U1 - Nerve impulse transmission Flashcards
What is the resting membrane potential?
The 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?
It 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 neurons plasma membrane.
What are neurotransmitters?
They are ligand gated ion channels
What initiates a neurotransmitters response?
They trigger a response by binding to their receptors at a synapse.
What is depolarisation?
Depolarisation is a change in the membrane potential to a less negative value inside.
What does depolarisation do to the membrane?
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 membrane potential?
Inactivation of the sodium channels and the opening of potassium channels restores the resting membrane potential.
What triggers the opening ligand-gated channels at a synapse?
Binding of a neurotransmitter and depolarisation of the plasma membrane occurs.
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 do the cell to restore the resting membrane potential.
What is triggered after a patch of membrane is depolarised?
It triggers the 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.
What happens when a neurotransmitter with vesicle fuses with the membrane?
This releases neurotransmitter, which stimulates a response in a connecting cell.
What does restoring the resting membrane potential allow?
It 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.
What is re-established by the sodium potassium pump?
Ion concentration gradients
