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)
Anatomical adaptations in organisms in cold areas?
large body size = small surface area to volume ratio
more fur
more fat
small extremities
Behavioural/Physiological changes in Ectotherms?
warming up = expose to sun, press on warm surface, darker skin colouration to absorb heat, more respiration in liver, less breathing
cooling down = shade from sun, press on cold surface, lighter skin colouration, less respiration in liver, more breathing
Control of Body Temperature in Endotherms?
controlled by Hypothalamus in the brain
receives nerve impulse from peripheral thermoreceptors in the skin and central thermoreceptors in the hypothalamus
peripheral thermoreceptors monitor changes in external environmental temperature
central thermoreceptors monitor changes in core body temperature (blood supplying major organs)
How an Endotherm warms itself up?
- reduce blood flow to the skin surface = vasoconstriction, smooth muscle in arterioles to the skin contract, lumen narrows, less blood to skin surface, less heat lost from blood by radiation
- hair on skin stands up = hair erector muscles contract, hairs stand up, traps in air particles, forms an insulating layer, reduces heat loss
- shivering = involuntary contraction of muscles – friction in sliding filament mechanism generates heat and respiration generates heat
- increase respiration in liver = generates heat
How an Endotherm cools itself down?
increase blood supply to skin surface = vasodilation, smooth muscle in arterioles to the skin relax, lumen widens, more blood to skin surface, more heat lost from blood by radiation
sweating = evaporation of water particles from the skin surface using the heat in the blood
symptoms of diabetes?
tiredness, increase urination, thirst
diagnosis of diabetes?
high blood glucose levels on random testing & blood glucose levels remain high following a fasting blood glucose test (person fasts for a number of hours, then consumes a drink of glucose, should normally rise then decrease due to insulin)
gluconeogenesis?
non-carbohydrate molecules into glucose
glycogenesis?
glucose to glycogen
