SB7-Animal coordination,control and Homeostasis

SB7a-Hormones

Hormones are known as chemical messengers. They travel by blood after being secreted by the endocrine glands. They are detected by a target organ containing target cells which then changes the way it works due to the hormone.

Testosterone-Produced in the testes-Targets cells in many organs-Secondary characteristic development in boys.
Thyroxine-Produced in the Thyroid gland-Targets heart muscle cells and others-Increases the rate of cellular respiration.
Growth hormone-Produced in the Pituitary gland-Targets bone cells and all muscle cells-Increases growth rate of many tissues.
Adrenaline-Produced in the Adrenal gland-Targets heart muscle cells and others-Prepares body for 'fight or flight'.
Insulin-Produced in the Pancreas-Targets liver cells and muscle cells-increases the uptake of glucose from the blood.
Ostrogen-Produced in the Ovaries-Targets cells in many organs-Secondary sexual characteristic development in girls.
FSH-Produced in the Pituitary gland-targets egg follicles in ovaries-stimulates growth and maturation.
LH-Produced in the Pituitary gland-Targets mature egg follicles-triggers ovulation.
Glucagon-Produced in the Pancreas-Targets liver cells-Cells break down glycogen to glucose and release into blood.

Growth hormones stimulate mitosis in bone and muscle tissue which therefore increases the size.

There is a difference between neurones and hormones:

Neurones: Very fast action-act for a very short time-act on a very precise area.
Hormones: Slower action-Act for a long time-Act in a more general way.

SB7b-Hormonal control of metabolic rate

Metabolic rate: The overall rate at which chemical reactions take place in the body.
Resting metabolic rate: Metabolic rate when the body is at rest.

Thyroxine affects metabolic rate. It caused heart cells to contract more rapidly and strongly and increases the rate at which proteins and carbohydrates are broken down inside cells.

Adrenaline is usually released in small amounts. But, in frightening or exciting situations, there is an increase in impulses sent by hypothalamus which reach the adrenal glands from the spinal cord and triggers the release of large amounts.
When adrenaline reaches the liver, it causes a breakdown of glycogen. This is a polymer made of glucose which can be released into the blood to provide additional glucose for respiration.

Negative feedback: A control mechanism that reacts to a change in a condition, such as temperature, by trying to bring the condition back to a normal level.
An example of negative feedback is Thyroxine concentration in the blood. This is because an increase in thyroxine concentration directly causes changes that bring about a decrease in the amount of thyroxine released in the blood, and vice versa.
When blood thyroxine level is lower than normal, the hypothalamus is stimulated to release TRH (Thyrotropin releasing hormone). TRH stimulates the pituitary gland to release TSH (Thyroid stimulating hormone). This stimulates the thyroid gland to release thyroxine so the blood thyroxing level risis to wards normal. If the level is too high, TRH is inhibited, with reduces the process and the thyroxine level falls.

Homeostasis: The maintenance of a constant internal environment, despite external factors (hot or cold outside).

Extra adrenaline in the blood causes:

Heart rate to increase-this is needed so that there can be more respiration therefore producing more energy.
Pupils to dilate-so that more light waves can enter the eye so more can be seen.
muscles to contract-this increases the rate of respiration.
High blood glucose level-more respiration. Pancreas stops releasing insulin.

Adrenaline is sent to the liver. It breaks down glycogen o that glucose is released into the blood.

SB7c-The Menstrual cycle

Menstrual cycle-A monthly cycle involving the reproductive organs in women.
Fertilisation-Fusing a male gamete with a female gamete.
Menopause-when the menstrual cycle stops completely.
Menstruation-The breakdown and loss of thickened part of the uterus lining at the start of a woman's menstrual cycle.
Ovulation-the release of an egg from an ovary.
Period-The 'bleed' that occurs during menstruation.
pregnancy-The time during a fertilised egg develops in the uterus until the birth of the baby.
Puberty-The stage of life when the body develops to make it able to reproduce.

Day 1-5 of the menstrual cycle is when menstruation occurs. The uterus lining is lost during these days and then builds back up again, allowing ovulation to take place (about day 14).
The fall in concentration of progesterone triggers menstruation.
Oestrogen concentration increases to its most at ovulation to thicken the wall of the uterus. Menstruation is caused when both levels of Oestrogen and progesterone are low. The uterus lining and unfertilised egg ell are lost during a period.

