Homeostasis & Response Flashcards
what is homeostasis?
regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal & external changes
homeostasis maintains optimal conditions for enzyme action & all cell functions
what do all control systems involve?
receptors that detect stimuli (changes in internal or external environment)
coordination centre that receives & processes info (e.g. brain, spinal cord, pancreas)
effectors that cause responses to restore optimum conditions (muscles that contract & glands that release hormones)
describe negative feedback
if a change happens to organism, body responds in opposite direction to stop change.
this keeps conditions within narrow limits.
- receptor detects a stimulus e.g. level is too low
- coordination centre receives & processes information then organises response
- effector produces a response that counteracts the change & restores optimum level e.g. level increases
how is body temperature controlled?
stimulus: temperature of surroundings increases or decreases
receptors: temperature receptors (located near skin surface to detect changes in external temperature & in thermoregulatory centre to detect changes in temperature of blood)
coordinator: thermoregulatory centre in hypothalamus in brain receives info from receptors & automatically triggers effectors
effectors: produce a response dependent on whether body is too hot or too cold
what are body’s responses when core body temperature is too high? (be comparative)
sweat glands in skin produce more sweat (containing water & mineral ions) to cover skin surface
transfer heat energy from skin to environment to evaporate water
= more cooling of skin
= blood flowing through skin is cooled so core temp decreases
vasodilation
muscles in walls of arteries supplying blood to skin capillaries relax so blood vessels dilate
= more blood flow near surface
= more heat lost by radiation
= core body temp decreases
what are body’s responses when core body temperature is too low?
less sweat produced
skeletal muscles (e.g. in arm) contract & relax quickly - shivering
= increase rate of respiration in muscle cells
= releases heat energy as respiration is exothermic
= core body temp increases
vasoconstriction
muscles in walls of arteries supply blood to skin capillaries contract so blood vessels constrict/narrow
= less blood flow near surface
= less heat lost by radiation
= core body temp increases
(hairs stand up on end to trap insulating layer of air)
what does the endocrine system include?
glands that secrete hormones (chemicals) into bloodstream
blood carries hormone to target organ where it produces an effect
compare the effects of endocrine system vs nervous system
endocrine system effects:
involves hormones
slower
longer-lasting
general (affect more of body)
nervous system effects:
involves nerves
faster
shorter-lasting
precise
what is the pituitary gland?
‘master gland’ in the brain
secretes several hormones which act on other glands to stimulate other hormones to be released to cause effects
label pituitary gland
pancreas
thyroid
adrenal gland
ovary
testes
see book
what is the purpose of adrenaline & where is it produced?
produced in adrenal glands in times of fear & stress
increases heart rate
increases rate of oxygen & glucose supply to brain & muscles
prepares body for ‘fight of flight’ survival response
what is the purpose of thyroxine & where is it produced?
produced from thyroid gland
stimulates basal metabolic rate
important role in growth & development
stimulates other organs to increase metabolism
describe negative feedback loop for thyroxine
thyroid stimulating hormone (TSH) released from pituitary gland travels in blood & causes thyroxine to be released from thyroid gland
thyroxine travels in blood to pituitary gland
what organ monitors & controls blood glucose concentration?
pancreas
what happens when blood glucose concentration is too high?
pancreas secretes insulin
= affects target organs liver & muscle cells
= causes glucose to move from blood into cells e.g. liver & convert it into glycogen for storage
= blood glucose concentration decreases
what happens when blood glucose concentration is too low?
pancreas secretes glucagon
= causes glycogen to be converted into glucose which is released into bloodstream
= increase blood glucose concentration
what is diabetes?
when the body does not respond correctly to changes in blood glucose concentration
what is type 1 diabetes & how is it treated?
pancreas fails to produce enough insulin
uncontrolled high blood glucose levels
treated with insulin injections
what is type 2 diabetes & how is it treated?
caused by lifestyle
obesity is a risk factor for type 2 diabetes
body cells no longer respond to insulin
treated with a carbohydrate controlled (low carb) diet & regular exercise
how do water, mineral ions & urea leave the body?
what is this controlled by?
why is this important?
no control over:
1. via skin in sweat
2. (only) water leaves via lungs during exhalation
control over:
3. excess are removed via kidneys in urine
controlled by kidneys
cells do not function effectively if gain or lose too much water by osmosis
how do proteins (containing nitrogen) leave the body?
digestion of proteins from diet produces excess amino acids
in liver amino acids are deaminated to form ammonia
ammonia is toxic
ammonia immediately converted into urea (safer & is excreted)
urea is released into blood, filtered out of blood by kidneys & excreted in urine
what is the function of the kidneys?
to maintain water balance in the body
produce urine by filtration of blood & selective reabsorption
what 3 steps are involves in maintaining water & nitrogen balance in the body?
- filtering
- selective re-absorption
- urine release
describe kidney filtering
water & dissolved substances (urea, glucose & ions) are filtered out of blood & pass into tubule
large molecules (proteins & blood cells) stay in blood & do not go into tubule
