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Lecture 2

Biological Sciences
Course Code
Catherine Nash

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Mammalian Physiology BIOB30 Lecture 2
Typical concentration of ions in intracellular (IC) and extracellular solutions (EC)
-cell comprises of salt
-higher sodium concentration in the extracellular solution
-higher potassium concentration in the intracellular solution
-such difference creates a concentration or chemical gradient between the inner and outer
-IC and EC are separated by plasma membrane
-plasma membrane is impermeable, only water and non-polar molecules can diffuse easily into
the membrane
-glucose has a slow rate of diffusion
-polar molecules cannot pass through due to the impermeable membrane
Na/ K ATPase pump
-electrogenic pump, electro refers to the positive charge and geneic refers to the net movement of
3 sodium ions vs. 2 potassium ions
-3 sodium ions are transported out of the cell and 2 potassium ions are transported into cell
-the cell is negatively charged
-greater sodium concentration outside of the cell and a greater potassium concentration inside the
without energy, ions flow from high to low concentration, the sodium ions should flow inside
the cell and potassium ions should flow outside
-but, 3 sodium ions are transported outside and 2 potassium ions are transported inside
against the concentration gradient
energy is required to undergo active transport
ATP is used and it is hydrolyzed into ADP
-recording electrode is placed inside the cell and reference electrode is placed outside the cell in
the solution
-difference between them is calculated by voltmeter, similar to a battery
-difference creates an electrical gradient, known as the potential difference
-such difference generates energy that flows from one compartment to another
Resting Membrane Potential
-what makes muscle and nerve cells different from other cells is they are excitable
-all cells have negative charge at rest
-average value of resting membrane potential is -70mV
-red blood cell has -9mV and spinal cord has -100mV
Ion channel
-voltage gated means the channel opens and closes in response to change in voltage of potential
difference between the inside and outside environment
-sodium ion channel is closed at rest so there is no net sodium ion movement
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