PHSI3010 Module 3: Muscle & Nerve

Oligodendrocytes, like (A - example), form (B - structure)

A - glial cells

B - myelin sheath

Somatic motor neurons have cell bodies in (A - 2 areas) with a (B - type) axon to (C - target).

A - ventral horn of spinal cord OR in the brain

B - long, single

C - skeletal muscle target

One motor neuron can control (A - how many) muscle fibres.

One motor unit refers to (B)

A - many

B - one alpha motor neuron + all the muscle fibres it innervates

All neuromuscular junctions with skeletal muscle use (A)

A - Acetylcholine (neurotransmitter)

Recruiting additional motor units can increase (A - property).

Recruitment is controlled by (B) and proceeds in a standardised sequence of (C - 3).

A - force of contraction

B - the nervous system

C - slow, then fast fatigue-resistant (FR), then fast fatiguable (FF)

What are two examples of proprioceptors?

1. Muscle spindles (detects muscle stretch)

2. Golgi tendon organs (detects muscle tension)

Describe the 3 types of movements generates by motor systems

1. Reflexive

   • Involuntary, coordinated patterns of muscle contraction and relaxation elicited by specific peripheral stimuli

   • Circuits in the spinal cord

   • E.g. knee reflex

2. Rhythmic

   • Movements can occur spontaneously, or more commonly triggered by peripheral stimuli that activate the circuits

   • Circuits lie in the spinal cord and brain stem

   • E.g. chewing, swallowing, gut motility

3. Voluntary

   • Initiated to achieve a specific goal and improves with practice (feed-forward (anticipate response) and feed-back (evaluates past response) mechanisms)

Stages of nervous system maturation (7)

1. Neurulation

2. Proliferation

3. Cell migration

4. Differentiation

5. Synaptogenesis

6. Synapse pruning

7. Myelination