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
In a lever system what do:
- bones act as
- joints act as
- lever
- fulcrum/pivot point
In a lever system what is:
-moved
what causes:
- muscle contraction
- load or resistance
- a force / pull
What are the three different types of lever arrangements in the body?
- first class
- second class
- third class levers
What determines muscle action ( shortening of muscle) in the body?
Lever systems - as type and extent of movement is determined by
- lever, pivot point, load, force/pull
What does the first class lever allow?
stabilised joint position
What does the second class lever allow?
effective at overcoming loads
What does the third class lever allow?
large ROM & speed
