Myotatic Reflexes in the Lower Limb

Question 1

List the myotatic reflexes in the lower limb.

Answer 1

patellar tendon (knee jerk) reflex
calcanel (achilles) tendon (ankle jerk) reflex

Question 2

The knee jerk reflex is connected to which spinal segment/nerve roots?

Answer 2

L2, L3 & L4 (via femoral nerve)

Question 3

The ankle jerk reflex is connected to which spinal segment/nerve roots?

Answer 3

S1 & S2

(via tibial nerve)

Question 4

A typical reflex pathway consists of?

Answer 4

sensory receptors in muscle spindle > afferent sensory neurones > spinal cord > efferent motor neurones in anterior grey columns > effector organ

Question 5

Are most of the myotatic reflexes monosynaptic or multisynaptic?

Answer 5

monosynaptic

Question 6

If you can’t elicit any reflexes, applying reinforcement can include?

Answer 6

clenching the teeth while interlocking the flexed fingers of both hands and pull apart strongly (Jendrassik manoeuvre)

Question 7

An alternative to reinforcement for the the elicitation of knee jerk is?

Answer 7

patient voluntarily dorsiflexing the foot strongly whilst the knee jerk test is performed on the same lower limb

Question 8

When eliciting reflexes, what should you tap with the hammer?

Answer 8

relevant tendon

Question 9

What is the law of reciprocal innervation?

Answer 9

in the same limb, the flexor and extensor muscles cannot contract simultaneously

Question 10

What prevents flexors and extensors in the same limb contracting together?

Answer 10

afferent nerves responsible for the flexor reflex muscle action have branches to synapse with extensor motor neurons to inhibit contraction.

Question 11

What do abnormally exaggerated myotatic reflexes suggest?

Answer 11

lead to a clinical picture of an upper motor neurone lesion (higher brain centres modulate reaction)

Question 12

If there is disorder in any of the components of the reflex arc, what will you see on testing of the reflex?

Answer 12

complete absence of reflexes