Sensivity and co ordination: the synapse

Action Potential

A rapid change in membrane potential that occurs when a neuron sends a signal along the axon.

Synaptic Cleft

The small gap, approximately 20 nm wide, that separates the presynaptic and postsynaptic neurones.

Neurotransmitter

Chemical messengers that transmit signals across the synaptic cleft from one neuron to another.

Exocytosis

The process by which neurotransmitters are released from synaptic vesicles into the synaptic cleft.

Cholinergic Synapse

A type of synapse where the neurotransmitter acetylcholine is used.

Postsynaptic Membrane

The membrane of the neuron or cell receiving a signal, containing receptors for neurotransmitters.

Acetylcholinesterase (AChE)

An enzyme that breaks down acetylcholine in the synaptic cleft to terminate the signal.

Calcium Ion Channels

Proteins in the presynaptic membrane that open during depolarization, allowing Ca²⁺ ions to enter the cell.

Receptor Proteins

Proteins on the postsynaptic membrane that bind specific neurotransmitters and initiate a cellular response.

Depolarization

A decrease in the membrane potential, making the inside of the neuron less negative, which can lead to an action potential.

Threshold Potential

The critical level to which a membrane potential must be depolarized to initiate an action potential.

Spatial Summation

The process by which multiple presynaptic neurones converge onto a single postsynaptic neurone, potentially leading to an action potential.

Temporal Summation

The additive effect of neurotransmitter release from a single presynaptic neurone over time.

Inhibitory Synapses

Synapses that make the postsynaptic membrane hyperpolarized, reducing the likelihood of an action potential.

Modulation by Drugs

The alteration of synaptic transmission by various substances that can enhance or inhibit the action of neurotransmitters.