nerve impulse transmission Flashcards
what is the resting membrane potential?
resting membrane potential is a state where there is no net flow of ions across the membrane
What is the value for the resting potential in neurons?
In neurons the resting membrane potential is typically between -60 and -80mV (millivolts).
the transmission of a nerve impulse requires?
the transmission of a nerve impulse requires changes in the membrane potential of the neurons plasma membrane
what is an action potential?
an action potential is a wave of electrical excitation along a neuron’s plasma membrane
how do neurotransmitters initiate a response?
neurotransmitters initiate a response by binding to their receptors at a synapse
what are neurotransmitter receptors?
neurotransmitter receptors are ligand gated ion channels
what is depolarisation
depolarisation is a change in the membrane potential to a less negative value inside
why does the membrane become depolarised?
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 restores the resting membrane potential?
Inactivation of the sodium channels and the opening of potassium channels restores the resting membrane potential
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. 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.
A short time after opening, 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.
Depolarisation of a patch of membrane
causes neighbouring regions of membrane to depolarise and go through the same cycle, as adjacent voltage-gated sodium channels are
opened.
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 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 the sodium and
potassium ion concentration gradients are reduced.
The sodium-potassium pump
restores the sodium and potassium ions back to resting potential levels.
