Biology Questions and Answers

Biology Questions and Answers

The two main ions that participate in the

electricalneurons ar impulse transmission ine the sodium cation (Na+) (^)
and the potassium cation (K+).

41. Which is the normal sign
    of the electric charge between
    the two sides of the neuron
    plasma membrane? What is
    the potential difference
    (voltage) generated between
    these two sides? What is that
    voltage called?

As in most cells the region just outsidethe surface of the neuron plasma
membrane presents a positive electricalcharge in relation to the region just
inside that thus is negative.
The normal (at rest) potential difference
across the neuron membrane is a70 mV (millivolts). This voltage is callebout –d
the resting potential of the neuron.

42. How do the sodium and
    potassium ions maintain the
    resting potential of the
    neuron?

The plasma memwhen at rest maintains an brane of the neuronelectric
potential difference between its externaland internal surfaces. This voltage is
called resting potential. The resting
potential about –70 the interior is more negative mV indicatesthan the that
exterior (negative polarization). This
condition is maintainsodium and potassiumed by trans ions acrossport of the
plasma membrane.

The membrane is permeable to

potassiumAt rest the positive potassium ions e ions but not to sodium ions.xit (^)
the cell in favor of the concentration
gradient since withipotassium concentration n the cell theis higher than (^)
in the extracellular space. The positive
sodium iocell. As positive potassium ions ens cannot however go into thexit the
cell with not enough compensation of
positive ions entering the cell, theintracellular space becomes more
negative and the cell stays polarized.

43. How is the depolarization
    of the neuronal plasma
    membrane generated? How
    does the cell return to its
    original rest?
    When the neuron receives a the binding of neurotransmittersstimulus to by
    specific receptors sodium and the permeability of the plasmachannels op en
    membrane in the postsynaptic region is

altered. Sodium cell causing lowering (less neions then go into thgative) eof (^)
the membrane potential. If this
reduction of reaches a level callethe membrane potentiald the excitation
threshold, or threshold potential, about
–50 mV, thgenerated, i.e., e action potthe depolarizationential is (^)
intensifies until reaching its maximum
level antransmitted alod the depolarization currng the remaining lengthent is (^)
of the neuronal membrane.
If the excitation threshold is reached
voltage-dependent sodium the membrane open allowinchannels ing more
sodium ions to enter the cell in favor of
the concentration gapproximate –35 mV lradient and anevel of positive (^)
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