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B11 - Hormonal Coordination - Coggle Diagram
B11 - Hormonal Coordination
B11.1
The pituitary gland is known as the master gland because it coordinates and controls many other endocrine glands. It secretes a variety of different hormones into the blood in response to changes in body conditions.
Role of hormones
Hormones are chemicals secreted by your endocrine glands directly into the bloodstream, which are transported around your body to the target organ where it produces an effect. Hormones coordinate many processes in your body. Some of the hormones are insulin, adrenaline, growth hormones and sex hormones.
B11.4
Function of adrenaline and thyroxine
Adrenaline
Adrenaline prepares your body for fight or flight. It causes: your heart rate and breathing rate to increase, stored glycogen to be converted to glucose for respiration, the pupils of your eye to dilate to let in more light, your mental awareness to increase, and your blood to be diverted away from your digestive system to the big muscles of the limbs.
Thyroxine
Thyroxine controls the basal metabolic rate of your body - how quickly substances are broken down and built up, how much oxygen your tissues use, and how the brain of a growing child develops.
B11.2
What happens when blood glucose levels become too high or too low?
When your blood glucose level rises after you have eaten, the pancreas produces insulin, which allows glucose to move from the blood into your cells where it is used as energy. Soluble glucose is also converted into glycogen, and insulin controls the storage of glycogen in your liver and muscles. When these stores are full, any excess glucose is converted into lipids and stored. It is these stores that can make you obese if you consume a lot of sugary food.
When your blood glucose concentration falls below the normal level, your pancreas secretes another hormone called glucagon. This makes your liver break down glycogen, converting it back into glucose. In this way the stored glucose is released back into the blood.
Difference in the causes of Type 1 & 2 diabetes
Type 1
Type 1 diabetes is when your pancreas doesn't make enough (if any) insulin, so your blood glucose concentration is not controlled. This causes your blood glucose concentration to be very high after you have eaten, and eventually your kidneys excrete glucose in your urine. You produce a lot of urine and feel thirsty all the time. Without insulin, glucose can't get into your cells, so you lack energy and feel tired. You break down fat and protein to use as energy instead, so you lose weight.
Type 2
Type 2 diabetes is often linked to obesity, lack or exercise or both. In type 2 diabetes, the pancreas still makes insulin, it just makes less than your body needs. Your body cells stop responding to the insulin that your pancreas makes.
B11.3
Type 1 diabetes is treated with insulin injections because it allows glucose to be taken into your body cells and converted into glycogen in the liver. This stops the concentration of glucose in your blood from getting to high. As a result, your blood glucose levels are kept as stable as possible.
Type 2 diabetes is linked to obesity, lack or exercise and old age. Most people can therefore restore their normal blood glucose balance by eating a balanced diet with carefully controlled amounts of carbohydrates and exercising.
How the production of insulin for people with diabetes has developed over time
In 2005, scientists produced insulin-secreting cells from embryonic stem cells and used them to cure diabetes. In 2008, they discovered a new technique. By using genetic engineering, they turned mouse pancreas cells that normally make enzymes into insulin-producing cells. Scientists hope that soon they will be able to genetically engineer faulty human pancreatic cells so they work properly.
B11.5
What happens during the menstrual cycle?
The menstrual cycle lasts for 28 days on average. Each month the lining of the uterus thickens ready to support a developing baby. At the same time, the egg starts maturing in the follicles of the ovary. About 14 days after the egg starts maturing, one is released from the ovary in ovulation. The lining of the uterus stays thick for several days after the egg is released. If the egg is not fertilised, about 14 days after ovulation the lining of the uterus and the egg are shed from the body in the monthly period.
