homeostasis

• what is homeostasis

  -refers to the stable operating conditions in the internal environment

  -how the human body maintains a rather constant internal environmet despite the changing external conditions
• how does the homeostatic loop work

  receptor

  control centre(the brain)

  effector
• what is the key structure in homeostatic control

  the hypothalamus which is situated in the brain. located above the pituitary gland
• what is a negative feedback loop

  -a way that the bodys systems are maintained.

  
• what is a positive feedback loop

  -these amplify the stimulus

  -there is no set end point for positive feedback loops

  -an example of a positive feed back loop is during childbirth.

  
• what are the 4 main homeostatic systems.

  -temperature control

  -regulation of blood sugar

  -regulation of water

  -excretion
• describe thermoregulation

  -control of temperature

  • a change in body temperature is detected in the hypothalamus which triggers the thermoreceptors to change the temperature of the body accordinaly.
• what happens when the core body temperature decreases

  -vasoconstriction occurs

  • where the arteries and veins are made narrower in order to retain heat. sending blood to the core of the body so less heat escapes through the skin.
• how do the hairs on our skin help with retaining heat

  -if the body temperature is too low then the erector pili muscles contract causing the hairs to stand up and trap air so less heat is loss as there is an extra layer.

  -if there is an increase in body temperature these hairs lay flat so it is easier for the heat to escape.
• what are some of the bodys responses to a low body temperature.

  -shivering

  • the contraction and relaxation of skeletal muscles increases respiration rate which in turn generates more heat.

  -increased metabolic rate

  • adrenaline causes a rapid increase in the metabolic rate which produces heat.
• what are some of the bodys responses to a high body temperature

  -sweating

  • causes the body to cool down as less heat is generated and as the water evaporates from the skin the body cools.

  -behavioural responses

  • such as turning the heating on or wearing extra layers of clothing.
• what body temperatures are dangerous

  27-25 degress can cause organs to fail and a risk of death.

  42 and above causes enzymes to denature and cells to die.
• what is osmoregulation

  the regulation of water and ion concentration within the body. this is done within the kidneys nephrons.
• how is osmoregulation completed within the body.

  the hypothalamus detects changes in the water potential of the blood causing the pituitary gland to release the antiduretic hormone (ADH)
• what does the antiduretic hormone (ADH) do

  makes the kidneys retain more water by opening the aquaporins so more water can flow in. so less urine is formed. and the urine formed is more concentrated.
• describe the regulation of blood sugar.

  -the hormones insulin and glucagon are responsible for maintaining a healthy blood sugar balance.

  -if the blood sugars are too high this is detected by the hypothalamus which signals the pancreas to release more insulin to lower the blood sugar.

  -if the blood sugar is too low more glucagon is produced which converts glycogen to glucose.
• where is glycogen stored

  in the liver. the hormones insulin and glucagon both act within the liver.
• what is excretion

  the removal of waste products from the body.

  waste products inculde water, urea, ions.