homeostasis and hormones Flashcards
define hormones
chemical messengers used in the body that are carried in the plasma
what are glands
organs that secrete or release substances
endocrine glands:
- no ducts
- release hormones directly into blood stream
- e.g. pituitary and thyroid gland
exocrine glands:
- have ducts
- hormones secreted into blood stream via ducts
- e.g. salivary glands, tear glands
where is FSH produced
pituitary gland
role of FSH
stimulates egg maturation and oestrogen secretion in females
stimulates sperm production in males
where is LH produced
pituitary gland
role of FSH
stimulates egg release (ovulation) in females
stimulates testosterone production in males
where is ADH produced
pituitary gland
role of ADH
controls water content of blood
where is thyroxine produced
thyroid gland
role of thyroxine
controls metabolic waste
where is insulin produced
pancreas
role of insulin
lowers blood glucose
where is glucagon produced
pancreas
role of glucagon
raises blood glucose
where is adrenaline produced
adrenal gland
role of adrenaline
prepares body for physical activity
where is oestrogen produced
ovaries
role of oestrogen
controls development of female secondary sexual characteristics
stimulates thickening of uterus lining
where is progesterone produced
ovaries
role of progesterone
regulates menstrual cycle
maintains uterus lining
where is testosterone produced
testes
role of testosterone
controls development of male secondary sexual characteristics
stimulates sperm development
how do messages move around the body in the nervous system
impulses are transmitted through nerve cells (although chemical at synapse)
how do messages move around the body in the endocrine system
hormones are transported in the blood
speed of impulse travel and time taken for effect to happen in nervous system
impulses travel fast and have an ‘instant effect’
speed of hormones and time taken for effect to happen in endocrine system
travel more slowly and generally take longer to act
length of response time in nervous system
response is usually short-lived
length of response time in endocrine system
response is usually longer lasting
is the effect localised or widespread in the nervous system
impulses act on individual cells such as muscle fibres, so have a very localised effect
is the effect localised or widespread in the endocrine system
can have a widespread effect on different organs (although they only act on particular tissues and organs of they have the correct receptors)
when do adrenal glands secrete adrenaline
when you are excited/scared/angry
what does adrenaline do
prepares the body for action / physical activity
effect of adrenaline on the heart
heart rate increases
why does the heart rate increase when adrenaline is released
pumps MORE blood to transport MORE oxygen and glucose to respiring cells in the muscles so MORE aerobic respiration can occur, releasing MORE energy, so there can be MORE muscle contraction
effect of adrenaline on the lungs
breathing rate increases
why does the breathing rate increase when adrenaline is released
MORE oxygen for more aerobic respiration, which releases MORE energy, leading to MORE muscle contractions
effect of adrenaline on the arterioles in muscles
arterioles dilate to increase blood flow
why do arterioles in muscles dilate when adrenaline is released
increased blood flow -> MORE oxygen and glucose transported to respiring cells in muscles -> MORE aerobic respiration -> MORE energy produced -> MORE muscle contractions
effect of adrenaline on arterioles in digestive system
constrict to decrease blood flow
why do arterioles in digestive system constrict when adrenaline is released
constrict to decrease blood flow as there is no need for digestion of food; oxygen and glucose used in respiration in muscles cells instead
effect of adrenaline on the liver
releases glucagon to convert glycogen into glucose
why does the liver release glucagon when adrenaline is released
glucagon converts glycogen into glucose -> glucose gets released into bloodstream and transported to respiring cells in the muscles -> MORE glucose available for respiration -> MORE energy released -> MORE muscle contraction
effect of adrenaline on the eyes
pupils dilate
why do pupils dilate when adrenaline is released
allows MORE light into retina so you can see surroundings/danger BETTER
effect of adrenaline on skin hairs
hairs stand up
why do skin hairs stand up when adrenaline is released
in animals they appear larger and scarier
effect of adrenaline on the brain
mental awareness (alertness) increases
why does mental awareness (alertness) increase when adrenaline is released
can react faster
what is homeostasis
the maintenance of a constant internal environment in the body
what are some internal conditions that are controlled?
