2. Voltage gated Na+ channels have three state: open, closed and inactivated. Observe the following diagram of a neuron. The place marked with a "X" is where an action potential has just occurred. The circle marks where an action potential is about to occur. а. At each arrow in the diagram, A, B & C, indicate whether voltage gated Na+ channels are open, closed or inactivated. C B A

Under what conditions could the opening of a chloride channel actually depolarize a neuron rather than hyperpolarize it? i. The neuron is resting at -75 mV ii. The extracellular chloride concentration is lower than the intracellular chloride concentration iii. The neuron is close to its threshold of -55 mV O a. i only O b. ii only O c. i and ii only O d. ii and iii only O e. i, ii, and i O f. None of these

9. You are performing an experiment at with an artificial membrane (i.e not a living cell). You place a NaCl solution on each side of the membrane. You discover that if you place a 10-fold NaCl concentration gradient across this membrane (higher NaCl concentration outside than inside) you initially see a +20 mV membrane potential develop. If the Cl permeability is assigned a value of 1, what value would you assign to the Na" permeability? Assume 2.3RT/F = 60 mV.

Membrane Potential (mV) The Action Potential 1. Label the significant membrane potentials and phases of the action potential in a neuron. Indicate which gates are open/closed as well as the direction of the net movement of sodium and potassium ions across the cell membrane for A-G. +30- 0 -55-B -70- -80- 0 H [T E 2 F 3 Time (ms) G 4 5

9. All of the followings are incorrect about the Graded Potential, except ------------------------- A. It spreads Electrotonically B. It is amplified by distance C. It is inversely proportional to the duration and magnitude of stimulus D. It is regenerative E. it is generated at the axon hillock

20. Explain how a chemical synapse works when a nerve meets the muscle fiber. address the following concepts -the name of the specific new transmitter, how the neurotransmitter is released from the presynaptic cell into the synapse ,the action of the new transmitter on the receptor on the postsynaptic cell ,and how the levels of neurotransmitters are regulated. be specific and detailed in your response

7. Draw a standard action potential compared to an action potential whose voltage gated potassium channels have been inactivated with tetraethylammonium (TEA). a. Draw the curves. Label all axes. b. Describe how and why they are different.

Match the description with the statement that best describes the following regions                                                             synaptic knob                                                             axon hillock                                                             dendrites                                                             axon A. elongated projection that conducts electrical signals over long distances B. receives input from other neurons C. region of high denisty of voltage-gated channels, known as the trigger zone D. contains numerous vesicles containing neurotransmitter