Unit 9 - Homeostasis Flashcards
Definition of homeostasis?
Maintaining the internal environment within restricted limits, to prevent damage to cells.
Importance of maintaining core body temp?
Too high:
Hydrogen bonds break within enzymes, changing their tertiary structure and the shape of the active site. Less enzyme-substrate complexes
Too low:
Enzymes have too low kinetic energy, less enzyme-substrate complexes, so metabolic rate is reduced.
Importance of maintaining blood pH?
Too high:
Hydrogen + ionic bonds break within proteins, changing their tertiary structure.
Too low:
Hydrogen + ionic bonds break within proteins, changing their tertiary structure.
Importance of maintaining blood glucose concentration?
Too high:
Blood has lower water potential than in cells, water leaves cells into blood by osmosis. Cells lack water for metabolic reactions such as hydrolysis and as a solvent.
Too low:
Glucose is not provided to cells fast enough for a high enough rate of respiration.
Importance of maintaining blood water potential?
Too high:
Water enters cells by osmosis. Too much can cause cell lysis. Lots of water in the blood causes high blood pressure.
Too low:
Water leaves cells into blood by osmosis. Cells lack water for metabolic reactions such as hydrolysis and as a solvent.
What is negative feedback?
Negative feedback reverses the direction of change back to its original level.
How is the regulation of body temperature an example of negative feedback?
When body temp is too high, the body responds to decrease it back to its original (37)
When body temperature is too low, the body responds to increase it back to its original.
What is the advantage of having separate mechanisms to increase and decrease the factor?
Separate mechanisms are used to increase or decrease the factor, as this gives a greater degree of control.
What is positive feedback?
Positive feedback is where a change in one direction is amplified, i.e. an increase and leads to a further increase.
Give a biological example of positive feedback?
-Oxygen binding to haemoglobin
-Labour
-Opening of Na+ channels as depolarisation occurs along a neurone
What type of messenger is a hormone?
Chemical messenger
Where are hormones produced and secreted from?
glands
How are hormones transported around the body?
in the blood stream
Where do specific hormones act?
Target cells that contain receptors complementary to the specific hormone.
How is the effect of hormones different to that of the nervous system?
-Hormones effect is widespread + long lasting
-Nervous systems effect is local + short term
What will make blood glucose go up?
Eating foods high in glucose and starch. Glucose is absorbed into the blood from the small intestine.
What will make blood glucose go down?
Increase in cell respiration, e.g. muscle contraction. Glucose enters the cell from the blood.
Which cells produce insulin?
Beta-cells in Islets of Langerhans in the pancreas.
What effect does insulin have on blood glucose?
Decreases blood glucose concentration
What are insulin’s targets cells?
Liver + muscle cells
How does insulin decrease blood glucose?
-Inserting more glucose channel proteins into the cell membrane, glucose enters cell by facilitated diffusion
-Activating enzymes to convert glucose to glycogen for storage (glycogenesis)
Which cells produce glucagon?
Alpha-cells in Islets of Langerhans in the pancreas
What effect does glucagon have on blood glucose?
Increases blood glucose concentration
What are glucagon’s target cells?
Liver cells
How does glucagon increase blood glucose concentration?
-Activating enzymes to hydrolyse glycogen to glucose (glycogenolysis)
-Activating enzymes to convert glycerol/amino acids to glucose (gluconeogenesis)
What are insulin and glucagon both?
Hormones and proteins
Overview of how adrenaline also increases blood glucose?
-Adrenaline is released from adrinal glands
-It binds receptors on liver cells
-Enzymes are activated which hydrolyse glycogen to glucose (glycogenolysis)
Diagram of the secondary messenger pathway?
Steps of the secondary messenger pathway of glucagon and adrenaline?
1) When glucagon and adrenaline bind their receptors they activate the enzyme adenylate cyclase.
2) Adenylate cyclase converts ATP to cyclic AMP (cAMP)
3) cAMP is the second messenger and activates the enzyme protein kinase
4) Activates enzymes to cause glycogenolysis (hydrolyse glycogen to glucose)
What is diabetes?
