AQA GCSE Human Nervous System (Biology)

AQA GCSE Human Nervous system (Biology)

Human Nervous system

The purpose of the nervous system is:

1.Allow humans to react to their surroundings

2.Coordinates behaviour by linking receptors to effectors

3.Works quickly using electrical impulses

In summary the nervous system allows humans to detect stimuli and produce a rapid response.

Basic organisation of the nervous system

Nerves vs Neurones

A nerve is a bundle of neurones

A neurone is a single nerve cell

A neurone is a single specialised cell that carries electrical impulses.

See the image below for the difference between a nerve and neurone.

Types of Neurones

There are three types of neurones

Sensory neurone (Carries electrical impulses from receptors to the CNS)

Relay neurone (carries electrical impulses within the CNS and connects the sensory neurone to the motor neurone.)
No diagram is needed for a relay neurone, you will see one though in the notes on reflex arc.

Motor neurone (Carries electrical impulses from the CNS to an effector)

Pathway of information (stimulus → response)

Information from receptors passes along neurones as electrical impulses to the CNS, which coordinates the response of effectors.

1.Stimulus (change in environment)

2.Receptor detects the stimulus (table below summarising receptors)

3.Electrical impulse travels along a sensory neurone

4.Impulse reaches the CNS (coordinator)

5.CNS processes the information and coordinates a response

6.Impulse sent to an effector along a motor neurone

7.Response occurs

Summary table for receptors and stimuli

The table below has been included as background information purposes only.

Receptor	Stimulus detected	Location
Light receptors	Light	Retina of eye
Sound receptors	Sound vibrations	Ear
Touch receptors	Pressure or touch	Skin
Temperature receptors	Heat or cold	Skin
Chemical receptors	Chemicals (taste/smell)	Tongue and nose

Effectors

An effector will bring about a response.

Effectors are either muscles or glands.

If a muscle is stimulated it will contract to cause movement.

If a gland is stimulated it will secrete hormones. The adrenal gland is an example of a gland that is stimulated by the nervous system and in response it will secrete the hormone adrenaline.

Practice Questions

1.Outline how the nervous system is organised

2. State the sequence of steps that occur from a stimulus to a response

3. Give two examples of effectors