muscle anatomy and function

Question 1

what is a fascicle

Answer 1

it is a group of fibres any they can break down into even more fibres and inside of them are myofibrils.

Question 2

what is a myofibril

Answer 2

inside of them are proteins which are called myosin and actin. myosin is thicker and actin is thinner.

Question 3

what is a sarcoplasmic reticulum

Answer 3

each myofibril is enveloped in a membrane bag and it also stores calcium

Question 4

what is the t tubular system

Answer 4

this is a network that transfers an impulse in to the myofibril to contract to release the stored calcium

Question 5

what is the z line

Answer 5

this is the joining of the sarcomere beginning and end.

Question 6

what is huxleys sliding filament theory

Answer 6

this is when actin and myosin slide into eachother shortening it.

Question 7

what is the sarcolemma

Answer 7

this is the outside membrane around the fibres

Question 8

What is the actin

Answer 8

it is a protein which has a thin filament but a double helix bond

Question 9

what is tropomyosin and troponin and its functions

Answer 9

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.

Question 10

what is the sarcomere

Answer 10

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.

Question 11

what is the steps of the sliding filament theory ?

Answer 11

1. an electrical impulse reaches the muscle fibre
2. calcium ions are released from the sarcoplasmic reticulum
3. calcium binds with troponin and tropomyosin uncovers the anchor sites on the actin
4. cross bridge formation- myosin attaches to the actin
5. atp energy is released
6. cross bridges racket- actin is pulled over the myosin and the muscle shortens
7. stimulation stops and calcium is reabsorbed in the sarcoplasmic reticulum and there’s relaxation in the muscle.

Question 12

what is a motor neurone

Answer 12

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.

Question 13

what is the structure of a motor neurone and it’s functions

Answer 13

1. axon- it joins head to the tail
2. nodes of ranvier- they allow an impulse and jump between the myelin sheath which is the point where the nerve reaches the muscle fibre
3. dendrites- they receive an electrical impulse
4. motor + plate- point where the nerve reaches the fibre

Question 14

what is a motor unit

Answer 14

a motor neurone and the fibres it controls.

Question 15

what is the motor end plates function ?

Answer 15

to transfer an impulse from the motor neurone to the muscle fibre and is done via a neurotransmitter

Question 16

what is a example of a neurotransmitter and what is it

Answer 16

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

Question 17

motor end plate steps

Answer 17

1. 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

Question 18

what is unit summation

Answer 18

where a motor unit depends on how much force is willing to be used

Question 19

what is the all or none law

Answer 19

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

Question 20

how does the muscle vary it’s strength production

Answer 20

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.

Question 21

how can the body change how force is

Answer 21

talk about
-unit summation
-wave summation
-spacial summation

Question 22

what is wave summation (vary muscle force)

Answer 22

the ability to vary total force of contraction within a motor unit by varying the speed and frequency of nerve impulses

Question 23

what is the steps of wavesummation

Answer 23

1. when a action potential is recieved the fibres contract for under a second
2. the all or none law is a law stating there all turned on or off
3. 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
4. the speed of action potential matters

Question 24

what is spacial summation and how is it done (sustains muscle force)

Answer 24

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

Question 25

what are the types of muscle fibres

Answer 25

SLOW TWITCH
1. type 1- red (myoglobin is high)

FAST TWITCH
1. type II- white
2. type IIx- fg (fast glycolytic)
3. type IIa- fog ( fast oxidative glycolytic)

Question 26

all muscles contain a proportion of fibre types but what are the differences of the types related too ?

Answer 26

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

Question 27

what does the muscle spindle do ?

Answer 27

1. it detects muscle movement (proprioceptor)
2. when it lengthens it causes a contraction of a few fibres in the centre of the muscle (intrafusal)
3. this is called the stretch reflex

Question 28

what ar ethe 3 stages of the stretch shortening cycle

Answer 28

1. eccentric phase- preload the muscle spindle stimulation
2. Amortization phase- this is between the eccentric and the concentric phase, there’s a pause period for a short amount of time to utilise elastic rebound and stretch reflex
3. concentric phase- additional force gains from the stretch reflex and elastic rebound