6.6 Hormones, Homeostasis And Reproduction

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Homeostasis

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Blood PHBlood temperatureBlood carbon dioxideWater balance within tissuesBlood glucose concentration

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negative feedback mechanisms

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The physiological processes that bring a value back towards to a set point

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Thyroxin

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The gland that produces and secretes thyroxin is a butterfly shaped gland located in your neck called the thyroid gland.

exists in two forms t4 and t3.

Thyroxin helps to regulate body temperature, An increase in metabolic rate produces more heat from the increase chemical reactions that are occurring.

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Leptin

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A hormone that is produced by adipose (fat) tissue in the body.

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Melatonin

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The pineal gland, many animals use their gland to help regulate their 24 daily cycle of activity called the circadian rhythm.

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Insulin and glucagon help regulate glucose levels

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Insulin and glucagon are hormones that are both produced and secreted by the pancreas. In addition, they are both involved in the regulation of blood glucose levels. Cells rely on glucose for the process of cell respiration. Cells never stop cell respiration this are constantly lowering the concentration of glucose in the blood. However even though blood glucose is expected to fluctuate slightly above and below the homeostatic normal level it must be maintained reasonably close to the body set point for blood glucose level and negative feedback mechanisms ensure this.

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What happens when blood glucose begins to rise above the set point?

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Insulins effect on the body cells is to open protein channels in their plasma membranes these channel allow glucose to diffuse into the cell by the process known as facilitated diffusion. When blood that is relatively high in glucose enters the liver by the hepatic portal vein, insulin stimulates the hepatocytes to take in the glucose and convert it to glycogen.

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What happens when blood glucose begins to fall below the set point?

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The blood glucose level typically begins to drop below the set point when someone has not eaten for many hours or exercises vigorously for a long time. In either situation the blood needs to use glycogen made and stored by the liver.

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Diabetes

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Type 1 is typically when the b cells of the pancreas do not produce sufficient insulin

type 2 diabetes is caused by body cell receptors that do not respond properly to insulin.

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Effects of diabetes

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Many serious effects of diabetes include:Damage to the retina, leading to blindnessKidney failureNerve damageIncreased risk of cardiovascular diseasePoor wound healing (and possibly gangrene, thus making amputation necessary)

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Testosterone

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Determines the development of male genitalia during embryonic development, ensures the development of secondary sec charactersitics during puberty Ensure sperm production as well as maintains sex drive following puberty

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Role of sex hormones during puberty (female)

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The secondary sex characteristics of females that arise as a result of increased oestrogen and progesterone production at puberty are:Enlargement of breastsGrowth of pubic and underarm hairWidening hips

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ROle of sex horomes during puberty (male)

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The secondary sex characteristics of male that arise as a result of increased testosterone production at puberty are: Growth of facial underarm,chest and pubic hairEnlargement of the larynx and associated deepening of voiceIncreased muscle massEnlargement of the penis

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The menstruation cycle

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Front 15

Hormones from the hypothalamus and pituitary gland

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The hypothalamus produces a hormone known as gonadotropin - releasing hormone (GnRH). The target tissue of GnRH is the nearby pituitary gland, and it results in the anterior pituitary producing a secreting two hormones into the bloodstream.These two hormones are follicle stimulating hormone and luteinizing hormone.

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The effect of FSH and LH on the ovaries

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One of these effects is to increase the production and secretion of another reproductive hormone by the follicle cell of the ovary.

This hormone is oestrogen, like all hormones, oestrogen enters the bloodstream, its target tissue is the endometrium of the uterus.

production of structures within the ovaries known as graafian follicles within the ovaries are cells known as follicle cells and the true reproductive cells that are at stage of development called oocytes

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Oestrogen

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One effect of oestrogen is an increase in the density of blood vessels of the endometrium that is as stated earlier the endometrium becomes highly vascular

Another effect of oestrogen is to stimulate the pituitary gland to release more FSH and LH this is the positive feedback loop of the menstrual cycle specifically these two sets of hormones increasing because of the increase of the others

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Some couples are unable to bear children there is a wide variety of possible reasons for infertility including:

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Male with low sperm countsMale with impotence Female who cannot ovulate normallyFemales with blocked fallopian tubes

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Hormone therapy

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As part of IVF procedure a woman must have egg harvested for her ovaries. In order to ensure the proper timing for this and to maximize the number of available ova, the woman undergoes about a month of hormone therapy, during the first 2 weeks she injects a drug that suspends her own natural hormones associated with her menstrual cycle. Then for the next 12 days or so she takes hormone injections that include FSH.

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Progesterone

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a hormone that maintains the thickened highly vascular endometrium as long as progesterone cenobites to be produced, the endometrium will not break down and an embryo will still be able to implant.