Lecture 2.2 Flashcards
(18 cards)
What is voltage?
The electrical force between the inside and outside of the cell.
What does a transporter do?
Facilitates reuptake of neurotransmitters.
What do enzymes do?
Breakdown neurotransmitters that aren’t taken back to ensure no prolonged effects.
What is a ligand?
A chemical that binds with a protein to affect a biological process, varying as a function of location.
What is depolarisation?
Reducing the voltage difference, making it easier for cells to fire (generating an action potential; excitatory post-synaptic potential).
What is hyperpolarisation?
Increasing the voltage difference, making it harder for cells to fire (inhibitory post-synaptic potential).
What is the refractory period?
The time during which another action potential cannot be generated.
What is the absolute refractory period?
The action potential cannot be generated at all.
What is the relative refractory period?
The action potential can be generated, although difficult.
In what way is chemical and electrical neuronal communication an ‘approximate’?
The distinction between electrical and chemical communication is a simplification with inconsistencies.
What are the 2 stages in chemical communication? What happens in each?
1) The presynaptic neuron fires, causing synaptic vesicles to move and fuse with the membrane; 2) Neurotransmitters are released into the synaptic cleft and trigger a response in the postsynaptic neuron.
For neurons to communicate, what needs to happen?
The presynaptic neuron needs to get the message to the axon terminal so it can pass on the message to other neurons.
Can chemical stimulation from one neuron cause a lot of depolarisation?
No, chemical stimulation from one neuron doesn’t cause a lot of depolarisation.
What are the 6 stages of an action potential?
□ Hypopolarisation.
® There’s an initial increase of the membrane potential from -65mV to the threshold of -55mV via ligand-gated ion channels.
□ Depolarisation.
® The opening of voltage-gated sodium channels, which causes a huge influx of sodium ions and the inside of the cell becomes more positive.
□ Overshoot.
® The inside of the cel becomes more positive until it reaches equilibrium for sodium (around 30mV-40mV) –> sodium channels close and permeability decreases.
□ Repolarisation.
® The opening of voltage-gated potassium channels, which causes a huge efflux of potassium ions and the inside of the cel to decrease in positivity.
□ Hyperpolarisation.
® The membrane potentials are more negative than the default membrane potential since potassium channels stay open a bit longer than the sodium ones to let ions through.
□ Refractory period.
® There are 2 types of refractory:
◊ Absolute.
◊ Relative.
® The sodium-potassium pump works to re-establish the resting state via active transport.
What is the principle that action potentials operate under?
All-or-nothing.
Do neurons send the same sized action potential? How are they differentiated?
Yes, neurons send the same sized action potential. They are differentiated by the frequency of the signals where the stronger the signal, the higher the frequency.
If the action potential process was passive and automatic, what can be explained?
It would be too clunky to explain our thoughts and behaviour.
