Skeletal Muscle Flashcards
What are the two regions of the spinal cord?
Anterior and Posterior
Where are the cell bodies found in the spinal cord?
The Anterior Horn
What cell bodies are associated with skeletal muscle?
alpha-motoneurones form synapses with skeletal muscle at the neuromuscular junction
What happens along an alpha-motoneurone?
Action Potentials along alpha-MNs release acetylcholine at the NMJ, binding with nicotinic receptors on muscle fibres causing the muscle to contract
What is a motor unit?
A single alpha-MN and all the fibres that it makes a synapse with
Each motor unit is made up of only one fibre type
What is the safety factor to prevent motoneurone disease?
Nerve terminals always release 8-10x the acetylcholine necessary so we always get a muscle contraction when synapses fire
What is contractile precision?
How accurate and fine a movement can be
Contractile precision is inversely proportional to the number of fibres innervated by the same alhpa-MN
eg. fingers are very dextrous: 5-15fibres per alpha-MN
abdominal muscles are not: 200-1500 fibres per alpha-MN
How can contractile strenght be improved?
- Recruit more alpha-MNs
- Increase the AP firing rate of alpha-MNs
Rapid AP firing > fused muscle contractions leads to summation
Which muscle fibres are recruited first?
Generally, slow twitch motor units are recruited first
-heavy loads also require fast twitch but glycolytic fatigue happens quickly
What are the cells in the anterior horn?
Alpha-motoneurone - send acetylcholine to nicotinic receptors in skeletal muscle fibres, causing muscle contractions
Renshaw cells - inhibit alpha-MN activity within the anterior horn
gamma-MNs - attach to muscle spindles
What are muscle spindles?
Mechanoreceptors within the muscle that are sensitive to the stretch of the muscle fibres
-innervated by gamma-MNs
What does the gamma loop do?
Moniters muscles contraction and corrects when required
What are golgi tendon organs?
Mechanoreceptors between muscles and tendons
- when the muscle is stretched, so are the fibres in the GTO
- this distorts the afferent terminal endings and generates APs in the Type Ib afferents
What are the functions of the golgi tendon organs?
- Protect tendons from being overloaded (inverse stretch reflex)
- Controlling isotonic contractions (same tension
