Nervous System - Spinal Reflexes

Question 1

What are stretch reflexes?

Answer 1

Deep tendon reflexes aka spinal myotatic reflexes.

Question 2

Describe the neuron pathway in stretch reflexes?

Answer 2

Involve two neurons with one synapse - monosynaptic reflex arc.

Question 3

What happens if you tap the tendon momentarily?

Answer 3

It stretches the spindles within the muscle -> stimulates the afferent (Ia) fibres of the primary (annulospiral) nerve endings surrounding the intramural fibres to pass into the spinal cord by the posterior nerve root.

Question 4

What do the afferent fibres synapse with?

Answer 4

Directly with alpha motor neurons of the anterior horn.

Question 5

What do the axons of the alpha motor neurons form?

Answer 5

Efferent side of the arc.

Question 6

What happens when the efferent fibres are stimulated?

Answer 6

They cause the extramural fibres to contract and produce the ‘jerk’ at the joint.

Question 7

What are the segments in the biceps jerk?

Answer 7

C6.

Question 8

What are the segments in the triceps jerk?

Answer 8

C7.

Question 9

What are the segments in the knee jerk?

Answer 9

L3.

Question 10

What are the segments in the ankle jerk?

Answer 10

S1.

Question 11

What does it mean if there is an absence or a decrease in the jerk?

Answer 11

Interruption of the arc or a muscular defect.

Question 12

What does it mean if there is an exaggeration of the jerk?

Answer 12

Upper motor neuron lesion - this is due to alterations in the supraspinal control of the anterior horn cells - these become unduly excitable.

Question 13

What is the fusimotor neuron loop?

Answer 13

This is where the pathway goes from the gamma motor neuron to the intramural muscle fibres of the spindle, then from the afferent fibres of the spindle to the alpha motor neuron, thus to the extramural fibres.

Question 14

What is the plantar reflex?

Answer 14

Flexion of the great toe (toe goes down to ground) when there is firm stroking of the lateral surface of the sole of the foot.

Question 15

What is babinski’s sign?

Answer 15

Extension of the great toe.

Question 16

What does babinski’s sign indicate?

Answer 16

Upper motor neurone lesion.

Question 17

What is the exemption of babinski’s sign?

Answer 17

In infants <1yo - this is the normal response in this age group.

Question 18

What causes the abdominal reflex?

Answer 18

Light stroking across each quadrant of the abdominal wall.

Question 19

What happens with the abdominal reflex?

Answer 19

Contraction of underlying muscles.

Question 20

What happens with the abdominal reflex in upper motor neuron lesions?

Answer 20

The abdominal reflex is absent.

Question 21

What is Beevor’s sign?

Answer 21

When the umbilicus moves downward when people are trying to lift their shoulders up.

Question 22

What patients will you see a beevor sign in?

Answer 22

Paraplegic patients.

Question 23

Why will you see the beevor sign?

Answer 23

Weakness of the muscles below the umbilicus.

Question 24

What is the anal reflex?

Answer 24

Visible contraction of the external anal sphincter following pinprick of the perianal skin.

Question 25

What is the bulbocarvernosus reflex?

Answer 25

Contraction of the external anal sphincter when there is squeezing of the glans penis.

Question 26

What does both the anal reflex and bulbocarvernosus reflex depend on?

Answer 26

Intact sacral segments of the cord - mainly S3.