Chapter 13 Study Topics – Spinal Cord and Nerves

Question 1

Can nerves regenerate? If so, where in the body can this happen?

Answer 1

Yes : occurs in the peripheral nervous system (PNS)

Question 2

List the 4 principal functions of the spinal cord

Answer 2

Conduction,
neural integration,
locomotion
refluxes

Question 3

Where are enlargements of the spinal cord found? What areas of the body do each enlargement supply?

Answer 3

Cervical, thoracic, lumbar, and sacral regions
They supply in the: cervical enlargement, lumbosacral enlargement

Question 4

What are the meninges in order from superficial to deep?

Answer 4

Dura mater, arachnoid mater, and pia mater

Question 5

Compare the structures found in gray matter versus white matter of the spinal cord.

Answer 5

Gray matter: dull in color; containing neuron cells bodies and dendrites
Spinal cord: cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull

Question 6

Compare the gray matter’s dorsal horns to the ventral horns. What type of information is each horn in charge of?

Answer 6

Two posterior (dorsal) horns—receive sensory nerve fibers, synapse with interneurons in horn​
Two anterior (ventral) horns—contain cell bodies of motor neurons

Question 7

Compare ascending tracts to descending tracts. What type of information travels through each?

Answer 7

Descending tracts: carry motor information down
Ascending tracts: carry sensory information up

Question 8

What is the purpose of decussation? Define contralateral and ipsilateral tracts.

Answer 8

Decussation: crossing of the midline that occurs in many tracts so that the brain senses and controls contralateral side of body
Contralateral: when the origin and destination of the tracts are on opposite sides of the body
Ipsilateral: when the origin and destinations of a tract are on the same side of the body ; does not decussate

Question 9

Compare poliomyelitis to ALS. What causes each disease? What happens in the nervous system in individuals with either of these diseases?

Answer 9

Poliomyelitis : destroys motor neurons in brainstem and anterior horn of spinal cord, signs of polio include muscle pain, weakness, and loss of some reflexes
ALS : destruction of motor neurons and muscular atrophy, and also sclerosis of lateral regions in the spinal cord
What happens : cause destruction of motor neurons leading to skeletal muscle atrophy from lack of innervation

Question 10

What are mixed nerves?

Answer 10

Mixed nerves : consist of both afferent and efferent fibers

Question 11

What is a ganglion?

Answer 11

Cluster of nerve cell bodies outside the CNS

Question 12

Describe the proximal branches of spinal nerves. What are the differences between the dorsal roots and ventral roots?

Answer 12

Dorsal roots: sensory input to spinal cord
Ventral roots: motor output out of spinal cord
Proximal branches : spinal nerves formed from two roots

Question 13

Describe the distal branches of the spinal nerves. What part of the body do the anterior rami innervate? What part of the body do the posterior rami innervate?

Answer 13

Distal branches : beyond the vertebrae the nerve divided into distal branches
Innovate in: thoracic

Question 14

What is the communicating rami? Which rami do the communicating rami branch from?

Answer 14

Communicating rami : connects with a string of sympathetic chain ganglia alongside the verbal column

Question 15

What is chickenpox? How is it different from shingles?

Answer 15

Differences: chickenpox is an itchy rash that clears up without complications, and shingles; painful trail of skin discoloration and itching

Question 16

List the 5 major nerve plexuses discussed in class. Be able to list the nerves associated with each plexus and what part of the body those nerves supply. Remember, you do not need to identify these nerves in a picture, just be able to list them include what plexus they are part of, and what parts of the body they innervate.

Answer 16

Cervical plexus in the neck C1 to C5: supplies neck and phrenic nerves to the diaphragm

Brachial plexus near the shoulder, C5 to T1: supplies upper limb and some of shoulder and neck
Divided into roots, trunks, divisions, and cords

Lumbar plexus in the lower back, L1 to L4: supplies abdominal wall, anterior thigh, and genitalia

Sacral plexus in the pelvis, L4, L5, and S1 to S4: supplies remainder of lower trunk and lower limb, including sciatic nerve

Coccygeal plexus, S4, S5, and Co1

Question 17

What is a dermatome?

Answer 17

Dermatom: a specific area of skin that conveys sensory input in a spinal nerve

Question 18

List 4 characteristics of reflexes. What type of muscle is activated in somatic reflexes?

Answer 18

Reflexes require stimulation
Not spontaneous actions, but responses to sensory input

Reflexes are quick
Involve few, if any, interneurons and minimum synaptic delay

Reflexes are involuntary
Occur without intent and are difficult to suppress

Reflexes are stereotyped
Occur essentially the same way every time

Question 19

List the 5 components of a reflex arc

Answer 19

1.Afferent nerve fibers carry information from receptors to posterior horn of spinal cord or
2.to the brainstem
3.Integrating center—a point of synaptic contact between neurons in gray matter of cord or brainstem
Determines whether efferent neurons issue signal to muscles
4.Efferent nerve fibers carry motor impulses to muscles
5.Effectors—the muscles that carry out the response

Question 20

What are proprioceptors?

Answer 20

Specialized sense organs to monitor position and movement of body parts

Question 21

Compare the 4 following reflex types: stretch reflex, flexor (withdrawal reflex), Crossed extension reflex, and tendon reflex

Answer 21

1. Stretch reflex: when a muscle is stretched it “fight back” and contacts
2. Flexor: the quick contraction of flexor muscles resulting in the withdrawal of a limb from and injurious stimulus
3. Crosses extension reflex: contraction of extensor muscles in limb opposite of the one that is withdrawn
4. Tendon reflex: response to excessive tension on the tendon

Question 22

Compare ipsilateral reflex arcs to contralateral reflex arcs. What is an intersegmental reflex?

Answer 22

Ipsilateral reflex: stimulus and response on the same side
Contralateral reflex: input and output are on opposite sides

Question 23

What is reciprocal inhibition?

Answer 23

Reflex phenomenon that prevents muscles from working against each other by inhibiting antagonist when agonist is excited

Question 24

Above what spinal level can spinal cord trauma cause respiratory failure?

Answer 24

Above C4

Question 25

What are the 3 forms of paralysis?

Answer 25

1. paraplegia
2. quadriplegia
3. hemiplegia