Download Edexcel Biology GCSE (9-1): Animal Coordination, Control, and Homeostasis and more Exams Health sciences in PDF only on Docsity!
coordination, control and homeostasis…
7.1: Describe where hormones are produced and how they are transported from endocrine glands to their target organs, including the pituitary gland, thyroid gland, pancreas, adrenal glands, ovaries and testes - well answered PITUITARY GLAND produces: TSH targetting the THYROID GLAND ADH targetting the KIDNEY FSH + LH targetting the OVARIES Growth hormone Thyroid gland produces: Thyroxine targetting the THYROID PANCREAS produces: Insulin + glucagon targetting liver, muscle, adipose tissue ADRENAL GLANDS produce adrenalin targetting the heart, blood vessels, liver OVARIES produce: Oestrogen and Progesterone targetting the (Ovaries +) Uterus + the PITUITARY GLAND TESTES produce Testosterone targetting male reproductive organs 7.2 Explain that adrenalin is produced by the adrenal glands to prepare the body for fight or flight, including: a increased heart rate b increased blood pressure c increased blood flow to the muscles d raised blood sugar levels by stimulating the liver to change glycogen into glucose - well answered Adrenalin is released by the adrenal glands to prepare the body for the "fight-or-flight" response. (More in scary/exciting/stressful times)
coordination, control and homeostasis…
INCREASED HEART RATE: Adrenalin binds to heart receptors, causing more rapid/frequent muscle contractions to increase heart rate (carry oxygen fast) INCREASED BLOOD PRESSURE: Muscle contractions have more force/strength. Diameter of blood vessels leading to other organs narrows -> reduced blood flow/increased blood pressure. INCREASED BLOOD FLOW TO MUSCLES: Diameter widens of blood vessels that lead to muscles to increase blood flow to muscles so cells receive more oxygen for respiration. STIMULATING THE LIVER TO CHANGE GLYCOGEN INTO GLUCOSE: Adrenaline binds to liver receptors. This causes liver cells to convert glycogen stores into glucose, released into blood to be transported Blood glucose concentration increases -> more glucose to respire. 7.3: Explain how thyroxine controls metabolic rate as an example of negative feedback, including: a low levels of thyroxine stimulates production of TRH in hypothalamus b this causes release of TSH from the pituitary gland c TSH acts on the thyroid to produce thyroxine d when thyroxine levels are normal, thyroxine inhibits the release of TRH and the production of TSH - well answered Thyroxine is released from the thyroid gland to regulate METABOLIC rate (rate all of the energy transfers from food in the body occurs) NEGATIVE FEEDBACK keeps the amount of thyroxine constant. When blood THYROXINE CONCENTRATION is TOO LOW, STIMULATES the HYPOTHALAMUS to release TRH. TRH stimulates the PITUITARY GLAND to release TSH
coordination, control and homeostasis…
A HIGH OESTROGEN CONCENTRATION causes in a SURGE OF LH from the PITUITARY GLAND. This stimulates OVULATION (the egg is released). The RUPTURED FOLLICLE becomes a CORPUS LUTEUM secreting PROGESTERONE (causing further thickening.) PROGESTERONE INHIBITS FSH + LH. If the egg isn't fertilised, the corpus luteum BREAKS DOWN + PROGESTERONE LEVELS FALL, triggering MENSTURATION. FSH is no longer inhibited so is released again. 7.6: Explain how hormonal contraception influences the menstrual cycle and prevents pregnancy - well answered Hormonal contraception (pills, implants or injection) release hormones to raise hormone concentrations which naturally fall. OESTROGEN can prevent egg release if taken every day to keep it at high levels (inhibits FSH release). Egg maturation is stopped. PROGESTERONE can stimulate production of THICK CERVICAL MUCUS (preventing sperm getting to the uterus) + reaching the egg. 7.7: Evaluate hormonal and barrier methods of contraception - well answered HORMONAL METHOD examples: OESTROGEN + PROGESTRONE examples: combined pill /contraceptive patch. OESTROGEN example: mini-pill/contraceptive injection. More effective at preventing pregnancy. Couples don't have to stop to think about contraception. DON'T PROTECT AGAINST STIs.
