Homeostasis - blood glucose Flashcards
Define homeostasis (1)
The maintenance of a stable/constant internal environment within strict limits
Advantages of organisms controlling their own internal environment (3)
More independent of their environment
Leads to greater geographical range so can colonise more habitats and ecosystems
Greater chance of finding food, shelter and mates
Define negative feedback (2)
When there is an increase/decrease from the set point, the opposite effect is instigated - produces a response that returns the value to the norm
Define positive feedback (2)
Occurs when a deviation from an optimum causes even greater deviation from normal
Define thermoregulation (1)
Regulation of body temperature
How do endotherms thermoregulate (1)
Maintain body temperature by both physiological and behavioural means
How do ectotherms thermoregulate and give examples (4)
Maintain body temperature by behavioural means only
Exposing themselves to the sun
Taking shelter
Gaining warmth from the ground
Why is it important that blood glucose concentration remains stable? (2)
Maintains constant blood water potential - prevent osmotic lysis of cells
Maintain constant concentration of respiratory substrates - allows organisms to maintain constant level of activity regardless of environmental conditions
Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors (2)
Receptors may send conflicting information
Optimum response may require multiple types of effectors
Why is there a time lag between hormone production and response by an effector? (3)
Takes time to:
Produce hormone
Transport hormone in the blood
Cause required change to the target protein
Name the factors that affect blood glucose concentration (3)
Amount of carbohydrate digested from diet
Rate of glycogenolysis
Rate of gluconeogenesis
Define glycogenesis, glycogenolysis, gluconeogenesis (3)
Glycogenesis - liver converts glucose into the storage polymer glycogen
Glycogenolysis - Liver hydrolyses glycogen to produce glucose
Gluconeogenesis - Liver makes glucose from organic compounds such as amino acids
What organ controls blood glucose concentration and why? (3)
Pancreas
Has glucose receptors which monitor the concentration of blood glucose
Has endocrine cells called the islets of Langerhans which secrete hormone
What are the Islets of Langerhans (1)
Endocrine cells in the pancreas which secrete hormones
Name the hormone used to reduce blood glucose levels to the normal range and where is it secreted from? (2)
Insulin
Secreted by beta cells in the Islets of Langerhans in the pancreas
Outline the role of insulin in reducing blood glucose levels to normal range (3)
Insulin binds to complementary receptors on cell surface membrane of target cells
This controls the uptake of glucose by regulating the inclusion (addition) of glucose carrier proteins in the surface membrane of target cells
Also activates enzymes that stimulate glycogenesis. This therefore reduces blood glucose concentration
Name the hormone used to increase blood glucose levels to the normal range and where is it secreted from? (2)
Glucagon
Secreted by alpha cells in the Islets of Langerhans in the pancreas
Outline the role of glucagon in increasing blood glucose levels to normal range (3)
Glucagon binds to complementary receptors on cell surface membrane of target cells (liver)
Activates enzymes for glycogenolysis and gluconeogenesis . This therefore increases blood glucose concentration
Describe the role of glycogen formation and its role in lowering blood glucose levels (4)
Glucose concentration in cell/liver falls
Below that in blood plasma
Maintains glucose concentration
Glucose enters cell/leaves blood by facilitated diffusion/via carrier/channel proteins
Describe how blood glucose levels can be increased using hormones (3)
Release of glucagon from alpha cells
Leads to formation of glucose in liver cells
From non-carbohydrates/amino acids/fatty acids
Describe how insulin leads to a decrease in blood glucose concentration (3)
Increases permeability of cells to glucose
Increases glucose concentration gradient
Triggers inhibition of enzymes for glycogenolysis
How does insulin increase permeability of cells to glucose (2)
Increases number of glucose carrier proteins
Triggers conformational change which opens glucose carrier proteins
How does insulin increase glucose concentration gradient (2)
Activates enzymes for glycogenesis
in liver and muscles
Stimulates fat synthesis in adipose tissues
Outline the role of adrenaline and glucagon in increasing blood glucose levels to normal range (4)
Both bind to specific transmembrane protein receptors on the surface of the target cell membrane (liver cell) - first messenger
Hormone-receptor complex forms
Hormone-receptor complex activates adenylate cyclase that results in the conversion of ATP into cyclic AMP - second messenger
The cAMP is the second messenger and activates protein kinase enzymes which produce a cascade of chain of reaction that catalyse the conversion of glycogen to glucose
Explain the cause of Type 1 diabetes and how it can be controlled (3)
Body cannot produce insulin due to autoimmune response which attacks beta cells
Treat by injecting insulin
Explain the cause of Type 2 diabetes and how it can be controlled (3)
Glycoprotein receptors are damaged or become less responsive to insulin
Strong positive correlation with poor diet/obesity
Treat by controlling diet and exercise regime
Name some signs and symptoms of diabetes (5)
High thirst due to osmosis of water from cells to the blood, which has a low water potential
Larger volume of urine production due to excess water in blood
Poor vision due to osmotic loss of water from the eye lens
Tiredness due to loss of glucose in urine and poor uptake of glucose by liver and muscle cells
Muscle wasting due to gluconeogenesis caused by increased glucagon
Why is it important that core temperatures remain stable (3)
Maintain stable rate of enzyme-controlled reactions and prevent damage to membranes
Too low - less KE - Less ESC
Too high - enzymes denature
Why is it important that blood pH remains stable (2)
Maintain stable rate of enzyme controlled reactions
Any change away from pH alters tertiary structure
