1. Lab3: Neurophysiology

2. Resting Membrane Potential
K+ Channel is LEAKY
K+ leaks out of cell by diffusion
Inside of cell becomes MORE NEGATIVE (-)
ECF
Membrane Permeability to K+
is major determinant of
RESTING POTENTIAL
ICF
Concentrations

3. Action Potential
Rapid reversal of membrane charge (+) and then return to resting charge (-)
Threshold Stimulus to depolarize membrane
Volatage-Gate Na+ Channels OPEN and Na+ moves into Cell- Depolarization
Na+ channels CLOSE
Voltage-gated K+ Chanels OPEN – Repolarization
K+ channels slowly close and Na+-K+ ATPase Pump resets [Na+] and [K+] to resting potential

4. 2) Voltage-gated Na+ Channels OPEN - DEPOLARIZE

5. 3 and 4: V-gated Na+ channels CLOSE and K+ channels open

6. 5) K channels close and Na-K ATPase PUMP resets concentration gradients to RESTING
K+ Ion Channel (CLOSED, but leaky)
Na+ Ion Channel (CLOSED) 3
Na+
Na+
Na-K ATPase K+ K+ 2

7. Myelin Sheaths Increase Speed of Signal Propagation down a Neuron
Figure Overview

8. QOD
A 23-year old patient is admitted to the hospital with numbness and tingling in the entire body and muscular weakness. Shortly after being admitted the patient loses the ability to move his arms and legs and cannot feel any sensations (touch, temperature, pain). After another two hours the patient loses his ability to breathe (from diaphragmatic paralysis) and must be put on an artificial ventilator. The nurse takes the patients’ history from his girlfriend, who says that they ate sushi for dinner that evening at a high-end sushi bar, and that her boyfriend ordered fugu.
What is fugu? Why is the patient paralyzed (Hint, look back at the simulations in Neurosim)? What function do Na+ channels serve in signal transduction through biological membranes? Why would blocking Na+ channels inhibit muscular contraction? In addition to losing the ability to contract muscles will the patient experience any loss of consciousness or perception of their surroundings?
Other organisms that carry similar toxins: blue-ringed octopus, harlequin frog, newts, salamanders, some crabs and snails!