Muscle Contraction

Front 1

Skeletal muscle (voluntary muscle)

Back 1

. The muscle used for movement

. Controlled consciously

. Cross striation under light microscope

. Made of muscle fibres which are multinucleate

. Sarcolema - the cell mebrane of the muscle fibres

. Bits of Sarcolema fold and stick into the sarcoplasm (cytoplasm). Theses folds are called transverse tubules and help spread the electrical impulse

. Sarcoplasmic reticulum - internal membrane which stores and releases calcium ions needed for muscle contraction

. Muscle fibres have lots of mitochondria and myofibrils

Hint 1

Front 2

Myofibrils

Back 2

. Made of sarcomeres

. Contains thick and thin myofilaments

. Thick myofilament is made of myosin

. Thin is made of actin

Under microscope you see :

A-bands - dark bands that contain thick myosin and some overlapping thin actin

I-bands - light bands containing only thin actin

Each of a sarcomere is marked with a z line

In the middle is an m line which is in the middle of the myosin filament

Around the m line is the h zone which contains only myosin

Hint 2

Front 3

The sliding filament model

Back 3

Myosin and actin filaments slide over one another to make the sarcomeres contract

Contraction of lots of sarcomeres means myofibrils and muscle fibres contract

Hint 3

Front 4

Muscle contraction

Back 4

.action potential stimulates the muscles and depolarises the sarcolema and spreads through the t tubules into the sarcoplasmic reticulum

. It releases stored ca 2+ ions into sarcoplasm

. Ca2+ binds to troponin changing its shape so it pulls out the attached tropomayosin head attached to the myosin filament site

. Now myosin head can attach to the binding site and form actin myosin cross bridge

. Ca 2+ also activates ATPase which breaks down ATP to provide energy to move the myosin head to the side bringing the actin with it

. ATP also provides the energy to detach the myosin so it goes back to its original position and attaches to another binding site, this cycle continues and shortens the sarcomere

. When the muscle stops being stimulated ca 2+ leave the binding site on troponin and are moved back into sarcoplasmic reticulum by active transport.

. Troponin return to original shape and the tropomayosin blocks the actin myosin binding site again

Hint 4

Front 5

Smooth muscle (involuntary muscle)

Back 5

. Controlled unconsciously

. Found in guts to move food along and in blood vessels to reduce blood flow

. Each muscle fibre is uninucleate

. Muscle fibres contract slowly and don't fatigue

. About 0.2mm long

Hint 5

Front 6

Cardiac muscle

Back 6

. Myogenic

. Found in walls of heart to help pump blood around the body

. Muscle fibres are connect interculated disc which have low electrical resistance to allow nerve impulses pass easily between cells

. Muscle fibres are branched so the impulse spread quickly

. Uninucleate.

. Contract rythmatically and don't fatigue

. Cross srations under microscope

Hint 6

Front 7

Neuromuscular junctions

Back 7

. It's the synapse between Motor neurones and muscle cells

. It realses the neurotransmitter acetyl choline binds to receptors called nicotinic cholinergic receptors and cause the depolarisation of the muscle cell

. Acetlycholinesterase stored in the clefts on the postsynaptic membrane is released to break down the acutely choline after use