A positive feedback loop occurs when the outcome of an event causes the event to continue occurring and amplifies its effects. Which of the following aspects of an action potential constitutes a positive feedback loop?Multiple ChoiceThe sodium-potassium pump exactly balances ion leaks by pumping three sodium and two potassium ions across the membrane.An initial flow of sodium ions into the neuron causes the opening of more voltage-gated sodium channels, rapidly causing more sodium to enter.The threshold potential is around -55mV.Opening of voltage-gated sodium channels causes voltage-gated potassium channels to open and release potassium to the extracellular environment, slowly counteracting sodium influx.

Which of the following is the best example of a positive feedback loop?Group of answer choicesTemperature regulationBlood clots following an injuryBlood glucose regulationpH regulationAll of these are examples of positive feedback

Complete the following true statement. Negative feedback loops ______ the initiating stimulus and positive feedback loops _____ the initiating stimulus.

When Is an Action Potential Triggered?When is an action potential triggered?Multiple ChoiceWhen EPSPs exceeds IPSPsWhen potassium channels openWhen IPSPs exceeds EPSPsWhen chloride channels open

The upstroke of the action potential (ie: its rising phase) is largely due to voltage activated Na channels opening, which cause depolarisation, which open more voltage activated Na channels, causing more depolarisation etc (ie: “positive feedback”). Which of the following mechanisms contributes to terminating the upstroke?  Na channels inactivate when depolarised for more than a few hundred µs   the sodium ion concentration inside the cell becomes too high to allow any more sodium ions to enter   activation of voltage-dependent chloride channels   opening of voltage dependent calcium channels   voltage-activated Na channels are only opened between threshold potential and 0mV – above this they are inhibited

An example of a positive feedback loop is:Group of answer choices Formation of a blood clotShivering due to muscle contraction in case of cold temperatureIncrease breathing after exercise to bring the blood oxygen level back up to normal.Maintenance of body temperature by sweating in hot summer.