Motor Control #1

Question 1

Movement disorders are commonly caused by? And what are some examples of this?

Answer 1

Neurological disorders eg) myasthenia gravis, epilepsy, parkinsons

Question 2

What are the three types of movement?

Answer 2

1) Voluntary
2) Reflexes (somatic)
3) Rhythmic motor patterns

Question 3

What controls voluntary movement?

Answer 3

The forebrain, the cerebellum, thalamus, basal ganglia

Question 4

What controls Reflexes and rhythmic motor patterns

Answer 4

The spinal cord and brainstem

Question 5

What are rhythmic motor patterns?

Answer 5

breathing, locomotion, chewing. Semiautomatic movements that are inbetween reflex and will. We can control to a point.

Question 6

What are the two subcortical loops that impact our decision making?

Answer 6

CC > Basal ganglia > thalamus

CC > Brain stem > cerebellum > thalamus

Question 7

Where are the two places you’ll find motoneurons

Answer 7

Motor nuclei in the ventral horns of spinal cord
Motor nuclei in the brain stem (midbrain pons and medulla oblongata) this is done through cranial nerves sending axons to muscles

Question 8

how many cranial nerves actually send axons

Answer 8

9/12

Question 9

Two types of motoneurons, and what do they innervate?

Answer 9

alpha motoneurons, innervate extrafusal fibres (the most common muscle fibres)
Gamma motoneurons, innervate intrafusal muscle fibres. this controls the excitability of stretch receptors muscle spindle fibres

Question 10

Are Alpha and gamma motoneurons independent?

Answer 10

No, a and g motoneurons often have co-activation

Question 11

Sir John Eccles

Answer 11

studied and characterised motoneurons, lectured in otago, the 1st to measure RMP, AP, synaptic potential.

Question 12

What was sir John Eccles technique?

Answer 12

Used a glass microelectrode. If you add dye you can see the morphology of nerve cells.

Question 13

What are the components of motor units

Answer 13

a) Cell body of an a-MN
b) axon
c) all neuromuscular junctions (synapses) formed by a single motoneuron
d) all muscle fibres (extrafusal muscle fibres) innervated by a single motoneuron

Question 14

what is the innervation ratio?

Answer 14

the amount of muscle fibres a MN can innervate (between 5 to 20,000).

Question 15

Motor unit types

Answer 15

FF type 11B - fast fatigable
S type (type 1)  - slow twitch

Question 16

FF type 11B

Answer 16

Glycolytic, short twitch time (20ms), large, powerful, a few, rapidly fatigue

Question 17

S type (type 1)

Answer 17

oxidative, slow (50ms+), small, weak, there are many and they are slow to fatigue

Question 18

What makes S-type a good choice over FF type

Answer 18

There are many, and they are slow to fatigue, unlike FF type

Question 19

What are S type and FF type useful for?

Answer 19

S type- continuous, weak contractions

FF type - brief, strong contractions

Question 20

What is the size principle of motor units?

Answer 20

S type recruited first, FF type are recruited only at highlevels of muscle force

Question 21

What are the physiological consequences of the size principle?

Answer 21

S type MU fire almost always
S type are for sustained, small loads
Weak contractions are graded better then strong
Atrophy of FF will occur without excercise

Question 22

What motor neurons are activated during REM sleep?

Answer 22

eyes, respiratory, sphinters

Question 23

How are muscles ‘slaves’ to nerves?

Answer 23

The properties, types of contractions are changed with cross innervation! This is done with experiment between soleus and gastrocnemius

Question 24

What do gamma MN innervate and what does this do?

Answer 24

They innervate the periphery of intrafusal fibres (muscle spindles) where there are contractile elements. This enhances the ability of the spindle to stretch

Question 25

What do gamma MN sense?

Answer 25

the changes in muscle length

Question 26

Whats the difference between somatic and autonomic neurons

Answer 26

Somatic go directly to muscles, whereas autonomic use parasympathetic/sympathetic ganglia as ‘switches’