week 2 lecture

 

Lecture 2: Altering the resting membrane potential: Graded potentials & Action potentials

Friday, April 19

• Pre-Class Slides Download Pre-Class Slides
  
• HandoutDownload Handout
  note that you'll turn the handout in as a group (here is a digitally copy for those of you who also want to work on it on your devices)
• Post-Class Slides  Download Post-Class Slides(annotated with Dr. Y's notes from class)
• Lecture recordingLinks to an external site.

 

Videos from the week or extra videos/resources:

• Electrochemical gradients video from lectureLinks to an external site.
• Resting membrane potential video 
• Note: Dr. Mike gives a slightly different value for the potential driven by the Na/K pump and that's okay, he's just going off a different estimate. It's still pretty small relative to the large potential driven by leaky K pumps.
• Resting membrane potential video 2 (if and only if you like mathy explanations)
• Resting membrane potential text (Khan academy)

 

Guiding Questions:

The resting membrane potential

• From last week: Describe the mechanism of the Na+/K+ pump and explain how it contributes to the resting membrane potential of a cell.
  • What would happen to the resting membrane potential if the Na+/K+ pump was mutated and not working?
• Describe several ways that intracellular fluid (ICF) differs from extracellular fluid (ECF). What ions are higher in the ICF vs ECF?
• Describe what a concentration gradient is and how it leads to diffusion and the establishment of a dynamic equilibrium.
  Can you identify the flow of ions in/out of cells based on concentration gradients?
• Describe the mechanism of Na+ and K+ leak channels. How do they contribute to the resting membrane potential of a cell? How do they contribute to membrane permeability?
• What is the resting membrane potential? What voltage value is it typically for most cells in your body?

 

Altering the resting membrane potential

• If the concentration gradient of K+ decreases across the cell membrane, what happens to the membrane potential?
  • If the cell all the sudden became permeable (think gated membrane channels opening) to K+, what would happen to membrane potential? What about Ca2+? Na+?
• What is hyperpolarization vs depolarization of the membrane potential? What ion channels should be opened to cause either?
  
  

Graded Potentials

• Draw and describe the structure of a neuron.
  • Identify each of the following structures on your drawing and describe their structures: dendrites, dendritic spines, cell body, axon, axon hillock, collateral, axon terminal, synapse, postsynaptic cell

• Where are the sensory receptors located on a neuron? From where on the neuron are neurotransmitters released?

• Where do graded potentials occur?

• What type of stimuli causes a graded potential? How does the strength of the stimulus affect the amplitude of the graded potential?

• As a graded potential travels through the cell body, they lose amplitude. Explain why. ***more on this next week
  

• What is an EPSP? What is an IPSP? What ion channels contribute to each? Are each caused by depolarizations or hyperpolarizations?
  • How does an EPSP contribute to triggering an action potential? What about an IPSP?
    
    

Action Potentials***

• Differentiate between graded potentials and action potentials.
• Where in the neuron do action potentials occur?
  • How does the strength of the stimulus effect the amplitude of the action potential? Why are they all-or-none?
    ***more on this next week
• Explain how ion permeability changes during the rising phase and falling phase of an action potential.

• What is the stimulus for opening EACH of the channels used during an action potential?
• What is the order of stimulus, opening and closing of all of these channels?
• How is the resting membrane potential reestablished after an action potential?
• Hint, we did this for our in-class activity! Can you visualize what’s happening with each of the channels?

• Voltage gated Na+ channels in the axon contain two gates. What are they? How are they triggered?

• What are the absolute and relative refractory periods?

• How does the inactivation gate on the Na+ channel cause the absolute refractory period?

• What causes the relative refractory period?

***I will update after lecture to see how much of APs we get through.