Contraception:

Condom-physical barrier-98% success.
IUD-placed in the uterus so it contracts.
Progesterone pill-Tricks the body into thinking it's pregnant. An egg cannot be released. 99% success. Thickens mucus at the cervix.
Diaphragm/cap-Placed above cervix so that entrance to uterus is blocked-92-96% success rate.

When used correctly, hormonal contraception methods are more effective than barrier methods. Hormonal methods mean the couple don't have to think about contraception each time they have intercourse.
However, hormonal methods can have unpleasant side effects and do not protect against STIs-male condoms are the only form of contraception that do this.

SB7d-Hormones and the menstrual cycle

FSH (follicle stimulating hormone) is made in the pituitary gland and stimulates one egg cell to develop and Oestrogen production.
Oestrogen is made in the ovary and stimulates the rebuilding of the uterus wall.
LH (luteinising hormone) is made in the pituitary gland and stimulates the follicle to burst and release the ovum=ovulation.
Progesterone is made in the corpus luteum (follicle) and completed development of the uterus wall and promotes glycogen storage.

Low levels of progesterone stimulates increased levels of FSH which increases Oestrogen levels and then LH levels. This leads to increased progesterone levels which inhibits the extra production of the other hormones.
Clomifene is a drug that stimulated the production of FSH and LH in the body-Assisted reproductive technology.

Another example of ART is IVF (in vitro fertilisation):

A drug is given to suppress the natural production of FSH and LH. This stops the usual cycle of a single egg cell maturing in an ovary and being released.
A larger than normal dose of FSH is given to the woman every day for several days. This causes egg cells to grow and begin to mature in the ovaries.
A larger than normal dose of LH is given to the woman. This completes egg cell maturation so that many mature egg cells are released at the same time.
While egg cells are fertilised in the lab, the woman is given progesterone. This prepares the uterus for the implantation of an embryo, by causing the uterus lining to thicken.

SB7e-Control of blood glucose

This is an example of homeostasis-maintaining blood glucose levels means maintaining a constant internal environment.

Insulin and glucagon control blood glucose concentration. When eating carbohydrates, glucose is sent into the blood stream via the small intestine. The normal metabolism removes glucose from the blood and when exercising, it removes excess glucose. Excess glucose can be stored as glycogen in the liver and muscles. When these stores are full then excess glucose is stored as fat in tissues. Changes in blood glucose are monitored and controlled by the pancreas, using insulin and glucagon hormones.

When blood glucose concentration is too high, insulin is added. It is secreted by the pancreas and travels around into the liver as well as the glucose which is turned into glycogen.
When blood glucose concentration is too low, glucagon is added. It is secreted by the pancreas and enters the liver so that glucose can be made from glycogen. It is then released into the blood and blood glucose is increased.

SB7f-Diabetes

Type 1 diabetes is where the pancreas produces little or no insulin therefore a person's blood glucose levels can rise to a very high amount and can kill them. This person would need to be treated with insulin therapy e.g. injecting insulin into the blood. They often do this at mealtimes to make sure the glucose is removed quickly from the blood when food has been digested. This is very effective and stops the level of glucose from rising too high. Insulin is injected into fatty tissue and the amount of insulin injected depends on the type of person and their activity. These people must think about their intake-avoiding too many carbohydrates and also they could exercise regularly which removes excess glucose from the blood.

Type 2 diabetes is when the pancreas doesn't produce enough insulin or the person has become resistant to it. Therefore blood glucose levels rise. There is a correlation between obese people and who develops type 2 diabetes. This means that obese people have a greater risk of developing it. If they have a BMI of over 30, they are considered as obese. Where the body stores excess fat is important. When fat is stored around the abdomen, it is said that there is an increased risk in type 2 diabetes. Calculating the waist to hip ratio gives an indication of how fat is stored. This can be controlled by eating healthily, getting regular exercise and losing weight if necessary. Some also have medication of injections.

	Created by Jessica Diamond about 7 years ago

Year 10 Biology Note on SB7-Animal coordination,control and Homeostasis, created by Jessica Diamond on 09/09/2017.

SB7-Animal coordination,control and Homeostasis