Hormonal Coordination

• The endocirne system is composed of glands that secrete chemicals called hormones directly into the blood stream. The blood carries the hormone to a target organ where it produces an effect.
• Compared to the nrevous system, the effects of hormones are often slower but longer lasting.
• The pituitary gland is the master gland and secretes several hormones into the blood in response to body conditions. Some of these hormones act on other glands and stimulate them to releases hormones to bring about specific effects.
• The key endocrine glands are the pituitary, thyroid, pancreas, adrenal glands, ovaries and testes.
• Your blood glucose concentration is monitored and controlled by your pancreas.
• The pancreas produces the hormone insulin, which allows glucose to move from the blood into the cells and to be stored as glycogen in the liver and muscles.
• The pancreas also produces glucagon, which allows glycogen to be converted back into glucose and released into the blood.
• Glucagon interacts with insulin in a negative feedback cycle to control glucose levels.
• In type 1 diabetes, the blood glucose may rise to fatally high levels because the pancreas does not scerete enough insulin.
• In type 2 diabetes, the body stops responding to its own insulin.
• Insulin resistance can lead to obesity, hypertension, heart disease, stroke, kidney failure, blindness, nerve damage, and amputations.
• Type 1 diabetes occurs when the immune system destroys the beta cells that produce insulin.
• Type 1 diabetes is normally controlled by injecting insulin to replace the hormone that is not made in the body
• Type 2 diabetes is often treated with a carbohydrate-controlled diet and taking more exercise. If this doesn't work, drugs may be needed
• Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.
• Adrenaline is produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'fight or flight'.
• Thyroxine is controlled by negative feedback whereas adrenaline is not.
• During puberty reproductive hormones cause secondary sexual characterisitcs to develop.
• Oestrogen is the main female reproductive hormone produced by the ovary. At puberty eggs begin to mature in the ovary and one is released approximately every 28 days at ovulation.
• Testosterone is the main male reproductive hormone produced by the testes and stimulates sperm production
• Hormones involved in the mestrual cycle of a woman include follicle stimulating hormone (FSH), luteinising hormone (LH), oestrogen and progesterone
• The interactions of four hormones control the maturing and release of an egg from the ovary and the build-up of the lining of the uterus in the menstrual cycle
• FSH from the pituitary stimulates eggs to mature in the follicles of the ovary and the ovary to produce oestrogen
• Oestrogen secreted by the ovaries stimulates the growth of the lining of the uterus and the release of LH and inhibits FSH
• LH stimulates ovulation
• Progesterone is produced by the empty follicle after ovulation. It maintains the lining of the uterus for around 10 days and inhibits FSH and LH
• Fertility can be controlled by a number of hormonal and non-hormonal methods of contraception.
• Contraceptive methods include oral contraceptives, hormonal injections, implants, patches, condoms, diaphrams, intrauterine devices, spermicidal agents, abstinence and surgical sterilisation
• FSH and LH can be used as a fertility drug to stimulate ovulation in women with low FSH levels
• In vitro fertilisation (IVF) uses FSH and LH to stimulate maturation of ova that are collected, fertilised, allowed to start development, and replaced in the uterus
• IVF is emotionally and physically stressful, often unsuccessful and can lead to risky multiple births