Year 1 - Nerve Impulses and Synapses Flashcards
What is the charge of the neurone at rest?
Positive on the outside and negative on the inside.
What is the charge of the neurone when an impulse passes through?
Positive on the inside and negative on the outside.
What is the word that is when a neurone becomes more positive on the inside?
Depolarisation
What is the word that is when a neurone going back to its original “resting” charge?
Repolarisation
What is an impulse jumping from node of Ranvier to node of Ranvier known as?
Saltatory conduction
What is the advantage of saltatory conduction?
The impulse travels faster down the axon
What are the cells that form the myelin sheath?
Schwann cells
What is the function of the myelin sheath?
Electrical insulation and protection of the axon
Impulses never go ________ along neurones or across synapses
backwards
What does a stronger stimulus lead to?
A higher frequency of nerve impulses
What is a neurotransmitter?
Chemical messenger that allows communication between neurones
What is acetylcholine an example of?
Neurotransmitter
What is the gap between presynaptic and postsynaptic neurones called?
Synaptic cleft
What is the more technical name for a nerve impulse?
Action potential
What does the impulse when it arrives at the synaptic knob cause?
It causes calcium ion channels to open, causing calcium ions to flood in to synaptic knob
What does calcium ions cause?
Synaptic vesicles to migrate to and fuse with the presynaptic membrane
What happens to the synaptic vesicles upon fusing with the presynaptic membrane?
They release their neurotransmitter into the synaptic cleft.
What happens whens the neurotransmitter diffuses across the synaptic cleft?
It binds to receptors on the post-synaptic membrane
What does the receptors activating and lead to upon binding by neurotransmitter?
The diffusion of sodium ions into the postsynaptic neurone.
What is cholinesterase?
An enzyme that breaks down acetylecholine
What is the process by which calcium ions are piped out of the synaptic knob?
Active transport (requires energy)
What can the neurotransmitter or products of the neurotransmitter breakdown be taken up by?
The synaptic knob to be recycled and repackaged in synaptic vesicles
Why do the synaptic knobs contain many mitochondria?
To release enough energy for the active transport of calcium ions out of the knob and repackaged neurotransmitter in synaptic vesicles.
Why is the transmission across a synapse unidirectional?
Because neurotransmitter can only be released from the synaptic knob bu the acetylcholine receptors are only found on the postsynaptic membrane.
What does unidirectional?
It means occurs in one direction
Why are drugs that Inhibit cholinesterase very dangerous?
Because acetylcholine does not break down, leading to excessive impulses to muscles, which go in to permanent contraction (t.g. diaphragm/intercostal muscles, so can’t breathe.)
What does it mean that the sodium ions are positively charged?
So if more of these move into a neurone, the more positively charge it becomes inside.
