The CNS consists of...
The brain and the spinal chord
The Human nervous system consists of two main divisions - what are they?
- the central nervous system (CNS) - the peripheral nervous system (PNS)
The PNS consists of...
The nerve cells / nerves
In a word, what is the function of the nervous system?
The responses of the human nervous system are coordinated by...
What are "receptors"?
Receptors are specialised cells inside and outside the body that can detect changes in the environment. Once detected they convert them into electrical impulses. When stimulated, the receptor sends a signal along the nerve cells (neurones) to the brain where the response is reacted to.
Where are receptors often found and what stimuli do they detect?
They are often found in the sense organs.
- the skin (pressure, pain, temperature, touch)
- the nose (chemicals in the air)
- the ears (sound and position of the head)
- the tongue (chemicals in food)
- the eyes (light levels)
Give and example of a receptor in the body that is made from single cells...
Give an example of a receptor that is made from many different cells to create a 'single sense organ'..
The body's responses to stimuli are carried out by the ....... or the ......
- effector glands
Give three examples of effectors...
- a muscle contracting to move a part of the body
- a muscle squeezing saliva from the salivary gland
- a gland releasing a hormone, enzyme or sweat
Neurones are nerve cells that carry information as electrical signals. They contain a nucleus, a cells body and cytoplasm.
Name one way in which neurones differ from other cells...
The cytoplasm looks like a long extension lead and is called an axon.
What is the axon in nerve cells and what is its function?
The axon in a neurones is the cytoplasm, extending out like an extension lead. It is through the axon that the nerve cells communicate with each other and carry info all around the body.
How many types of neurone are there? Describe them...
There are three types of neurone.
- SENSORY neurones carry signals from the receptors to the spinal chord and brain
- RELAY neurones carry messages from one part of the CNS to another
- MOTOR neurones carry signals from the CNS to effectors
What is the myelin sheath?
Many neurones are insinuated against each other by the myelin sheath. It is a fatty substance that is wrapped around the outside of the cell. It is not quite complete as it has breaks in it every now and then which allow the nerve signals to across the gap making the and mission of nerve impulses quicker.
What are synapses and how do they work?
Where two neurones meet they do not quite touch and the gap between them is called a synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone transmit an electrical signal.
What form does the nerve impulse take when passing from one neurone to the next?
What is a receptor and effector?
A receptor is a specialised cell which detects a change (a stimulus). An effector is an organ or gland that produces a response to a stimulus.