Muscle spindle anatomy (365/351)

Question 1

what are intrafusal fibres

Answer 1

non force producing muscle fibres that lengthen and stretch with changes in muscle length (muscle spindles)

Question 2

what are extrafusal fibres

Answer 2

fibres that cause muscle contraction in parallel with muscle spindles (skeletal muscle fibres)

Question 3

do afferent axons measure or send signals

Answer 3

measure

Question 4

where do afferent axons innervate

Answer 4

sensory endings of muscle endings (send feedback to spinal cord)

Question 5

do efferent axons measure or send signals

Answer 5

send signals

Question 6

are efferent axons the axons of aMNs or yMNs

Answer 6

yMNs - needs to contract to keep the muscle spindle tight with skeletal muscle

Question 7

where do efferent axons innervate

Answer 7

polar (contractile) ends of intrafusal fibres (sends excitatory inputs from the spinal cord)

Question 8

where do yMNs attach to / stimulate

Answer 8

intrafusal muscle fibres (muscle spindles)

Question 9

what is the capsule of a muscle spindle

Answer 9

connective tissue surrounding intrafusal fibres and sensory receptors in the spindle

Question 10

does the central portion of a muscle spindle contract

Answer 10

no - non contractile (only polar ends contract)

Question 11

what do the sensory endings of muscle fibres sense

Answer 11

length of muscle spindles - measure strength