Biology Questions and Answers
Resting potential is the membrane
voltage when the cell is not excited,about –70 mV.
Excitationabout –50 mV, that th threshold is the voltage le initial evel,
depolarization must reach for the action
potential to be attained.
- In chemical terms how is
the neuronal repolarization
achieved?
Repolarization is thmembrane potential from the return of thee action (^)
potential (+35 mV) to the resting
potential (-70 mV).
When the membrane reaches its action
potential voltagclose and voltage-ge-gated sodium chaated potassium nnels
channels open. So sodium stops
entering into the cell anstarts to exit. Therefore thed potassium
repolarization is due to exiting of
potassium cations from the cell.
The repolarization causes the potential
difference tem–70 mV, below the resting pporarily to increase uotential, ander
phenomenon known as
hyperpolarization.
- What is the mechanism by
which the neural impulse is
transmitted along the axon?
The neural imthe neuronal mpulse is transmitted aloembrane through ng
depolarization of consecutive
neighboring regions. Wthe internal surface of the memhen a region inbrane is (^)
depolarized it becomes more positive in
relation to thregion. So positive ele neighboring internalectrical charges (^)
(ions) move towards this more negative
region and voltagchannels are activated ane-gated sodiumd open. The (^)
action potential then linearly propagates
along the membrane until near thepresynaptic region of the axon.
- What is the structure
through which the neural
impulse is transmitted from
one cell to another? What are
its parts?
The structure through which the neural
impulse pis the synapsasses from one cell to ae. The synapse is nother
composed by the presynapticmembrane in the terminal portion of the (^)
axon of the transmitter cell, the
synaptic cleft (the postsynapticor syna membrane in theptic space) and
dendrite of the receptor cell.
- How does synaptic
transmission between neurons
take place?
The propagatioalong the axon reaches thn of the action potentiale region
immediately antmembrane causinerior to thg its permeability toe presynaptic
calcium ions to change and these ions
to enter the cell. Iof the axon there are manyn the presyna ptic area
neurotransmitter-by means of exocytosisrepleted vesicles activated b thaty the (^)
calcium influx release the
neurotransmitters into the synaptic
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