Chapter 16 - Homeostasis Flashcards
(23 cards)
Define homeostasis
A set of physiological systems that maintain a stable and constant internal environment
Why is temperature maintained in the body
- Metabolism controlled by enzymes which have an optimum temperature
- Too hot causes denaturation
- Too cold slows reaction
Why is pH maintained in the body?
- Metabolism controlled by enzymes which have an optimum pH
- Too extreme causes denaturation and slows reaction
Why is glucose maintained in the body?
- Minimum amount of glucose needed
- Too much decreases water potential so water leaves by osmosis
- Cells shrivel up
Define negative feedback system
When the product of a reaction leads to a decrease in that reaction. In this way, a negative feedback loop brings a system closer to a target of stability or homeostasis
How does a negative feedback system operate?
- Receptors detect change away from normal
- Effectors activate mechanisms to return to normal
Why does the body have separate negative feedback systems?
- More control
What is a positive feedback system?
A system that results in effectors amplifying the change away from the normal more produces more
What is the point of a positive feedback system?
- Rapid changes and responses
Give two examples of positive feedback systems
Action potentials and blood clotting
How is high blood glucose controlled?
- Concentration increases
- Receptors in the pancreas detect this
- Beta cells in the isle of langerhans secrete insulin
- Binds to receptors in the liver and muscle
- Increases permeability to glucose
- More glucose absorbed by facilitated diffusion
- Glycogenesis occurs
- Increase in rate of respiration
- Blood glucose concentration decreases
How is low blood glucose controlled?
- Concentration decreases
- Receptors in the pancreas detect this
- Alpha cells in the isle of langerhans secrete glucagon
- Glucagon binds to receptors on the liver cells
- Rate of respiration decreases
- Glycogenolysis occurs
- Gluconeogenesis occurs
What is glycogenolysis
The breaking down of glycogen to produce glucose molecules promoted by glucagon and adreanline
Define gluconeogensis
The production of glucose from non carbohydrate respiratory substrates promoted by glucagon
Define glycogensis
The production of glycogen from glucose promoted by insulin
Summarise the glucagon hormone
- Secreted by alpha cells
- When blood glucose low
- Attached to liver receptors
- Increases blood glucose
- Decreases rate of respiration, causes glycogenolysis and gluconeogensis
Summarise the adrenaline hormone
- Secreted by alpha cells
- When blood glucose low
- Attached to liver receptors
- Increases blood glucose
- Activates glycogenolysis and inhibits glycogenesis
Summarise the insulin hormone
- Secreted by B cells
- When blood glucose high
- Attaches to liver and muscle receptors
- Decrease blood glucose
- Increases rate of respiration, causes glycogenesis and increases permeability to glucose
How does insulin increase permeability to glucose?
- Glucose carrier proteins stored in vesicles inside the cells
- Insulin binds to receptors and vesicles fuse with cell membrane
- Carrier proteins join membrane and glucose absorbed by facilitated diffusion
Define diabetes
Illness where the body fails to control blood glucose levels
Distinguish between hyperglycaemia and hypoglycaemia
Hyper = too much glucose and hypo = too little glucose
Summarise type I diabetes
- Caused by immune system destroying B cells that produce insulin
- Hyperglycaemia so glucose in urine
- Inject insulin/pump
- However this can cause low glucose (hypoglycaemia) so avoid carbs, eat regularly and exercise
Summarise type II diabetes
- Obesity, lack of exercise and poor diet so lack of production/stop responding
- Hyperglycaemia so glucose in urine
- Eat healthy, lose weight, regular exercise and use drugs to increase sensitivity to insulin, produce more insulin and reduce glucose released
