Neuronal communication - keywords

Acetylcholinesterase

An enzyme in the synaptic cleft that breaks down the neurotransmitter acetylcholine

Action potential

A brief reversal of the potential difference across the cell surface membrane of a neurone: +40 mV

Cholinergic synapse

A junction between neurones that uses acetylcholine as the neurotransmitter

Depolarisation

The loss of polarisation across a membrane - when the membrane loses its resting potential

Hyperpolarisation

The generation of the condition of a membrane that is highly polarised than the usual resting state

Local current/circuit

Movement of sodium ions along a neurone inside the cell, caused by the influx of ions when a region of membrane is depolarised

Motor neurone

Neurone that transmits action potentials to effectors e.g. muscles

Myelinated

Neurone whose axon is insulated which many tightly wrapped Schwann cells separated by nodes of Ranvier

Neurotransmitter

A chemical that is released by exocytosis from the presynaptic neurone to transmit a nerve impulse to another neurone

Node of Ranvier

Gap in myelin sheath where depolarisation occurs

Non-myelinated

Many neurones may be enshrouded by one loosely wrapped Schwann cell providing no insulation

Polarised

Membrane with a potential difference across it

Refractory period

The short period of time after firing during which it is more difficult to stimulate a neurone

Resting potential

The potential difference across the plasma membrane when the neurone is at rest

Saltatory conduction

Refers to the way in which the action potential appears to jump from node to node

Stimulus

Any change in the environment of an organism that causes a response

Summation

The way that several small potential changes combine to determine if an action potential is produced in a post synaptic neurone

Synapse

The junction between two neurones - the point at which they communicate by neurotransmitter

Synaptic bulb

The swelling at the end of a neurone where it forms a junction (synapse) with another neurone

Threshold potential

A potential difference (around -50 mV) across the membrane. If depolarisation reaches this potential difference then an action potential is generated

Transducers

Describes sensory receptors that can convert one form of energy into the electrical energy of a nerve impulse

Transmission

The propagation of an action potential along neurones from a receptor to, ultimately, an effector

Voltage-gated

Channel in the plasma membrane that opens to allow the passage of ions and close again in response to particular potential differences