B5~Homeostasis and response

• Homeostasis definition:

  is the regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions.
• Automatic control= recognises when there is a change from optimum conditions and then send a signal to reverse that change.


  3 MAIN COMPONENTS of automatic control system:

  (1)Receptors=detect a change

  (2)Coordination centre-Brain, spinal cord-interpret that change (3)Effectors=carry out the change-they consists of muscles that contract or glands that release hormones.
• Negative Feedback loop:

  is the response when conditions change from the ideal point and returns conditions to normal by counteracting the change.
• How does the body react to hot conditions? (Thermoregulation)

  -Hair erector muscle relaxes

  -VASODILATION=blood supply to surface of the skin which transfers the energy from the skin to the environment.

  -Sweat glands produce sweat and evaporates from skin.
• How does the body react to cold conditions?

  -Hair erect= hair stand up to trap an insulating layer of air.

  -No sweat

  -shiver(muscles contract automatically), enables respiration that transfer energy to warm the body.
• Types of nerve cells:

  (1) SENSORY NEURONES: neurones that carry information as electrical impulses from the receptors to the CNS.

  (2)MOTOR NEURONES: neurones that carry electrical impulses from the CNS to effectors.

  (3)RELAY NEURONES: neurones end with either a muscle or gland responding to the electrical impulses (EFFECTORS)
• Stimulus=

  anything that can trigger a physical or behavioural change external or internal.
• Reflex action=

  an automatic (involuntary) and rapid response to a stimulus, which minimises any damage to the body from potentially harmful conditions.

  -Unconscious part of the brain.
• Factors that effect the rate of transmission:

  -it is controlled by drugs..

  (1) Caffeine makes more neurone transmitter to diffuse.

  (2)Drugs combine with receptor molecules, which slows down the time of reaction.
• The Endocrine System=

  Consists of glands that secrete hormones,

  Hormones are chemical messengers sent in the blood- they are also long lasting.
• Pituitary gland:

  • Attached to the brain
  • Known as the "Master gland"
  • Produces hormones that act on other glands, directing them to release hormones that bring about change
• Thyroid:

  • Located in the neck
  • Produces thyroxine, which regulates the rate of metabolism, heart rate, and temperature
• Adrenal gland:

  • Located above the kidneys
  • Produces adrenaline, which prepares the body for a "fight or flight" response
  • Increases heart rate and blood pumping faster
• Pancreas:

  • Located just in front of the kidneys
  • Produces insulin, which regulates blood glucose levels
• Testes:

  • Produces testosterone, which controls puberty and sperm production in males
• Ovaries:

  • Produces oestrogen, which is involved in the menstrual cycle and holds female gametes
• Differences between Nervous & Endocrine system=

  METHOD OF TRANSMISSION= nervous system travels ad electrical impulses and as chemical transmitters between neurones. Whereas endocrine travels as hormones through the bloodstream.

  SPEED OF COMMUNICATION= in nervous information travels faster because of myelin, where in endocrine it travels more slower.

  DURATION OF RESPONSE= nervous is very short, however endocrine is more long lasting.
• In vitro fertilisation (IVF)=

  (1) Patient is given FSH and LH to stimulate eggs to mature.

  (2)Eggs are collected from the ovaries and fertilised by sperm from the father- this is done in the lab. OR If the man is unable to produce a lot of sperm= Intra cytoplasmic sperm injection (ICSI)-where the sperm is injected into the egg cell with a tiny needle.

  (3)Eggs are placed into an incubator and left to grow into embryos.

  (4)Embryos are taken out and inserted into the mothers uterus
• A pro of IVF is it allows infertile couples to have kids.


  Whereas a con is that -it doesn't always work, often leads to multiple births, higher risks of miscarriages and some are against IVF because it often results in unused embryos that are eventually destroyed even though they have a potential to have a human life.(Whole process is unethical).
• Recent advances in microscope technology have improved the success rate of IVF. They've also allowed to remove single cells from an embryo so it enables genetic tests on them and see if they have any diseases.

  Used to find the characteristics of the future baby. (gender, eye colour)