Spinal Nerves And Reflexes

Question 1

how many pairs of spinal nerves are there

Answer 1

-31
()all are mixed nerves named for point of issue from spinal cord
() Supply all body parts except head and part of neck 4 general regions

Question 2

name the pairs of cervical, thoracic, lumbar and sacral nerves

Answer 2

8 pairs-cranial (c1-C8)( even though everything else says 12, and you only have 7 cervical vertebrae)
12 pairs of thoracic nerves
5 pairs of lumbar nerves
5 pairs of sacral nerves

Question 3

how is each spinal nerve connected to the spinal cord

Answer 3

ventral and dorsal roots

Question 4

ventral roots

Answer 4

contain MOTOR(efferent) fibers from ventral horn ‘motor neurons that innervate skeletal muscles

Question 5

Dorsal roots

Answer 5

contain SENSORY(afferent) fibers from sensory neruons in a dorsal root 
ganglia that conduct impulses from peripheral receptors

Question 6

Innervation of skeletal muscles

Answer 6

takes place a neuromuscular junction

neurotransmitter ACh is released when a nerve impulse reaches axon terminal

Question 7

inborn reflex

Answer 7

rapid, involuntary, predictable motor response to a stimulus

ex: maintain posture, control visceral activities
- can be modified by learning and conscious effort

Question 8

Learned(acquired) reflexes

Answer 8

the result from practice or repetition

Ex: driving skills

Question 9

reflex arc

Answer 9

1) Receptor: site of stimulus action
2) Sensory neuron: transmits afferent impulses to CNS
3) Integration Center: either monosynaptic or polysynaptic region within CNS
4) Motor neuron: conducts efferent impulses from integration center to effector neuron
5) Effector: muscles fiber or gland cell that responds to efferent impulses by contracting or secreting

Question 10

whats the 2 classifications of reflexes

Answer 10

somatic: activate skeletal muslce

Autonomic(visceral) activare visceral effectors(smooth,cardiac muscle or glands)

Question 11

Spinal reflexes

Answer 11

occur w/o direct involvement of higher brain centers.

The brain is still advised of spinal reflex activity and may have an effect on the reflex

Question 12

what does an exaggerated, absent or distorted reflex mean

Answer 12

indicate degeneration or pathology of specific nervous system regions

Question 13

wha’st the most commonly assess reflexes

Answer 13

stretch,flexor,superfical

Question 14

Stretch

Answer 14

brain sets muscle’s length via stretch reflex
Ex: knee jerk, keeps knees from buckling when erect
stretch reflexes maintain muscle tone in large postural muscles and adjust it reflexively

Question 15

what does the stretch reflex cause in muscle contraction

Answer 15

causes muscle contraction on one side of the spine in response to increase muscle length(stretch) on other side of spine

Question 16

how does a stretch reflex work

Answer 16

• activates muscle
• sensory neurons synapses directly with motor neurons in spinal cord
• motor neurons cause muscles of stretched muscle to contract

Question 17

Superficial reflexes

Answer 17

elicited by gentle cutaneous stimulation of area

-clinically important reflexes signal problems in uper motor pathways or cord-level reflex arcs

Question 18

what the best known reflexes

Answer 18

plantar

abdominal

Question 19

Babinski sign

Answer 19

great toe dorsiflexes; smaller toes fan laterally

normal for 1-year-olds b/c myelination still incomplete