The Neurone
L.O. To understand the basic
structure of a neurone, synapse,
neurotransmitters and their
impact on behaviour.
Organisation of the nervous
system
• The Nervous System has 2 main parts – the Central
Nervous System (CNS) and the Peripheral Nervous
System.
• The CNS consists of the brain and the spinal cord.
• The brain is within the skull and the spinal cord is
within the vertebrae.
What are neurones?
Neurones are specialized cells that conduct electrical impulses
through the body.
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.
nerve
nerve fibre
What do neurones look like?
Neurones are elongated cells consisting of a cell body and long, thin axon.
dendrites
myelin
sheath
cell
body
axon
Thin projections called dendrites extend from the cell body and connect with other
neurones, allowing electrical impulses to pass from one to the other.
The axons of most neurones are wrapped in an insulating lipid layer called the myelin
sheath. Why is this important?
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 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
When a nerve impulse arrives at the end of one neurone it triggers the release of
neurotransmitter molecules from synaptic vesicles.
synaptic
vesicle
neurotransmitter molecules
Continuing the impulse
The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the
next neurone, triggering another impulse.
synaptic cleft
nerve impulse
receptor
Neurotransmitters
•
•
•
Neurotransmitters are chemical messengers that act between the
neurones in the brain. This allows the brain to process thoughts and
memories.
The nervous system contains neurones and glia – glial cells carry out
repairs and remove waste products from the brain.
Neurones receive and transmit messages, passing them from cell to cell.
Neurotransmitters continued:
• RECEPTORS can be thought of as locks – if a certain
chemical (neurotransmitter) fits like a key, then the
message is passed on: if it does not then the message
is blocked.
• Manufactured drugs work in this way – they mimic
neurotransmitters, more or less fit certain receptors,
are received like neurotransmitters and the message
from them ‘works’. Some drugs block the message –
they fit the receptor, so the natural
neurotransmitter cannot pass the message on because
the receptor is not available.
Impact of neurotransmitters
• Stories in the news:
– http://www.telegraph.co.uk/health/331110
6/A-dangerous-sleep.html
– http://www.telegraph.co.uk/news/uknews/1
555294/Gene-breakthrough-against-braindiseases.html
Homework
• Research the neurotransmitter:
– Endorphin
– Dopamine
– Serotonin
– Endocannabinoids