Neurones, neurotransmitters, and synaptic transmission

Neuron

nerve cell that transfers info throughout the nervous system

Neurotransmitter

Chemicals that transmit signals from one neuron to another

What are all the parts of a neuron?

Cell body/soma, axon, dendrites, myelin sheath, nodes of ranvier, terminal buttons

What is the cell body? What does it do?

Core of the neuron. Carries genetic information, maintains neurones structure, and provides energy to drive activities

What is the axon? Where does it join?

Long tail

What does the axon do?

carries impulses away from the cell body

What is the axon insulated in? Why?

Myelin, a fatty substance that helps axon to conduct electrical signals.

What are dendrites? Where do they connect? What do they do?

Fibrous roots that branch from cell body. They receive and process signals from the axons of other neurones

Dendrite tree

all the dendrites of a single neuron

What do myelin sheaths do?

Help axons conduct an electrical signal to ensure it doesn't get lost by insulating it

What are nodes of ranvier?

Periodic gaps in the myelin sheath on the axon to facilitate the rapid conduction of nerve impulses

What are terminal buttons? What do they do?

Small knobs at the end of an axon that release neurotransmitters. They form the presynaptic neuron of the synapse

What does a sensory neuron do?

Tells brain about internal and external environment by processing info from the 1 of the 5 senses

What is a unipolar neuron?

a neuron that has one process coming off of the cell body; sensory neurons are unipolar ( transmits messages in one direction)

In a motor neuron, where is the cell body located?

Spinal chord

In a motor neuron, where is the axon and why?

Projects outside spinal cord to directly or indirectly control effector organs, muscles and clands

Motor neurones act on messages sent from…

The CNS

In a motor neuron, what are the terminal buttons connected to? Why?

It connects to the tissue that it needs to activate (uncles, glands or organs) to cause it to move

Why is a motor neuron also unipolar?

Only role is to send electrical impulses towards the target it needs to activate

Is a sensory neuron unipolar or multipolar?

unipolar

What do relay neurones do?

carry messages from one part of the CNS to another, and connect motor and sensory neurons

Why are relay neurons multipolar?

They send information back and forth between motor and sensory neurons

Where are relay neurons located?

CNS (brain or spinal cord)

Differences in the structure of relay neuron and why

No myelin sheath and nodes of ranvier, as relay neurones are already protected by spinal cord and brain tissue. Also don't need to compromise speed to ensure transference so don't end more insulation.

Synaptic transmission

The relaying of information across the synapse by means of chemical neurotransmitters.

Each terminal button of one neuron connects to _ of the next

Dendrites

presynaptic neuron

neuron that sends the signal

post

synaptic neuron

Synaptic cleft

The narrow gap that separates the presynaptic neuron from the postsynaptic cell.

Synaptic vesicle

storage site for neurotransmitters

Neurotransmitter

chemical messengers that cross the synaptic gaps between neurons

Postsynaptic receptors

a receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter

Outline the structures and processes involved in synaptic transmission

Information from the environment is received by our senses, triggering an electrical impulse. The electrical impulse (action potential) reaches the presynaptic terminal. These electrical impulses trigger the release of neurotransmitters such as dopamine and serotonin. The neurotransmitters cross the synapse one they have been released from the vesicles. The neurotransmitters combine with receptors on the post-synaptic membrane. The stimulation of postsynaptic receptors by neurotransmitters result in either excitation or inhibition of the post synaptic membrane.

Excitatory signalling

Makes the latter cell more likely to fire

Inhibitory signalling

Makes latter cell less likely to fire

Neurotransmitters are either…

Excitatory or inhibitory

Summation

The excitatory and inhibitory influences are summed, if the net effect on the post synaptic neuron is inhibitory, the neuron will be less likely to 'fire' and if the net effect is excitatory, the neuron will be more likely to fire.

Balance between neural excitation and inhibition is crucial to…

Healthy cognition and behaviour

A brain dominated by excitation

repeated bursts of activity, similar to an epileptic seizure

A brain dominated by inhibition

only be capable of quiet whispers of activity, with little synchronization necessary for meaningful communication between brain areas