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 and the responses to these stimuli are carried out by
effectors. Receptors communicate with effectors via their nervous or hormonal system to
coordinate the response.
How is the nervous system structured?
The nervous system consists of the central nervous system and the peripheral nervous
CNS = brain and spinal cord
Peripheral nervous system = neurones that connects CNS to the rest of the body
The peripheral nervous system consists of two different systems:
1. Somatic ­ controls conscious activities
2. Autonomic ­ controls unconscious activities e.g. digestion
The autonomic system is then split further into two:
1. Sympathetic :
Gets the body ready for action
Releases adrenaline
`Fight or flight' response
2. Parasympathetic:
`rest and digest' system
Calms the body down
Stephanie Smith ­ OCR and CGP bio notes

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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.…read more

Page 3

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Types of muscle
There are three muscle types
1. Involuntary muscle
2. Cardiac muscle
3.…read more

Page 4

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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.…read more

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Stephanie Smith ­ OCR and CGP bio notes…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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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 is inherited in the genome of an organism, with no need for learning.
The key features of innate behaviour include:
Genetically determined i.e.…read more

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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.…read more


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