Medicine Questions

Follicle stimulating hormone (FSH) is secreted from the anterior pituitary and stimulates growth of ovarian follicles. The dominant follicle produces estrogen, which inhibits FSH secretion (negative feedback) to prevent other follicles growing. Estrogen acts on the uterus to stimulate the thickening of the endometrial layer

If fertilisation occurs, the developing embryo will implant in the endometrium and release hormones to sustain the corpus luteum. If fertilisation doesn't occur, the corpus luteum eventually degenerates (forming a corpus albicans after ~ 2 weeks). When the corpus luteum degenerates, estrogen and progesteron levels drop and the endometrium can no longer be maintained. The endometrial layer is sloughed away and eliminated from the body as menstrual blood (i.e. a woman's period). As estrogen and progesterone levels are too now low to inhibit the anterior pituitary, the cycle can now begin again

LH is produced by pituitary (stimulus) promotes the formation of the corpus luteum. The corpus luteum then produces progesterone (response). The progesterone Inhibits LH secretion

In vitro fertilization (IVF) is a procedure for couples with fertility problems to have children. During the first half of the cycle, drugs are given to inhibit FSH and LH secretion. This suspends the menstrual cycle. High doses of FSH are given for about 12 days. This is to stimulate ovaries to develop multiple follicles. This is called superovulation. When the follicles are fully developed, HCG is given to stimulate the follicles to mature. Mature eggs are collected a day and a half later. Eggs and sperm are mixed in a culture dish and placed in an incubator for 2 days. Prior to implantation, the female is given progesterone to thicken the lining of the uterus. One to three embryos are implanted into the uterus. The remaining embryos can be frozen.

Promotes the release of an egg during ovulationand the formation of the corpus luteum.

This experiment was conducted using mice that were either obese due to a leptin gene mutation or a defective leptin receptor. When the obese mouse with no leptin was parabiotically fused to a healthy mouse: Leptin in the blood of the healthy mouse was transferred to the obese mouse. The obese mouse responded to the leptin and began to lose weight, demonstrating the potential viability of leptin treatment. However, when the obese mouse with a defective leptin receptor was parabiotically fused to a healthy mouse: Leptin was transferred to the healthy mouse (the obese mouse overproduced leptin to compensate for low receptor sensitivity). The obese mouse remained obese as its body could not respond to leptin. The healthy mouse became emaciated due to the abnormally high levels of leptin transferred into its bloodstream

FSH and LH are produced by the pituitary gland; estrogen and progestin are produced by the ovary; FSH stimulates the ovary to promote development of a follicle; The developing follicles secrete estrogen, which inhibits FSH (negative feedback); Estrogen stimulates growth of endometrium; Estrogen stimulates LH secretion (positive feedback); LH stimulates follicle growth and triggers ovulation;(the secondary oocyte leaves the ovary and) follicle becomes corpus luteum; The corpus luteum secretes estrogen and progesterone; Estrogen and progesterone maintain the endometrium; Estrogen and progesterone inhibit LH and FSH (negative feedback); After (two weeks) the corpus luteum degenerates progesterone and estrogen levels fall; This triggers menstrual bleeding, the loss of endometrium; The pituitary gland secreted FSH and LH, as they are no longer inhibited (and the menstrual cycle continues);

Insulin is released from beta (β) cells of the pancreas and cause a decrease in blood glucose concentration. This may involve stimulating glycogen synthesis in the liver (glycogenesis), promoting glucose uptake by the liver and adipose tissue, or increasing the rate of glucose breakdown (by increasing cell respiration rates)

In the 17th century, it was still unknown that gametes fuse to form a zygote. Aristotle proposed that the sperm forms an egg when inside the female, which then forms an embryo. Harvey thought that animals came from eggs and that semen (provided by sexual intercourse) was needed to cause the egg to form an embryo. Harvey dissected a uterus from a female deer that had recently mated; he could not find an embryo. He only saw embryos in deer that had mated several weeks earlier. He was unable to to gain the evidence he needed to describe the process of gamete fusion. He thought his own ideas were not fully correct. The magnifying equipment that existed at that time was not good enough for him to see sperm, eggs, or early stage embryos (these were too small). The discovery of sperm fusing with eggs and embryo development required the invention of the microscope.

