Homeostasis Flashcards
What is a hormone
Chemical messenger transported in the blood
What increases glucose levels
Eating or break down of starch
Breakdown stored glycogen
Making new glucose from glycerol and amino acids in the liver
Why do glucose levels fluctuates
Respiration levels
Eating
Different demand depending on what activity doing
What are the Islets of Langerhans
Group of hormone producing cells
What hormone does alpha cells produce
Glucagon
What hormone does beta cells produce
Insulin
What is glucagon
Hormone that raises blood glucose
What is insulin
Hormone that lowers blood glucose
How does adrenaline raise glucose levels
Activated enzyme that breaks glycogen into glucose
Inactivates enzyme that synthesises glycogen from glucose
How does adrenaline affect glucose levels
Raises them
What happens when blood glucose levels increases
Pancreas detects rise in glucose levels
Beta cells secrete insulin
Insulin binds to cell surface receptors
Respiration increases so more glucose taken up by cells
Glucose transporters change shape so Moore glucose absorbed into cells
Negative feedback = beta cells reduce insulin secretion when glucose levels return to normal
What happens when blood glucose levels decreases
Pancreas detects fall in glucose levels
Alpha cells secrete glucagon
Glucagon bonds to cell surface receptors
Increase in conversion of amino acids and glycerol to glucose
Enzyme activated to convert glycogen to glucose
Negative feedback = alpha cells reduce glucagon secretion when glucose levels return to normal
What is diabetes
Inability to metabolise carbohydrates properly
Either due to lack of insulin (type 1)
Or loss of responsiveness to insulin (type 2)
Explain diabetes symptoms
Frequent weeing (getting rid of excess glucose)
Thirsty (wee lot taking water)
Blurred vision (glucose build up in lense)
Tiredness (glucose not entering cells)
What is conduction, convection and radiation?
Conduction = energy transfer solids
Convection = energy transfer liquids
Radiation = energy transferred by electromagnetic waves
What are endotherms
Heat from metabolic activities from inside body
Eg mammals
What are ectotherms
Heat from environment
2 methods of losing heat
Evaporation of water
Lose to environment
2 methods of gaining heat
Metabolism of food during respiration
Gain from environment
How do ectotherms control body temperature using the environment
Expose to sun Take shelter Gain warmth from ground Generate metabolic heat Colour variations
How do endotherms control body temperature
Using thermoregulatory centre
How does the thermoregulatory centre work
Measures temperature
Sends impulses along autonomic nervous system to hypothalamus
What happens when you’re too hot
Sweat glands produce sweat which evaporates from skin to cool us down
Erector muscles relaxes so hair lies flat so no air trapped under hair for insulation
Arteriolar dilate so blood flow increases so more heat radiates from surface
Negative feedback = temperature returns to normal so body stops altering it
What happens when we’re too cold
Metabolic rate increases so more heat generated
Arterioles constrict so blood flow in capillaries decrease so less hear radiated from skin
Muscles contract and relax rapidly (shiver) and respiration generates heat
Sweat production stops
Erector muscles contracts and hair pulls up - layer of trapped air under hair acts as insulation
Negative feedback = temperature normal so body stops altering it
The importance of homeostasis
Enzymes sensitive to PH and temperature changes
Water potential changes can stop cells operating properly as shrink or burst
What does glucagon do
Stimulate conversion of stored glycogen to glucose
suggest one way in which insulin receptors might be abnormal
different amino acid sequence so different tertiary structure
explain why the glucose conc. falls in diabetics even when there is no insulin present in the blood
glucose excreted in urine
where is glycogen stored
liver
name an organ in the human body containing cells with glucagon receptors
liver
describe the role played by negative feedback in maintaining a constant blood temperature
triggers effects which return set level
