hormonal coordination

• the endocrine system is made up of glands that secrete chemicals called hormones directly into the bloodstream. the blood carries the hormone to its targets organ/s where it produces an effect. the target organ has receptors on the cell membranes that pick up the hormone molecules, triggering a response
• compared to the nervous system, the hormonal effects are slower but longer lasting. hormones that give a rapid response include insulin, which control your blood glucose and adrenaline, which prepares your body for fight or flight. slow-acting hormones with long-term effects include growth and sex hormones.
• hormones provide chemical coordination and control for the body and are produced by the endocrine glands. lots of glands are controlled the the pituitary gland, found in the brain. it acts as a master gland and secretes a variety of different hormones in response to different changes.
• some hormones produced by the pituitary gland in response to internal environment have a direct effect on the body. e.g. ADH (anti-diuretic hormone), which affects the amount of urine produced by the kidney, and the growth hormone which controls the rate of growth in children
• other hormones released by the pituitary gland affect specific endocrine glands, stimulating them to release hormones the bring about an effect. eg. FSH (follicle stimulating hormone) is released, to stimulate the ovaries to make the female sex hormone oestrogen. the pituitary gland also produces TSH which stimulates the thyroid gland to make thyroxine, a hormone that helps control the rate of your metabolism
• the pituitary gland secretes hormones that control growth in children, stimulates the thyroid gland with TSH to make thyroxine to control the rate of metabolism, stimulates the ovaries with FSH to produce and release eggs alongside oestrogen OR stimulates the testes to make sperm alongside testosterone.
• the thyroid gland produces thyroxine which controls the metabolic rate of the body.
• the pancreas produces insulin for the liver which controls blood glucose concentration. the effects it has include increasing conversion of glucose into glycogen for storage
• the adrenal gland produces adrenaline which targets many places including the respiratory and circulatory system. it prepares the body for fight or flight. the effects of this include increasing breathing rate, heart rate, flow of blood to the muscles and conversion of glycogen to glucose
• the ovaries produce oestrogen which controls the development of the female secondary sexual characteristics and is involved in the menstrual cycle
• the testes produce testosterone which controls the development of the male secondary sexual characteristics and is involved in the production of sperm
• ADH (anti-diuretic hormone) is made in the pituitary gland and targets the kidneys. it controls the water content of the blood and will increase reabsorption of water by collecting ducts
• it is essential that your cells have a constant supply of glucose they need for respiration. to achieve this one of your body systems responds to the changes in your blood glucose levels. this is an example of homeostasis in action
• glucose is a sugar used in respiration to release energy. glycogen is a storage carbohydrate made of glucose, it is stored in the liver and muscle cells. insulin is a hormone (chemical messenger) which tells your body to change glucose into glycogen. glucagon is a hormone that tells the body to change glycogen back into glucose, this is also made by the pancreas
• when you digest food, glucose passes into your blood. without a control mechanism, you glucose levels would be extremely high after the meal, then very low several hours later, so low that the cells wouldn't have enough glucose to respire. this situation is prevented by the pancreas
• when glycogen stores in the liver and muscles are full, excess glucose will be converted into lipids and stored as fat. if you regularly take in food that results in having more glucose that can be held, you will gain weight and could become obese
• if levels of glucose are too high, the brain will detect the high levels, it will send a signal to the pancreas to start producing and releasing insulin, the pancreas is now stimulated and will release insulin, the insulin stimulates the liver to take glucose from the blood and convert it into glycogen. the blood glucose levels will then return to normal and the brain will be signaled.
• if levels of glucose are too low, the brain will detect this, it will send message to pancreas to start producing glucagon, it will do this. the glucagon will stimulate the liver to convert the glycogen stored there back into glucose. when levels are normal, the pancreas will stop producing glucagon and will signal brain
• if your pancreas does not make enough (or any) insulin, your blood glucose levels will not be controlled, this is called type 1 diabetes. without insulin, your blood glucose levels will get very high after you eat, eventually glucose will be excreted in the urine but because there is so much, you will produce a lot of urine and feel thirsty. without insulin, glucose cannot get into the cells of your body, so you lack energy and feel tired. you break down fats and protein to use as fuel instead, so you lose weight
• type 2 diabetes is caused when the person's body cells no longer respond to insulin produced by the pancreas. it is genetic but you can also develop it. the pancreas doesn't make enough insulin, but most importantly, the body doesn't respond to the insulin that is actually made
• symptoms for both types of diabetes include thrush/ genital itching, blurred vision, lethargy, weight loss, urination and slow healing wounds
• if you have type 1 diabetes, you need replacement insulin before meals. insulin is a protein that would be digested by your stomach so is usually given as an injection to get into the bloodstream. this allows the concentration of glucose to not get too high and levels to stay stable. you need to have regular meals and carefully plan exercise to not allow glucose levels to get too low.
• to cure type 1 diabetes, doctors can transplant a pancreas from a donor. however, it can be really hard to find a donor and you risk organ rejection. doctors can also transplant the pancreatic cells that make insulin.
• to treat type 2 diabetes, patients can eat a balanced diet with controlled amounts of carbohydrates, loose weight, do regular exercise but if this doesn't work, there are drugs that help insulin get to body cells, help pancreas make more insulin and reduce the amounts of glucose you absorb from your gut
• negative feedback systems work to maintain a steady state. it is the reversing of changes in the internal environment. a change needs to be detected, the change must be signalled to other cells and there must be a response to reverse the change
• the thyroid gland uses iodine from your diet to produce the hormone thyroxine. thyroxine controls the basal metabolic rate of your body. in adults, the level of thyroxine stays relatively stable, this happens as a result of negative feedback control involving the pituitary gland and the production of TSH (thyroid stimulating hormone)
• if levels of thyroxine in the blood begins to fall, it is detected by receptors in the brain. as a result, the amount of TSH released from the pituitary gland increases. this is a negative feedback system. TSH stimulates the production of thyroxine by the thyroid gland
• when you become angry, excited, frightened or stressed, your adrenal glands located at the top of your kidneys will secrete adrenaline that is rapidly carried around the body. adrenaline causes the heart rate and breathing rate to increase, stored glycogen in the liver to be converted into glucose for respiration, the pupils of your eyes dilate to let in more blood, your mental awareness increases and blood is diverted away from the digestive system to the muscles. it boosts the delivery of oxygen and glucose to the brain, preparing your body for fight or flight
• during puberty, the reproductive hormones control the development off secondary sexual characteristics. the primary characteristics are the ones you are born with e.g. ovaries in girls and testes in boys. these organs produce the sex hormones
• the main female reproductive hormone is oestrogen, produced by the ovaries. rising oestrogen levels trigger the development of the secondary sexual characteristics like growth spurt, growth of pubic and underarm hair, the breasts develop, skin darkens, fat is deposited on hips, buttocks and thighs, brain changes and matures, mature eggs form every month in ovaries and menstrual cycle begins
• in the menstrual cycle, eggs begin to mature in the ovaries. at the same time, the uterus produces a thickened lining ready for pregnancy. every 28 days, a mature egg is released, this is called ovulation. if the egg is not fertilised the lining of the uterus is shed along with the egg around 14 days later.
• in the menstrual cycle, FSH causes the eggs in the ovary to mature, LH (lutenising hormone) stimulates the release of an egg at ovulation and oestrogen and progesterone stimulate the build up and maintenance of the uterus lining
• eggs mature and are released every month for around 35-40 years, except if she is pregnant. eventually, the supply of eggs will run out and the woman goes through menopause, she can no longer have children
• as levels of testosterone rise, the males will go through puberty. changes include pubic hair growth, growth spurt, facial hair growth, larynx growth and voice will break, testes grow, shoulders and chest broaden and brain matures
• in the menstrual cycle

