homeostasis and excretion Flashcards
(21 cards)
what is homeostasis?
keeping conditions constant in the body
what are kidneys role
1) homeostasis- control the concentration of water and solutes
2) excretion- filter blood remove substances
what is an example of homeostasis
every day we gain and loose the same volume of water so that the total content of our bodies stays more or less the same
what is our internal environment?
the surrounding of the cells inside the body, particularly means the blood and tissue fluid
what is tissue fluid?
a watery solution of salts and glucose and it surrounds all cells of the body
It is formed by leakage from blood capillaries- it is similar in composition to blood plasma but lacks the plasma proteins
some examples of maintaining internal environments:
blood PH
concentration of dissolved glucose
body temperature
why is homeostasis important?
cells will only function properly if they are bathed in tissue fluid which provides them with their optimum conditions
for instance if the tissue contains too many solutes, the cells will loose water by osmosis and become dehydrated- thats why we need to control conditions inside our bodies.
what is nitrogenous waste?
contain the element nitrogen eg urea and ammonia
what does our body do with this nitrogenous waste?
The body produces nitrogen waste like urea and ammonia from protein, which cannot be stored. Extra proteins are broken down in the liver, making urea. Urea is removed from the body in urine by the kidneys.
describe the process of the urinary system
each kidney is supplied with blood through a short renal artery, which leads straight from the body’s main artery (the aorta) so the blood entering is at high pressure
inside each kidney, the blood is filtered and the ‘‘clean’’ blood passes out through each renal vein to the vena cava.
the urine leaves the kidneys through two tubes, the ureters and is stored in the bladder.
the bladder has a tube leading to the outside called the urethra - walls are ringed shaped so they can contract and hold back the urine
structure of the kidneys
cortex- darker outer region- contains many tiny blood vessels that branch from the renal artery.
nephrons - microscopic tubes found in the cortex- filtering units
medulla- where the nephrons run down, middle layer of the kidney- has its own bulges called pyramids pointing inwards, the tubules in the medulla eventually join up and lead to the tips of these pyramids where they empty urine into the pelvis
pelvis- funnel shaped structure that connects with the ureter carrying the urine to the bladder
what is the bowman’s capsule and the glomerulus and what happens there?
at the start of the nephron is a hollow cup of cells called the bowmans capsule
The bowman’s capsuale is surrounded by a ball of blood capillaries called a glomerulus .
It is here where blood is filtered.
process of filtration of blood
Blood comes through the kidney through a small artery and goes to a ball of capillaries called the glomerulus.
these capillaries are under high pressure, which forces small substances (water, glucose, salt and urea) out of the blood
These substances pass through the capillary wall and into a structure called Bowmans capsule, this process is called ultrafiltration.
bigger substances like blood cells and proteins stay in the blood because they are too large to pass through
what is glomerular filtrate
the fluid that is filtered out of the blood through the walls of the glomerular into the bowman’s capsule of the nephron in the kidney
most of our glomerular filtrate is
reabsorbed back into the blood
what is the role of the loop of henle?
it is involved with concentrating the fluid in the tubule by causing more water to be reabsorbed into the blood.
mammals with long loops of henle can make a more concentrated urine than ones with short loops
what does homeothermic mean
homeothermic= the mammals that keep their body temp constant despite changes in the temperature of the surroundings.
eg body temp of humans is kept at around 37 degrees
what is the difference between homeotherms and other animals
homeotherms can keep their temperatures constant by using physiological changes for generating or loosing heat. for this reason, mammals and birds are also called endotherms meaning ‘‘heat from the inside’’
endotherms uses heat from chemical reactions in its cells to warm its body, endotherms also use behavioural ways to control their temp too. Eg penguins huddle together in groups to keep warm and humans put on extra clothes
why do humans maintain a temp of 37 degrees?
means all the chemical reactions in the cells of the body can go at a steady, predictable rate. Metabolism doesnt slow down in cold environments.
It is also important body doesnt become too hot- cells enzymes work best at 37 degrees if higher proteins get denatured.
where is the core body temp monitored?
a part of the brain called thermoregulatory centre located in the hypothalamus of the brain acts as body’s thermostat.
what does our brain do when its warm or cold
temp receptors in the skin send electrical impulses to the hypothalamus which stimulates the brain to alter our behavior eg finding shade, putting on more clothes.
