Unit 1 - Topic 4 - Communication and signalling - Section D - Nerve impulse transmission - Part I - Generation of a nerve impulse Flashcards
What is resting membrane potential
Resting membrane potential is a state where there is no net flow of ions across the membrane
What does the transmission of a nerve impulse require
Changes in the membrane potential of the neuron’s plasma membrane
What is an action potential
A wave of electrical excitation along a neuron’s plasma membrane
What do neurotransmitters initiate
A response by binding to their receptors at a synapse
What are neurotransmitter receptors
Neurotransmitter receptors are ligand-gated ion channels.
What triggers the opening of voltage-gated sodium channels
Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the opening of voltage-gated sodium channels, and further depolarisation occurs
What is depolarisation
A change in the membrane potential to a less negative value inside
Inactivation of the sodium channels and the
opening of potassium channels restores what
The resting membrane potential
What does the binding of a neurotransmitter trigger and what is this followed by
Binding of a neurotransmitter triggers the opening of ligand-gated ion channels at a synapse. Ion movement occurs and there is depolarisation of the plasma membrane
What happens if sufficient ion movement occurs, and the membrane is depolarised beyond a threshold value
The opening of voltage-gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient. This leads to a rapid and large change in the membrane potential.
What happens a short time after the sodium channel opens
The sodium channels become inactivated. Voltage-gated potassium channels then open to allow potassium ions to move out of the cell to restore the resting membrane potential
What does depolarisation of a patch membrane cause
Neighbouring regions of membrane to depolarise and go through the same cycle, as adjacent voltage-gated sodium channels are opened
What happens when the action potential reaches the end of the neuron
It causes vesicles containing neurotransmitter to fuse with the membrane this releases neurotransmitter, which stimulates a response in a connecting cell
Restoration of the resting membrane
potential allows what
The inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane. Ion concentration gradients are re-established by the sodium-potassium pump, which actively transports excess ions in and out of the cell
Following repolarisation what happens to the sodium and potassium ion concentration gradients
Following repolarisation the sodium and potassium ion concentration gradients are reduced. The sodium-potassium pump restores the sodium and potassium ions back to resting potential levels.
