Biology topic 5- homéostats

• What is homeostasis?

  Homeostasi is the process by which an organism or cell regulates its internal conditions in response to internal and external changes
• Give the two type of response that effectors can produce

  Chemical response or nervous response
• What happens when the level of a certain condition is too low


  1. The change is detected by receptors
  2. CNS process the information And organise a response
  3. effectors produce a response which will increase the level of the condition
• describe how an electrical impulse crosses a synapse?

  1. The impulse arrives at the end of the first neurone and causes the release of a neurotransmitter
  2. the neurotransmitter diffuses across the gap
  3. the neurotransmitter binds yo receptors on the second neurone
  4. this causes a new electrical impulse to travel along the second nuerone
• A person stands on something sharp. Describe how the body will respond through a reflex arc?

  1. The sharp object will be detected by a receptor in the foot
  2. this wills send an impulse along a sensory neurone to CNs
  3. the impulse will be passed along to relay neurone to a motor neurone
  4. the month neurone will vary the electrical impulse to muscle cells in the leg and foot causing them to contract
  5. this moves the foot away from the sharp objects
• Name 2 way neurones are adapted to their function

  • Long axon to transport impulses over long distances
  • branched at both ends to pass signals easily
  • axon is insulated in a fatty sheath to help impulses travel along quickly
• What is the Pituitary Gland

  The pituitary gland (Master gland) releases lots of hormones that regulate body conditions and also some that act on other glands. This causes specific hormones to be released
• What is a thyroid?

  Produces thyroxine that helps regulate rate of metabolism
• What is the role of a Pancreas

  Produces insulin which is important in controlling blood glucose levels
• What is the role of Ovaries

  Produces oestrogen in females which is a vital part of the menstrual cycle
• What is the role of Testes


  Produces Testosterone in males which controls puberty and sperm production
• State 2 differences between message transport by nerves and by hormones

  • Nerves transport information quicker than hormones
  • nerves carry electrical impulses hormones carry electrical
  • Hormones produces long response Nerves produce short term responses
• What is Glucose stored as

  Glycogen
• What do Hormones control

  Hormones control the blood glucose concentration in a negative feedback cycle
• What happens when blood glucose concentration is too high

  The pancreas releases the hormone insulin: insulin causes glucose to move out of the blood and into the surrounding cells
• What happens when blood glucose levels are too low

  The pancreas releases the hormone glucagon: glucagon turns Glycogen in the liver back to glucose -!: then releases into the bloodstream and the blood glucose concentration increases again
• type 1 diabetes

  • Pancreas produces very little insulin or bone at all
  • this cause uncontrolled high blood sugar levels and can be fatal
  • latients can be treated with regular insulin injections z
  • this helps reduce the amount of glucose in the blood
• What happens on day 1 of the Menstrual cycle

  Menstruatio- the uterus lining is broken down if there’s no fertilised egg, causing bleeding
• What happens on day 4 on the Menstrual Cycle

  The lining of The uterus begins to build back up in preparation for a fertilised egg
• What happens on day 14 on the menstrual cycle

  Ovulation- an egg is released from the ovary and travels down the oviduct into The uterus
• What happens on day 28 on the menstrual cycle


  The wall is maintained for 14 days until day 28, if there is no fertilised egg on the lining of the uterus then the menstrual cycle will begin again
• Where are FSH produced

  Produces by the pituitary gland in the brain and causes eggs to mature in the ovaries
• How are Luteinising hormone (LH) produced

  Produced by the pituitary gland and causes the release of the egg from the ovaries
• Where are Oestrogen produced

  produced in the ovaries and causes the lining in the uterus to grow and thicken
• Where are progesterone produced

  produced in the ovaries by an empty egg follicle and maintains the lining of the uterus
• How Does IVF work

  1. Mother is given LH and FSH to stimulate the maturation and release of several eggs
  2. Eggs are collected from the mother and fertilise by Sperm from the father
  3. the fertilised eggs then develop into embryos and a few are implanted into the mothets uterus where they develop into babies
• Explain how contraceptive pills reduce the chance of pregnancy

  Contraceptive pills contain oestrogen and progesterone

  these hormones inhibit the production of FSH

  so eggs cannot mature in the ovaries and so eggs cannot be fertilised by sperm
• What are negative feedback cycles vital for

  Negative feedback cycles are vital for maintaining homeostasis in the body l
• How do negative feedback cycles work

  They work by detecting and counteracting changes in bodily conditions, returning levels back to their optimum.
• What is Thyroxine

  Thyroxine is a hormone that controls metabolism. It has many uses within the body such as regulating the speed of chemical reactions elements at rest
• What happens when Thyroxine levels are too high

  the secretion of Thydroid stimulating hormone is inhibited reducing the amount of thyroxine released from the thyroid gland. This allows thyroxine lèves to talk back to the normal amount
• what happens when THyroxine levels become too low

  The secretion of TSH is increased, increasing the amount of thyroxine released from the thyroid gland
• what does Adrenaline trigger

  Adrenaline triggers systems that will increase the delivery of oxygen and glucose to the brain and muscles, increasing heart rate and increasing breathing rate, increasing r break down of glucose
• What are the structures of the two control systems

  • Nervous system- electrical impulses transmitted along neurone/ quick and last short time
  • Endocrine system- hormone release/ transported in blood plasma to target cells/ slower and longer effects
• What does insulin causes glucose to do

  Causes glucose to move out of the blood and into cella
• What does the pancreas do if the blood glucose concentration is too low

  The pancreases releases a hormone called glucagon. Glucagon causes liver and muscle cells to convert glycogen into glucose