Neurons and synaptic transmission Flashcards
What are neurons?
The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals.
What are the three types of Neurons?
Sensory
Relay
Motor
Outline the structure of a Neuron.
Soma: AKA The cell body includes a nucleus, containing genetic material of the cell.
Dendrites: Branchlike structures stick out from the cell, these carry nerve impulses from neighbouring neurons to the cell body.
Axon: carries impulses away from the cell body down the neuron.
Myelin sheath: Protects the axon and increases the speed of transmission of the electrical impulse.
Axon terminal: These communicate with the next neuron across the synapse.
What is the role of the Sensory Neuron?
These carry messages from the PNS to the CNS.
Long dendrites and short axons
What is the role of the Motor Neuron?
These connect the CNS to effectors such as muscles and glands.
Short dendrites and long axons.
What is the role of the Relay Neuron?
These connect sensory neurons to motor neurons and other relay neurons (interconnect).
They have short dendrites and short axons
What are the differences in the 3 neurons?
The relay neuron is NOT myelinated. (motor and sensory are)
The sensory neurons cell body is found in the middle of the neuron, whereas it is at the end in the motor neuron.
What is a synapse?
The gap between neurons where one neuron (presynaptic) can send a chemical message to an adjacent neuron (postsynaptic).
What is Synaptic Transmission?
The process by which neighbouring neurons communicate with eachother by sending chemical messages (neurotransmitters) across the gap (synapse) which seperates them.
Explain the process of Synaptic Transmission.
- Define Synaptic Transmission
- Information is passed down the axon of the neuron as an electrical impulse known as action potential.
- Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue.
- It must cross over the synaptic gap between the presynaptic neuron and post-synaptic neuron.
- At the end of the neuron (in the axon terminal) are the synaptic vesicles, which contain chemical messangers known as neurotransmitters.
- When action potential reaches these vesicles, they release their contents of neurotransmitters.
- These then carry the signal accros the synaptic gap.
- They bind to receptor sites on the PS-cell, thereby completing the process of synaptic transmission.
What is an Excitatory neurotransmitter?
Excitatory neurotransmitters are those which stimulate an action potential, increasing its postitive charge, making it more likley to fire.
E.g Adrenaline
What is an Inhibitory neurotransmitter?
Inhibitory neurotransmitters are those which inhibit an action potential, increasing the neurons negative charge, making it less likley to fire.
E.g Serotonin
What is Summation?
The combined effect of all the excitatory and inhibitory nuerotransmitters influences on the post synaptic neurone. If a threshold is reached, then a new Action potential will from in the postsynaptic cell.
How do SSRIs work in the synapse?
SSRIs block the reabsorption of seretonin back into the PSC increasing its level in the synapse.
