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
Describe endorphins
Neurotransmitters that stimulate neurons involved with reducing the intensity of pain. Production increases following severe injury, prolonged and continuous exercise, stress and certain foods.
Describe dopamine
Neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activating the reward pathway in the brain. The reward pathway is activated when an individual engages in behaviour that is beneficial to them.. eg. eating when hungry.
What are agonists
Agonists are chemicals (drugs) which bind to and stimulate receptors on the membrane of the post-synaptic neuron, mimicking the neurotransmitters and triggering and enhanced cellular response.
What are antagonists
Antagonists are chemicals (drugs) that bind to specific receptors on the postsynaptic membrane blocking the action of the neurotransmitters at a synapse. The reduces or halts transmission of nerve impulses.
Describe inhibitor drugs
Other drugs can inhibit certain parts of the normal neurotransmission process. Some inhibit the enzymes that degrade neurotransmitters in the synaptic cleft and others inhibit re-uptake of the neurotransmitter causing an enhanced effect.
What can recreational drugs affect
An individual’s mood, perception, behaviour and cognition.
What causes drug addiction
Repeated use of antagonistic drugs. They constantly block the receptors and force the nervous system to increase both the number and sensitivity of the receptors. This sensitisation leads to addiction where the indivual craves more of the drug.
What causes drug tolerance
Repeated use of agonistic drugs. They constantly stimulate the receptors and force the nervous system to decrease both the number and sensitivity of the receptors of the receptors. This desensitisation leads to drug tolerance where the individual must take more of the drug to get an effect.
