Reflexes Flashcards
What is the reflex at C5-6
Wrist, biceps, front of arm
What is the reflex at C7-8
triceps, back of arm
What is the reflex at C3,4,5
Diaphragm (C3,4,5 keeps the diaphragm alive)
what nerve innervates the diaphragm
Phrenic nerve (vagus derivative)
What is the reflex at L3-4
knee jerk; L3-4 keeps your foot off the floor
What is the reflex at S1-2
ankle jerk
What is the reflex at S2,3,4
erection of penis (S2,3,4 keeps your penis off the floor)
what is the spinal level for the diaphragm reflex innervation
C3,4,5
what is the spinal level for the wrist, biceps, front of arm reflex
C5-6
what is the spinal level for the triceps, back of arm reflex
C7-8
what is the spinal level for the knee jerk
L3-4 (keeps your foot off the floor)
what is the spinal level for the ankle jerk
S1-2
what is the spinal level for the erection of penis
S2,3,4 (keeps your penis off the floor)
what nerve innervates the penis
prudental nerve - vagus derivative
what is the other name for a stretch reflex
myotatic reflex
what is the role of stretch/ myotatic reflex
control of skeletal muscle tone
what is an example of a stretch reflex
knee jerk reflex
describe the knee jerk reflex
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
why are stretch reflexes called monosynaptic
afferent fibres synapse directly with MN without any interneurons
name monosynaptic reflex arcs
stretch reflexes ONLY
describe the structure of a polysnaptic reflex arc
have at least 1 interneuron between afferent and efferent neuron
describe the general path of a stretch reflex
afferent fibres from muscle spindle enter CNS, 1 path makes a excitatory synapse directly onto MN which returns to muscle that was stretched
describe the polysynaptic path in general
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
describe the withdrawal reflex of stepping on a pin
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
describe what happens to the contralateral part of the body in the withdrawal reflex (e.g stepping on a pin)
MN to extensors on contralateral; side are activated while flexor muscle MN are inhibited
- this is a crossed-extensor reflex
what is the purpose of a crossed-extensor reflex (e.g. stepping on a pin)
enables contralateral limb to support body’s weight as injured limb is lifted by flexion
