Common
fibular
Tibial
Sural (cut)
Deep
fibular
Superficial
fibular
Plantar
branches
(c) Sacral plexus, posterior view
Figure 7.26c

31. PNS: Autonomic Nervous System
Motor subdivision of the PNS
Consists only of motor nerves
Also known as the involuntary nervous system
Regulates activities of cardiac and smooth muscles and glands
Two subdivisions
Sympathetic division
Parasympathetic division

32. PNS: Autonomic Functioning
Sympathetic  “fight or flight”
Response to unusual stimulus
Takes over to increase activities
Remember as the “E” division
Exercise, excitement, emergency, and embarrassment

33. PNS: Autonomic Functioning
Parasympathetic  “housekeeping” activities
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division
digestion, defecation, and diuresis

34. Homeostatic Imbalance
Cerebral Palsy
Neuromuscular disability in which the voluntary muscles are poorly controlled and spastic because of brain damage
About half have seizures, are mentally retarded, and/or have impaired hearing and vision
Largest single cause of physical disabilities in children

35. Homeostatic Imbalance
Anencephaly
Failure of the cerebrum to develop
Results in a child who cannot hear, see, or process sensory inputs
Spina Bifida
Results when the vertebrae form incompletely (typically lumbar region)
Can lead to paralysis of all organs and muscles at and below the hips