  in days 1-5, an unfertilised egg is passed out along with the thickened uterus lining

  in days 5-20, the lining or the uterus builds up again

  in days 20-28, lining of the uterus begins to break down again if there is no fertilised egg

  in days 0-12, eggs mature in the ovary

  in days 12-16, egg is released from ovary (ovulation)

  in days 16-23, unfertilised egg travels to the uterus.
• contraception is a way of preventing sperm and eggs cells meeting. a hormone based method is the pill which contains oestrogen and progesterone. chemical methods like spermicides. barrier methods like a condom, IUD deviced, abstinence which is not having sex and surgical methods. e.g. oviducts cut or tied and sperm ducts cut or tied
• some women want children but dont produce enough FSH to stimulate the maturation of eggs. fortunately, artificial FSH can be used as a fertility drug
• IVF (in-vitro fertilisation) involves giving the mothers FSH and LH to stimulate the production of eggs. the eggs are then collected and put with sperm in a dish. these fertilised eggs develop into embryos. these wmbryos will be implanted into the uterus. this means that the eggs have bypassed the faulty tubes that were preventing fertilisation.
• advanatges of IVF iclude it allows people to have kids, safe, low chance of miscarriage and unused eggs can be used for research and/or given to someone. disadvantages include side effects from drugs used, possibility of multiple births which is dangerous, low success rate, risk of depression from false hope
• when seeds are dispersed and plants begin to grow, it is important that the roots grow downwards to anchor the seedling and keep it stable as well as absorbing water and mineral needed for healthy growth. the shoots need to grow upwards towards the light so they can photosynthesise as much as possible. plants shoot are sensitive to gravity and light. they grow against gravity and towards light