Check Your Understanding - Membrane Potentials

Question 1

Describe what is meant by the term: potential difference. What dictates the potential difference between the intracellular and extracellular environment?

Answer 1

refers to the difference in electrical charge (voltage) between the intracellular and extracellular environments of a cell. This potential difference is dictated by the distribution of ions (charged particles) across the cell membrane, particularly sodium (Na+), potassium (K+), chloride (Cl-), and negatively charged proteins. The selective permeability of the cell membrane to these ions, along with the activity of ion channels and pumps, establishes and maintains the resting membrane potential, which typically ranges from -40 to -90 millivolts (mV) in most cells.

Question 2

What is the average resting membrane potential of a neuron?

Answer 2

-70mV

Question 3

Differentiate between the following ion channels: leak, voltage-gated, chemically-gated, mechanically- gated

Answer 3

1. Leak channels: Ion channels that permit the passive movement of ions across the membrane in a non-selective manner, contributing to the resting membrane potential.
2. Voltage-gated channels: Ion channels that open or close in response to changes in membrane potential, allowing ions to move across the membrane in response to electrical signals.
3. Chemically-gated channels: Ion channels that open or close in response to the binding of specific neurotransmitter molecules, regulating ion flow and neuronal excitability.
4. Mechanically-gated channels: Ion channels that open or close in response to physical deformation of the cell membrane, such as pressure or stretching, allowing ions to enter or exit the cell.

Question 4

How is the concentration gradient between the intra- and extracellular environment established?

Question 5

Describe the neuronal membrane permeability to K+ and Na+ under resting conditions

Question 6

Define the following terms (regarding membrane potentials): depolarize, repolarize, polarized, hyperpolarized

Question 7

The membrane potential has been altered by over 90mV. Is this a graded potential or an action potential?

Question 8

Which voltage-gated ions channels are first to open during the initiation of an action potential?
What effect does this have on the membrane permeability and membrane potential?

Question 9

Describe how increasing the threshold stimulus strength affects the strength of the action potential.

Question 10

What is the “refractory period?” What role does this have in the direction of flow of the action potential?

Question 11

Describe how the propagation of action potentials differs between myelinated and unmyelinated fibres.