1. Nervous System: Spinal Cord and Peripheral Nerves
Chapter 11
Lisa Ochs RN, BSN 2008

2. Structure of the Spinal Cord
Spinal cord is a continuation of the brain stem
About the thickness of the thumb
Extends from the foramen magnum to the level of L1 in adults; in infants, the cord extends the length of the spinal canal
Lumbar puncture is done to sample the CSF- needle is inserted between L3 and L4

3. Structure of the Spinal Cord
Grey Matter
Center of the spinal cord, butterfly shaped
Composed of cell bodies and interneurons
Two projections- dorsal (posterior) horn and ventral (anterior) horn
Central canal runs through the middle- opening to the ventricular system of the brain and contains CSF (cord is also surrounded by CSF in the subarachnoid space)

4. Structure of the Spinal Cord
White Matter
Composed of myelinated axons grouped together to form nerve tracts
sensory tracts relay information from the periphery, up the spinal cord and to the brain; called ascending tracts
Motor tracts carry information from the brain, down the spinal cord and toward the periphery; called descending tracts

5. Figure 11-2 Cross section of the spinal cord showing the inner gray matter ("butterfly") and the outer white matter.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

6. Function of the Spinal Cord
Sensory pathway
Provides a pathway for sensory information traveling from the periphery to the brain
Motor pathway
Provides a pathway for motor information coming from the brain and going to the periphery
Reflex center
Acts a major reflex center; many automatic reflexes occur in the spinal cord, not the brain

7. Reflexes An involuntary response to a stimulus
Occurs repeatedly without conscious thought or voluntary input
Relexes that occur through the spinal cord bypass the complicated circuitry of the brain-responses happen quickly
Touch a hot pan and your hand will be withdrawn quickly, before the brain has time to interpret pain

8. The Reflex Arc The nerve pathway involved in a reflex Involves 4 parts
Receptor
Sensory (afferent) neuron
Motor (efferent) neuron
Effector organ

9. Figure 11-5 Reflex arc. The knee-jerk reflex illustrates the four components of the reflex arc.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

10. Normal Abnormal- damage to CNS
Figure 11-6 Many reflexes. A, Withdrawal reflex. B, Pupillary reflex. C, Blood pressure, or baroreceptor, reflex. D, Babinski reflex. E, Knee-jerk reflex.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

11. Peripheral Nervous System
Neuron vs. Nerve
Neuron- a single nerve cell
Nerve- many neurons bundled together with blood vessels and wrapped in connective tissue; located outside of the CNS (within the CNS, bundles of neurons are called tracts)

12. Figure 11-7 Difference between a neuron and nerve.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

13. Structure of the PNS
The peripheral nervous system can be classified in 2 ways:
Structurally (by anatomical parts)
Functionally (by physiological action)

14. Cranial Nerves 12 pairs of cranial nerves
Always described with a specific number (Roman numeral) and a name
Numbers indicate the order in which they exit the brain (from front to back)
Generally, the name indicates the area innervated by the nerve (mostly head and neck)

15. Cranial Nerves Four main functions:
Carry sensory information for the special senses (smell, taste, vision and hearig)
Carry sensory information for the general senses (touch, pressure, pain, temp)
Carry motor information that results in contraction of skeletal muscle
Carry motor information that results in secretion from glands and contraction of smooth and cardiac muscle

16. Cranial Nerves CN I olfactory (smell) CN II optic (sight)
CN III oculomotor (mvmt of eyeball, pupil)
CN IV trochlear (mvmt of eyeball)
CN V trigeminal (sensation face)
CN VI abducens (mvmt of eyeball)
CN VII facial (expression, tears, taste, blink)
CN VIII vestibulocochlear (hearing & balance)
CN IX glossopharyngeal (swallowing, taste, gag)
CN X vagus (visceral muscle, BP)
CN XI accessory (swallowing, speaking)
CN XII hypoglossal (speech & swallowing)

18. Testing Cranial Nerves
CN II Optic nerve
How would you test the patient’s optic nerve?
Snellen chart or other test of visual acuity

19. Testing Cranial Nerves
CN I Olfactory Nerve
How would you test the patient’s olfactory nerve?
Have the patient identify various smells (alcohol pad, coffee, etc.)

20. Testing Cranial Nerves
CN III, IV & VI Oculomotor, Trochlear & Abducens
How would you test a patient’s CN III, IV & VI?

21. Testing Cranial Nerves
CN IX Glossopharyngeal
How would you test a patient’s glossopharyngeal nerve?

22. Structure of the PNS Spinal Nerves
Thirty one pairs of spinal nerves emerge from the spinal cord
Each pair is numbered according to the level of the cord
Cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1)

24. Structure of the PNS
Lumbar and spinal nerves extend the length of the spinal canal before exiting the spinal column (remember the cord ends at L1); the nerves below are called the cauda equina

26. Structure of the PNS Nerve Plexuses Networks of nerve fibers
Three major plexuses: cervical, brachial and lumbosacral
Each has major nerves that emerge from them
Cervicle- phrenic nerve
Brachial- axillary, radial, median
Lumbosacral- femoral, sciatic

27. Examples of nerve plexuses in the body

29. Structure of the PNS Dermatome
The area of skin innervated by each spinal nerve

30. Functional Classification of PNS
Explains where the nerves go and what they do
Somatic afferent nerves (sensory information from the periphery to the CNS)
Somatic efferent nerves (bring motor information from the CNS to the skeletal muscles)
Autonomic nervous system (made up of nerves that supply organs and glands)

31. Cervical spine dislocation C4-C5
With cord compression

32. Cervical Spine fracture and dislocation (C6)
Posterior dislocation with cord contusion and edema

33. NCLEX Question
A client has an impairment of the cranial nerve II. Specific to this impairment, the nurse would plan to do which of the following the ensure client safety?
Speak loudly to the client
Test the temperature of the shower water
Check the temperature of the food on the client’s meal tray
Provide a clear path for ambulation without obstacles

34. Rationale
4. Cranial nerve II is the optic nerve. This patient would be expected to have visual disturbances, and therefore need to have trip hazards removed from their room.

35. NCLEX Question
When assessing the pupil’s ability to constrict, which cranial nerve (CN) is being tested? II
III IX X

36. Rationale
Cranial Nerve III (Oculomotor) is one of three cranial nerves that affect pupillary constriction

37. NCLEX Question
A patient sustained an injury to his spinal cord at the C2 level. Based on a spinal cord injury at this level, the nurse would most likely expect the patient to be treated with:
Diuretics
Oxygen via a ventilator
Oxygen via a nasal cannula
Vasopressors

38. Rationale
A spinal cord injury at the level of C2 would cause paralysis of the diaphragm (phrenic nerve exits at the level of C4). The patient will need to be on a ventilator in order to breathe