Nerves

objectives

• nerves help us react to our surroundings and control our behaviour.

• key parts of the nervous system include senses, neurones, brain, spinal cord, and effectors.

• understand what is meant by a reflex

• describe the pathway of information from stimulus to response.

Nerves copy thiscopy this

starter

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The brain can respond to touch, smell or taste stimuli in just 0.1 seconds, but sound and vision take longer.

How fast are nerve signals?

Nerve impulses travel at up to 320 mph and take just0.02 seconds to reach the brain.

do NOT

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do NOT

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if not, why not?stimulus

coordinator

receptor

effector

response

all this takes time !

light from note

eye

brain

nerve

nerve

muscles in fingers

movement of fingers

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Interpreting signalsHow can you find your reaction time?

1. Extend your arm over the edge of a table and have a partner hold a ruler between your fingers at the 0 cm mark.

2. The partner drops the ruler – catch it between your fingers and thumb as quickly as possible.

3. Repeat the test 10 times, recording the results and calculate the mean (average) distance. Then convert the distance into a reaction time.

What types of reflexes do you know?Common reflexes

Reflexes are fast, automatic protective control systems that link a stimulus to a response.

Reflex reactions happen without you thinking– they are involuntary.

This is because the central nervous system (CNS) sends electrical signals to the muscles FROM THE SPINAL CORD before the brain can pick up the message.

What are reflexes?

a stimulus could be pain or heat or a loud sound

a response could be blinking or moving away

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the CNS is the brain and spinal cord

What are neurones? Neurones are specialized cells that conduct electrical impulses through the body.

nerve

nerve fibre

A nerve is a bundle of many nerve fibres enclosed within a protective sheath. Nerve fibres are the long axons of neurones together with any associated tissues.

What do neurones look like?

The axons of most neurones are wrapped in an insulating lipid layer called the myelin sheath. Why is this important?

Thin projections called dendrites extend from the cell body and connect with other neurones, allowing electrical impulses to pass from one to the other.

Neurones are elongated cells consisting of a cell body and long, thin axon.

myelin sheath

axon

dendrites

cell body

What are sensory neurones?Sensory neurones transmit messages from sense receptors, such as the eye or nose, to the brain or spinal cord.

cell body

nerve impulse from sense organ

nerve impulse to CNS

What are motor neurones?Motor neurones transmit messages from the brain and spinal cord to the muscles and glands.

cell body

muscle

what are the differences and similarities? (use the pictures to help)

do this in groups of 4 ( one picture each)

motor neurones sensory neurones

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• end of part one on nerves

• I’ll be back !

A reflex arc

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What is a synapse?A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses.

presynaptic cell

postsynaptic cell

The release of neurotransmitters from a synapseWhen a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles.

synaptic vesicle

neurotransmitter molecules

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synaptic cleft

Continuing the impulseThe neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse.

nerve impulse

receptor

pass the zap

• 17 students have a card with a word or two on.

• you must arrange yourself in the correct order, facing the front of the class

• some cards are at the same time as others

True or false?

What can go wrong?

Multiple-choice quiz

homework

• b1a.1a

• b1a.1c

extra questions1) What do these words mean:

- stimulus- response- effector

2) What is the special name given to the nerve that carries the impulse from the receptor to the brain or spinal cord?

3) What is the special name given to the nerve that carries the impulse from the brain or spinal cord to the effector?

4) What is the name given to the brain and spinal cord together?

5) Write the chain of events for the following scenario:‘a stupid year 11 boy has just thrown a pen towards a year 7 boys face. What does the year 7 boy do? Is it a reflex or does he have to think about doing it?’