Biology Lecture Notes
FINAL END OF YEAR
2023
(STEMer’s guide)
2024
Lecture (3)
Resting potential – Action potential
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ION PUMP AND ION CHANNELS ESTABLISH THE RESTING POTENTIAL OF A NEURON
As you know, ions are unequally distributed between the interior of cells and the fluid ...
,ION PUMP AND ION CHANNELS ESTABLISH THE RESTING POTENTIAL OF A NEURON
As you know, ions are unequally distributed between the interior of cells and the fluid that
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, surrounds them.
As a result, the inside of a cell is negatively
charged relative to the outside. Because the
attraction of opposite charges across the plasma
membrane is a source of potential energy, this
charge difference, or voltage, is called the
membrane potential.
• The membrane potential of a resting neuron—one that is not sending a signal— is its
resting potential and is typically between 60 and 80 mV (millivolts).
• Inputs from other neurons or specific stimuli cause changes in the neuron’s membrane
potential that act as signals, transmitting and processing information.
• Rapid changes in membrane potential are what enable us to see a flower, read a book, or
climb a tree. Thus, to understand how neurons function, we first need to examine how
chemical and electrical forces form, maintain, and alter membrane potentials.
FORMATION OF THE RESTING POTENTIAL
Potassium ions (K+) and sodium ions (Na+) play an essential role in the formation of the
resting potential. Each type of ion has a concentration gradient across the plasma
membrane of a neuron, (as shown in the table).
• In case of mammalian neurons, the concentration of K+ is highest inside the cell, while the
concentration of Na+ is highest outside.
• These Na+ and K+ gradients are maintained by sodium-potassium pumps in the plasma
membrane. These ion pumps use the energy of ATP hydrolysis to actively transport Na+ out
of the cell and K + into the cell (as shown in the Figure).
• There are also concentration gradients for chloride ions (Cl-) and other anions, but we will
ignore these for the moment.
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