Neuromuscular Reflexes

Question 1

what is proprioception
how is it achieved

Answer 1

somatic sense - sense of what our muscles are doing, where they are and their state of contraction
afferent sensory information from the skeletal muscle is sent to spinal cord

Question 2

what are extrafusal muscle fibres
what innervates them

Answer 2

force generation fibres (majority of skeletal muscle)
alpha motor neuron

Question 3

what are intrafusal muscle fibres
what innervates them

Answer 3

muscle spindles, afferent sensory fibres
gamma motoneuron (contractile) and type 1a and type 2 afferents (sensory)

Question 4

why do muscle spindles need contractile elements

Answer 4

allows them to relay information while the muscle is in use, need to know how much other fibres around them are contracting

Question 5

what does a reflex arc consist of

Answer 5

sensory receptors
sensory afferents (group 1a and 2)
interneurons in the spinal cord
motor efferents (alpha motor neurons)

Question 6

explain the stretch (myotatic) reflex

Answer 6

muscle is stretched and group 1a afferent fibres in the muscle spindle start firing
these afferent fibres synapse on the alpha motoneurons in the spinal cord
alpha motoneurons cause contraction of the muscle allowing it to stop stretching and return to resting length

Question 7

why is the antagonistic muscle to the stretched muscle inhibited by the stretch (myotatic) reflex
how is this achieved

Answer 7

to allow the reflex muscle to jerk without opposing action
afferent signal causing inhibition of the alpha motor neurons stimulating the antagonist muscle to the stretching muscle

Question 8

explain the Golgi tendon (inverse myotatic) reflex

Answer 8

muscle contracts and extrafusal fibres shorten which stimulates the Golgi tendon organ
Group 1b afferents fire from Golgi tendon organ synapsing on interneurons in the spinal cord
inhibit aloha motor neurons of the muscle which sent the signal
excitation of the antagonist muscle

Question 9

explain the flexion-withdrawal reflex

Answer 9

painful stimulus detected by nociceptor which sends afferent signal to spinal cord via cutaneous afferent fibre
polysynaptic in spinal cord on inhibitory and excitatory interneurons
withdrawal of the hurt leg and simultaneous extension of other leg to maintain balance and posture