Physiology: reflexes

Question 1

what is a reflex action

Answer 1

a stereotyped response to a specific stimulus, simplest form of coordinated movement

Question 2

describe what a stretch reflex is

Answer 2

serves as a negative feedback that resists passive change in muscle length to maintain optimum resting muscle length

Question 3

what is the sensory receptor in a stretch reflex and what is it activated by

Answer 3

sensory receptor = muscle spindle

activated by muscle stretch

Question 4

describe what happens when the muscle spindle is stretched in stretch reflex

Answer 4

increases firing of afferent neurons, which synapse in spinal cord at alpha motor neurons

Question 5

what does stretch reflex activation result in

Answer 5

contraction of stretched muscle

Question 6

how can the stretch reflex be elicited

Answer 6

by tapping the muscle tendon with a rubber hammer

Question 7

give some examples of stretch reflexes that can be elicited

Answer 7

knee jerk, ankle jerk, bicep jerk, brachioradialis, tricep jerk

Question 8

what is a muscle spindle

Answer 8

collection of specialised muscle cells

Question 9

where are muscle spindles found

Answer 9

within the belly of muscles and run parallel to ordinary muscle fibres(extrasfusal)

Question 10

what is another name for ordinary muscle fibres and for muscle spindles

Answer 10

ordinary = extrafusal fibres
spindle = intrafusal fibres

Question 11

what are the sensory nerve endings of muscle spindles called

Answer 11

annulospiral fibres

Question 12

describe the innervation of muscle spindles

Answer 12

have their own efferent(motor) nerve supply called gamma motor neurons

Question 13

describe the function of gamma motor neurons in muscle spindles

Answer 13

adjust level of tension in the spindles to maintain their sensitivity when the muscle shortens during contraction