Summarize the roles of homeostatic/allostatic/circadian factors, brain regions, flip-flop circuits, and neurotransmitter systems in regulating transitions between sleep and wake.

The homeostatic control of sleep sustains the balance of wake/sleep at an adequate level. Slep can also be monitored by allostatic control that reacts towards the environmental stressors to override homeostatic control when required.  

The circadian factors entrain periods of sleep to specific parts of the dark or light cycle. The slow-wave sleep takes place when the neurons in the vlPOA (ventrolateral peropic area) becomes active. These neurons prevent the neurons systems, which encourage wakefulness. In turn, the vlPOA is restricted by this similar wakefulness promoting regions, therefore, flip-flop circuit either keeps us asleep or awake.  

The gathering of adenosine encourages sleep by stimulating and preventing the sleep-promoting neurons of the vlPOA. The function of the orexinergic neurons of the lateral hypothalamus maintains the flip-flop, which monitors the waking and sleep state in the waking state.  

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.