Homeostasis- BP Flashcards
Job of the hormonal system?
- coordinates the response to certain stimuli
- involves chemical messengers released by endocrine glands into the blood, travels to target cells causing changes
- protein hormones bind to complementary receptors on target cells
- activates enzymes that convert ATP into Cyclic AMP in the cell
- the Cyclic AMP then makes changes in the cell (=2nd messenger system) e.g. insulin
- lipid hormones enter cells by simple diffusion and cause direct changes e.g. oestrogen
control of blood glucose levels?
if high = should be in cells for respiration, also lowers blood water potential
if low = not enough to supply cells of the brain, also increases blood water potential
controlled by the Pancreas
contains the Islets of Langerhans
made of alpha and beta cells
alpha cells produce glucagon
beta cells produce insulin
What happens with High Blood Glucose Levels?
occurs after a meal
insulin is released
most cells in the body have complementary receptors (particularly muscle, liver, brain cells)
causes increase in glucose channels and carriers
glucose taken up and used in respiration
in muscle and liver cells, glucose also converted into glycogen for storage (glycogenesis)
in liver cells, glucose also converted into fat
What happens with Low Blood Glucose Levels?
occurs after starvation or exercise
glucagon is released
only liver cells have complementary receptors
converts glycogen into glucose (glycogenolysis)
converts fats and amino acids into glucose (gluconeogenesis)
glucose is released into blood
Diabetes?
person loses control of blood glucose levels
normally high (hyperglycaemia)
2 types: type 1 and type 2
type 1 starts at young age, person does not make insulin, beta cells damaged by an autoimmune disorder (treatment = insulin injections)
type 2 starts at middle age, person makes insulin but cells are less sensitive, caused by obesity and diet high in simple sugars (treatment = diet and exercise, drugs, insulin injection)
What is Homeostasis?
maintenance of a constant internal environment (the blood and tissue fluid) in animals
control body temperature, blood pH, blood glucose levels, blood water levels, blood salt levels, blood pressure
Homeostasis and Negative Feedback?
- the response to the change is to oppose the change to bring levels back to normal
- (e.g. body temperature increases – response is to bring it down to normal, blood glucose levels decrease – response is to increase it back to normal)
What is Positive Feedback?
the response to the change is to continue the change (e.g. Na+ ions entering a neurone stimulating more to enter in depolarisation)
Why do organisms need to maintain a constant body temperature?
for enzyme activity
What are Endotherms and Ectotherms
endotherms = animals that maintain a strict constant internal body temperature irrespective of external environmental temperature (e.g. mammals)
ectotherms = animal’s internal body temperature maintained more generally and varies with changes in external environmental temperature (e.g. reptiles)
Benefit of being an Endotherm?
can maintain activity over a range of settings e.g. early morning or winter
Benefit of being an Endotherm?
can maintain activity over a range of settings e.g. early morning or winter
Benefit of being an Ectotherm?
require less food/energy
How is internal body temperature controlled?
anatomical, behavioural, physiological changes
ecotherms mainly rely on behavioural changes
endotherms mainly rely on physiological changes
Anatomical adaptations in organisms in warm areas?
small body size = large surface area to volume ratio (lose heat)
less fur
less fat
large extremities e.g. ears/hand/feet (lose heat)
