Chapter 16 - Homeostasis Flashcards
What is meant by homeostasis
Physiological control systems that maintain a constant internal environment
What are the 3 main parts to homeostasis
Thermoregulation
Blood pH
Blood glucose
Why does temperature have to be controlled
- Metabolism is controlled by enzymes
- Enzymes have optimum
- Too got will denature
- Too cold rate of respiration will slow
Why does pH have to be controlled
- Metabolism controlled by enzymes
- Have optimum
- Too acidic or too alkaline will cause rate of reaction to fall and maybe enzymes denature
Why does glucose have to be controlled
- Minimum amount is needed as a respiratory substrate
- Too much glucose decrease the water potential of blood, causing water to move out of cells by osmosis and then cells will shrivel
Explain negative feedback
Receptors detect a change away from the normal/optimum, so effectors activate mechanisms to return the body to optimum
Explain positive feedback
A response that results in the effectors further amplifying the change away from the normal eg sodium channels threshold and depolarisation
Or
Blood clotting
Explain control of blood glucose when it is too high
- Receptors in pancreas detect an increase eg after eating carbs
- Beta cells in the islets of langerhans (pancreas) secrete insulin
- Insulin binds to receptors in liver and muscle cells
- Increasing their permeability to glucose
What are the 3 responses to reduce glucose levels
- Increase absorption of glucose (as explained before)
- Perform glycogenesis (concerting glucose into glycogen)
- Increase rate of respiration to burn off glucose
Explain control of glucose when it is too low
- Receptors in pancreas detect low levels
- Alpha cells only the islets of langerhans (pancreas) secrete glucagon
- Glucagon binds to receptors on liver cells
What are the 3 responses to increase glucose levels
- Decrease rate of respiration
- Glycogenolysis (converting glycogen into glucose)
- Gluconeogenisis (turning non-carbs into glucose)
What is glycogenesis
- Making glucose into glycogen
- Insulin is the hormone that does this
- Occurs when blood glucose is too high
What is glycogenolysis
- Splitting glycogen to make glucose
- Promoted by glucagon and adrenaline
- Occurs when blood glucose is too low
What is gluconeogenesis
- Making new glucose from non-carbs
- Promoted by glucagon
- Occur when blood glucose is too low
Glucagon
Where is it secrets from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for
Alpha cells in islets on langerhans Low blood glucose Liver Increase - Decrease R.O.R - Glycogenolysis - Gluconeogenesis
Adrenaline
Where is it secrets from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for
Adrenal glands Low blood glucose Liver Increase Activates Glycogenolysis and secretion of glucagon Inhibits glycogenesis and insulin
Insulin
Where is it secreted from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for
Beta cells in islets of langerhans High blood glucose Liver and muscles Decrease - Increase R.O.R - Glycogenesis - Increase muscle and liver cells permeability to glucose
Explain how muscle and liver cells permeability is increased by insulin
- Glucose Cartier proteins are stored in vesicles inside liver and muscle cells
- Insulin binds with cell surface receptors on membranes causing vesicles to fuse with cell membrane
- Carrier proteins join the membrane and glucose is absorbed by facilitated diffusion
What is diabetes
An illness where blood glucose levels are not controlled
What is meant by hyperglycaemia
Dangerously high blood glucose concentration
What is meant by hypoglycaemia
Dangerously low blood glucose concentration
What is type I diabetes and how is it caused
Body doesn’t produce insulin
Immune system kills Beta cells in the islets of langerhans so can’t produce insulin
What is the effect of Type I on blood glucose
Hyperglycaemia after eating carbs
This stays high as kidneys can’t remove all glucose from urine
What treatments are there for type I
- Insulin injections or pump (too much insulin can cause hypoglycaemia)
- Avoid simple carbs and sugars
- Eat at regular intervals
- Regular exercise to use glucose and reduce need for insulin
What is Type II diabetes and how is it caused
Beta cells don’t produce enough insulin so
Or
Liver and muscle cells stop responding to it
