IGCSE Biology Revision Notes The nervous System

Key word DefinitionStimulus An environmental factor that influences the activity of an organism eg

light, sound, touch, temperature and chemicalsVoluntary action An action which requires conscious thought and that is controlled by the

brain eg catching a ball, standing up etc. Involuntary action An action controlled by the brain or spinal cord that does not require

thinking, eg breathing, adjustments to heart rate etc. Nerve impulse An electrical signal that passes along nerve cells called neuronesReceptor A group of specialised cells, which respond to a particular stimulusReceptor cell Specially adapted cells that are located in sense organs which detect stimuliNerve A bundle of nerve fibres Nerve cell (neurone) A specialised cell that transmits a nerve impulseNervous system A biological system which coordinates and regulates body functionsCentral nervous system (CNS)

The part of the nervous system that consists of the brain and the spinal cord

Peripheral nervous system

The parts of the nervous system excluding the brain and the spinal cord

Sensory neurone The neurone that links the sense organ to the spinal chordMotor neurone The neurone which links the spinal cord to the effector Relay neurone A neurone which carries an impulse from one part of the CNS to anotherCell body The part of a nerve cell which contains the nucleus and the cytoplasmDendron Part of the neurone that carries the nerve impulse prior to the cell bodyAxon The part of a neurone which transmits the nerve impulse away from the cell

bodyMyelin sheath A fatty substance which surrounds and insulates that axonNodes of Ranvier Gaps in the myelin sheath which are able to speed up the transmission of

the nerve impulseDendrites Branches of a neurone which are stimulated in order for the neurone to

become activeAxon terminal Parts of the neurone which from a synapse with another neurone or

connect to effector cells (motor end plate)Effector The part of the body that responds to the stimulus, eg a muscle contracting

or a gland producing a hormone Reflex A rapid and automatic response to a stimulusReflex arc Involvement of the following in a response: sensory neurone, relay

neurone, motor neurones and effector Synapse A junction between two neuronesSynaptic cleft The small gap that exists between two neurones at a synapsePresynaptic neurone The neurone which release the neurotransmitterPostsynaptic neurone The neurone which is stimulated by the neurotransmitterNeurotransmitter A chemical that will pass across the synaptic cleft in order to transmit the

nerve impulse from one nerve to the nextVesicle A bag that contains a neurotransmitter located in the presynaptic[tic

neuroneNeurotransmitter receptor

The receptors on the postsynaptic neurone to which the neurotransmitter attaches

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IGCSE Biology Revision Notes Neurones (nerve cells)

Complex organisms have a well developed nervous system.

This usually consists of the:

Types of neurones.

Sensory neurone

Motor neurone

Relay neurone

Normal neurone response.

Effectors.An effector can be defined as

Examples include

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IGCSE Biology Revision Notes

Reflexes

A reflex response can be defined as

Examples include

A diagram demonstrating a reflex response:

Receptors

Receptors are ________________, they contain ____________________.

These provide us with the 5 senses of...

Receptors detect stimuli such as ...

See 144-147 of your textbook

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IGCSE Biology Revision Notes Synapse

A synapse is defined as

Diagram of a synapse

Explanation of synaptic transmission

Factors that affect synaptic transmission include

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IGCSE Biology Revision Notes Comparison of the endocrine system and the nervous system

How do we see?

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IGCSE Biology Revision Notes

The Eye

Structure.

PART FUNCTION

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IGCSE Biology Revision Notes The Pupil Reflex. This happens when....

Accommodation

Accommodation is defined as:

When we look at an object in the distance..

When we look at an object close by

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IGCSE Biology Revision Notes What can go wrong with the eye?

PROBLEM METHOD OF CORRECTION

Explain how lenses may be used to correct short and long sightedness

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IGCSE Biology Revision Notes

Muscles as effectors.Muscles can only __________________ and __________________ they can not _____________________.

Because of this, muscles usually work in pairs, when one is contracting the other is relaxing. We say that muscles which work in pairs are_________________.

Examples.

A FLEXOR is ..

An EXTENSOR is...

In order to contract muscles require ____________ in the form of _______ They

get this __________ from cellular respiration, which requires.

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