temperature, water, pH, oxygen, blood sugar, carbon dioxide
how is homeostasis control achieved
using negative feedback mechanisms
what is negative feedback
whenever a change occurs in the system, this automatically causes a corrective mechanism to start, which reverses the original shape and brings the system back towards the normal
what is the name of the hormone responsible for controlling water levels in the blood
ADH (anti-diuretic hormone)
what is the region of the brain that regulates the concentration of blood
hypothalamus
water loss (negative feedback cycle):
- loss of water means concentration of blood starts to increase
- this is detected by special cells in the hypothalamus
- these cells cause the pituitary gland to release MORE ADH
- ADH causes the collecting duct to become MORE permeable to water
- this means MORE water is reabsorbed back into the blood
- this makes the urine more concentrated, less volume
water gain (negative feedback cycle)
- water gain means the concentration of the blood begins to decrease
- this is detected by special cells in the hypothalamus
- these cells cause the pituitary gland to release LESS ADH
- less ADH causes the collecting duct to become less permeable to water
- this means less water is reabsorbed back into the blood
- makes urine more dilute, increased volume
in humans, what is glucose stored as and where
stored as glycogen in the liver
what happens when the body is short of glucose
it releases glucagon to convert glycogen into glucose
what does insulin do
activates conversion of glucose to glycogen
what does glucagon do
activates conversion of glycogen to glucose
in mammals what part of the brain monitors the core body temp and where is it located
thermoregulatory centre - located in hypothalamus
what happens when there is a change in temperature
- temperature receptors in brain and skin send electrical impulses to hypothalamus
- usually stimulates brain to change our behaviour (eg. find shade, have a cool drink, take off a layer of clothing)
when these changes are not enough:
- thermoregulatory centre in hypothalamus detects a change in temp of the blood running through it
- sends a signal via nerves to other organs in the body which then regulates temperature by physiological means
what are homoeothermic organisms
warm blooded
what are poikilothermic organisms
cold blooded
does body temp fluctuate in homoeothermic organisms
less fluctuations -> body temp kept constant despite changes in surroundings
does body temp fluctuate in poikilothermic organisms
yes
are homoeothermic organisms endo or exotherms
endothermic
are poikilothermic organisms endo or exotherms
exothermic
do homoeothermic organisms have heating from inside or outside
inside -> trap heat from chemical reactions to warm body
do poikilothermic organisms have heating from inside or outside
outside -> manage to keep core body temp more constant by adapting their behaviour
advantages of being homeothermic
- all chemical reactions in body can go on at a steady, predictable rate
- metabolism doesn’t slow down in cold environments
- stops enzymes from denaturing about a certain temp - kept at their optimum
- warmer - metabolism increases
functions of the skin
- barrier to entry of disease-causing microorganisms
- prevents water loss
- tough outer layer to resist mechanical damage
- sense organ - touch and temp changes
- receptor and effector
- leading role in temp regulation. responds to nerve impulses from hypothalamus. controls heat loss.
role of capillary network in skin
blood flows through to radiate heat outside (vasodilation) and blood flow is restricted when cold (vasoconstriction)
role of erector muscle in skin
tightens to give goose bumps when cold. controls movements of hair
role of sweat pore in skin
hole where sweat is released
role of hair in skin
stand up to trap air when cold to provide insulation as air is a poor conductor of heat. lie flat when hot
role of epidermis in skin
tough outermost layer of skin, provides waterproof barrier and prevents the entry of pathogens
role of dermis in skin
contains tough connective tissue, hair follicles and sweat glands. provides strength, stability and support
role of sweat glands in skin
antibacterial properties. sebaceous gland, oils skin to prevent skin drying out. helps to cool us down
role of fat cells in skin
provides insulation to help body conserve heat
role of sensory cell in skin
receptor send messages to hypothalamus
what happens when a rise in core body temp is detected
sweat glands produce a greater volume of sweat
- sweat evaporates off skin which requires energy - latent heat of vasodilation
- only cools skin down when it evaporates
hairs lie flat against skin surface
- relaxation of hair erector muscles
vasodilation
- increased blood flow to skins surface
- more heat is lost via radiation
what happens when a decrease in core body temp is detected
hairs on skin stand up
- hair erector muscles contract
- hairs trap a layer of air next to the skin which acts as insulation
- much more effective in hairy mammals
bodies metabolism speeds up
- generates more heat (from chemical reactions)
- adrenaline stimulates this
vasoconstriction
- restricted blood flow to surface of skin
- less heat is lost via radiation
shivering
- muscles contract + relax rapidly
- generates a large amount of heat
vasoconstriction
- arterioles constrict, reduced blood flow to surface capillaries
- little heat lost by radiation
vasodilation
- arterioles dilate, larger volume of blood flows through capillaries near skin surface
- blood able to lose heat via radiation
what is auxin
a hormone that plants respond to which controls growth in a plant
what is the growth response to a directional stimulus in a plant called
a tropism
what is it called when plants grow towards a stimulus
positive tropism
what is it called when a plant grows away from a stimulus
negative tropism
what is it called when plants grow in response to light
phototropism
what is it called when plants grow in response to gravity
geotropism
what are tropisms caused by
plant hormones
what is the hormone responsible for the bending of shoots towards the light
auxin
where is auxin produced
produced at the tip of the shoot and roots
it then diffuses down the stem to the region of growth
what does auxin control and how
controls the growth of cells (cell elongation) by increasing the growth in shoots of plants and decreasing the growth in roots of plants
what does auxin stimulate in the growing region
mitosis, as well as causing individual cells to elongate
does the root of a plant have a response to light
most of the time there is not response
does the shoot/stem/leaves have a response to light
grow towards the light -> positive phototropism
does the root grow in response to gravity
grow towards gravity -> positive geotropism
does the shoot/stem/leaves grow in response to gravity
grow away from gravity -> negative geotropism
what happens when a plant has uniformed light
auxin distributes evenly on each side of the shoot -> mitosis is stimulated evenly on each side -> cell elongation is the same -> plants grow upwards towards light -> more photosynthesis
what happens when a plant has unidirectional light
auxin accumulates on dark side -> more mitosis and cell elongation on dark side -> cells on dark side grow faster -> bend towards light -> more photosynthesis
does auxin stimulate or inhibit growth in shoot due to gravity
stimulates
does auxin stimulate or inhibit growth in roots due to gravity
inhibits
auxin in roots (due to gravity)
auxin accumulates in lower side of roots
in roots the extra auxin inhibits growth -> this means cells on top will elongate faster, therefore grow faster, so the roots will bend downwards
where does auxin accumulate due to gravity
lower side of root and shoot
auxin in shoots (due to gravity)
auxin accumulates on lower side (auxin stimulates growth in shoots) -> more mitosis on lower side -> more cell growth -> causes shoot to bend upwards as lower side is growing faster
why do roots need to grow down
to get water/minerals/anchorage
why does shoot need to grow up
needs to grow towards sun -> photosynthesis
