Animal Coordination, Control and Homeostasis Flashcards
Where are hormones produced?
the endocrine glands
What is the general role of hormones in the body?
to control things in organs and cells that need constant adjustment
How are hormones transported around the body?
In the bloodstream
Describe the production and release of hormones from the pituitary gland.
The pituitary gland produces many hormones which regulate body conditions. It is sometimes called the master gland as these hormones act on other glands to release hormones that bring about change
Describe the production and release of hormones from the thyroid gland.
Produces thyroxine, which is involved in regulating rate of metabolism, heart rate, temperature, etc…
Describe the production and release of hormones from the pancreas.
Produces insulin and glucagon, used to regulate blood glucose level
Describe the production and release of hormones from the adrenal glands.
Produce adrenaline, used to prepare the body for a fight or flight response
Describe the production and release of hormones from the ovaries.
Produce oestrogen, involved in the menstrual cycle.
Describe the production and release of hormones from the testes.
Produce testosterone, which controls puberty and sperm production in males.
What are the effects of adrenaline on the body?
It prepares the body for fight or flight by activating processes which increase flow of oxygen to cells. E.g. Adrenaline binds to specific receptors in the heart, causing the heart muscle to contract more frequently & with more force so heart rate & blood pressure increase, increasing blood flow to muscles so cells receive more oxygen & glucose for respiration. Adrenaline also binds to receptors in the liver so it breaks down glycogen stores to release glucose, increasing blood glucose level to aid respiration.
What is metabolic rate?
The speed at which chemical reactions in the body occur.
What is the effect of thyroxine on metabolic rate?
More thyroxine causes metabolic rate to rise.
How does a negative feedback system work and why is it important?
A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback. In general, if the level of something rises, control systems reduce it again; if the level of something falls, control systems raise it again
How does negative feedback control the production of thyroxine?
When blood thyroxine lovel is lower than normal the hypothalamus is stimulated to release thyrotropin releasing hormone (TRH). TRH stimulates the pituitary gland to release thyroid stimulating hormone (TSH) which stimulates the thyroid gland to release thyroxine so blood thyroxine level rises. When it is too high release of TRH from the hypothalamus is inhibited, reducing production of TSH so blood thyroxine level falls.
What happens during the menstrual cycle?
Stage 1- Day 1: menstruation starts- uterine lining breaks down and is released
Stage 2- uterus lining is repaired (day 4-14) until it is a thick spongy layer full of blood vessels ready for a fertilised egg to implant there
Stage 3- Ovulation (day 14)
Stage 4- Lining is then maintained for about 28 days until day 28, whereupon, if no fertilised egg has implanted,the uterine lining breaks down and menstruation occurs.
How can barrier methods be used as contraception?
A barrier is put between the sperm and egg so they don’t meet. E.g. male and female condoms and diaphragms (with spermicide)
How can hormones be used as contraception?
If oestrogen is taken daily to keep levels of it high, it inhibits FSH production so egg development and production stop. Progesterone stimulates production of thick cervical mucus, preventing sperm breaching the entrance to the uterus (the cervix). Some hormonal contraceptives contain both oestrogen and progesterone e.g. the combined pill and the contraceptive patch (worn on the skin). Some contain progesterone only e.g. mini-pill and contraceptive injection.
What is the difference between hormonal and barrier methods?
Hormonal methods are more effective when used correctly and mean the couple don’t have to stop and think about contraception before intercourse. However, they can have unpleasant side effects (e.g. headaches, acne and mood swings) and don’t protect against STIs.
How do oestrogen, progesterone, FSH and LH interact in the menstrual cycle?
FSH (released by the pituitary gland) causes a follicle to mature in an ovary and stimulates oestrogen production. Oestrogen (released by the ovaries) causes the lining of the uterus to thicken and grow. A high level stimulates an LH (lutenising hormone) surge. The LH (released by the pituitary gland) surge stimulates ovulation at day 14 - follicle ruptures and egg is released- and stimulates the remains of the follicle to develop into a corpus luteum which secretes progesterone. Progesterone maintains uterine lining and inhibits release of FSH and LH. When level of progesterone falls and oestrogen level is low the uterus lining breaks down and FSH level increases, allowing the cycle to restart.
How is clomifene used to stimulate ovulation?
Some women are infertile as they don’t ovulate or don’t ovulate regularly. The clomifene drug causes more FSH and LH to be released by the body, stimulating egg maturation and ovulation. By knowing when the woman will be ovulating , the couple can have intercourse during this time period to improve chances of becoming pregnant.
How does IVF work?
Eggs are collected from the woman’s ovaries and fertilised in a lab using the man’s sperm. These are then grown into embryos. Once the embryos are little balls of cells, 1 or 2 of them are transferred to the woman’s uterus to improve chances of pregnancy. FSH and LH are given before egg collection to stimulate egg production so more than 1 egg can be collected. IVF is an example of Assisted Reproductive Technology (ART) as it involves eggs being handled outside the body.
What is homeostasis and why is it important?
Maintaining a constant internal environment.
Cells need the right conditions in order to function properly, including the right conditions for enzyme action.
Why do blood glucose levels change?
Eating carbohydrate-containing foods puts glucose into the blood from the small intestine. Normal cell metabolism removes glucose from the blood. Vigorous exercise removes more glucose from the blood. Excess glucose can be stored as glycogen in the liver and muscles. When these stores are full the excess glucose is stored as lipid (fat) in the tissues.Changes in blood glucose are monitored and controlled by the pancreas
How do insulin and glucagon regulate blood glucose concentration?
When blood glucose concentration is too high, the pancreas secretes insulin, which stimulates the liver to take in glucose and store it as glycogen. When blood glucose concentration is too low, the pancreas secretes glucagon, which stimulates the liver to break down glycogen into glucose and release it into the bloodstream.
