Neurons and synaptic transmission Flashcards
What are neurons?
Specialised cells that are specalised to carry out neutral information throughout the body.
What are the three types of neurons?
Sensory
Relay
Motor
What do neurons typically consist of?
A cell body
Denrites
An Axon
What do dendrites receive?
Signals from other neurons or sensory receptors
What are dendrites connected to?
The cell body
What is the cell body know as?
Control centre of the neuron
From the cell body where does the impulse travel along and to?
Along the axon
terminates at the axon terminal
What is the insulating layer that forms around the axon called?
Myelin sheath
What does the Myelin sheath allow?
Allows nerve impulses to transmit more rapidly along the axon
What happens if the Myelin sheath becomes damaged?
Impulses slow down
What is the length of a neuron?
A few millimetres up to one metre
What do sensory neurons carry?
Nerve impluses from sensory receptors to the spinal cord and the brain
Where are sensory receptors found?
Various locations around the body For example: Eyes Ears Toungue Skin
What do sensory neurons convert information from these sensory receptors?
Neural impulses
What happens when these impulses reach the brain?
Translated into sensations of
for example
visual input
heat pain
Why does not all sensory information travel as far as the brain?
They are terminated at the spinal cord
Allows reflect actons to occur quickly without delay of sending impulses to the brain
What do relay neurons allows?
They allow sensory and motor neurons to communicate with each other.
Where do you find relay neurons?
In the brain and spinal cord
What do motor neurons form?
Synapses with muscles and control their contractions
What happens when motor neurons are stimulated?
neurotransmitters are released
What happens when the neurotransmitters are released?
They bind to receptors on the muscles which triggers a reponse which leads to muscles movement
What causes muscles relaxation?
Caused by inhibition of the motor neuron
What needs to happen to the action potential when it arrives at the terminal at the end of an axon?
It needs to be transferred to another neuron or to tissue
For the action potential to be successful transferred what must occur?
It must cross a gap between the presynaptic neuron and the postsynaptic neuron
What is the area of the end of the presynaptic neurom and the membrane of the postsynaptic neuron called?
Synapse
What is the physical gap between the pre- and post synaptic call membranes known as?
Synaptic gap
What is found at the end of axon of the nerve cell?
A number of sacs
AKA
Synaptic vesticles
What do synaptic vesticles contain?
Chemical messengers
What do the chemical messengers do?
Assist in the transfer of the impulse
As the action potential reaches the synaptic vesticles what happens?
It causes them to release their contents through a process called EXOCYTOSIS
What happens after the transmitter has diffused across the gap between pre- and post synaptic cell?
Binds to specialised receptors on the surface of the cell that recognised it and are activated by that particular neurotransmitter
What happens once receptors have been activated?
Receptors molecules produce either excitatory or inhibitory effects on the postsynaptic neuron
How long does the process of post synaptic transmission take?
A fraction of a second
What is the process of re-uptake?
Neurotransmitter is taken up again by the presynaptic neuron, where it is stored and made available for later release
What does the speed that the presynaptic neuron takes back the neurotransmitter from the synaptic cleft determine?
how prolonged the effects will be
If it is taken back quickly what does this mean?
The shorter the effects on the presynaptic neuron
Some examples of excitatory neurotransmitters?
Acetylcholine and noradrenaline
What are excitatory neurotransmitters?
Neurotransmitters that increase the likelihood of a new action potential forming in the postsynaptic cell
What happens when excitatory neurotransmitters are detected in the postsynaptic cell?
Electrical charge inside becomes more positive and more likely to fire - depolarisation
What are inhibatory neurotransmitters?
Neurotransmitters that decrease the likelihood of a new action potential forming in the postsynaptic cell
What happens when inhibitory neurotransmitters are detected by receptors in the postsynaptic cell?
Electrical charge inside becomes more negative and less likely to fire - Hyperpolarisation
What is summation?
Effect of all th excitatory and inhibitory neurotransmitters influences on the postsynaptic neuron
What happens in the threshold is met?
A new action potential will form in the postsynaptic cell
