homeostasis

• homeostasis


  the tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry around a particular level in response to changes in both internal and external conditions
• the conditions inside your body need to be kept...

  steady, even when the external environment changes
• why is homeostasis important?

  it keeps conditions constant for optimum enzyme action and cell functions
• bodily automatic control systems

  these regulate the body's internal environment, including nervous and hormonal communication systems
• what are some things that the body's automatic control system control?

  body temperature, blood glucose and water content
• all automatic control systems are made up of...

  three main components which work together to maintain a steady condition. these include cells called receptors, coordination centres (including the brain, spinal cord and pancreas) and effectors
• negative feedback counteracts...


  changes
• negative feedback


  a mechanism of response in which a stimulus initiates reactions that reduce the stimulus
• how is negative feedback used when a receptor detects a stimulus level too high?

  the coordination centre receives and processes the information, then organises a response that the effector produces, which counteracts the change and restores the optimum level - the level decreases
• how is negative feedback used when a receptor detects a stimulus level too low?


  the coordination centre receives and processes the information, then organises a response that the effector produces, which counteracts the change and restores the optimum level - the level increases
• how long do the effectors continue to carry on producing responses?

  for as long as they're stimulated by the coordination centre - this might cause the opposite problem, making the level change too much, however the receptor detects if the level becomes too different and negative feedback starts again.
• body temperature must be kept...

  constant
• the body has to balance the amount of energy ... and ... to keep the core body temperature ...

  gained, lost, constant
• thermoregulatory centre


  the area of the brain that is sensitive to the temperature of the blood flowing through the brain and also receives impulses from temperature receptors in he skin, giving information about skin temperature
• what happens when temperature receptors detect that the core body temperature is too high?

  the thermoregulatory centre acts as the coordination centre, receiving information from the temperature receptors and triggers the effectors immediately, which produce a response
• what happens when you're too hot?

  - hairs lie flat

  - sweat is produced

  - blood vessels dilate
• what do hairs lie flat when you're too hot?

  to prevent heat from being trapped by the layer of air between the hairs
• what is sweat produced when you're too hot?

  sweat glands produce sweat, which the evaporates from the skin, cooling you down by transferring energy to the environment
• why do blood vessels dilate when you're too hot?

  blood vessels supplying to the skin dilate so ore blood flows close to the surface of the skin - this is vasodilation, which helps transfer energy from the skin to the environment and cools you down
• what happens when temperature receptors detect that the core body temperature is too low?

  the thermoregulatory centre acts as the coordination centre, receiving information from the temperature receptors and triggers the effectors immediately, which produce a response
• what happens when you're too cold?

  - hairs stand up

  - no sweat is produced

  - blood vessels constrict

  - you shiver
• why do hairs stand up when you're too cold?


  to trap a layer of insulating hair between the hairs and warms you up
• why do you not sweat when you're too cold?

  the body does not need to cool down by having sweat evaporate from the body
• why do blood vessels constrict when you're too cold?

  blood vessels supplying skin capillaries constrict to close off the skin's blood supply - this is vasoconstriction, which helps the body from losing too much heat
• why do you shiver when you're cold?

  your muscles contract automatically and this need respiration, which transfers some energy to warm the body
• antagonistic effectors


  opposing effectors that move conditions in opposite directions at the same time (e.g. one effector heats and another cools) to achieve a very precise temperature- this mechanism allows a more sensitive response
• what controls blood glucose level?

  insulin and glucagon
• what puts glucose into the blood?

  eating foods containing carbohydrates
• What removes glucose from the blood?

  the normal metabolism of cells and vigorous exercise removes much more
• excess glucose can be...

  stored as glycogen in the liver and muscles
• the level of glucose in the blood must be kept...


  steady
• changes in blood glucose level are monitored and controlled by...

  the pancreas, using hormones insulin and glucagon in a negative feedback cycle
• what happens when blood glucose levels are too high?

  the pancreas secretes insulin that causes glucose to move from the blood into the cells. in liver and muscle cells excess glucose is converted to glycogen for storage
• what happens when blood glucose levels are too low?

  the pancreas releases the hormone glucagon. This travels to the liver in the blood and causes the break-down of glycogen into glucose. the glucose enters the blood stream and glucose levels increase back to normal
• diabetes


  a condition in which the body is unable to produce enough insulin, the hormone required for the metabolism of sugar
• type 1 diabetes


  - usually develops during childhood or adolescence

  - when the pancreas produces little to no insulin, leading to high blood glucose levels
• type 1 diabetes symptoms

  frequent urination, unusual thirst, extreme hunger, unusual weight loss, extreme fatigue, irritability
• type 1 diabetes treatment

  insulin therapy, which usually involves several injections of insulin throughout the day to make sure that glucose is removed from the blood quickly once the food has been digested, stopping the level getting to high. the amount of insulin hat need to be injected depends on the person's diet and how active they are
• type 2 diabetes


  - usually develops in adults and most often obese individuals

  - where a person becomes resistant to their own insulin (they still produce it however the body's cells do not respond properly to the hormone), leading to high blood glucose levels
• type 2 diabetes symptoms

  increased thirst, polyuria, numbness in extremities, slow healing infections, blurred vision, fatigue