Physiology Exam I Essay Questions.Answers

Physiology Exam I Essay Questions.Answers - Physiology Exam...

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Physiology Exam I Essay Questions Exam I will include two essay questions (#9 plus one other bold-faced question). The other questions will not be given as an essay but more than likely will be part of the matching, multiple choice and/or short answer. If you have good answers for these question, I’d expect that you will do well on the exam Monday 9/24. 1. Describe in detail the initiation and propagation of an action potential include the following terms all-or- none, voltage gated channels, depolarization, hyperpolarization, dendrites, cell body, axon, graded response, and Na + /K + pump. Depolarization of an axon affects Na+ and K+ diffusion in sequence. First, the Na+ gates open and Na+ diffuses into the cell. After a brief period, K+ voltage gated channels open and K+ diffuses out of the cell. An inward diffusion of Na+ causes further depolarization, which in turn causes further opening of Na+ gates in a positive feedback fashion and Na+ pumps pump Na+ in. The opening of K+ voltage-gated channels and outward diffusion of K+ makes the inside of the cell more negative, and thus a negative feedback effect on the initial depolarization. These changes in Na+ and K+ diffusion and the resulting changes in the cell membrane potential they produce constitute an event called the action potential. As the Na+ channels are becoming inactivated, the gated K+ channels open and the membrane potential moves toward the K+ equilibrium as the K+ pumps pump K+ out of the cell. This outward diffusion of K+ hyperpolarizes the cell membrane. Depolarization of a cell body or dendrite is excitatory, whereas hyperpolarization is inhibitory, in terms of their effects on nerve impulses. Then, the resting membrane potential is reestablished. The Na+/K+ pumps are constantly working in the plasma membrane. They pump out the Na+ that entered the axon during an action potential and pump in the K+ that had left. The all-or-none law of action potentials states that there is a single, quick shock delivered to an axon that can serve as a depolarizing stimulus. If the stimulus is below threshold, no action potential is produced by the axon. Once the stimulus has reached threshold, a full action potential is produced. Any greater stimulus does not produce greater action potentials. Thus, it is not a graded response; they are all-or-none. 2 . Compare and contrast the three types of neurons. Sensory, or afferent, neurons conduct impulses from sensory receptors into the CNS. Motor, or efferent, neurons conduct impulses out of the CNS to effector organs (glands and muscles). Association neurons, or interneurons, are located entirely within the CNS and serve the associative, or integrative, functions of the nervous system. 3. How do supporting cells in the central and peripheral nervous systems differ?
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