FSH is secreted by the pituitary gland. It makes eggs mature in the ovaries, and also stimulates the release of oestrogen. Oestrogen is made and secreted by the ovaries in response to FSH. It stimulates the lining of the uterus to grow again after menstruation. High levels of oestrogen inhibit the production of FSH and stimulate the release of LH. LH from the pituitary gland stimulates the release of a mature egg from the ovary. Once ovulation has occurred, LH levels fall again. Progesterone is secreted by the empty egg follicle in the ovary after ovulation. It inhibits both FSH and LH and therefore maintains the lining of the uterus in the second half of the cycle, so it is ready to receive a developing embryo if the egg is fertilised.
Changes to boys and girls during puberty
Boys
Between ages of 9-15. Facial hair, voice breaks, sperm production, shoulders and chest broaden as muscle develops.
Girls
Between the ages of 8-14. Fat deposited on the hips, buttocks and thighs, breasts develop, menstruation begins.
Both
Growth spurt, underarm hair and pubic hair, skin darkens, brain develops and matures.
Hormones involved in the menstrual cycle
Progesterone
Inhibits the release of both FSH and LH
Maintains the lining of the uterus
Oestrogen
Stimulates the release of LH
Inhibits the release of FSH
Causes the lining of the uterus to develop
LH
Causes the egg to be released
FSH
Stimulates the ovary to produce oestrogen
Causes eggs to mature
B11.6
Glands that secrete the hormones in the menstrual cycle
Oestrogen - ovary
LH - pituitary
FSH - pituitary
Progesterone - empty egg follicle in the ovary
B11.7
Contraception is the process used to prevent the egg and sperm meeting.
Hormone-based contraception
Oral contraceptives
Uses female hormones to prevent pregnancy. The mixed pill contains low doses of oestrogen along with some progesterone. These inhibit the production and release of FSH so no eggs mature. It also stop the uterus lining developing and prevents sperm getting through.
Consequences include a slight risk of side effects, such as raised blood pressure, thrombosis and breast cancer
Some contraceptive pills only contain progesterone, which has fewer side effects. However, the pill must be taken regularly, because if they don't the artificial hormone levels drop and their body's own hormones take over. This can lead to an unexpected release of an egg, and an unexpected baby.
Doctors can insert a tiny tube into your skin which slowly releases progesterone.
The contraceptive patch contains a mixture of oestrogen and progesterone. The patch is stuck to your skin and replaced every 7 days. The hormones are absorbed directly into your blood stream and stop the egg maturing, as well as affecting the uterus lining.
Barrier methods
Prevent the sperm reaching the egg. They have no side effects and offer some protection against sexually transmitted diseases. They can however get damaged and let sperm through.
B11.8
Reasons for infertility
Infertility is not being able to have a baby when you try/want one. Can be linked to a lack of female hormones, damaged oviducts, or a lack of sperm. Common causes of infertility are obesity and eating disorders, but mostly it is age.
Lack of ovulation
The female doesn't make enough FSH or LH to cause the egg to mature then be released into the uterus.
IVF
IVF is a form of fertility treatment.
Steps involved
The mother is given artificial FSH , followed by LH.
The eggs are collected from the ovary of the mother and fertilised with sperm from the father outside the body in a laboratory.
The fertilised eggs are kept in special solution in a warm environment to develop into tiny embryos.
When they are minute balls of cells, one or two of the embryos are inserted back into the uterus of the mother. Now the normal process can happen.
Issues surrounding IVF
It is an expensive process
It is not always successful - success rates significantly decrease in older couples
Use of fertility drugs can have some health risks for the mother
It increases the chances of multiple pregnancy, also increasing the risk of stillbirths and very premature births
Ethical issues / religious issues
Advantages
Allows people to have a baby of their own, whereas without it they wouldn't be able to
It has a safe track record and has been used since 1978
Unused eggs can be used for research or donated to other couples
Embryos can be screened for genetic diseases
Disadvantages
It is an expensive process
It is not always successful; older parents are less likely to be able to have a baby
Use of fertility drugs can have some health risks for the mother
It increases the chances of multiple pregnancy. This increases the risk of stillbirths and very premature births.