Embryology Biology 441 Spring 2010 Albert Harris
Second Lecture: Wednesday, Jan 13, 2010
Positive outside, because positive potassium ions are more concentrated inside, and therefore diffuse outward through the membrane, carrying positive charges, and creating the positive-outside (=negative inside) resting potential. One way to depolarize a nerve, muscle or oocyte is to put a concentrated solution of potassium ions outside. When potassium ions are very concentrated outside, as well as inside, Then there is no longer a diffusion gradient of potassium, And no tendency to diffuse either outward, or inward. High concentrations of potassium ions outside cells stimulate all muscles to contract (constantly), including heart muscle, and stimulate all nerves nerves to depolarize, repeatedly, and briefly. Injection of large amounts of potassium chloride, to stop the heart, Has been the method of capital punishment in North Carolina! (Preceded by anesthesia, so the person is not supposed to feel anything) There has been discussion on the news whether the person would feel much pain if the general anesthetic failed to work, or its effect decreased.
Oocytes normally depolarize in response to sperm entry. ------------------------------------------------------------------------------------ Acrosome in sperm: enzymes to digest path through "jelly" around oocyte.
Cortical granules in oocyte: (20,000 or more per oocyte)
1) Enzymes to digest egg-sperm adhesion proteins. Sea urchins have all 4 of these Vertebrates have only #1. (and the voltage depolarization) "The fast block" "The slow block" enzymes and fertilization membrane. In mammals, the slow block is called the Zona Reaction. And the vitelline membrane of mammals is called the Zona Pellucida. (Not because itŐs different, but because different researchers worked on mammal embryos)
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