Animal coordination, control and homeostasis

• What is a hormone?


  a hormone is a chemical signal found in multicellular organisms. interact with target cells (and target organs) and travel in body fluids, like the bloodstream
• What is the endocrine system?


  collection of glands (called endocrine glands) that produce hormones
• What is the pituitary gland?

  - It produces many hormones that regulate body conditions

  - it can be called the 'master gland' because these hormones act on other glands, directing them to release hormones that bring about change
• What do the ovaries do?


  Produce oestrogen which is involved in the menstrual cycle
• What do the testes do?


  Produce testosterone which controls puberty and sperm production in males
• What does the thyroid do?

  Produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
• What does the adrenal gland do?

  Produces adrenaline which is used to prepare the body for a 'fight or flight' response
• What does the pancreas do?

  Produces insulin which is used to regulate the blood glucose level
• What endocrine glands do you need to know?

  pituitary gland, ovaries, testes, thyroid, adrenal gland, pancreas
• name some differences between nerves and hormones

  Nerves: faster, act for a short time, act in a precise area

  Hormones: slower, act for a long time, act in a more general way
• What is negative feedback?

  a system to keep body conditions within a set normal range through a mechanism counteracting an upwards or downwards shift
• What are the target organs of adrenaline?

  The heart and the liver
• What is the job of adrenaline?

  To prepare your body for a "fight or flight" response
• How does adrenaline affect the heart?

  - it causes the heart muscle to contract more frequently, and with more force, so heart rate and blood pressure increase

  - this increases blood flow to muscles, so the cells receive more oxygen and glucose for respiration, to increase the energy released
• How does adrenaline affect the liver?

  - it causes the liver to break down its glycogen stores to release glucose into the bloodstream.

  - therefore, there is more glucose to be transported to cells for respiration.
• How is adrenaline released?


  Brain sends an impulse to adrenal glands which pump adrenaline into the blood in anticipation of a fight or flight response.
• What is thyroxine?


  A hormone released by the thyroid gland

  Regulates the basal metabolic rate and stimulates protein synthesis for growth and development

  Plays a significant role in many other body processes

  Released in response to TSH (thyroid stimulating hormone), which is released from the pituitary gland
• Describe negative feedback in metabolism?

  Low thyroxine -> hypothalamus releases TRH -> TRH stimulates pituitary gland to release TSH -> TSH stimulates thyroid gland to release thyroxine

  
  

  (opposite happens (stops producing each hormone) when thyroxine levels are high)
• What is metabolism?


  the chemical processes that occur within a living organism in order to maintain life.
• What is metabolic rate?


  The rate at which all the chemical reactions in the cells of the body are carried out
• Describe stage 1 of the menstrual cycle

  It is when menstruation starts - the uterine lining is broken down and released (days 1-4)
• Describe stage 2 of the menstrual cycle

  The uterine lining is repaired. The uterus lining builds up again until it becomes a thick spongy layer of blood vessels, ready for a fertilised egg to implant there. (Days 4-14)
• Describe stage 3 of the menstrual cycle

  An egg develops and is released from the ovary about day 14
• Describe stage 4 of the menstrual cycle

  The lining is then maintained for 14 days, until day 28. If no fertilised egg is implanted in the uterine wall by day 28, the lining begins to break down again and the cycle starts again.
• Describe the role of FSH in the menstrual cycle

  - released by the pituitary gland

  - causes a follicle to mature in one of the ovaries

  - stimulates oestrogen production

  - levels are highest at day 14 (stage 3)
• Describe the role of oestrogen in the menstrual cycle

  - released by the ovaries

  - a rapid increase causes the lining of the uterus to thicken and grow

  - a high level stimulates an LH surge
• Describe the role of LH in the menstrual cycle

  - Secreted by the pituitary gland

  - Surge in LH triggers ovulation

  - Stimulates follicle remains to develop into a corpus luteum (yellow body) which then secretes progesterone
• Describe the role of progesterone in the menstrual cycle

  - Secreted by the corpus luteum after ovulation

  - Stimulates the growth of blood vessels in the uterus lining (in preparation for implantation)

  - Inhibits the release of FSH and LH

  - If no implantation occurs, progesterone levels decrease and the uterus lining sheds. FSH increases and the cycle starts again.

  - highest levels around days 20-25
• What is homeostasis?


  maintaining a constant internal environment
• Give examples of homeostasis

  blood glucose regulation, thermoregulation, oslo regulation
• What is insulin? What does it do?

  It is a hormone released by the pancreas when high blood glucose levels are detected. It causes the liver and muscle cells to absorb excess glucose, to reduce blood glucose levels.
• What is glucose stored as in the liver and muscles?

  glycogen
• What is glucagon? What does it do?


  It is a hormone released by the pancreas when blood glucose levels are too low. It causes the liver turn glycogen back into glucose and to release glucose back into the bloodstream, so blood glucose levels increase.
• What are the causes of type 1 diabetes?

  It is caused by a lack of insulin because the pancreas produces little or none.
• How is type one diabetes treated?

  - insulin therapy is used; insulin is injected into the bloodstream, often at mealtimes to prevent blood glucose rising too high

  - the amount depends on the person's diet, and how active they are, but this is a very effective treatment.

  - people with type 1 diabetes are also advised to consider taking regular exercise, and consider limiting their intake of foods rich in carbs
• What are the causes of type 2 diabetes?

  - when a person is resistant to insulin

  - obesity (BMI over 30) is also a risk factor, and so is having a lot of abdominal fat
• What is the formula for BMI?

  mass in kg/(height in m)^2
• What is the formula for waist-to-hip ratio?

  waist circumference (cm) / hip circumference (cm)
• What waist-to-hip ratios are associated with a higher risk of developing type 2 diabetes?

  over 1.0 for men, over 0.85 for women
• How can type 2 diabetes be controlled?

  - eating a healthy (carb-controlled) diet

  - regular exercise

  - losing weight if necessary

  - sometimes medication or insulin is also used