Topic 7: Animal Coordination

• Hormones are chemicals released directly into the blood and only affect target organs.

  They control things in organs/cells needing constant adjustment and are produced/secreted by endocrine glands in the endocrine system.
• Pituitary Gland (master gland) - produces many hormones that regulate body conditions and that can act on other glands to release hormones
• Thyroid Gland - produces thyroxine which regulates rate of metabolism, heart rate and temperature
• Adrenal Gland - produces adrenaline which prepares the body for a 'fight or flight' response
• Pancreas - produces insulin which regulates blood glucose level
• Ovaries - produces oestrogen which involves the menstrual cycle
• Testes - produces testosterone which controls puberty and sperm production
• Hormones and neurons have major differences:

  • Neurons have very fast actions and act for a short time in a precise area
  • Hormones have a slower action and act for a long time in a more general way
• Adrenaline is a hormone released by the adrenal glands which are above the kidneys.

  It prepares the body for a 'fight or flight' response by activating processes that increase the supply of oxygen and glucose to cells
• Adrenaline Effects:

  • Binds to specific heart receptors to make the heart contract with more force, more frequently so heart rate and blood pressure increases
  • Increased blood flow delivers more oxygen and glucose to muscles for increased respiration
  • Binds to liver receptors so glycogen stores are broken down into glucose
  • Increases blood glucose level for more energy in cells
• When the brain detects a stressful situation, it sends nervous impulses to the adrenal glands for adrenaline to be released
• Negative feedback systems are when the body detects if a substance level is above or below normal so a response will be triggered to correct it.

  For example, thyroxine is released by the thyroid gland to regulate metabolic rate
• Thyroxine Effects:

  • Hypothalamus detects low blood thyroxine levels and releases TRH
  • TRH stimulates the pituitary gland to release TSH
  • TSH stimulates the thyroid gland to release thyroxine until the blood thyroxine level rises to normal
  • If the hypothalamus detects high blood thyroxine levels, the release of TRH is inhibited which reduces the production of TSH so levels fall
• The menstrual cycle is the monthly sequence of 4 stages in which an egg is released and the uterus is prepared for fertilisation using 4 hormones
• Stages of the Menstrual Cycle:

  • Stage 1 (menstruation starts days 1 to 3) - lining of the uterus breaks down and is released
  • Stage 2 (uterus lining is repaired days 4 to 14) - becomes a thick spongy layer full of blood vessels ready for the fertilised egg to implant
  • Stage 3 (ovulation day 14) - an egg develops and is released from the ovary
  • Stage 4 (lining is maintained days 14 to 28) - spongy lining starts to break down if no fertilised egg lands on the uterus wall so the cycle restarts
• FSH (Follicle-Stimulating Hormone) is released by the pituitary gland and stimulates oestrogen production.

  It causes a follicle to mature in one of the ovaries
• Oestrogen is released by the ovaries and causes the uterus lining to thicken and grow.

  A high level stimulates an LH surge
• LH (Luteinising Hormone) is released from the pituitary gland and stimulates ovulation - follicle ruptures and egg is released.

  Also stimulates the follicle remains to develop into a corpus luteum which secretes progesterone
• Progesterone is released by the corpus luteum after ovulation and maintains the uterus lining as well as inhibits FSH and LH.

  When the level of progesterone falls and there's low oestrogen levels, the uterus lining breaks down.

  Low progesterone levels allows FSH to increase which restarts the cycle
• During pregnancy, the level of progesterone remains high to maintain the uterus lining for the fertilised egg.

