Dermatomes and Reflexes

Question 1

stretch and tendon reflexes of the biceps brachii can be innervated at what level

Answer 1

C5-C6

Question 2

stretch and tendon reflexes of the triceps brachii can be innervated at what level

Answer 2

C6-C8

Question 3

stretch and tendon reflexes of the quadriceps femoris can be innervated at what level

Answer 3

L2-L4

Question 3

pupillary and accommodation for near vision reflexes would indicate which nerves are properly working

Answer 3

sensory input via CN II (optic) and motor reaction as a parasympathetic reflex via CN III (oculomotor)

Question 5

reflexes of pupillary and accommodation for near vision would indicate which nerves are properly working

Answer 5

sensory input via CN II (optic) and motor reaction as a parasympathetic reflex via CN III (oculomotor)

Question 6

blinking upon touching of the cornea is a reflex which would indicate which nerves were correctly working

Answer 6

Sensory input via CN V (trigeminal) and motor reaction as blinking via CN VII (facial)

Question 6

shoulder dermatome

Answer 6

C4-C6

Question 7

a correctly working gag reflex would indicate…

Answer 7

touching the root of the tongue should elicit elevation of the soft palate and contraction of pharyngeal muscles

• sensory input via CN IX (glossopharyngeal)
• motor reaction via CN X (vagus)

Question 8

thumb and index finger dermatome

Answer 8

C6

Question 9

middle finger dermatome

Answer 9

C7

Question 10

ring and little finger dermatome

Answer 10

C8

Question 11

nipple dermatome

Answer 11

T4

Question 12

umbilicus dermatome

Answer 12

T10

Question 13

knee dermatome

Answer 13

L3

Question 14

ball of the foot, great toe dermatome

Answer 14

L5

Question 15

sole of the foot excluding the ball of the foot dermatome

Answer 15

S1

Question 16

how does a stretch reflex work

Answer 16

1. slight stretching stimulates muscle spindle
2. nerve impulse derives via sensory fibers of the spindle nerve into posterior horn
3. anterior horn
4. anterior root
5. muscle contraction

*this reflex is monosynaptic

Question 17

how does a tendon reflex work

Answer 17

• this reflex is polysynaptic; more than one synapse, and more than two neurons are involved
• operates with relaxation of agonist and contraction of antagonist muscles

Question 18

what is a flexor withdrawal reflex and how does it work

Answer 18

polysynaptic reflex arc

1. stimuli (ie: pain) –> afferent branch synapses on inter-neuron
2. somatic motor neurons to the same side muscles:flexion/withdrawal
3. opposite side muscles
4. cross extension