Neurons, Synaptic transmission and neurotransmitters Flashcards
What is a neuron?
The basic building block of the nervous system. Neurons are nerve cells that process and transmit messages through electrical and chemical signals.
What are neurotransmitters?
Brain chemicals released from synaptic vesicles. Neurotransmitters relay signals from one neuron to another across a synapse. Neurotransmitters can be broadly divided into those that perform and excitatory function and those that perform an inhibitory function.
What is synaptic transmission?
The process by which neighbouring neurons communicate with each other by sending chemical messages across a tiny gap (the synapse) that seperates neurons.
What consists in the basic structure of a neuron?
-The cell body (soma)
-The axon
-Terminal buttons
-Dendrites
-Nucleus
What is the role of the cell body?
-Includes the nucleus containing genetic material
What is the role of the denrites?
These carry impulses from neighbouring neurons towards the cell body
What is the role of the axon?
Is a tube like structure that carries the impulese away from the cell body down the length of the neuron
What is the fatty layer (myelin sheath)?
Formed from special cells which wrap themselves around the axon
It both protects the axon and speeds up electrical transmission of the impulse.
Gaps in the myelin sheath- called the noded of ranvier- allow for this increase in speed by forcing the impulse to jump acrosee the gaps along the length of the axon.
What are the roles of the terminal buttons?
These are not physically connected to the next neuron in the chain, but are involvede in communication across a gap known as the synapse.
What are the 3 types of neurons?
-Sensory
-Motor
-Relay
What is the role of a sensory neuron?
They carry messages from sensory receptors along nerves in the peripheral nervous system (PNS)to the central nervous system (CNS). They have long dendrites and short axons.
What is the role of a motor neuron?
They carry messages from the CNS, along nerves in the PNS, to effectors in the body (e.g. muscles and glands). They have short dendrites and long axons.
What is the role of the relay neuron?
They connect sensory and motor neurons together and also connect to other relay neurons. They have short dendrites and short axons and are only found in the CNS.
When a neuron is in resting state, what charge is inside the cell?
Negative
When a neuron is activated, what icharge is the inside of the cell?
Positive (for a split second)
What is the rapid switch from negative and postive charge called in a cell?
Depolarisation.
What does depolarisation create?
An electrical impulse (action potential AP)
When is the AP generated?
Once depolarisation reaches a certain threshhold
Does the instensity of AP depend on the stimulus?
No. It is always the same intensity regardless of the size of the stimulus
How much can most myelinated neurons conduct?
Up to 500 action-potential a second
Is synaptic transmission chemical or electrical?
chemical
What are the biochemical substances used in synaptic transmission?
neurotransmitters
Where are neurotransmitters released from?
Synaptic vesicles
Where do the neurotransmitters go after crossing the synapse?
Receptors on the postsynaptic neuron
What happens to the neurotransmitters that are in the postsynaptic neuron?
Converted back into an electrical signal - may fire another AP
Where do the remaining neurotransmitters that are left in the synapse go?
They are reabsorbed into the presynaptic neuron (usually broken down first).
What is the reabsorption of neurotransmitters called?
Reuptake
What are the 2 types of neurotransmitters called?
Excitation and Inhibitation
Why is seretonin an inhibitory neurotransmitter?
When in the postsynaptic neuron it makes the neuron more negative and less likely to fire
Why is dopamine a excitation neurotransmitter?
When in the postsynaptic neuron- it increases the positive charge making it more likely to fire.
What is the adding together of signals overtime called?
summation