Can be due to obesity, lack of exercise, poor diet and in elderly
What is the effect of type II on blood glucose
HyperGlycocaemia after eating carbs
Treatments for type II
Improved diet Regular exercise Insulin injections Can use drugs to: - Reduce amount of glucose released - Increase body’s sensitivity to insulin - Make the body produce more insulin
Explain the concept of second messengers
- Hormone acts as first messenger eg adrenaline or glucagon are complementary to the receptor protein in cell membrane of target cell
- Enzyme inside cell is activated
- This is adenyl cyclate
- This converts ATP into cAMP
- cAMP is the second messenger
- cAMP activates an enzyme called protein kinase A by changing its tertiary structure
What is the main purpose of kidneys
Filtration of blood
What is the renal vein and renal artery
To a from the kidney
Draw and label a nephron
In folder
Explain the process of ultrafiltration
- First stage of kidneys processing waste products from blood
- High hydrostatic pressure as afferent arteriolar is wider than the efferent
- Small molecules forced out into Bowman’s capsule to form the filtrate
- Filtrate consists of glucose H2O amino acids ions urea
- Larger molecules such as proteins and red blood cells don’t fit through caps
- Gaps in capillary walls, basement membrane and podocytes
What is the function of the gaps in capillary walls, the basement membrane and podocytes
Prevent large molecules coming through eg proteins
What is selective reabsorption
When useful products from filtrate are re-absorbed by the nephron
Mostly by the PCT but also by DCT and collecting duct and loop of henle
Explain the process of selective reabsoprtion
- Ultrafiltration forms filtrate
- Capillaries wrap around whole of nephron
- Useful substances tea sorbet into blood
- Mostly by PCT, has an adaptation of microvilli to increase
- Urine is filtrate with useful molecules removed so water, urea and excess ions and vitamins
How is each molecule transported from lumen and nephron to PCT
Glucose and amino acids (facilitated diffusion)
Urea (simple diffusion)
Water (osmosis)
Glucose and amino acids against concentration gradient and ions (active transport)
How are molecules transported into capillaries
Diffusion and osmosis
Explain the process at the loop of henle
- At ascending limb, sodium and calcium ions are pumped out by active transport (ATP)
- Decreasing water potential of medulla
- Ascending limb is impermeable to water, so water can’t leave by osmosis
- At descending limb it is permeable to water, so water moves out by osmosis
- Water absorbed into capillaries
- by removing water from filtrate, urine is more concentrated
Explain the process of osmoregulation
- If dehydrated blood has low water potential so is more concentrated
- This is detected by osmoreceptors in the hypothalamus
- Causes the posterior pituitary to secrete ADH (antidiuretic hormone)
- ADH is carried in bloodstream
- ADH binds to specific receptor proteins on the collecting ducts (and a bit on DCT)
- This increases their permeability to water
- Water moves out of collecting duct and DCT by osmosis
- Because medulla has a very low water potential
Explain osmoregulation in very basic terms
More ADH
collecting duct wall more permeable
Water moves out of collecting duct
Less puss
What is thermoregulation and what are the 2 things it allows for
Process whereby animals regulate their body temperature
- Optimal activity of enzymes and metabolic processes
- Independence from fluctuating external conditions
Describe characteristics of endotherms
- Maintain relatively constant temperature that is mainly independent of the environment
- Rely on physiological mechanism for temp control
- Can therefore exploit a wide range of environments and require an abundant food supply
How do endotherms gain heat
- Radiation and conduction from environment
- Muscle contraction
- General metabolism
How do endotherms lose heat
- Radiation, conduction and convection to environment
- Evaporation of sweat
- Expiration and excretion
Describe the characteristics of ectotherms
- Body temperature tends to fluctuate as environment temperature changes
- again heat from environment and rely on structural and behavioural mechanisms for control of body temperature
- Exploit few environments
How and where is urea produced
Deamination of amino acids in liver