coordination, control and homeostasis…
BARRIER METHOD examples: CONDOMS (a barrier that prevents sperm from entering the vagina) DIAPHRAGMS (fit over the cervix + prevents sperm entering). Spermicides have to be used. Don't have side effects e.g. mood swings/headaches. CONDOMS PROTECT AGAINST STIs. 7.8: Explain the use of hormones in Assisted Reproductive Technology (ART) including IVF and clomifene therapy - well answered ART increases the chance of pregnancy for woman who are infertile IVF can overcome issues like blocked oviducts. FERTILITY DRUGS are given to women to STIMULATE eggs to MATURE. Eggs released by follicles are TAKEN from the ovary + sperm is TAKEN from the man. Eggs + sperm are combined in a dish for fertilisation. Zygotes develop into embryos. One or two embryos turn into balls of cells then are then placed in the uterus to increase chances of pregnancy. CLOMIFENE causes an increased in FSH + LH, stimulating EGG MATURATION + OVULATION. Couples can have intercourse in the time period to improve pregnancy chances. 7.9: Explain the importance of maintaining a constant internal environment in response to internal and external change - well answered Homeostasis prevents damage as it keeps conditions at optimal levels despite internal and external change. It is important for ENZYME ACTION (Fastest in certain conditions + at lower temperatures chemical reactions could occur at a slower rate, which is harmful for the body) + CELL FUNCTIONS, e.g. growth, replication + controlled cell death. 7.10 B: Explain the importance of homeostasis, including: a thermoregulation - the effect on enzyme activity b osmoregulation - the effect on animal cells - well answered 7.11B: Explain how thermoregulation takes place, with reference to
coordination, control and homeostasis…
VASODILATION is the widening of blood vessels. When the HYPOTHALAMUS detects warmth, it sends nerve IMPULSES to skin arteries to cause them to widen. Blood flow in CAPILLARIES near the skin is REDUCED. Energy transfer to the surroundings is REDUCED to COOL DOWN the body. 7.13: Explain how the hormone insulin controls blood glucose concentration - well answered When BLOOD GLUCOSE CONCENTRATION is TOO HIGH (e.g. after meals when glucose is released from carbs), there's a risk it could DAMAGE ORGANS. If the PANCREAS detects a rise in BLOOD GLUCOSE CONCENTRATION, it increases SECRETION of INSULIN. Insulin causes MUSCLE/LIVER CELLS to remove glucose from the blood + change it into GLYCOGEN to be STORED. With a decreasing blood glucose concentration, there's decreasing insulin released until the level is normal (no insulin is released) 7.14: Explain how blood glucose concentration is regulated by glucagon - well answered If the PANCREAS detects a fall in BLOOD GLUCOSE CONCENTRATION, it increases SECRETION of GLUCAGON. Glucagon causes MUSCLE/LIVER CELLS to change GLYCOGEN into GLUCOSE to the blood + release it into the blood. With a decreasing blood glycogen concentration, there's decreasing glucagon released until the level is normal (no glucagon is released) 7.15: Explain the cause of type 1 diabetes and how it is controlled - well answered The IMMUNE SYSTEM has destroyed pancreatic insulin-secreting cells so the person produces little/no insulin. Blood glucose can rise to levels that can kill them. (Glucose in the urine tests for type 1)
coordination, control and homeostasis…
CONTROL: Inject insulin into the SUBCUTANEOUS TISSUE to enter the blood (mainly at mealtimes to remove glucose quickly from the blood to stop the blood glucose concentration getting too high). The amount depends on diet /activity. 7.16: Explain the cause of type 2 diabetes and how it is controlled - well answered Insulin-secreting cells don't produce enough insulin, target organs don't respond properly to it or a person (a person is RESISTANT to it) CONTROL: Some only need to eat healthily/eat a low amount of sugar. Physical activity takes glucose out of the blood so can help. MEDICINES are given to those with severe Type 2 diabetes, reducing the amount of glucose the liver releases in the blood/increases the sensitivity of target organ cells responding to insulin. 7.17: Evaluate the correlation between body mass and type 2 diabetes including waist:hip calculations and BMI, using the BMI equation: - well answered 7.18B: Describe the structure of the urinary system - well answered The URINARY SYSTEM removes excess amounts of water/mineral salts + removes waste products e.g. urea, produced from the breakdwno
