Neurotransmitters Flashcards
What is a synapse
A tiny gap between two neurones.
Where do neurones connect
Synaptic cleft
What do neurotransmitters do
They are chemicals that relay messages across the synaptic cleft.
Where are neurotransmitters stored
Vesicles in the axon endings of the presynaptic neuron
When are neurotransmitters released, and what do they then do
Upon arrival of an impulse. They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron
What does the type of receptor determine
The type of alteration to a post-synaptic membrane following the binding of a neurotransmitter.
Two types of signal
Excitatory or inhibitory
What determines the overall effect and whether a signal passes on
The sum of all the excitatory and inhibitory signals
What happens to weak stimuli
They are filtered out if there is insufficient secretion of neurotransmitter molecules and so the impulse fails to pass on.
A nervous impulse can only pass a synapse if…
a certain minimum number of neurotransmitter molecules are released into the synaptic cleft.
What is summation
Summation of a series of weak stimuli from many neurons at once can trigger enough neurotransmitters to fire an impulse.
What happens between impulses
Transmitter molecules are removed to prevent constant stimulation of post-synaptic neurons. This is achieved through enzyme degradation of neurotransmitters or reuptake.
Example of enzyme degradation
Acetylcholine is broken down by enzymes and the non-active products are reabsorbed into the neuron and resynthesized into an active neurotransmitter.
Example of reuptake
Noradrenaline is reabsorbed directly into the presynaptic membrane and stored in a vesicle ready for reuse.
What do neurotransmitters effect
Mood and behaviour
