ASU BIO 181 EXAM 3 | Actual Exam | Already Verified Answers | Graded A+

Explain how insulin and glucagon regulate the balance (i.e, homeostasis) between glycogen and glucose when epinephrine (i.e., adrenalin) is not involved. -----CORRECT ANSWER-------Glucagon and Insulin work in a negative feedback loop together to keep your blood sugar in a normal range (in a healthy person). Insulin works when your pancreas detects when you have high levels of glucose in your blood stream. Insulin binds to the cells, and some use glucose as energy, and others, like your liver store it as glycogen. Glucagon is the opposite of insulin. After you haven't eaten in a while, your blood glucose levels lower and glucagon signals the cells that have the stored glycogen (liver and muscle cells) to then turn it back into glucose for the other cells to use for energy. How do the glial cells (i.e., myelin sheath) speed up the firing of neurons? ----- CORRECT ANSWER-------The cell wraps extensions of a fatty insulating substance (myelin) around the axons of neurons which increase the speed because the action potential jumps from each node of ranvier rather than going down the entire length and firing each Na+K+ pump. Briefly explain why the action potential flows only from the axon hillock to the terminal web. -----CORRECT ANSWER-------The action potential originates from the axon hillock which initiates the flow of the action potential because of the presence of higher density voltage-gated ion channels. List the 4 types of glial cells and list a phrase to describe their function. -----CORRECT ANSWER-------- Microglia: Are part of the cellular immune system to protect the brain since the humoral immune system usually cannot cross the BB barrier. - Astrocytes: Contribute to the blood brain barrier - Schwann Cells: myelinates axons of the neurons in the PNS - Oligodendrocytes: Myelinates axons of the neurons of the CNS T/F Excitatory synapses cause hyperpolarization of post-synaptic cells. -----CORRECT ANSWER-------False The resting potential of neurons is: -----CORRECT ANSWER--------60 mv (The answer is not on this list.)