physiology of motor control

Question 1

what are the two types of fibres ?

Answer 1

1) Dynamic nuclear bag, which senses velocity

2) Static nuclear chain , which senses overall length

Question 2

What is the stretch reflex ?

4

Answer 2

1) monosynaptic reflex
2) Intrafusal muscle fibres detect muscle tone
3) Afferent neurone synapses to the spinal chord
4) Efferent neurone goes to innervate the extramural muscle fibres causing muscle contraction

Question 3

Outline the importance of the alpha - gamma system?

Answer 3

Alpha gamma system
Gamma fibres on the end x nuclear intramural fibres = allow contraction so that the fibres don’t go slack !
this allows us to detect change even when the muscle is contracted , which is really important !
- we remain sensitive to change in length and velocity

Question 4

outline the nuclear chain fibres ?

Answer 4

-Group 1A and
and mostly group 2 fibres = slow adapting

At the ends = gamma motor fibres
they detect over all length change

Question 5

Outline the nuclear bag fibres ?

Answer 5

-Nuclear bag fibres
1a fibres = fast adapting, sense velocity
-Gamma motor fibres at the end too

Question 6

what are the 4 motor tracts for skeletal muscle ?

Answer 6

1) Rubrospinal (lateral)
2) Reticulospinal
3) Vestibulospinal tracts
4) Tectospinal tracts

Question 7

outline rubrospinal tract

Answer 7

1) red ( rubro ) nucleus
- Upper motor neurones
- cross over in the midbrain
2) descends to medulla –> spinal chord
3) synapse with lower motor neurones to skeletal muscle = alpha and gamma

• IT CROSSES OVER ( so contralateral control )

Function :

• controls fine hand movements
• posterior compartment of forearm

Question 8

outline the vestibular-spinal tracts ?

Answer 8

these have 2 pathways which are both IPSILATERAL ( so they stay on same side)

• activates extensor muscles
• posture muscles
• balance muscles

Question 9

Outline reticulospinal tracts ?

Answer 9

2 opposing tracts
- medial reticulospinal tracts => increase muscle tone
= facilitates voluntary movements

• Lateral reticulespinal tract = inhibits voluntary movements =decreases muscle tone

= posture and balance

Question 10

what is the putamen pathway ?

Answer 10

( basal ganglia )

-It is involved in a very complex feedback loop that prepares and aids in movement of the limbs

Question 11

what is the Caudate circuit ?

Answer 11

1- Cognitive control of movement
- common to both excitatory dopaminergic pathway from SN–>Striatum
2-
The caudate nucleus = paired, “C”-shaped subcortical structure which lies deep inside the brain near the thalamus