B3.3 Flashcards
define homeostasis
the maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions
state 3 conditions which need to be controlled within the body
temperature
water levels
blood glucose concentration
why does the temperature need to be controlled
to provide a suitable environment for enzymes so that they can work fastest at their optimum temperature
give 2 processes involving the skin which cools the body down
sweating - water evaporates from skin surface resulting in increased energy transfer away from body
vasodilation - allows blood to flow closer to the surface of the skin allowing more heat to be released from the body
describe the process of vasodilation
the body detects a rise in temperature
blood vessels supplying the capillaries at the skin surface dilate ( the muscles in the vessels relax)
more blood flows closer to the skin where more heat energy can be released
give 3 processes that work to keep the body warm
vasoconstriction
shivering
hairs standing up
describe the process of vasoconstriction
the body detects a drop in temperature
blood vessels supplying the capillaries at the skin surface constrict ( the muscles in the vessels contract)
less blood flows closer to the skin surface so less heat is lost to the surroundings
state 2 effects caused by insulin secretion
more glucose is taken up by cells
glucose is converted to glycogen for storage
(both cause a decrease in blood glucose levels)
What does the secretion of glucagon cause?
glucagon secretions cause glycogen to be broken down into glucose to raise the blood glucose concentration
what is the difference between type 1 and type 2 diabetes?
type 1 diabetes is where the body doesn’t produce enough insulin
type 2 diabetes is where the body no longer responds to insulin
how can type 1 diabetes be treated
insulin injections
how can type 2 diabetes be treated
reducing number of simple carbohydrates in diet, losing weight and increasing exercise.
There are also drugs to make insulin more effective in body cells, help the pancreas make more insulin to reduce the amount of glucose absorbed from the gut
what happens if an animal cell is placed in a solution of lower water potential
the cell will shrink
what happens if an animal cell is placed in a solution of higher water potential
water will move into the cell and it will burst
what happens if an animal cell is placed in a solution of equal water potential?
there will be no net movement of water in or out of the cell
what is the function of the kidneys?
maintaining the balance of water and other substances in the body through urine production
filtering out the waste products, such as water, ions and urea (from amino acids) from the body
selectively reabsorbing useful substances such as glucose, ions and water into the body
describe the general structure of a kidney
contains a cortex and medulla
renal artery carries blood to the kidney
renal vein carries blood away from the kidney
each kidney contains many nephrons
ureter carries fluid from the kidneys to the bladder
what does ADH do
when ADH is secreted into the bloodstream it increases the permeability of the kidney tubules to water
this increases the reabsorption of water, where more water leaves tubule to move into the bloodstream
describe the negative feedback loop when dehydration is detected
thirst signals activated
more ADH released ( water retained by kidneys)
describe the negative feedback loop when overhydration is detected
less ADH is released
dilute urine is produced
salts are retained
