Both the sympathetic and the parasympathetic nervous systems are essential for homeostasis and for survival. For example, when we are trying to run away from a threat, the sympathetic nervous system is in full effect to allow us to escape from danger. However, when there is no obvious threat, the parasympathetic nervous system tends to be more in control.

There are similarities and differences between the sympathetic and the parasympathetic nervous systems. In preganglionic nerve fibers, both the sympathetic and the parasympathetic nervous system utilize the neurotransmitter acetylcholine. Closer to the target organ, the parasympathetic nervous system remains dependent on acetylcholine whereas norepinephrine and epinephrine are the predominant neurotransmitters utilized by the sympathetic nervous system.

When norepinephrine and epinephrine bind to their receptors, different effects are carried out based on the type of receptor, affinity, and location of the receptor. For example, epinephrine has a higher affinity for the beta-2 receptor. When epinephrine binds to the beta-2 receptor, common effects include vasodilation and bronchodilation. Norepinephrine has a stronger affinity for the alpha-1, alpha-2 and beta-1 receptors. When norepinephrine binds to its receptor, common effects on the body include vasoconstriction (alpha-1), increased heart rate (beta-1) and uterine contraction (alpha-1).

When a patient has a severe allergic reaction, a common prescribed drug is epinephrine. Which of the follow best explains the effects of epinephrine on a patient experiencing a severe allergic reaction?

Whales are active at great, underwater depths for extended periods of time. Which of the following would LEAST contribute to such an ability?

Which of the following is a physiological consequence of breathing air with a slightly increased partial pressure of carbon dioxide?

Where in the brain is respiration rate regulated?

Give the equation for total lung capacity.

The carbonic anhydrase reaction is shown below.

Which of the following outcomes seems the most reasonable for someone who has an increase in blood CO2 levels during exercise?