Unit 7

• Hormones


  Chemical messengers produced in endocrine glands and carried by the blood to the target organ which they affect
• Homeostasis


  The body's method of maintaining the optimum, physical, or chemical conditions for survival
• Endocrine glands


  • Pituitary gland
  • Thyroid gland
  • Adrenal glands
  • Pancreas
  • Testes
  • Ovaries
• Pituitary gland


  • Releases hormones including FSH, LH, and growth hormone
• Thyroid gland


  • Produces hormones including thyroxine
• Adrenal glands


  • Release hormones including adrenalin
• Pancreas


  • Contains cells that produce insulin and glucagon
• Testes


  • Release the hormone testosterone
• Ovaries


  • Produce oestrogen and progesterone
• Basal metabolic rate (BMR)


  The rate at which energy stored in food/body (fat) is transferred by all the reactions that take place in the body to keep you alive, measured at rest
• Adrenaline


  1. Prepares the body for a "fight or flight" response by:

  2. Increasing heart rate

  3. Increasing blood pressure

  4. Increasing blood flow to muscles

  5. Raising blood sugar levels
• Thyroxine


  1. Increases the concentration of itself if concentration levels are low, and decreases the release of itself if concentration levels are high (negative feedback loop)

  2. Causes heart muscles to contract more rapidly

  3. Increases the rate at which proteins and carbohydrates are broken down inside cells, resulting in more aerobic respiration
• Thyroxine mechanism


  1. If thyroxine levels are low, the hypothalamus produces TRH which causes the pituitary gland to release TSH, which acts on the thyroid gland to produce thyroxine

  2. Increased thyroxine levels inhibit the production and release of TSH and TRH
• Hormones involved in the menstrual cycle

  • Oestrogen
  • Progesterone
  • Luteinising Hormone (LH)
  • Follicle Stimulating Hormone (FSH)
• Menstrual cycle


  1. FSH stimulates egg maturation

  2. Oestrogen levels increase, causing uterus lining to develop

  3. Surge in FSH and LH causes ovulation

  4. Corpus luteum releases progesterone to maintain uterus lining

  5. If egg not fertilised, progesterone levels decrease, causing uterus lining to break down (menstruation)
• Contraception


  Measures to prevent pregnancy
• Types of contraception


  • Oral contraceptive pill (contains oestrogen and/or progesterone)
  • Condoms
  • Diaphragm
• Assisted Reproductive Technology (ART)

  Used to aid those who have trouble conceiving, uses hormones to increase chance of pregnancy
• Clomifene therapy


  Increases FSH and LH levels to encourage egg follicle maturation
• In vitro fertilisation (IVF)

  Hormones given to woman to cause ovulation, egg taken and combined with sperm, embryos placed in uterus
• Homeostasis


  Self-regulating physiological processes allowing humans to perform tasks at optimum rate given environmental conditions
• Thermoregulation (body temperature below 37°C)

  1. Shivering to generate heat

  2. Hair erector muscles raise body hairs for insulation

  3. Vasoconstriction reduces blood flow near skin to retain heat
• Thermoregulation (body temperature above 37°C)


  Sweating, as evaporation of sweat cools the body
• Thermoregulation


  1. Hypothalamus detects blood or brain temperatures below 37°C

  2. Body begins to shiver

  3. Hair erector muscles cause body hairs to stand upright

  4. Narrowing of capillaries near skin reduces blood flow

  5. Hypothalamus detects body temperatures above 37°C

  6. Body begins to sweat

  7. Capillaries near skin widen to increase blood flow
• Vasoconstriction


  Narrowing of capillaries near skin to reduce blood flow and heat transfer
• Vasodilation


  Widening of capillaries near skin to increase blood flow and heat transfer
• Controlling Glucose Levels


  1. Insulin released when blood glucose too high

  2. Insulin causes excess glucose to be stored as glycogen

  3. Glucagon released when blood glucose too low

  4. Glucagon causes liver to convert glycogen back to glucose
• Hyperglycaemia


  High blood glucose levels
• Hypoglycaemia


  Low blood glucose levels
• Type 1 diabetes


  • Pancreas produces not enough/no insulin
  • Controlled by insulin injections and lifestyle changes
• Type 2 diabetes


  • Body no longer responds to insulin
  • Caused by lack of exercise and poor diet
  • Controlled by improved diet and exercise
• Urinary System and Osmoregulation

  1. Blood flows through glomerulus under pressure

  2. Bowman's capsule filters small molecules into nephron

  3. Selective reabsorption of minerals and glucose in proximal convoluted tubule

  4. Water reabsorbed by osmosis in loop of Henle and collecting duct

  5. Remaining fluid exits as urine
• Nephron


  • Has large surface area and cells with many mitochondria for active transport
• Antidiuretic hormone (ADH)


  Makes kidney tubules more permeable, allowing more water to re-enter bloodstream
• Blood water levels too high

  Less ADH released, kidney tubules less permeable, more water excreted
• Blood water levels too low

  More ADH released, kidney tubules more permeable, more water reabsorbed
• Kidney transplant


  • Permanent cure, no need for frequent hospital visits
  • Possibility of rejection, need for immunosuppressants
• Kidney dialysis


  • Keeps patient alive, very time consuming, requires diet control
  • Diffuses urea from blood into dialysis fluid
• Urea is the breakdown of excess amino acids in the liver, a process called deamination