Muscle revision - Biology OCR F215 module 4

A document I have made using the OCR textbook for biology, CGP textbook, and own knowledge on muscles.

The document includes information on:

- muscle types

- in depth knowledge of voluntary/striated muscle

- the sliding filament theory

- coordination of movement

- neuromuscular junctions

Hope they help!

A whole document, which includes this, plus the rest of module 4, F215 will be upload in the next few days.

Good luck with revision and A-level exams!

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First 245 words of the document:

Types of muscle
There are three muscle types
1. Involuntary muscle
2. Cardiac muscle
3. Voluntary / striated/ skeletal muscle
1) Involuntary muscle
These are stimulated by neurones of the autonomic nervous system
Hence, these muscles cannot be controlled voluntarily
Contain small bundles of actin and myosin, but are not striated, and have a single
nucleus
Contraction is slow
Tires slowly
Examples include:
o The walls of the intestine, where the muscle is found in
circular and longitudinal bundles and moves food along the
intestine
o The iris of the eye, where the muscle is found in circular
and radial bundles, controlling the intensity of light
entering the eye
o Walls of blood vessels, where muscle is found in circular
bundles, important in temperature regulation, blood
pressure and redirection of blood flow
2) Cardiac muscle
Myogenic and found in walls of heart to pump blood around the body
Consists of muscle fibres that are connected by intercalated discs (the cell
membranes)
The discs have low electrical resistance which means that nerve impulses are able
to easily pass between cells due to gap junctions,
allowing diffusion of ions
Muscle fibres are branched, which allows nerve
impulses to quickly spread through whole muscle
Muscle fibres have one nucleus each
The fibres contract rhythmically
The muscle does not fatigue

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Skeletal muscle
Skeletal muscle is made up of many fibres
found in bundles
Each fibre is a separate cell
The name of the cell surface membrane is the
`Sarcolemma'
Parts of the sarcolemma fold inwards and stick
to the sarcoplasm, forming Transverse tubules
The transverse tubules allow the spread of an
electrical impulse throughout the whole
sarcoplasm
There are a network of internal fibres that run
through each cell, known as the sarcoplasmic
reticulum
The sarcoplasmic reticulum releases and stores calcium ions during muscle contraction…read more

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SARCOMERE…read more

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The sliding filament theory
Myosin and actin filaments slide over each other to make the sarcomeres contract
When lots of sarcomeres contract simultaneously, myofibrils and muscle fibres contract
Relaxation of the muscles (i.e.…read more

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The breaking of the cross bridge
The ATP provides enough energy to
also break the stable cross bridge
The breakage detaches the actin
filament, and it is removed
The actin head returns to its original
position, allowing it to bind with
another binding site
Because the head it back in its original
position, a new bond is formed, and
the process continues
4.…read more

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Neuromuscular junction
A neuromuscular junction is a synapse between a motor neurone and a muscle cell.
The neurotransmitter at this type of junction is acetyl choline, and the receptors to which they bind to
are nicotinic cholinergic receptors.
This type of junction works in the same way as the synapses between neurones i.e. they releases
neurotransmitters which trigger the depolarisation in the postsynaptic cell.…read more

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