Control of Movement Two

Question 1

Whats a spinal reflex?

Answer 1

Stereotyped responses (contraction or relaxation) of muscles in response to stimuli that excite receptors in the muscles, tendons or skin

Question 2

What are the five elements of a spinal reflex?

Answer 2

1) Receptors
2) Afferent (sensory) fibers
3) Synaptic Relays
4) Efferent (motor) fibers making synaptic connections with muscle fibers (or glands)
5) Effectors (muscle or glands)

Question 3

What causes muscle reflexes vs glands secretion reflex/

Answer 3

Somatic system causes muscles while the glands are caused by ANS

Question 4

What is the role of receptors in muscle movement?

Answer 4

• Informs brain of muscle/ limb position and muscle length pre-movement
• During movement receptors ensure smooth movement via feedback
• Some receptors initiate reflex movements i.e muscle spindles mechanoreceptors

Question 5

What are the major groups of receptors that control muscle movement?

Answer 5

Muscle spindles
Golgi Tendon Organs
Nociceptive Receptors
Joint receptors

Question 6

What are the role of neuromuscular spindles?

Answer 6

Monitor size and rate of muscle length change

Innervation:

• 1A afferents
• 2 afferents

Motor:
efferent = gamma mns

Question 7

What is the role of golgi tendon organs?

Answer 7

Monitor muscle tension

• Innervation; 1b afferents

Question 8

What is the role of nocioceptive receptors?

Answer 8

Evoke a flexor (withdrawal) reflex and a crossed extensor reflex

Question 9

Whats the function of joint receptors?

Answer 9

Monitor joint position and signal hyperextension or hypoextension

Question 10

Are tendon reflexes evoked form golgi tendon organs?

Answer 10

NO!!!!

Question 11

Where is the stretch (tendon) refex evoked from?

Answer 11

Muscle spindles, by stretch, vibration or passive extension of the muscle

Question 12

What is special about the stretch reflex?

Answer 12

It is the only monosynaptic reflex in the body

Question 13

What are the components of the stretch reflex?

Answer 13

1) Receptors (muscle spindles- mechanoreceptors)
2) Afferents (1a afferents to AMNs and Group 2 afferents
3) Synaptic connections Glutamanergic excitatory synapses on AMNs (and 1a inhibitory neurons + Posterior spinocerebellar tracts- for info on length of muscle)
4) Efferents: Axons of AMNs
5) Effectors : Same muscle and synergisitic one ( inhibitory neurons cause antagonist to relax)

Question 14

Why do the effectors of the stretch relflex include tha antagonist muscle?

Answer 14

The reflex relaxation is causes by type 1a inhibitory neurons so that the tension of the homogynous muscle isnt inhibited.

Question 15

Where are gamma MNs located?

Answer 15

In motor nuclie near alpha motor neurons, innervating intrafusal muscles fibres in the distal parts of the muscle spindles

Question 16

Whats the role of gamma motor neurons?

Answer 16

• Activated before AMNs
• Always GMN and AMN co-activation never isolated
• GMNs activated intrafusal muscle fibres that stretch the central zone of the muscle spindle (loading the stretch receptors- so info about muscle length is available to the CNS) activating 1a afferents (necessary)

Question 17

What is the reflex evoked by golgi tendon organs?

Answer 17

Inverse myotatic reflex

Question 18

Whats the role of the inverse myotatic reflex?

Answer 18

Plays a role in adjusting tension among muscles during a motor task.

• Evoked through an inhibition of muscle tone whose tendon has being stretched and excitation of motorneurons of the antagonistic muscle (protects muscle from being stretched)

I.e tendon becomes stretched and causes antagonist to activated to protected the homogeneous muscle

Question 19

Whats the flexion (withdrawl) reflex?

Answer 19

Evokes a fast withdrawl of a limb from a noicioceptive stimulus

Question 20

Whats involved with the flexion reflex?

Answer 20

1) Receptors : Nocioceptors
2) Afferents : Type 3 (Ad) and 4 (c) fibres
3) Synaptic relays : Excitatory interneurons which excite AMNs controlling flexors (afferents project to mutliple spinal segments (i.e can activate many muscles)
4) Efferents: Axons of AMNs
5) Effectors : Muscles (flexors)

Question 21

Whats the cross extension reflex?

Answer 21

When the flexion reflex causes the opposite limbs muscles to flex i.e stand on a sharp object, other leg is flexed to enable you to lift that foot off the sharp object without falling over.

Question 22

The stretch reflex has what afferent neurons?

Answer 22

1A and 2 afferents