Chapter 13: Spinal Cord, Spinal Reflexes

Question 1

Functions of the spinal cord

Answer 1

Conduction, Neural Integration, Locomotion and Reflexes

Question 2

Two areas of the cord are thicker than elsewhere

Answer 2

Cervical enlargement—nerves to upper limb

- Lumbar enlargement—nerves to pelvic region and lower limbs

Question 3

Ascending tracts

Answer 3

carry sensory signals up the spinal cord. First-order neurons: detect stimulus and transmit signal to spinal cord or brainstem
Second-order neurons: continues to the thalamus at the upper end of the brainstem
Third-order neurons: carries the signal the

Question 4

Descending tracts

Answer 4

Descending tracts—carry motor signals down brainstem and spinal cord
Involve two motor neurons
Upper motor neuron (UMN): originates in cerebral cortex or brainstem and terminates on a lower motor neuron
Lower motor neuron (LMN): neurosoma is in brainstem or spinal cord

Question 5

Poliomyelitis

Answer 5

infectious viral disease that effects the CNS and can cause temporary or permanent paralysis

Question 6

Amyotrophic lateral sclerosis (ALS) or Lou Gehrig disease

Answer 6

Destruction of motor neurons and muscular atrophy
Also sclerosis (scarring) of lateral regions of the spinal cord
Astrocytes fail to reabsorb the neurotransmitter glutamate from the tissue fluid

Question 7

Nerve

Answer 7

a cord-like organ composed of numerous nerve fibers (axons) bound together by connective tissue

Question 8

Sensory (afferent) nerves

Answer 8

Carry signals from sensory receptors to the CNS

Question 9

Motor (efferent) nerves

Answer 9

Carry signals from CNS to muscles and glands

Question 10

Mixed nerves

Answer 10

Consists of both afferent and efferent fibers

Question 11

31 pairs of spinal nerves (mixed nerves)

Answer 11

8 cervical (C1–C8)
First cervical nerve exits between skull and atlas 
Others exit at intervertebral foramina
12 thoracic (T1–T12)
5 lumbar (L1–L5)
5 sacral (S1–S5)
1 coccygeal (Co1)

Question 12

Somatosensory Function

Answer 12

carry ensory signals from bones, joints, muscles, and skin

Question 13

Dermatome

Answer 13

a specific area of skin that conveys sensory input to a spinal nerve

Question 14

Reflexes

Answer 14

quick, involuntary, stereotyped reactions of glands or muscle to stimulation

Question 15

Somatic Reflexes

Answer 15

reflexes involving the somatic nervous system innervating skeletal muscle

Question 16

Muscle Spindle

Answer 16

stretch receptors embedded in skeletal muscles

Question 17

Proprioceptors

Answer 17

specialized sense organs to monitor position and movement of body parts

Question 18

Flexor (withdrawl) reflex

Answer 18

the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus

Question 19

Polysynaptic reflex arc

Answer 19

pathway in which signals travel over many synapses on their way to the muscle

Question 20

Crossed extension reflex

Answer 20

contraction of extensor muscles in limb opposite of the one that is withdrawn

Question 21

Tendon Reflex

Answer 21

in response to excessive tension on the tendon