Lesson 2 - Neurones/Nerve Cells

All information from Miss Elliots second lesson on Homeostasis taken place on Monday 8th September 2025

What do nerve cells do?

Carry electrical signals called impulses around the body

What are the 3 types of neurones?

sensory, motor and relay neurones

What do sensory neurones do?

carries impulses from the receptors to the CNS

What is a relay neurone?

transmits impulse from the sensory to the motor neurone

What do motor neurones do?

carries impulses from the CNS to effectors

What are the adaptations of neurones?

• long

• contrain mylelin sheath

• dendrites

Why are neurones long?

so they can reach all parts of the body

What is the myelin sheath made of?

fat

Why do neurones have a myelin sheath?

the fatty myelin sheath insulates the neurones so the electrical impulses can’t pass out of the axon

What is an axon?

What the impulse travels along

Why do neurones contain dendrites?

the branched endings of the dendrites are used to communicate with other neurones

What does the Nervous System do?

they allow you to react to your surroudings and coordinate your behaviour

What does CNS stand for?

Central Nervous System

What does the Central Nervous System deal with?

• brain

• spinal cord

• relay neurones

What does PNS stand for?

Peripheral Nervous System

What does the Peripheral Nervous System deal with?

all other nerves (sensory/motor neurones)

What is a reflex action?

an action that is automatic, rapid and a protective response

Reflex Action Flow Chart

stimulus→receptor→sensory neurone→relay neurone (spinal cord)→motor neurone→effector→response

Voluntary Action Flow Chart

stimulus→receptor→sensory neurone→cordination centre (brain)→motor neurone→effector→response

What is a synapse?

A gap between neurones

Why is it hard for impulses to travel across synapses?

since synapses are a gap between neurones and impulses can’t cross the gap

How do impulses travel across synapses?

• nerve impulse arrives at the end of one neurone

• this triggers the release of chemical molecules in the synapse

• the chemicals diffuse across the synapse and bind to the receptors on the next neurone generating a new electrical impulse