Motor control 1

Question 1

What are the three types of movement?

Answer 1

Voluntary
Reflexes (Somatic i.e vistibular, stretch. Not autonomic)
Rhythmic motor patterns i.e walking, breathing

Question 2

What are the major components of the motor system?

Answer 2

Cerebral cortex;
- Thalamus, Basal ganglia
Brain stem - Cerebellum
Spinal cord
Muscles

Question 3

Where are motor neurons located?

Answer 3

Spinal cord, Ant horn cells
Cranial nerves (except 1,2,8 which are purely sensory) - Rest are mixed.

Question 4

What are the type of motor neurons?

Answer 4

Alpha and gamma motorneurons

Question 5

What do alpha motor neurons innervate?

Answer 5

Innervate extrafusal muscle fibres, directly responsible for generation of force

Question 6

What are the types of AMNs?

Answer 6

Fast Firing; elements of FF motor units (type 2B)

Slow firing; Elements of s motor units (type 1)

Question 7

What do gamma motor neurons do?

Answer 7

Control the excitability of stretch receptors in muscle spindles, innervate intrafusal muscle fibres. (alpha gamma co activation)

Question 8

Describe the four components of the motor unit?

Answer 8

Cell body of alpha motorneuron
Axon
All neuromuscular junctions (synapses) formed by a single motor neuron
All muscle fibres (extrafusal muscle fibres) innervated by a single motorneuron.

Question 9

What are the two types of motor units?

Answer 9

FF type (type 2B) Fast twitch fatigable
S type (type 1) Slow twitch

Question 10

How do motor neurons reflect the muscle properties?

Answer 10

Properties of muscles match the properties of motorneurons which innervate the muscles.

Question 11

Which type of muscle fibre is recruited first?

Answer 11

S type muscle fibres are recruited before FF type. This is the size principle/.

Question 12

What are the physiological consequences of the size principle?

Answer 12

• Some s type fibres fire always
• S type fibres best for sustained loads that are small.
• Weak contractions can be graded with better greater precision than strong contractions
• Necessary to exercise to prevent atrophy of F type fibres.

Question 13

When do s type fibres not fire?

Answer 13

During sleep; except cranial, tongue, resp and sphincters.

Question 14

How is the control of force produced by muscles modulated?

Answer 14

Frequency control;
Muscles and motor neurons are matched in properties i.e soleus;slow gastrocnemiusl; fast

Recruitment of additional motor units.

Question 15

Describe the synapses and neurotransmitter of somatic, sympathetic and parasympathetic systems;

Answer 15

Somatic; CNS->Target, Ach (Skeletal muscle)
Symp; CNS->PNS (Ach)->Target (NA) Smooth muscle
Parasymp; CNS->Target(Ach)