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
components of urine (in 1 litre)
23.3g of urea, 0.4g of ammonia, 1.6g of other nitrogenous waste, 10g of sodium chloride (salt), 1.3g of potassium, 2.3g of phosphate
nitrogenous waste
meaning they contain the element nitrogen, they are nitrogen compounds through which excess nitrogen is eliminated from organisms. all animals have to excrete a nitrogenous waste product
why all animals have to excrete a nitrogenous waste product
carbohydrates and fats only contain the elements carbon, hydrogen, and oxygen. Meanwhile proteins also contain nitrogen.
If the body has too much carbohydrate or fat, these can be stored, e.g as glycogen in the liver or fat under the skin and around other organs.
Excess proteins or amino acids cannot be stored. Amino acids are first broken down in the liver, they are converted into carbohydrate (stored as glycogen) and the main nitrogen-containing waste product, urea.
The urea passes into the blood to be filtered out by the kidneys during the formation of urine. The urea is made by chemical reactions in the cells of the body. Excretion means getting rid of waste of this kind.
why faeces aren’t part of excretion
when the body gets rid of solid waste from the digestive system (faeces) this is known as defecation not excretion since it contains few products of metabolism, just the ‘remains’ of undigested food, along with bacteria and dead cells
control of body temperature
mammals and birds are homeothermic/endothermic (warm-blooded). these animals keep their body at a constant temperature, for humans this is 37 degrees celsius. metabolic reactions inside the animal produce heat from inside (endothermic). all other animals are poikilothermic/exothermic (cold-blooded). these animals have the same temperature as their environment
why it’s important to keep a constant body temp
too cold: enzymes have less kinetic energy, fewer successful collisions between substrates and active site, therefore a slower rate of metabolic reactions
too hot: three-dimensional protein enzymes can have too much kinetic energy, change shape of their active site meaning can no longer bind with the substrate, resulting in denaturing, loss of enzyme activity=loss of metabolism
advantage of a human maintaining a body temp of 37 degrees celsius
it means that all the chemical reactions taking place in the cells of the body can go on at a steady, predictable rate
monitoring body temperature
the thermoregulatory centre in the hypothalamus monitors our core body temperature. If you are too hot or cold, temperature receptors in the skin send electrical impulses to the hypothalamus which stimulates the brain to alter our behavior.
if changes in behaviour are not enough to keep our body temperature constant, the thermoregulatory centre in the hypothalamus detects a change in the temperature of the blood flowing through it. it then sends signals via nerves to other organs of the body which regulate the temperature by physiological means.
functions of the skin
forming a tough outer layer able to resist mechanical damage
acting as a barrier to the entry of pathogens
forming an impermeable surface, preventing loss of water
acting as a sense organ for touch and temperature changes
controlling the loss of heat through the body surface
