Neurons and the Process of Synaptic Transmission Flashcards
Order of neurons
Sensory ~> relay ~> motor
Structure of sensory neuron
Long dentrites
Short axons
Unipolar
“Cell body in the middle”
Unipolar
Only TRANSMITS information
Function of sensory neuron
Afferent nerve cell
Carries sensory impulses from the sense organs (e.g skin) to the CNS (brain and spinal cord)
Afferent
Towards CNS
Efferent
Away from CNS
Structure of relay neuron
Short dendrites
Short axons
Multipolar
Found in the brain / CNS
Multipolar
SENDS and RECIEVES information from many sources
Function of relay neuron
Relay neurons connect with other neurons (e.g sensory and motor)
Involved in analysis of the sensation and deciding how to respond to it
DECISION MAKING
Structure of motor neuron
Short dendrites
Long axons
Multipolar
Function of motor neuron
Efferent nerve cell
Transmits nerve impulses from the CNS to muscles or glands
Synapse
Junction between the axon of one neurone and the dendrites of another.
Synaptic transmission
The process of transmitting an electrical impulse from the presynaptic to the post synaptic neuron
Ingredients for neurotransmitters:
Precursor chemicals
Four processes of synaptic transmission:
1) Synthesis
2) Release
3) Receptor activation
4) Inactivation
What occurs during synthesis:
Precursor chemicals are transported into the axon terminal in the presynaptic neurone
The precursor chemicals are used to produce neurotransmitters and are packaged into vesicles
What occurs during release:
Neurotransmitters are released into the synapse
What occurs during Receptor activation:
Neurotransmitters diffuse across the synapse and bind to specific receptors on the postsynaptic neurone
What occurs during the process of Inactivation:
Neurotransmitters then unbind and either :
- go through re uptake into the presynaptic neuron via active transport
- is packaged back into vesicles
- it is broken down by enzymes in the synapse
Where are neurotransmitters
Presynaptic neuron
Diffusion
Movement of neurotransmitters from areas of high ~> low concentration
Pre to post synaptic membrane
Explain the process of synaptic transmission {4}
~ electrical impulses reach the presynaptic terminal
~ electrical impulses trigger the release of neurotransmitters from synapse vesicles
~ neurotransmitters diffuse across the synaptic cleft
~ neurotransmitters bind to receptors on the postsynaptic membrane
The two types of neurotransmitters:
Excitatory
Inhibitory
What happens when an excitatory neurotransmitter binds to receptor site in the post synaptic neurone:
Produces excitatory post synaptic potential (EPSP)
How is EPSP produced:
When an excitatory neurotransmitter binds to receptor site in the postsynaptic neurone
EPSP
Makes postsynaptic neurone MORE likely to fire
What happens when an inhibitory neurotransmitter binds to a receptor site in the postsynaptic neurone:
Produces inhibitory post synaptic potential (IPSP)
How is IPSP produced:
When inhibitory neurotransmitter binds to the receptor site in the postsynaptic neurone
IPSP
Makes postsynaptic neurone less likely to fire
Fire
The speed of electrical impulse
Sammation
When the postsynaptic neurone aggregates the overall amount of IPSP and EPSP to determine whether or not to fire
What charge is it if the EPSP is greater than IPSP?
Overall positive charge in the post synaptic neurone
Excitation (or depolarisation)
When the EPSP is greater than the IPSP so there is an overall positive charge in the postsynaptic neurone and is therefore more likely to fire
The signals in a synapse can only travel
In one direction
The synaptic bisected containing neurotransmitters are only released from:
Presynaptic neurone
The receptors for neurotransmitters to bind with are only present on:
Post synaptic neurone
Why can neurons only transmit information in one direction at a synapse?
~ The synaptic vesicles containing neurotransmitters are only released from the presynaptic neurone
~ neurotransmitters in the synapse travel via diffusion (high to low concentration) ~ so only pre to post synaptic membrane
~ the receptors for neurotransmitters to bind with are only present on the postsynaptic neuron and it is the binding which passes on the information
Differences between neurotransmitters and hormones:
Neurotransmitters are produced within neurons and pass very quickly from one neurone to another nearby neurone ~ whereas
Hormones are secreted by glands and travel less quickly through the bloodstream to often quite distant target organs
