Nerve Impulse Transmission- Generation Of A Nerve Impulse Flashcards
What is resting membrane potential?
The state where there is no net flow of ions across the membrane
What does the transmission potential require?
Changes in the membrane potential of the neuron’s plasma membrane
What is an action potential?
It is a wave of electrical excitation along a neuron’s plasma membrane
How do neurotransmitters initiate a response?
By binding to their receptors at a synapse
What are neurotransmitters receptors?
Ligand-binding ion channels
What is depolarisation of the plasma membrane 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
What restores the resting membrane potential?
The inactivation of the sodium channels and the opening of potassium channels
What are the steps involved in a nerve transmission?
The 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.
What does depolarisation of a patch of membrane cause?
It causes 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 neurotransmitters which stimulates a response in a connecting cell
What does the restoration of the resting membrane potential allow?
It allows the inactive voltage-gated sodium channels to return to a confirmation that allows them to open again in response to depolarisation of the membrane
What happens following repolarisation?
The sodium and potassium ion concentration gradients are reduced.
What does the sodium-potassium pump restore?
the sodium and potassium ions back to resting potential levels
What are ion concentration gradients re-established by?
By the sodium-potassium pump which actively transports excess ions in and out of the cell
