Biology Questions and Answers
polarization of the membrane is
achieved. The voltagsodium channels then close ane-dependentd more (^)
voltage-dependent potassium channels
open. Potassiumin favor of the concentration ions then exit the cellgradient
and the potential difference of the
membrane decreases, a process calledrepolarization.
The action potential triggers the electrical phenomenon in neighboringsame
regions of the plasma membrane and
the impulse is thdendrites to the terminal reus transmittedgion of the from the
axon.
- What is the excitation
threshold of a neuron? How
does this threshold relate to
the “all-or-nothing” rule of the
neural transmission?
The excitationthe depolarization lev threshold of a neuron isel that must be
caused by a stimulus to bas a neural impulse. This vale transmittedue is about (^)
–50 mV.
The transmissionalong the neuronal membrane obeys an of the neural impulse (^)
all-or-nmaximum othing rule: or it happens withintensity or nothing happens. (^)
Always and only when the excitation
threshold is reached the depolarizationcontinues and the membrane reaches
its maximum possible positive
polarization, aexcitation threshold is not reachedbout +35 mV. If the (^)
nothing happens.
- How does the
depolarization of the neuronal
membrane start?
The primary causdepolarization is the of the neuronale binding of
neurotransmitterssynapse (by the axon released in theof the neuron that (^)
sent the signal) to specific receptors in
the membrane of the neuron that isreceiving the stimulus. The binding of (^)
neurotransmitters to those receptors is
a reversible pmembrane permeability of henomenon that alters ththe region e
since the binding causes sodichannels to open. When positive sodium (^) um
ions enter the cell in favor of their
concentration gvoltage increases, thus lesseninradient, the memg thebrane
negative polarization. If this
depolarization rthreshold (about –50 eaches thmV) thee excitation
depolarization continues, the action
potential is reactransmitted along the cell membrane.hed and the impulse is
- How different are the
concepts of action potential,
resting potential and
excitation threshold
concerning neurons?
Action potential is the maximum
positive voltage neuron in the process of neuronallevel achieved by the
activation, around + 35 mV. The action
potential triggers ththe neighboring regions oe depolarization of the plasmaf
membrane and thus ththe impulse along the neuron.e propagation of
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