Reflexes

Question 1

What is the reflex at C5-6

Answer 1

Wrist, biceps, front of arm

Question 2

What is the reflex at C7-8

Answer 2

triceps, back of arm

Question 3

What is the reflex at C3,4,5

Answer 3

Diaphragm (C3,4,5 keeps the diaphragm alive)

Question 4

what nerve innervates the diaphragm

Answer 4

Phrenic nerve (vagus derivative)

Question 5

What is the reflex at L3-4

Answer 5

knee jerk; L3-4 keeps your foot off the floor

Question 6

What is the reflex at S1-2

Answer 6

ankle jerk

Question 7

What is the reflex at S2,3,4

Answer 7

erection of penis (S2,3,4 keeps your penis off the floor)

Question 8

what is the spinal level for the diaphragm reflex innervation

Answer 8

C3,4,5

Question 9

what is the spinal level for the wrist, biceps, front of arm reflex

Answer 9

C5-6

Question 10

what is the spinal level for the triceps, back of arm reflex

Answer 10

C7-8

Question 11

what is the spinal level for the knee jerk

Answer 11

L3-4 (keeps your foot off the floor)

Question 12

what is the spinal level for the ankle jerk

Answer 12

S1-2

Question 13

what is the spinal level for the erection of penis

Answer 13

S2,3,4 (keeps your penis off the floor)

Question 14

what nerve innervates the penis

Answer 14

prudental nerve - vagus derivative

Question 15

what is the other name for a stretch reflex

Answer 15

myotatic reflex

Question 16

what is the role of stretch/ myotatic reflex

Answer 16

control of skeletal muscle tone

Question 17

what is an example of a stretch reflex

Answer 17

knee jerk reflex

Question 18

describe the knee jerk reflex

Answer 18

patellar tendon tapped, tendon pushed in, thigh muscle stretched, stretch receptors within are activated, stimulates burst of AP in afferent nerve fibres from stretch receptors which activates excitatory synapse on MN that control these mucles causing contraction of motor units of thigh muscle so they contract so lower leg extends

Question 19

why are stretch reflexes called monosynaptic

Answer 19

afferent fibres synapse directly with MN without any interneurons

Question 20

name monosynaptic reflex arcs

Answer 20

stretch reflexes ONLY

Question 21

describe the structure of a polysnaptic reflex arc

Answer 21

have at least 1 interneuron between afferent and efferent neuron

Question 22

describe the general path of a stretch reflex

Answer 22

afferent fibres from muscle spindle enter CNS, 1 path makes a excitatory synapse directly onto MN which returns to muscle that was stretched

Question 23

describe the polysynaptic path in general

Answer 23

afferent fibres from muscle spindle enter CNS, in 1 path branches of afferent nerve fibres from stretch receptors end on inhibitory interneurons controlling antagonistic muscles whose contraction would interfere with reflex response

Question 24

describe the withdrawal reflex of stepping on a pin

Answer 24

painful stimulation activates flexor muscles, inhibits extensor muscles of ipsilateral limb so affected limb moves away from harmful stimulus
at same time, stimulus causes opposite response on contralateral side of body

Question 25

describe what happens to the contralateral part of the body in the withdrawal reflex (e.g stepping on a pin)

Answer 25

MN to extensors on contralateral; side are activated while flexor muscle MN are inhibited
- this is a crossed-extensor reflex

Question 26

what is the purpose of a crossed-extensor reflex (e.g. stepping on a pin)

Answer 26

enables contralateral limb to support body’s weight as injured limb is lifted by flexion