muscle anatomy and function Flashcards
what is a fascicle
it is a group of fibres any they can break down into even more fibres and inside of them are myofibrils.
what is a myofibril
inside of them are proteins which are called myosin and actin. myosin is thicker and actin is thinner.
what is a sarcoplasmic reticulum
each myofibril is enveloped in a membrane bag and it also stores calcium
what is the t tubular system
this is a network that transfers an impulse in to the myofibril to contract to release the stored calcium
what is the z line
this is the joining of the sarcomere beginning and end.
what is huxleys sliding filament theory
this is when actin and myosin slide into eachother shortening it.
what is the sarcolemma
this is the outside membrane around the fibres
What is the actin
it is a protein which has a thin filament but a double helix bond
what is tropomyosin and troponin and its functions
tropomyosin is near the actin and it’s like the security and the troponin makes all of the decisions e.g. bouncer. calcium binds to the troponin and it notifies the tropomyosin to move out of the way so it can reach the myosin through the sarcoplasmic reticulum.
what is the sarcomere
this shows the presence of 2 proteins actin and myosin and at the end of each sarcomere is the z line, which the actin is attached too. the thin actin filaments overlap the thick myosin filaments.
what is the steps of the sliding filament theory ?
- an electrical impulse reaches the muscle fibre
- calcium ions are released from the sarcoplasmic reticulum
- calcium binds with troponin and tropomyosin uncovers the anchor sites on the actin
- cross bridge formation- myosin attaches to the actin
- atp energy is released
- cross bridges racket- actin is pulled over the myosin and the muscle shortens
- stimulation stops and calcium is reabsorbed in the sarcoplasmic reticulum and there’s relaxation in the muscle.
what is a motor neurone
there cells in the brain and spinal cord that allows us to move, speak, swallow and breath by sending commands from the brain to the muscles that carry out these functions.
what is the structure of a motor neurone and it’s functions
- axon- it joins head to the tail
- nodes of ranvier- they allow an impulse and jump between the myelin sheath which is the point where the nerve reaches the muscle fibre
- dendrites- they receive an electrical impulse
- motor + plate- point where the nerve reaches the fibre
what is a motor unit
a motor neurone and the fibres it controls.
what is the motor end plates function ?
to transfer an impulse from the motor neurone to the muscle fibre and is done via a neurotransmitter
what is a example of a neurotransmitter and what is it
acetylcholine- A ch
this is released from the terminal membrane and transmits an impulse across the synapse where it is picked up by receptor cells on the sarcolemma
motor end plate steps
- nerve action potential- following an impulse from the brain and it will travel along the motor neurone and it will travel along the axon which is insulated in a myelin sheath and the nodes of ranvier speed up the delivery
what is unit summation
where a motor unit depends on how much force is willing to be used
The bodies recruitment of motor units and it depends on how much is willing to be used
what is the all or none law
when it is stimulated by a action potential all of the fibres within the motor unit will contract equally and in unison at the same time to thier maximum extent
how does the muscle vary it’s strength production
the motor unit responds to an impulse by producing a twitch. if a second impulse arrives before the first twitch has had time to relax then the motor unit responds with a stronger force therefore maximum force production is achieved.
how can the body change how force is
talk about
-unit summation
-wave summation
-spacial summation
what is wave summation (vary muscle force)
the ability to vary total force of contraction within a motor unit by varying the speed and frequency of nerve impulses
what is the steps of wavesummation
- when a action potential is recieved the fibres contract for under a second
- the all or none law is a law stating there all turned on or off
- when many action potentials are received in a quick recession they climb or escalate due to it coming to early and it not being completed
- the speed of action potential matters
what is spacial summation and how is it done (sustains muscle force)
when a muscle contracts maximally it becomes very fatigued but during continuous submaximal contractions the muscle can conserve it’s endurance and the fatigue across the muscle
this is done by activating different motor units at different times, work load is shared across muscles and fatigue is reduced
what are the types of muscle fibres
SLOW TWITCH
1. type 1- red (myoglobin is high)
- slow speed of contraction
- very resistant to fatigue
- high aerobic capacity
- high mitochondria energy
- high capillary density
FAST TWITCH
1. type II- white
2. type IIx- fg (fast glycolytic)
- fast speed of contraction ‘
- high anaerobic capacity
- lower resistance to fatigue compared to type a
- low mitochondria energy’
- high pc store
- type IIa- fog ( fast oxidative glycolytic)
- fast speed of contraction
- high anaerobic capacity
- more resistant to fatigue
- moderate mitochondria density
- moderate capillary density
- high pc store
all muscles contain a proportion of fibre types but what are the differences of the types related too ?
speed of contraction- the slow twitch fibres contract at 20% the speed of the fast
force- fast twitch fibres are bigger in size and have larger motor neurones which therefore generates a bigger force
endurance- the slow twitch can resist fatigue more
what does the muscle spindle do ?
- it detects muscle movement (proprioceptor)
- when it lengthens it causes a contraction of a few fibres in the centre of the muscle (intrafusal)
- this is called the stretch reflex
what ar ethe 3 stages of the stretch shortening cycle
- eccentric phase- preload the muscle spindle apparatus sends signal to the brain as they have detected movement
- Amortization phase- this is between the eccentric and the concentric phase, there’s a pause period where the intrafusal muscles contract for a short amount of time to utilise elastic rebound and stretch reflex
- concentric phase- additional force gains from the stretch reflex and elastic rebound and the muscles shorten
