Lecture 13: Muscle - Actions and Roles Flashcards
What is a motor neuron?
A nerve cell that stimulates a muscle fibre - movement
What is transmitted down motor neurons?
Nerve impulses
What are neuron transmitters?
- motor neuron causes neuron transmitter molecules to be released
- molecules that diffuse/cross the neuron junction/synaptic cleft & transmit signals
What is the synaptic cleft? What happens?
It is fluid filled, neuron transmitters diffuse through it
What happens at the sacrolema?
An electrical voltage / Action potential is conducted over the sacrolema & inward along t-tubules
What are the extensions of the sacrolema called?
T-tubules
What do t-tubles do?
- Allows electrical impulses to move deeper into the cell
- triggers the release of Ca ions from adjacent sacs of the sarcoplasmic reticulum
Why is Ca ions important for muscle contraction?
When Ca binds to troponin (part of actin filament)
- it causes a position shift of tropomyosin
- this exposes active bonding sites on the actin molecule
- Myosin ( thick filament) can now bind with actin molecule
- mysin pulls actin filaments past them - muscles contract
Ca ions binds to:
troponin
As Ca binds to troponin ( part of the thin filament) it causes:
A position shift of tropomyosin
- exposes active bonding sites on actin molecule
The exposure of active bonding sites on actin means that:
Myosin ( thick filament) can now bind to the actin molecule & pull actin filaments past them so muscles contract
What does a motor unit consist of?
- motor neurons
- axon ( contains myelin which speeds up conductor velocity)
- branches
- muscle fibres which it attracted to & initiates
What effects the force of contraction in muscle?
- muscle fibres
- motor units
- muscle attachement
What factors determine muscle fibre function?
- length
- number
- arrangement
What factors determine motor unit function?
- size
- number
- rate of firing
