1) In the space below, explain in detail how insulin and glucagon regulate blood
ID: 3483660 • Letter: 1
Question
1)
In the space below, explain in detail how insulin and glucagon regulate blood glucose during an 8 hour fast and after eating a high carbohydrate meal. Next discuss the similarities and differences between type I vs. type II diabetes. Lastly compare the physiological consequences of "insulin shock" vs. a type I diabetic who has forgotten to take their insulin for several days.
2)
In the space below draw how the blood concentrations of LH, FSH, estradiol, and progesterone respond during a typical 28-day ovarian cycle. Next, explain in detail the 3 phases of the ovarian cycle and how they influence the 3 phases of the uterine cycle. Lastly, explain how birth control pills work to prevent pregnancy.
Explanation / Answer
1.) Insulin and glucagon are secreted from islet cells within the pancreas, and thus are referred to as pancreatic endocrine hormones.The stimulus for insulin secretion is a HIGH blood glucose. Although there is always a low level of insulin secreted by the pancreas, the amount secreted into the blood increases as the blood glucose rises, during the conditions like after high carbohydrate meal. Similarly, blood glucose falls during fasting and hence the amount of insulin secreted by the pancreatic islets goes down.
Insulin causes the liver to convert more glucose into glycogen by a process called glycogenesis. The insulin makes the muscle and fat tissue cells to absorb glucose from the blood through the GLUT4 transporter, thus decreasing blood sugar. When insulin binds to the receptors on the cell surface, vesicles containing the GLUT4 transporters come to the plasma membrane and fuse together by the process of endocytosis, thus enabling a facilitated diffusion of glucose into the cell.
Glucagon is secreted by the alpha cells of the pancreatic islets similar to insulin.If the blood glucose level falls during conditions like fasting , the glucagon effects on liver cells to increase blood glucose levels. They convert glycogen into glucose by a process called glycogenolysis. The glucose is released into the bloodstream, increasing blood sugar. Hypoglycemia, the state of having low blood sugar, is treated by restoring the blood glucose level to normal by eating high carbohydrate foods or administration of dextrose.
Diabetes is caused either when the pancreas don't produce enough insulin or when the body cells don't respond properly to insulin .
Insulin Shock
Too high level of insulin in blood can lead to too little blood glucose. If blood sugar falls too low, the body no longer has enough energy for its regular functions. In insulin shock, the body becomes so starved for energy and starts shutting down.
The hormonal process a woman’s body goes through each month to prepare for a possible pregnancy is known as Menstrual Cycle. Each cycle can be divided into three phases based on events in the ovary known as ovarian cycle or in the uterus known as uterine cycle.The ovarian cycle consists of the follicular phase, ovulation, and luteal phase whereas the uterine cycle is divided into menstruation, proliferative phase, and secretory phase.
Ovarian Cycle : Day 1-5
a. Follicle-stimulating hormone (FSH) a gonadotropin synthesized and secreted by the gonadotropic cells of the anterior pituitary gland, produces more estrogen to prepare the uterus for pregnancy. FSH and luteinizing hormone (LH) work together during this phase.
b. The rise in FSH levels recruits five to seven tertiary-stage ovarian follicles also known as a Graafian follicle or antral follicle, for entry into the menstrual cycle.
c. When the implantation fails, the inner lining of soft tissue (endometrium) sheds in the uterus causing the menstruation.
Day 6-13
a. Luteinizing hormone (LH) produced by gonadotropic cells in the anterior pituitary gland triggers ovulation.
b. The uterus develops a new endometrial layer. LH rise in level triggers ovulation, thereby releasing the egg from the follicle and initiate the conversion of the residual follicle into a corpus luteum that, in turn, produces progesterone to prepare the endometrium for a possible implantation.
c. High estrogen levels initiate the formation of a new layer of endometrium in the uterus
Day 14
a. Ovulation is the rupture of follicles which release the secondary oocyte ovarian cells, the ovum.
In simple terms, Ovulations is the release of an ovum (egg) from the ovaries.
b. LH release matures the egg and weakens the wall of the follicle in the ovary, causing the fully developed follicle to release its secondary oocyte.The secondary oocyte promptly matures into an ootid and then matures into an ovum.
c. The oocyte remains viable for 24 hrs.
d. Approximately, it takes 5-6 days for the fertilised egg to get implanted.
Day 15-28
1. The remnants of the follicle after ovulation is referred to as the Corpus Luteum
2. The corpus luteum continues to produce progesterone and secrete the hormone human chorionic gonadotropin. This maximises the chance of implantation into the endometrium; it reaches a maximum size at ~10 weeks and finally resolves at around 16-20 weeks .
3. Progesterone & Relaxin are produced
4. The corpus luteum stops secreting progesterone and degenerates into a mass of fibrous scar tissue known as corpus albicans. The uterine lining (endometrium) is expelled .
Birth Control
a. Ovulation: hormonal contraceptives work by disrupting the menstrual cycle.
Ethinylestradiol/etonogestrel popularly known as NuvaRing is a contraceptive vaginal ring containing the estrogen ethinylestradiol and the progestin etonogestrel can be used.
b. Transport of Sperm : A surgical procedure known as the Vasectomy, where the male vas deferens are severed and then tied or sealed to prevent sperm from entering into the urethra and thereby prevent fertilization.
c. Transport of Egg: A surgical procedure known as Tubectomy, in which a woman's fallopian tubes are clamped and blocked or severed and sealed, either of which prevents eggs from reaching the uterus for implantation.
d. A small, often T-shaped birth control device made of copper known intrauterine contraceptive device(IUCD or ICD) is inserted into a woman's uterus to prevent pregnancy. IUDs are one form of long-acting reversible birth control also an emergency contraception within five days of unprotected intercourse.
e. Barrier methods are the usage protective contraceptions during intercourse, preventing the sperm from reaching the egg.This includes the diaphragm, cervical cap, male condom, and female condom and spermicidal foams etc.
f. Abortifacient , also known as abortion pills, is a substance that induces abortion, eg.Mifepristone.
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