It is a disease where an individual is unable to lower their blood glucose level.
What is type 1 diabetes?
When you can’t produce insulin due to death of beta cells of the Islets of Langerhans (autoimmune disease)
What is type 2 diabetes?
When insulin is produced by the beta cells but the insulin receptors do not respond to the insulin.
-Blood glucose decreases more slowly
-Type 2 can be caused by obesity
What are 2 ways to control type 1 diabetes?
1) inject insulin
2) complex carbohydrates (polysaccharides) should be eaten rather than sugar
How does injecting insulin work as a treatment for type 1 diabetes?
As insulin cannot be produced due to beta cells being destroyed. Its a way of getting insulin into your blood. Cannot be taken orally as insulin (a protein) will be digested or denatured by stomach acid.
Why is eating complex carbohydrates (polysaccharides) good if you have type 1 diabetes?
Prevents a rapid increase/spike in blood glucose. Absorbed more slowly than monosaccharides because glycosidic bonds need to be hydrolysed first before absorption.
3 ways to treat type 2 diabetes?
1) regular exercise
2) loss of weight
3) glucose lowering medication
Why not inject insulin into someone who has type 2 diabetes?
Because they already produce insulin as beta cells are present, but their insulin receptors do not respond to insulin.
How does regular exercise help type 2 diabetes?
More respiration so more glucose used so decreased concentration of glucose in cells so more glucose enters by facilitated diffusion.
How does loss of weight help type 2 diabetes?
Due to obesity being a cause of type 2 diabetes.
Definition osmoregulation?
the control of blood water potential
Overview of the role of the kidney?
-at the kidney substances are filtered out of the blood, including water
-useful substances are reabsorbed back into the blood
-unwanted substances travel to the bladder where they are excreted within urine.
If blood water potential is too high, what will happen in the kidney?
-Less water is reabsorbed
-Increased urine volume
-Decreased urine concentration
If blood water potential is too low, what will happen at the kidney?
-More water reabsorbed
-Decreased urine volume
-Increased urine concentration
Structure of the kidney?
What does the renal artery do?
Brings blood from the heart to the kidney
What does the renal vein do?
Takes blood away from the kidney
Role of the nephron?
Blood is filtered and substances are reabsorbed here.
Structure of the nephron?
What is the glomerulus?
Bundle of capillaries which sits in the Bowman’s capsule
What is the basement membrane?
membrane between the capillaries of the glomerulus and bowman’s capsule
Role of the bowman’s capsule?
where ultracentrifugation takes place
Role of the podocytes?
cells which make up the bowman’s capsule epithelium
have large gaps between them which allow the glomerular filtrate through
Role of the proximal convoluted tubule?
where selective reabsorption occurs here which reabsorbs water, glucose, amino acids and other useful substances back into the blood
Role of the loop of Henle?
regulates blood water potential by maintaining a gradient of sodium ions in the medulla
Role of the distal convoluted tubule?
more reabsorbtion of water occurs here
Role of the collecting duct?
final place for the reabsorbtion of water
Steps of ultrafiltration?
-There is a high blood pressure in the glomerulus
-Water, glucose, amino acids and other small molecules are forced through:
1. Pores in the capillary endothelium
2. basement membrane
3. Bowman’s capsule epithelium which is lined with podocytes
-This forms the glomerular filtrate in the tubule.
-Proteins and cells are too large to pass through so remain in the blood.
What is proteinurea?
It is where there is a high quantity of protein in the urine when there should be none. Damage to the basement membrane causes proteinurea.
How is the bowman’s capsule adapted to its function?
-The capillary endothelium contains pores which allow water, glucose, amino acids and other small molecules through but not blood cells/large plasma proteins
-The basement membrane acts as a fine filter to allow only small molecules to pass through
-The podocytes have large gaps between them which allow the glomerular filtrate into the lumen of the proximal convoluted tubule.
