topic 8 Flashcards
homeostasis
negative feedback
set-point to be maintained
stimulus: change in environment
receptor: sends signal to control center
effector: carries out corrective mechanism
negative feedback is applied when set-point is reached, corrective mechanism stops
hormone
a chemical substance produced in minute quantities by an endocrine gland released transported by bloodstream to target organ to exert a profound effect
target organ
responds to chemical signalling by a specific hormone
speeds up, slows down or alter activity
secrete vs release
secrete: produce
release: dispense
eg. bile is secreted by liver but stored and released by gall bladder
endocrine system
secrete hormones directly into bloodstream, ductless
islets of langerhans
beta cells: insulin
alpha cells: glucagon
insulin: decrease blood glucose concentration by increasing permeability of cell membranes to glucose (increase uptake of glucose by cells), stimulating liver and muscles cells to convert excess glucose into glycogen for storage, increasing oxidation of glucose during tissue respiration
glucagon: increases blood pressure by stimulating the conversion of glycogen into glucose, stimulating the conversion of fats and amino acids into glucose
lack of insulin
development of disease (diabetes)
- glucose is lost in urine
body grows weak (lack of glycogen reserve)
ketone (poisonous, produced when body oxidises fats instead of glucose for energy)
too much insulin
abnormal decrease in blood glucose concentration
result in shock and coma, maybe even death
diabetes types
type 1:
developed early (genetic)
early-onset diabetes
unable to secrete enough insulin
type 2:
later
late-onset
most likely in overweight
target cells do not respond well to insulin (insulin resistant)
diabetes cures
type 1:insulin injection into bloodstream
eat sugary food such as glucose sweets, dont exercise too much or eat too little
type 2: carefully regulate carbohydrate content in diet and exercise
take medication and insulin injections
pituitary gland
growth hormone: control rate of bone growth
adh: promote reabsorption of water in kidney tubules and reduce urine volume
pineal gland
melatonin: involved in human biological clock
thyroid gland
thyroxine: controls metabolism (influence growth)
layers of skin
epidermis, dermis, subcutaneous fats
skin epidermis parts
outer cornified layer, granular layer, malpighian layer
outer cornified layer
prevent uncontrolled water loss by evaporation
prevent microorganisms from entering body
protective covering
dermis parts
blood vessels, hair, sebaceous gland, sweat gland, sensory receptors
subcutaneous fats parts
fat layer
advantages of constant body temperature
can remain active throughout the day
no need to hibernate (feed throughout the year)
enzyme work best at constant optimum temperature
gain heat
chemical reactions: respiration (release heat)
heat from sun
hot food and drink
lose heat
convection, radiation
evaporation (sweat)
faeces and urine
expired air
temperature detection
hypothalamus receives information from thermoreceptors in skin and hypothalamus, detecting change in temperature of environment and blood
when overcooling
arterioles constrict shunt vessels dilate, less blood, less heat lost by convection, conduction, radiation
sweat glands less active, less sweat produced
metabolic rate increase
spasmodic contraction of muscles (shivering) increase release of thermal energy
hair traps layer of still air (poor thermal conductor)
when overheating
skin arterioles dilate shunt vessels constrict, more blood through superficial blood capillaries in skin
skin receives more heat and loses it by radiation, convection and conduction
sweat glands become more active, produce more sweat
metabolic rate slows down
rapid breathing helps remove heat
