homeostasis Flashcards
what is homeostasis
homeostasis is the maintenance of a constant internal environment via physiological control systems
what are factors that are controlled by homeostasis
- temperature
- blood ph
- blood glucose concentration
what happens in the body when the temperature is too low
if it is too low then there is not enough kinetic energy for enzyme-substrate complexes to be formed
this means the rate of important biological reactions/ processes is too slow
what happens if body temperature is too high
is it is too high then enzymes will denature
the body will react to the deviation from normal and return the body back to normal temperature
what happens if ph deviates from the norm
if ph deviates from optimum, it causes enzymes to denature
what happens if blood glucose levels are too low
if it is too low then it leads to cell death as glucose is required for respiration (both aerobic and anaerobic)
what happens if blood glucose levels are too high
it leads to the blood water potential to decrease, s water leaves cells by osmosis
this increases the water potential of cells so water can move back into the cells causing it to burst
what is negative feedback
negative feedback restores systems back to their normal level when there is a change vai the nervous system
what are the stages of negative feedback
stimulus →receptor →CNS→effector→response
the receptor detects the change
it then sends the impulse along a sensory neuron to the CNS which contains a relay neurone
the impulse is then sent along a motor neurone to an effector that elicits a response
what is positive feedback
positive feedback:
when deviation from the optimum stimulus changes which results in an even bigger deviation from the optimum e.g. contractions during labour
contractions releases oxytocin which stimulates even more contractions
is positive feedback part of homeostasis
positive feedback is not involved in homeostasis because it does not keep your internal environment stable.
Positive feedback is useful to rapidly activate processes in the body
when else can positive feedback occur
positive feedback can also happen when a homeostatic system breaks down
for example, hypothermia is low body temperature.
It happens when the body has lost heat quicker than it can produce it. As the body temp falls the brain does not work properly and shivering stops. This makes body temp to fall even more
Positive feedback takes body temp further away from the normal and continues to decrease unless action is taken
what are factors that can influence blood glucose concentration
diet
exercise levels
insulin
adrenaline
glucogon
what is glycogenesis
excess glucose converted to glycogen by the liver only occurs when blood glucose levels are too high
glycogenolysis
breakdown of glycogen back to glucose in the liver when glucose levels are too low
what is gluconeogenesis
creates glucose from non- carbohydrates stores in the live e.g. amino acids and glycerol
it occurs when glucose levels are still too low despite glycogenolysis occurring
when is insulin secreted
insulin is secreted when beta cells in the Islets of Langerhans (which are in the pancreas) detect blood glucose levels that are too high
describe how insulin works to decrease blood glucose levels
- Insulin attaches to receptors on target cells and changes the tertiary structure of the channel proteins so more glucose is absorbed into the cells by facilitated diffusion
- more protein carriers are incorporated into the membranes so even more glucose is absorbed from the blood into the cells
- glycogenesis occurs - which is catalysed by activating enzymes once it is absorbed in the cells
why is glucagon produced
- glucagon attaches to receptors on the surface of target cells
- this stimulates adenylate cyclase to convert ATP into cyclic AMP (cAMP)
- cAMP acts as a second messenger model which contains 1 phosphate unlike three like ATP
- cyclic AMP activates an enzyme called protein kinase which hydrolysis glycogen to glucose→ so glycogen action stimulates glycogenolysis
- It can also activate enzymes involved in glyconeogensis
what is second messenger model
molecules inside a cell that transmit signals intracellularly from the binding of an extracellular molecule to a receptor
explain adrenaline action
- adrenaline attached to a receptor on the surface of a target cell
- this causes a G protein to be activated and to convert ATP to cAMP
- cAMP activated an enzyme that hydrolyses glycogen to glucose
this whole process is the flight or flight mechanism
what is type 1 diabetes
this occurs when the body is unable to produce insulin
this starts at childhood
most often, the results of an autoimmune disease where beta cells are attacked by antibodies
TREATMENT: insulin injections
what is type 2 diabetes
Receptors on target cells lose responsiveness to insulin and so it leads to a decrease in insulin sensitivity
This usually develops in adulthood due to obesity and poor diet → if you have too much glucose/ sugar in your blood due to diet, insulin works soo hard to decrease it your body becomes resistant to insulin
TREATMENT: regulating the uptake of carbohydrates, increasing exercise and sometimes insulin injections
What is the co tr of nlood water potential called
It is called osmoregulation
