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PSU BIOL 240W - Exam 4 Study Guide

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Exam # 4 Study Guide Lectures: 27-32Lecture 27 (April 3)Female Reproductive EndocrinologyWhat are the types of hormones and their effects in the regulation of female reproduction? What occurs during ovulation? Menstruation?The ovarian cycle begins with the release of GnRH (gonadotropin-releasing hormone) secretion from the hypothalamus. The target for GnRH is the anterior pituitary, and this stimulates the production of FSH and LH. This begins the follicular phase. During this time, FSH stimulates follicular growth, and follicle cells release a small amount of estrogen (estradiol). This lowest level of estradiol production causes the production of FSH and LH, but inhibits the release of FSH and LH. The follicle continues to grow and secrete a medium amount of estrogen. These normal levels trigger the release of the produced hormones. The surge of LH triggers ovulation (one day after surge) with the rupture of the follicle and adjacent ovary wall. The luteal phase begins (first two weeks of follicular phase), and this is marked by the transformation of the ruptured follicle into a structure named the corpus luteum. The corpus luteum secretes estrogen and progesterone. While these hormones are released, their rising levels produce negative feedback on the hypothalamus and pituitary, which in turn inhibits secretion of LH and FSH. Thus, another egg is prevented from maturing. The corpus luteum begins to disintegrate (apoptosis; occurs ten days after ovulation) without LH levels to maintain it. Since the corpus luteum is disintegrated, estrogen and progesterone are no longer produced. A drop of these hormones no longer inhibits the hypothalamus and pituitary release of FSH. Therefore, FSH production/secretion then stimulates the growth of new follicles and the start of another ovarian cycle begins.The ovarian cycle involves changes in the ovaries. The menstrual cycle involves changes in the uterus (and hormones secreted by the uterus). Estrogen secreted by the growing follicle causes the endometrium (inner lining of the uterus) to thicken. This is called the proliferative phase (correlates with the follicular phase of the ovarian cycle). The endometrium continues to thicken because of the estradiol and progesterone released from the corpus luteum of the ovarian cycle. During the luteal phase of the ovarian cycle, the secretory phase of the menstrualcycle occurs. A rapid drop in ovarian hormones occurs because of the disintegration of the corpus lutuem. This causes a reduction in the blood supply to the endometrium and the menstrual flow phase occurs. The secretory phase is progesterone controlled.BIOL 240W 1st EditionFollicular phaseOvl’nLuteal phaseLecture 28 (April 10)DevelopmentWhat happens during conception?Fertilization/conception occurs in the oviduct. The zygote divides 24 hours later. A ball of cells produced by cleavage is present by the time the embryo reaches the uterus. Morula, orball of cells, is produced after 3 days. A hollow sphere of cells, or blastocyst, forms after 6 days. This produces human chorionic gonadotropin (hCG), which maintains the corpus luteum’s secretion of progesterone and estrogens. The blastocyst implants in the endometrium 7 days after fertilization. During days 7-12, the outer later of the blastocyst (trophoblast) grows and dissolves away layers of the endometrium, which are reformed. Thetrophoblast, epiblast (give rise to embryo), and endometrial cells form the placenta (interesting---organ made from mother and baby). The inner cell mass flattens and forms disk (epiblast and hypoblast). The hypoblast cells give rise to tissues that support embryo. Gastrulation results in a disk made of 3 layers of embryonic cells (ectoderm, mesoderm, andendoderm). Folding and moving of cells occurs epiblast cells move in and push out endoderm cellsLecture 29-31 (April 10-15)The Nervous SystemWhat are Neurons? What are the characteristics of the nervous system?Neurons are nerve cells that generate and carry electric impulses call action potentials. Membranes do not touch, but connections still exist with other neurons called synapse (not a physical connection) Neurons create large, complex circuits to make up the nervous system. The brain has over 500 trillion connections/synapses between neurons in the brain. A pre-synaptic neuron communicates with post-synaptic neuron by releasing a neurotransmitter into the synapseA voltage, also called potential is a separation of charge. Greater potential means that there is a greater separation of charge. A current is the flow or movement of charged particles. Resistance measures the ability of charged particles to flow. All of these terms apply to cell membranes. Charges exist inside and outside the cell, separated by a membrane. When all ions are at equilibrium, the cell is at its resting membrane potential. Differences of sodium and potassium concentrations inside and outside the cell create a gradient. This graidient facilitates a flow of ions inside/outside the cell down a concentration gradient (diffusion; does not require ATP) through ion channels.Example: if more sodium exists outside the cell and the protein channel opens, sodium will enter the cell, causing the inside of the cell to become more positive. This results in depolarization, because the charges become less separated (loss of voltage). Depolarization is the process of bringing the charge/potential closer to 0. Repolarization is increasing the separation of charge/voltage. If the potassium channel opens, potassium will diffuse down its concentration gradient outside of the cell. However, more potassium ions leaving the cell cause the cell to become more negative, increasing the separation of charge. The cell is more polar than before. This is called hyperpolarization. The process of going back to resting membrane voltage after hyperpolarization is still repolarization. Closing protein channels so the ions cannot flow creates resistance.**sodium ions moving into the cell cause depolarization.**potassium ions moving out of the cell cause hyperpolarization. Neurotransmitters are ligands because they bind to membrane proteins. Ligand-gated sodium channels exist on postsynaptic neurons. Gated means that these channels can open and close. Ligand-gated channels means that the presence of a bound ligand determines whether the channel is opened or closed. When a neurotransmitter (ligand) binds to the ligand gated Na+ channel on the postsynaptic


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PSU BIOL 240W - Exam 4 Study Guide

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