The menstrual cycle starts in females at puberty and continues until menopause. In the first half of the 28 day cycle, a follicle develops in the ovary and the lining of the uterus (the endometrium) is prepared for possible implantation. Ovulation (release of an oocyte) occurs mid-cycle. If no implantation occurs, the endometrium breaks down and menstruation occurs. The cycle is controlled by four hormones. Two are secreted from the pituitary gland and two are secreted by the ovaries. Pituitary hormones: FSH and LH. Ovarian hormones: Estrogen and progesterone. The cycle involves both negative and positive feedback. Negative feedback mechanisms act against a change. Positive feedback mechanisms will reinforce a change.

Glucagon is released from alpha (α) cells of the pancreas and cause an increase in blood glucose concentration. This may involve stimulating glycogen breakdown in the liver (glycogenolysis), promoting glucose release by the liver and adipose tissue, or decreasing the rate of glucose breakdown (by reducing cell respiration rates)

All embryos go through the initial stages of growth and development in the same way. By the time an embryo is five weeks old, embryonic gonads have developed that can become either male or female gonads. One gene located on the Y chromosome determines if the embryo will develop male or female gonads. The SRY gene is only found on the Y chromosome. If the embryo has a Y chromosome, SRY gene expression will occur after 7 weeks. The protein coded by the SRY gene will cause the embryonic gonads to develop into testes. A fetus with testes will become male. If there is no expression of the SRY gene by week 13, the embryonic gonads develop into ovaries. A fetus with ovaries will become female. The embryo is by default female; the expression of the SRY gene causes a change in gonad development.

Following ovulation, LH promotes the formation of the the corpus luteum. The corpus luteum secretes progesterone and some estrogen. Progesterone and estrogen maintain the thickened endometrium. Progesterone and estrogen inhibit the secretion of FSH and LH by the pituitary gland (negative feedback). If no embryo implants in the endometrium, the corpus luteum degenerates and no longer secretes progesterone and estrogen. This causes menstruation. FSH secretion is no longer inhibited and the cycle begins again.

Thyroxin is secreted by the thyroid gland, which is located in the neck. Thyroxin contains three or four iodine atoms. Most cells of the body are targets for thyroxin. It regulates metabolism. Thyroxin binding to target cells increases metabolic rate. A high metabolic rate will generate heat. Thyroxin plays a role in regulating body temperature: Low body temperature increases thyroxin release. This increases metabolic activity, which raises body temperature. High body temperature decreases thyroxin release. This reduces metabolic activity, which lowers body temperature. Iodine deficiency in the diet can lead to low levels of thyroxin (leading to an enlarged thyroid gland or goitre). Iodine is commonly added to table salt to avoid this problem.

Jetlag is caused by travelling through multiple time zones in a short period of time. Travelling eastwards is a particular problem. The circadian rhythm (set at the origin of travel) no longer matches the day-night times in the new location. This can result in the person feeling sleepy in the day or being awake during the night. It takes a few days for the circadian rhythm to adjust to local conditions, by light signals transmitted to the hypothalamus modifying melatonin secretion. Some travellers take melatonin to match the night time in their destination. Melatonin can help reduce jetlag.

surges cause ovulation, results in the formation of a corpus lutuem maturation of follicle cells

As obese people are constantly producing higher levels of leptin, their body becomes progressively desensitised to the hormone. This means they are more likely to feel hungry, less likely to recognise when they are full and are hence more likely to overeat. Leptin resistance also develops with age, increasing the potential for weight gain later in life (e.g. the 'middle-age spread'). Theoretically leptin hormone would reduce hunger and limit food intake in obese individuals, leading to weight loss.

Prenatal development of female reproductive structures. If the fetus has ovaries, then no testosterone is produced. In the absence of testosterone and the presence of estrogen and progesterone from the mother, regions of the fetus develop into female reproductive structures. Estrogen and progesterone are steroid hormones. Development of secondary sexual characteristics. Secretion of estrogen and progesterone by the ovaries increases at puberty.This causes: Enlargement of breasts. Pubic and underarm hair growth. Widening of the hips.

Type I diabetes is caused when beta cells are destroyed by the immune system. The disease can start during childhood. The body produces little or no insulin. The means there is a loss of control of blood glucose levels. To treat it, patients have to inject insulin. Blood glucose concentrations need to be regularly monitored. The timing of injections must correspond with high blood glucose concentrations. Injections are given before meal times.Type II diabetes is associated with various risk factors, such as obesity, lack of exercise, age, and genetic factors. It normally starts in adults. The body has a insulin insensitivity (due to reduced number of insulin receptors). Loss of control of blood glucose levels. To treat it, patients must try to changes their lifestyle by reducing carbohydrates in the diet, eating little and often, regularly exercising. Insulin injections can be given to some patients (as insulin production can reduce over time).

which drug is most rapidly absorbed fro the GI tract