neuromuscular reflexes

Question 1

posture and control of motor function involve the integration of what?

Answer 1

sensory and motor inputs/outputs

Question 2

what are the two types of muscle spindles

Answer 2

Extrafusal
Intrafusal

Question 3

explain extrafusal (contractile movements, alpha motor neuron) muscle fibers

Answer 3

o Bulk of skeletal muscle fibers - force generation
o Innervated by α motoneuron

Question 4

explain intrafusal (sensory components) muscle fibres

Answer 4

o Remaining specialized fibres – muscle spindles
o Innervated by γ motoneuron and sensory afferents

Question 5

what do muscle spindles do when they sense change

Answer 5

respond to changes in muscle length to return skeletal muscles to resting state after they have been used

Question 6

muscle spindles in action (abdomen)

Answer 6

→ Abdominus rectus is contracted to help us stand from sitting
→ Extrafusal (and intrafusal) fibres shorten
→ Sensory afferents (group Ia and II fibres) in the intrafusal fibres relay information to the α motoneuron inthe spinal cord
→ Activation of the α motoneuron stimulates abdominus rectus to relax
→ Helpfully, at the same time as the α motoneuron is stimulated, the γ motoneuron is activated

Question 7

what does the reflex arc consist of

Answer 7

→ Sensory receptors
→ Sensory afferents (group Ia and II afferents)
→ Interneurons in the spinal cord
→ Motor efferents (α motoneurons)

Question 8

what is an example of a stretch myotatic reflex

Answer 8

knee jerk

Question 9

what is an example of a golgi tendon (inverse myotatic) reflex

Answer 9

clasp knife

Question 10

what is an example of a flexion-withdrawal reflex

Answer 10

stubbing your toe

When you detect something painful/noxious, there are multiple afferents fibres activated which then synapse on multiple interneurons in the spinal cord

On the same side as the painful/noxious stimuli flexors are contracted and extensors are relaxed

On the opposite side as the painful/noxious stimuli flexors are relaxed and extensors are contracted

What this means is that if you stub your toe on the left, the left leg will flex and withdraw while on the right,the right leg will extend to maintain posture.

Question 11

summary

Answer 11

Sensory information from skeletal muscle help to integrate information about tension and position in space

This sensory information is relayed to the spinal cord from muscle spindles

These muscles spindles and afferent fibres are responsible initiating reflex responses involving skeletal muscle

These reflexes include the stretch (myotatic) reflex, golgi tendon (inverse myotatic) reflex and flexion-withdrawal reflex