- Muscle fibres have these long cylindrical shaped organs called "myofibril" which are made up of proteins and are HIGHLY specialised for contraction.

Muscle contraction Flashcards by taran matharu

what is the membrane of muscle fibres called?

Sarcolemma

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what is the muscles cell’s cytoplasm called?

Sarcoplasm

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What are the folds of sarcolemma called?

and what do they do?

Transverse tubules (T)

They help to spread electrical impulses throughout the sarcoplasm so they reach the muscle fibre

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What is the sarcoplasmic reticulum?

and what does it do?

INTERNAL membranes of the sarcoplasm

They store and release the calcium ions that are needed for muscle contraction.

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What does multinucleate mean?

Muscle fibres contain MANY nuclei

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What are myofibrils?

Muscle fibres have these long cylindrical shaped organs called “myofibril” which are made up of proteins and are HIGHLY specialised for contraction.

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What are the 2 types of filaments myofibrils consist of?

1) Thick myofilaments

2) Thin myofilaments

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What are thick myofilaments made up of?

Myosin

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What are thin myofilaments made up of?

Actin

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what are the short units that make up myofibrils?

Sacromeres

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Under a microscope what are the dark and light bands?

Dark bands are the - A bands- contain thick myosin filaments

Light Bands are the - I bands- contain thin actin filaments

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What are the z lines?

The ends of the sarcomere

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What is the M line?

Its in the middle of the sarcomere

The M- line is the middle of the myosin filaments

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Where is the H zone and what does it contain

H zone is roughly in the middle

- The H zone ONLY consists of myosin filaments.`

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When sarcomeres contract what gets shorter?

I band and h zone gets shorter
and the sarcomere size gets shorter

But A band stays the same length.

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How do sarcomeres contract?

myosin filaments and actin filaments slide over one another.

sliding- filament theory

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What does the myosin globular head do ?

Acts as a binding site for actin and ATP

The myosin globular head is hinged so it can move back and forth

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what is the binding site for the myosin heads, on the actin filaments called?

Actin-myosin binding site

This is where the myosin globular head binds.

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What do tropomyosin and troponin do and where are they found?

They help myofilaments move past each other

- these are found in between actin filaments.

How does tropomyosin affect the actin-myosin binding site?

actin-myosin binding site is blocked by tropomyosin
which is held up by troponin.
This means that myofilaments can not slide past each other.

Muscle contraction triggered by an action potential process : ( 3 steps) just label the steps

1) Action potential triggers an INFLUX in Calcium ions
2) ATP provides the energy needed to move the myosin head
3) ATP provides energy to break the cross bridge

1) The action potential triggers and influx in calcium ions:

1) action potential from a motor neurone stimulates a muscle cell, causing the sarcolemma to depolarise
- depolarisation spreads down transverse tubules to the sarcoplasmic reticulum

2) This causes sarcoplasmic reticulum to release the stored Calcium ions (Ca2+) into the sarcoplasm.
3) Calcium ions bind to troponin causing it to change shape, and this pulls tropomyosin out of the actin- myosin binding site, the binding site is now exposed and myosin globular head can bind to it.
4) Actin- myosin cross bridge is formed

What is the bond called where a myosin head binds to an actin filament

Actin- myosin cross bridge

2) ATP provides energy so that the myosin head can move:

1) Calcium ions also activate ATPase ( enzyme) which breaks down ATP -> ADP + pi
- to provide the energy needed for muscle contraction.

Energy released from ATP, allows the myosin head to move and it pulls the actin filament along in a “rowing kind of action”.

3) ATP provides energy to break the cross bridge:

1) ATP provides energy to break the actin-myosin cross bridge, so the myosin head DETACHES from the actin filament. 2) The myosin head then binds to a different binding site on the actin filament, and a new actin- myosin cross bridge is formed. - cycle repeats as long as there is calcium bound to the troponin.

What happens if many cross bridges form?

If many cross bridges are forming and breaking rapidly, this means that the sarcomere is getting shorter, causing the muscle to contract.

what happens to calcium ions after muscles have stopped being stimulated? ( WHEN EXICITATION STOPS)

- Calcium ions leave the troponin - calcium ions move back into sarcoplasmic reticulum by active transport - troponin returns to original shape and pulling the tropomyosin with it, causing tropomyosin to block the binding site again. - actin slides back to its relaxed position so the sarcomere becomes longer in length.

What are the 3 ways in which ATP is continuously being regenerated?

1) Aerobic respiration- good for long period of low intensity exercise 2) Anaerobic respiration- ATP made rapidly by glycolysis.- good for short period of high intensity exercise 3) ATP- Creatine Phosphate (CP) system

What is the ATP creatine phosphate system?

This system uses the phosphate from CP and gives it to ADP to form ATP. - This system is used during short periods of hard exercise as CP runs out very quickly This system is anaerobic and alactic ( doesn't produce lactate)

What is the synapse between a motor neurone and a muscle cell called?

A neuromuscular junction

What are the neuro transmitters at the neuromuscular junction?

Acetylcholine (ACh)

What receptors does acetylcholine bind to ?

Nicotinic cholinergic receptors

Does depolarisation cell cause contraction or relaxation?

CONTRACTION of muscle cells IF the threshold is reached

what does acetylcholinesterase do ?

AChE Is released to break down acetylcholine after use

where is AChE stored

Stored in the clefts of the postsynaptic membrane.

What are the 3 types of muscle cells?

1) Skeletal muscle- voluntary muscles- consciously contract 2) Smooth muscle- involuntary muscles- unconsciously contract 3) Cardiac muscle- myogenic - contract on its own - but rate of contraction controlled involuntarily by autonomic nervous system

When skeletal muscles contract is it controlled consciously or unconsciously?

consciously

DO skeletal muscles contain one nuclei or many nuclei

MANY nuclei

When you look under a microscope and your observing skeletal muscle, what do you see?

cross- striations ^ These are the A bands and I bands

Do skeletal muscles contract quickly or slowly?

They contract quickly for speed and strength but fatigue quickly - skeletal muscle fibres are many cm long

DO smooth muscles contract consciously or unconsciously?

unconsciously

What happens when blood vessel smooth muscle contracts

Flow of blood is reduced

What are the shape of muscle fibres for smooth muscle cells?

Spindle- shaped

Do smooth muscles and cardiac muscle only have one nuclei or many?

ONLY 1 nucleus in each muscle fibre Each muscle fibre is 0.2mm long

Does smooth muscle contract quickly or slowly

Contracts slowly and doesn't fatigue slow contractions are meant for endurance and posture