  If a person is infertile, they can't reproduce naturally so other methods include hormones like IVF and Clomifene Therapy
• Clomifene Therapy:

  • helps infertility caused by not regularly or never ovulating
  • causes more FSH/LH to be released to stimulate egg maturation and ovulation
  • improves chances of pregnancy
• IVF (In Vitro Fertilisation):

  • collect eggs to fertilise with sperms in a lab for an embryo
  • one embryos are tiny balls of cells, 1-2 are transferred into the uterus
  • FSH/LH given before egg collection to stimulate egg production
  • example of ART (Assisted Reproductive Technology) as fertilised eggs are handled outside the body
• Hormonal and barrier contraceptives are used to prevent pregnancy:

  • Oestrogen - taken everyday to keep levels permanently high to inhibit FSH so egg development and production stops
  • Progesterone - stimulates the production of thick cervical mucus which prevents sperm entering through the cervix
  • Condoms/Diaphragms - prevent the sperm/egg from touching
• Some hormonal contraceptives contain oestrogen and progesterone such as the combined pill and contraceptive patch.

  The mini pill and contraceptive injection both contain progesterone only
• Hormonal Methods:

  • more effective than barrier methods at preventing pregnancy when used correctly (advantage)
  • unpleasant side effects like acne, headaches and mood changes (disadvantage)
  • don't protect against sexually transmitted infections/diseases (disadvantage)
• Homeostasis - maintaining a constant internal environment despite changes in the external environment
• Homeostasis is important as cells need the right conditions to function properly at optimum enzyme action or else it's dangerous for your health.
• The body needs to respond to internal and external changes while balancing inputs and outputs:

  • Osmoregulation - balance between water gained and lost
  • Thermoregulation - regulating body temperature to multiple environments
  • Blood Glucose - regulate the concentration of glucose in the blood
• Insulin and glucagon control blood glucose concentration despite multiple changing factors:

  • eating carbohydrates puts glucose into the blood from the small intestine
  • normal metabolism of cells remove glucose from the blood
  • vigorous exercise removes even more glucose
  • excess glucose is stored as glycogen in the liver and muscles or lipids (fat) in tissues if those are full
• The pancreas monitors/controls blood glucose using the hormones glucagon and insulin:

  • concentration too low ---> pancreas secretes glucagon ---> liver turns glycogen into glucose ---> blood glucose increased
  • concentration too high ---> pancreas secretes insulin ---> liver turns glucose into glycogen ---> blood glucose decreased
• Type 1 diabetes is a condition where the pancreas produces little or no insulin meaning blood glucose can rise to a lethal level.
• Type 1 Diabetes Treatments:

  • injecting insulin into subcutaneous tissue (fatty tissue under skin) mostly after meals so glucose is quickly removed once food is digested
  • insulin injection amount varies in diet/activity (very effective treatment)
  • limiting intake of simple carbohydrates
  • regular exercise to help remove excess glucose
• Type 2 diabetes is a condition where the pancreas doesn't produce enough insulin or when the person becomes resistant so blood glucose levels rise
• There is a correlation between obesity and type 2 diabetes meaning they have an increased risk (Body Mass Index over 30).

  The body storing fat around the abdomen is also an increased risk shown with the waist-to-hip ratio (above 1 for men and 0.85 for women)
• Type 2 Diabetes Treatment:

  • healthy diet
  • losing weight
  • regular exercise
  • rarely need medication like insulin injections
• Thermoregulation - the process to keep the body's internal temperature steady
• Enzymes in the body mainly have the optimum temperature 37'C so homeostasis triggers a response to counteract changes so they don't slow or denature
• The thermoregulatory centre is the hypothalamus which contains receptors sensitive to blood temperature in the brain.

  It also receives impulses from receptors in the skin for external changes (found in epidermis/dermis)
• Increasing Body Temperature:

  • Erector muscles relax so hairs lie flat
  • Sweat (water/salts) produced by sweat glands in the dermis is released onto the skin surface through pores in the epidermis ------> sweat evaporates to transfer energy from skin to environment which cools the body
  • Vasodilation (blood vessels close to skin surface dilate) allows more blood to flow near the surface so it can transfer more energy into the surroundings
• Decreasing Body Temperature:

  • Erector muscles contract so hairs stand on end to trap an insulating layer of air
  • Very little/no sweat
  • Vasoconstriction (blood vessels near skin surface constrict) means less blood flows near the surface so less energy is transferred to environment
  • Shivering (muscles rapidly contracting and relaxing) increases the rate of respiration which transfers more energy to warm the body