Structure & Function of the Neuron Flashcards
What does the nervous system consist of?
Neurons (nerve cells) & glia (glial cells).
What do glial cells do?
They carry out repairs, act as insulators, and remove waste products from the brain.
What is the role of glial cells in relation to neurons?
Glia surrounds neurons, protects them, supplies them with nutrients, and removes dead neurons.
At first, it wasn’t thought that…
… glial cells have a role in transmitting messages.
How do glial cells in the hippocampus have a role in transmission?
Because they have a role in releasing gliotransmitters, which have a role in synaptic transmission.
They also have a role in clearing neurotransmitters away in the synaptic gap.
What are gliotransmitters?
Chemicals released from glial cells that facilitate neuronal communication between neurons and other glial cells.
What forms the myelin sheath of myelinated neurons?
Glial cells, which wrap around the nerve fibres to form it.
What are the 3 types of neurons?
1 - motor neurons
2 - sensory neurons
3 - inter-neurons
What are motor neurons?
Neurons that receive messages from the CNS to generate movements.
What are sensory neurons?
Neurons that transmit messages about senses, such as sight & sound, from the sense organ to the brain and spinal column.
What are inter-neurons?
Neurons that take messages from neuron to neuron
What are dendrites?
Finger-like structures that surround a cell body & form a tree-like structure.
They receive synaptic impulses from axons.
What is an axon?
A thin fiber that extends from a neuron.
Electrical impulses from the neuron travel away from the axon to be received by other neurons.
Where does an axon end?
At an axon terminal.
The axon is where…
… the electrical signal from the cell body travels.
An axon terminal has more than one…
… telodendron (terminating branch).
What is at the end of each telodendron?
A terminal button.
What is the axon protected by?
The myelin sheath.
Which type of glial cells make up the myelin sheath of neurons in the peripheral nervous system?
Schwann cells.
Which type of glial cells make up the myelin sheath of neurons in the central nervous system?
Oligodendroglial cells.
What are nodes of Ranvier?
Gaps in the myelin-sheath which speed up transmission.
What is the role of the neuron?
To pass messages between neurons using neurotransmitters to enable behaviour, thinking & emotions to be transmitted.
What do the electrical impulses travelling down the axon trigger?
They trigger the release of neurotransmitters from from the terminal at the end of the axon.
What happens after the neurotransmitters are released from the axon terminal?
They are then released into the synaptic gap.
What happens after the neurotransmitters are released into the synaptic gap?
They are either picked up by receptors on the dendrites of another neuron, or inhibited.
What is the process in the synaptic gap called?
Synaptic transmission.
The axon terminal of one neuron reaches out to…
… the dendrites of another neuron.
What is a synapse?
A gap between the terminal & the dendrites.
What is the synaptic gap also known as?
The synaptic cleft.
Location of the synaptic cleft?
Between 2 neurons.
What is located at the dendrites?
Receptors of a certain shape, prepared to receive the neurotransmitter from the other neuron.
What happens if the neurotransmitter fits the receptor?
The message is passed on.
What happens if the neurotransmitter doesn’t fit the receptor?
The impulse is inhibited, and so the message is blocked.
Receptor?
Receives neurotransmitters from other neurons.
The neurotransmitter that isn’t used by the receptors is taken up again to be reused. What is this called?
Reuptake.
What does reuptake do?
It regulates the amount of neurotransmitter in the synapse, which regulates how much message there is, and it also recycles the neurotransmitter.
What is the neurotransmitter picked up by?
Transport proteins.
Transport proteins for gamma-aminobutyric acid, norepinephrine, dopamine & serotonin are…
… very similar.
What do the transporters do?
They enable the neurotransmitter to be absorbed into the presynaptic neuron..
What is the presynaptic neuron?
The neuron that is sending the message & releasing the neurotransmitters.
What is the postsynaptic neuron?
The neuron receiving the message.
What is reuptake?
When the neurotransmitter is absorbed back into the presynaptic neuron.
How do manufactured drugs mimic natural neurotransmitters?
- more or less fit certain receptors
- they are received like neurotransmitters
- the message from them ‘works’
What is an example of prescribed drugs that affect synaptic transmission?
Selective serotonin reuptake inhibitors (SSRIs).
What are SSRIs for?
They are prescribed for depression and they enhance serotonin levels in the brain.
Serotonin is a neurotransmitter that…
… improves mood.
How do SSRIs work?
They block the reuptake of serotonin, leaving more serotonin at the synapse to be taken up again by the receptors of other neurons, thus improving the name.
4 SSRIs prescribed in the UK for depression?
- Fluoxetine
- Paroxetine
- Citalopram
- Fluvoxamine
