Biology Revision Cards Nervous System

A stimulus is a change in your environment.
You have 5 different sense organs:  eyes, ears, nose, tongue, skin.

These all have different receptors. Receptors are groups of cells which are sensitive to a stimulus. They change stimulus energy into electrical impulses.

A stimulus can be: light, sound, touch, pressure, chemical, a change in position or temperature.

Eyes - light receptors
Ears - sound and balance receptors
Nose - smell receptors and chemical stimulus
Tongue - Taste receptors and chemical stimulus
Skin - sensitive to touch, pressure, and temperature change

The CNS is where all the sense organs is sent and where reflexes and actions actions are co-ordinated.

The CNS consists of the brain and spinal cord. Neurones (nerve cells) transmit the information (as electrical impulses) very quickly to and from the CNS.

''Instructions'' from the CNS are sent to the effectors (muscles and glands) which respond accordingly.

Reflexes

Your brain can decide how to respond to a stimulus pretty quickly. But sometimes waiting for your brain to make a decision is just too slow. That's why you have reflexes.

Reflexes help prevent injury

Reflexes are automatic responses to certain stimuli - they can reduce the chances of being injured

If someone shines a bright light into your eye your pupils dilate automatically so less light gets into the eye or if you get a shock, your body releases the hormone adrenaline automatically.

The route taken by all the information in a reflex (from receptor to effector) is called a reflex arc. 

Stimulus - Receptor - Sensory Neurone - Relay Neurone- Motor Neurone - Effector- Response 

The neurons in reflex arcs go through the spinal cord or through an unconscious part of the brain.

When a stimulus is detected by receptors an impulse is sent along sensory neurones to the CNS.

In the CNS the sensory neurone passes on the message to another type of neurone - a relay neurone.

Relay Neurones relay the impulse to a motor neurone.

The impulse then travels along the motor neurone to the effector.

The muscle then contracts and moves your hand for example

You do not have to think about this response so it is quicker than he normal response.  

Neurones transmit information as electrical impulses around the body. Neurones have branched endings so they can connect with lots of other neurones. And they're long which speeds up the impulse.

The connection between two neurones is called a synapse.

The nerve signal is transferred by chemicals which diffuse across the gap.

These chemicals set off anew electrical signal in the next neurone.

Stimulus - changes in different environment that can be detected
Receptor - a cell detects the stimulus
Sensory Neurone - nerve cell that connects receptor to spinal cord
Spinal Cord - connects your nerve cells to your brain
Motor Neurone - co-ordinates and makes the decision
Effector - Muscle gland response
Response - Action generated by effector
Brain - co-ordinates and makes the decision
Spinal Cord - connects your nerve cells to your brain
Reflex - fast involuntary fixed response for your protection.

 Motor Neurone - Nerve cell - Spinal cord - Effector

Stimulus - Receptor - Sensory Neurone - Relay Neurone- Motor Neurone - Effector- Response