Reference no: EM133546371

Activity 1: Resting Membrane Potential (RMP)

1. What happens to the resting membrane potential (RMP) as the extracellular K+ is increased? Choose one word from each pair: (more/less & negative/positive).

2. What is the value of the RMP in a typical neuron?

3. What generates (and maintains) the gradients for Na+ and K+ in a living cell?

4. Which ion (Na+ or K+) has the largest impact on the RMP? Explain why this is so.

5. If the extracellular fluid (ECF) concentration of K+ was elevated, the membrane potential will become - Choose one word from each pair: (more/less & negative and positive). Explain your reasoning as to why this would occur.

6. If Na+ channels were suddenly opened in a resting neuron what would happen to the membrane potential? Explain your reasoning.

Activity 2: Receptor Potential

1. Neurons have a resting membrane potential based largely on the passive movement of K+ from the ICF to the ECF. What is the name of the channels that permit this movement of K+?

2. What are graded potentials?

3. Where in a neuron are graded potentials observed?

4. What is meant by the term "stimulus modality" with respect to sensory neurons?

5. Which stimulus modality induced the largest (highest amplitude) graded potential in the Pacinian corpuscle?

6. Which stimulus modality induced the largest (highest amplitude) graded potential in the olfactory receptor?

7. The olfactory receptor also contains a membrane protein that recognizes isoamyl acetate and transduces the odor stimulus into a graded potential (isoamyl acetate is a chemical used in air fresheners and perfumes- it has a pear/banana like odor). Do you think it is likely a Pacinian corpuscle would have isoamyl acetate receptors? Why or why not?

8. What kind pf receptor protein would a Pacinian corpuscle have? Explain how it might work (by what mechanism?)

Activity 3: The Action Potential Threshold

1. Define the term "threshold voltage" as it applies to an action potential (AP).

2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?

3. What is the value of the threshold voltage in a typical axon?

4. Did the amplitude (height) of the AP change as the stimulus was increased? Explain why or why not- what is the mechanism?

5. State the "law" that describes this property.

Activity 4: Importance of Voltage- Gated Na+ channels: Effect of drugs on the AP

1. What was the effect of tetrodotoxin (TTX) on the action potential (AP)?

2. How does TTX exert this effect? Describe the mechanism of action of TTX.

3. Where is TTX found in nature? Are there any native California organisms that produce it? If so which?

4. About how much tetrodotoxin would be fatal for a person of your body mass? *tetrodotoxin is a powerful neurotoxin. The LD50 is about 8 milligram per kg (Sigma-Aldrich).

5. What was the effect of Lidocaine on the axon?

6. Describe the mechanism of action lidocaine.

7. Relate the effect described above to Lidocaine's clinical use.