Assignment 6

Homeostasis of blood pressure is achieved through ANS control via two mechanisms—regulating heart rate and controlling blood vessel diameter. Neurons from both the sympathetic division and the parasympathetic division of the ANS utilize neurotransmitters to mediate these changes. Recall that neurons of the sympathetic division release epinephrine onto heart cells and smooth muscle cells in the walls of blood vessels, while neurons of the parasympathetic division rely on the neurotransmitter acetylcholine. This assignment is designed to examine the effects of both neurotransmitters on heart rate, blood vessel diameter, and resulting changes in cardiovascular parameters. Working within CardioLab and referring to the detailed instructions on Assignment 6, answer the questions below.


1 .		On the way home from meeting a friend for dinner, your car breaks down in a dark alley in an unfamiliar town at 1:30 a.m. The battery on your cell phone is dead, so you need to walk to the closest pay phone to call for help. As you walk down the alley you can feel the fight-or-flight response of your ANS starting to take effect as your heart rate increases, your temples throb, your pupils dilate, and you start to sweat. Simulate this situation as follows: Click on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds. In the Interventions view, select Epinephrine from the popup menu, then click on the Apply Intervention button once. Go to the Nerve Impulses view and observe what is happening to the activity of each group of neurons. Explain your results below.

2 .		Injections of epinephrine are used to treat certain patients with heart problems. Can you think of a condition or multiple condition(s) when it might be helpful to treat someone with epinephrine?