OCR F215 module 4 full notes

I have attached a revision document I have made using the OCR biology textbook, CGP biology textbook and my own knowledge/notes.

The notes are OCR unit 2 (F215) module 4 - responding to the environment.

I hope they help and good luck with exams/revision! :)

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Responding to changes in the environment increases an animal's chances of survival. They
must be able to respond to both their external and internal environments. Any change to
either of these two environments is known as a stimulus, and they must respond effectively
to them.

Stimuli are detected by receptors…

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Releases acetyl choline

Fight or flight?

A fight or flight response is coordinated by both the
nervous and hormonal systems. The sympathetic nervous
system becomes activated, triggering the release of
adrenaline. The effects of this are as follows:

Increased heart rate and increased strength of
heart beat
Conversion of glycogen…

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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…

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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
3. Skeletal muscle
Skeletal muscle is made up of many fibres
found in bundles

Each fibre is a separate cell


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Stephanie Smith ­ OCR and CGP bio notes

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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. the removal of calcium ions from the sarcoplasm) return
the sarcomeres to their original shape


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3. 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…

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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…

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This is an organism's response to changes in the environment, which in turn increases their
chances of survival.

It is important for organisms to detect stimuli so that they can response efficiently through
action of effectors.

Behaviour can either be innate or learned.

Innate behaviour

This is behaviour that…

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For example, an organism may respond to light intensity, where movement into the
higher light intensity would be positive phototaxis, and movement into a lower light
intensity would be negative phototaxis.

Innate behaviours can combine to form more complex innate behaviours. An example could
be the waggle dance exhibited by…


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