Which of the following is comparable to a negative feedback cycle? opening of voltage-gated Na* channels in response to a depolarizing graded potential O movement of K through leak channels opening of voltage-gated K* channels in response to a depolarizing graded potential operation of the Na*-K ATPase at rest opening of voltage-gated Ca<" channels in response to an action potential arriving at the axon terminal

Place the following events in chronological order from 1-8: Nat enters the cell, and depolarization occurs to approximately +30 mV. The voltage across the cell membrane is -70 mV, the resting membrane potential. Upon reaching the peak of the action potential, the VG Nat channels are inactivated by the closing of their inactivation gate and the activation gate of each VG K channel opens. VG K channels close by the closing of their activation gate, and the resting membrane potential is gradually restored. An excitatory post-synaptic potential depolarizes the membrane to threshold and the activation gate of VG Nat channels open. Upon returning to the resting membrane potential, VG Na channels are reset by opening of the inactivation gate and the closing of the activation gate. VG K+ channels are slow to close, resulting in an excess of K* efflux and hyperpolarization. Depolarization occurs as K+ flows out of the cell.

Inhibitory postsynaptic potentials cause what type of change at the post-synaptic membrane? Hyperpolarization Depolarization Decreased threshold No change

"After an action potential has just passed through the axon hillock, the voltage-gated Na+ channels there won t open for a period of time. However, if the stimulus is strong enough, another action potential can be triggered even during this resting time. This refers to"     refractory resting period     intermediate resting period     relative refractory period     absolute refractory period