Neuromuscular and spinal cord Flashcards
1
Q
Synapses
A
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2
Q
The neuromuscular junction
A
-Specialised synapse between the motor neuron and the motor end plate on the muscle fibre cell membrane
3
Q
Activation of the neuromuscular junction
A
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4
Q
The alpha motor neuron
A
- lower motor neurons of the brainstem motor nuclei and the ventral horn of the spinal cord
- innervate the extrafusal muscle fibres of the skeletal muscles
- activation causes skeletal muscle contraction (voluntary)
- the motor neuron pool contains all alpha motor neurons innervating a single muscle
5
Q
The motor unit
A
- single motor neuron together with all the muscle fibres that it innervates (one motor neuron activity and multiple muscle fibres)
- smallest functional unit with which to produce force
- stimulation of one motor unit causes contraction of all muscle fibres in that unit
- humans have ~420,000 motor neurons and 250 million skeletal muscle fibres
- each motor neuron supplies ~600 muscle fibres on average
6
Q
Type I (types of motor unit, slow, S)
A
- smallest diameter cell bodies
- small dendritic trees
- thinnest axons
- slowest conduction velocity
7
Q
Type IIA (types of motor unit, fast, fatigue resistant, FR0
A
- larger diameter cell bodies than type I
- larger dendritic trees
- thicker axons
- faster conduction velocity
8
Q
Type IIB (types of motor unit, fast, fatiguable, FF)
A
- larger diameter cell bodies
- larger dendritic trees
- thicker axons
- faster conduction velocity
9
Q
Mechanisms by which the brain regulates muscle force produced by a single muscle
A
- Recruitment
- Rate coding
10
Q
Recruitment
A
- motor units are not randomly recruited, instead governed by the ‘size principle’)
- smaller units are recruited first (generally slow twitch units)
- as more force is required, more units are recruited
- allows fine control, under which low force levels are required
11
Q
Rate coding
A
- a motor unit can fire at a range of frequencies with slow units firing at a lower frequency
- as the firing rate increases, the force produced by the unit increases
- summation occurs when units fire at frequency too fast to allow muscle relaxation between arriving action potentials
12
Q
Neurotrophic factors
A
- type of growth factor
- prevent neuronal death
- promote growth of neurones after injury
13
Q
Reflex
A
- An automated and often inborn response to a stimulus that involves a nerve impulse passing inward from a receptor to a nerve centre and then outward to an effector (muscle or gland) without reaching the level of the consciousness
- no higher control of action in reflexes so perform action unconsciously
14
Q
The effect of neurotrophic factors
A
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15
Q
The reflex arc
A
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