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Human Physiology (1) > Skeletal muscle > Flashcards

Skeletal muscle Flashcards

Define motor unit Explain the principle fibre types in human skeletal muscle Explain how the force of contraction is controlled by a-MNs Explain how muscle spindles and Golgi tendon organs regulate muscle contraction Explain the operation of the y-loop

1
Q

What are the 2 regions in the spinal cord?

A

Anterior and posterior

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2
Q

Where are cell bodies located in the spinal cord?

A

Anterior horn

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3
Q

What forms synapses with skeletal muscle?

A

a - MNs

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4
Q

What is a muscle?

A

Lots of muscle fibres bundled in big groups

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5
Q

How many synapses does a muscle fibre have?

A

A single one - focal innervation

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6
Q

Define motor unit:

A

A motor unit is made up of a motor neurone and the skeletal muscle fibers
These are innervated by that motor neurone’s axonal terminals

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7
Q

What can be used in surgery to stop muscles contracting?

A

Nicotinic antagonist neurotoxins

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8
Q

What happens when a muscle fibre is innervated by the same a-MN?

A

Spreads throughout the muscle - smooth contraction (asynchronously)

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9
Q

What is type 1 muscle fibre?

A

Slow twitch (0.1s)

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10
Q

What is type 2 muscle fibre?

A

Fast twitch (0.01s)

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11
Q

What are type 1 muscle fibres properties? (4)

A

Energy source: Oxidative
Colour: red
Function: posture
Examples: Abs

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12
Q

What are type 2 muscle fibre properties? (4)

A

Energy source: Glycolytic
Colour: White
Function: Rapid movements
Examples: Eye muscles

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13
Q

What happens if we want to lift something heavy? (3)

A

More a-MNs are recruited
Increased AP firing rate of a-MNs (summation)
Slow twitch recruited first but also fast twitch

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14
Q

What happens when a-MNs send ACh to nicotinic receptors in skeletal muscle? (2)

A

Renshaw cells inhibit a-MN (glycine) - literal inhibition

y-MNs attach to muscle spindles

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15
Q

What are muscle spindles and what do they do? (4)

A

Mechanoreceptors
Sensitive to stretch
Attached to muscle fibres
Innervated by y-MNs

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16
Q

Explain the y(gamma) loop: (5)

A 
Initial motor output excites a and y MNS
Dorsal root ganglia, glutamate released excites a-MNs
a-MN: AP for muscle fibre contraction
y-MN: AP for muscle spindle contraction
Type 1a afferent to excite again
17
Q

What are Golgi tendon organs? (4)

A

Mechanoreceptors sensitive to stretch
Located between muscles and tendons
When a muscle is stretched, this distorts afferent terminal endings in GTO
Generates APs in the type 1b afferents

18
Q

What are the 2 distinct functions of a Golgi tendon organs?

A

Protect tendons from being overloaded (inverse stretch reflex)
Controlling isotonic contractions

19
Q

What are the 2 types of contraction?

A

Isometric (same length)

Isotonic (same tension)

Human Physiology (1) (21 decks)

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