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
What are the 2 regions in the spinal cord?
Anterior and posterior
Where are cell bodies located in the spinal cord?
Anterior horn
What forms synapses with skeletal muscle?
a - MNs
What is a muscle?
Lots of muscle fibres bundled in big groups
How many synapses does a muscle fibre have?
A single one - focal innervation
Define motor unit:
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
What can be used in surgery to stop muscles contracting?
Nicotinic antagonist neurotoxins
What happens when a muscle fibre is innervated by the same a-MN?
Spreads throughout the muscle - smooth contraction (asynchronously)
What is type 1 muscle fibre?
Slow twitch (0.1s)
What is type 2 muscle fibre?
Fast twitch (0.01s)
What are type 1 muscle fibres properties? (4)
Energy source: Oxidative
Colour: red
Function: posture
Examples: Abs
What are type 2 muscle fibre properties? (4)
Energy source: Glycolytic
Colour: White
Function: Rapid movements
Examples: Eye muscles
What happens if we want to lift something heavy? (3)
More a-MNs are recruited
Increased AP firing rate of a-MNs (summation)
Slow twitch recruited first but also fast twitch
What happens when a-MNs send ACh to nicotinic receptors in skeletal muscle? (2)
Renshaw cells inhibit a-MN (glycine) - literal inhibition
y-MNs attach to muscle spindles
What are muscle spindles and what do they do? (4)
Mechanoreceptors
Sensitive to stretch
Attached to muscle fibres
Innervated by y-MNs