Unit 6: Homeostasis and blood glucose Flashcards
What is homeostasis?
physiological control systems that maintain the internal environment within restricted limits
What is homeostasis important to maintain
- stable core temperature
- stable blood pH
- stable blood glucose
- water potential of blood
what mechanism does homeostasis rely on
negative feedback
what are hormones
secreted by glands which secrete the hormones into the blood
carried in blood plasma
What are target cells
cells with receptors complementary to hormones
Why does a stable temperature need to be maintained
to provide optimum temp for enzyme activity.
Low temps dont provide sufficient KE for optimum enzyme activity and if temp is too high enzymes denature
why does a stable pH need to be maintained
to provide an optimum pH for enzyme activity
extreme changes in pH cause denaturation
why does a stable blood glucose concentration need to be maintained
to provide sufficient substrate for respiration to release energy for metabolic processes in the body
why does the water potential of blood need to be maintained
so excess water doesnt enter/leave cells causing them to burst/dehydrate/shrivle
what is glycogenesis
conversion of glucose to into glycogen
what is glycogenolysis
hydrolysis of glycogen into glucose
what is gluconeogenesis
conversion of glycerol and amino acids into glucose
how is glucose sourced from your diet
by the hydrolysis of carbohydrates (starch) it is then absorbed into the small intestine
How is glucose sourced from stores
glycogen is stored in the liver and muscle cells when excess glucose from the diet undergoes glycogenesis
How is glucose sourced by making new glucose
from non carbohydrate sources
the liver can make glucose from glycerol and amino acids (gluconeogenisis)
What is negative feedback
restores systems to their original level
How does the liver maintain blood glucose concentration
converts excess blood glucose into insoluble storage compound glycogen
What is insulin
globular protein made of 51 amino acids
How does insulin enter the blood
pancreas detects rise in blood glucose and pancreas beta cells secrete insulin
How does insulin work when theres an increase in blood glucose
- attaches to receptors on target cells (liver/muscle)
- increases permeability of target cells to glucose by stimulating the inclusion of more specific channel proteins
- allows glucose to enter by diffusion reducing the blood glucose concentrarion
How is glucose converted to glycogen (glycogenesis)
Insulin activates enzymes in the liver/muscles that convert glucose into glycogen
- excess glucose is converted to fat when glycogen stores are full
How does the pancreas work when blood glucose decreased
- detected by pancreas and alpha cells secrete glucagon
How does glucagon work when blood glucose decreases?
- glucagon attaches to receptors on target cells and activates enzymes which hydrolyse glycogen into glucose
- glucose is released into the blood increasing blood glucose concentration
How is glucose produced when the glycogen store is full?
(during extensive exercise or starvation etc)
glucagon activates enzymes which convert glycerol and amino acids into glucose (gluconeogenesis) which is released into blood
What gland releases adrenaline
adrenal gland
How does adrenaline produce glucose
- attaches to receptors on target cells and activate enzymes that hydrolyse glycogen into glucose
Why does adrenaline increase glucose production
to provide glucose to cells for respiration and increase blood glucose to normal
What is a first messenger ?
Hormones adrenaline and glucagon don’t enter target cells directly but bind to surface receptors
Outline how adrenaline/glucagon increases glucose
- binds to receptors on target cells
- this activates enzyme adenly cyclase
- adenlyate cyclase converts ATP into cyclic AMP (acts as second messenger)
- AMP activates enzyme protein kinase
- stimulates hydrolysis of glycogen to glucose and its released into blood
What is Type 1 diabetes
- cells in the pancreas responsible for production of insulin are destroyed
- individual produces no insulin at all
What is Type 2 diabetes?
- cells have fewer insulin receptors or they are faulty and dont respond to insulin
- so take up less glucose and convert less into glycogen so blood glucose remains high
How is type 1 diabetes managed
individual injects themselves with insulin
How is type 2 diabetes managed?
individual controls their blood glucose by controlling their diet - avoiding foods that cause rapid surge in blood glucose and by regular exercise