Physiology - Motor System

Question 1

What parts of the descending pathways are responsible for voluntary control vs. posture and locomotion?

Answer 1

Lateral = voluntary control

Ventromedial = posture and locomotion

Question 2

What is the purpose of the superior colliculus?

Where is it found?

Answer 2

Map of external world

Midbrain

Question 3

Lesions of the lateral columns are associated with what?

Answer 3

• loss of ‘fractionated’ movements -> can’t move limbs independently
• slowing and impairment of accuracy of voluntary movements
• little effect on normal posture

Question 4

Is it the lateral or ventral corticospinal tract that remains ipsilateral?

Answer 4

Ventral

Majority decussated at the medullary pyramids and form the lateral corticospinal tract

Question 5

The extrapyramidal tracts (not corticospinal/pyrmidal tract) are they ipsi/contralateral?

Answer 5

Ipsilateral

Question 6

Define a motor unit

Answer 6

alpha motor neuron and all of the skeletal muscle fibres that it innervates

Question 7

What is the name for a collection of alpha-MNs that innervate a single muscle?

Answer 7

Motor neuron pool

Question 8

What causes the cervical and lumbar enlargements in the spinal cord?

Answer 8

Greater number of motor neurons

Question 9

Antagonsitic muscles work against each other, what is the term for muscles that work with each other?

Answer 9

Syngerisitic

Question 10

Alpha MNs innervate fibres to generate force. (think alpha male at rugby etc.)

Gamma MNs innervate …

Answer 10

Sensory organ within muscle AKA muscle spindle

think gamma as being more touchy

Question 11

Within the ventral horn describe the pattern of distrubtion of the LMNs and what muscles they innervate

Answer 11

Medial - axial muscles
Laterally - distal muscles

Dorsal - flexors
Ventral - extensors

Really good image on one note to help with this

Question 12

What process allows for sustained contraction?

Answer 12

Summation of action potentials

Question 13

Each motor unit comprises of many different muscle fibre types. T/F?

Answer 13

F - only contain only muscle fibre type

Question 14

‘dark meat’ is comprised of what type of muscle fibre and explain why its dark

Answer 14

Slow twitch

Slow twitch uses oxidative phosphorylation as its energy source so is highly vascularised

Question 15

What are the 2 categories of fast twitch fibre?

Which one uses mainly glycolysis as its energy source and is NOT fatigue resistant?

Answer 15

Type IIa

IIx - mainly glycolysis + NOT fatigue resistant
- used in sprinting and jumping etc

Question 16

What type of sensory afferent is present in the spindle fibre which causes action potentials in response to stretch in the reflex response?

Answer 16

Ia

Question 17

Why are gamma MNs important in the reflex response?

Answer 17

They make sure to contract the spindle so that it doesn’t become slack when the muscle is stimulated by alpha MN

Means Ia fibres can keep firing