homeostasis and excretion Flashcards
homeostasis
the regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions
excretion
a process in which metabolic waste is eliminated from an organism
examples of excretion
the skin excretes water and mineral ions, the lungs excrete carbon dioxide and water, the liver produces urea from amino acids, the kidneys excrete water, mineral ions, and urea
what organ plays a major role in both homeostasis and excretion
the kidneys
kidneys role
they filter the blood, removing substances and controlling the concentration of water and solutes in the blood and other body fluids
internal environment
the surroundings of the cells inside the body, particularly the blood and tissue fluid
tissue fluid
a watery solution of salts, glucose and other solutes that surrounds all the cells of the body, forming a pathway for the transfer of nutrients between the blood and cells.
how tissue fluid is formed
tissue fluid is formed by the leakage of blood plasma from blood capillaries, it is similar in composition to blood plasma but lacks the plasma proteins and red blood cells as they are too big
things that are kept constant inside the body
water levels, salt levels, carbon dioxide levels in the blood, blood pH, concentration of dissolved glucose, and body temperature
why homeostasis is important
homeostasis is important because cells will only function properly if they are bathed in a tissue fluid which provides them with their optimum conditions
blood plasma and tissue fluid needs to be maintained at
optimum pH 7.35, optimum temperature 37 degrees celsius, correct solute and water concentrations, low waste (urea and CO2)
osmoregulation
osmoregulation is how we maintain the correct balance of water and salt/ions in our blood
the concentration of solutes and water
the concentration of solutes and water of blood matches the the concentration of solutes and water of tissue fluid
homeostasis of cells
animal cells prefer to be in an isotonic state (dilute glucose and salt solution). if tissue fluid has the SAME concentration of glucose and salt outside the cell as inside the cell, then no osmosis will take place (isotonic solution).
If tissue fluid has LOWER concentration of glucose and salt (more water) outside the cell than inside the cell, then osmosis will take place, water will ENTER the cell and it will BURST (hypotonic solution).
if tissue fluid has HIGHER concentration of glucose and salt (less water) outside the cell than inside the cell, then osmosis will take place, water will EXIT the cell and it will become DEHYDRATED and SHRIVEL up (hypertonic solution).
urine
an adult human produces about 1.5dm3 of urine every day, although this depends on the amount of water drunk and the volume lost in other forms, such as sweat