Lecture 3

Question 1

Define “excitable cell” and give examples of excitable cells

Answer 1

• Excitable cells are ones in which an action potential can be induced
  ( neurons, skeletal muscle, cardiac muscle, and smooth muscle cells)

Question 2

Which part of a neuron is capable of developing an action potential

Answer 2

• The axon is covered by the plasma membrane referred to as the axolemma
• The axolemma is characterized by the presence of voltage-gated ion channels and the ability to conduct an action potential

Question 3

Characterize the permeability of cell membranes in the absence of ion channels

Answer 3

• Membrane is a biphospholipid layer permeable only to hydrophobic substances, ions generally prohibited from crossing cell membrane

Question 4

Describe the permeability of cell membranes to ions under normal circumstances when at rest

Answer 4

• More permeable to K+ and Cl- when at rest

- Low permeability towards Na+ and Ca2+ when at rest

Question 5

List and compare the major types of ion channels present on the cell membranes of excitable cells

Answer 5

• Voltage gated channels
  
  • Changes in voltage
• Ligand gated channels
  
  • Binding of specific molecules (ligands) to receptors
• Modality gated channels
  
  • Mechanical deformation (ex. Pressure)

Question 6

Use Nernst equation to calculate membrane potential

Answer 6

EMF = Eion = z(61.5)*log([ion outside]/[ion inside])

- (look at powerpoint slide for example)

Question 7

Describe diffusion potential

Answer 7

• Caused by an ion concentration difference on either side of a membrane
• (Look at powerpoint slide for example)

Question 8

Describe equilibrium potential

Answer 8

• Equilibrium for an ion is determined not only by concentrational forces but also by electrical forces
• (Look at powerpoint slide for example)

Question 9

Describe electrical neutrality principle

Answer 9

• Sum of the concentrations of cations within a compartment must be equal to sum of the concentrations of anions in that compartment
• (Look at powerpoint slide for example)

Question 10

Describe Donnan equilibrium

Answer 10

• Product of permeable ions in outside of compartment must equal product of permeable ions in inside compartment
• (Look at powerpoint slide for example)