Neural signalling - synapses Flashcards
What is the synaptic cleft?
A very small gap that separates two neurones at a synapse
The synaptic cleft is crucial for synaptic transmission as it prevents direct contact between neurones.
What forms a synapse?
The ends of two neurones and the synaptic cleft
Synapses act as junctions between cells in the nervous system.
Where are synapses found in the nervous system? (give examples)
Between sensory receptor cells and sensory neurones, and between motor neurones and muscle fibres
Synapses play a crucial role in communication within the nervous system.
What cannot jump across the synaptic cleft?
Electrical impulses
This necessitates a different mechanism for communication at synapses.
What triggers the influx of calcium ions in the presynaptic neurone?
Depolarisation of the membrane when an electrical impulse arrives
The influx of calcium ions is essential for neurotransmitter release.
What are neurotransmitters?
Chemical messengers released into the synaptic cleft
They facilitate communication between neurones by binding to receptors.
Give an example of a common neurotransmitter.
Acetylcholine (ACh)
ACh is vital for synaptic transmission and is involved in various functions in the nervous system.
What occurs when neurotransmitters bind to receptors on the postsynaptic membrane?
Sodium ion channels open, allowing sodium ions to diffuse into the postsynaptic cell
This can generate an action potential if the threshold is reached.
What happens to neurotransmitters after they have acted?
They are broken down to prevent continued stimulation of the postsynaptic neurone
This is crucial for resetting the synapse for future impulses.
What enzyme breaks down acetylcholine?
Acetylcholinesterase
This enzyme catalyzes the hydrolysis of ACh, ensuring proper synaptic function.
What is the significance of unidirectionality in synapses?
Impulses can only pass in one direction, preventing incorrect transmission
This mechanism is essential for the proper functioning of the nervous system.
What are cholinergic synapses?
Synapses that use acetylcholine as a neurotransmitter
Cholinergic synapses are important for many physiological functions.
What is formed when choline combines with an acetyl group?
Acetylcholine (ACh)
This process occurs in the presynaptic neurone and is crucial for neurotransmitter synthesis.
What happens to ACh after it binds to receptors on the postsynaptic membrane?
It generates an action potential by allowing sodium ions to enter the postsynaptic neurone
This is a key step in the transmission of signals in the nervous system.
Fill in the blank: The enzyme _____ catalyses the hydrolysis of ACh molecules.
acetylcholinesterase
This enzyme is essential for regulating neurotransmitter levels in the synaptic cleft.
What happens to the products of ACh hydrolysis?
They are absorbed back into the presynaptic neurone
This recycling process is important for maintaining neurotransmitter availability.
