homeostasis Flashcards
hormones
chemical molecules produced by endocrine glands and released into the bloodstream to be carried to their target organs to bring about a response
name 6 endocrine glands
thyroid gland pituitary gland pancreas adrenal gland testes (male) ovaries (female)
what does the thyroid gland release
thyroxine
what does the pituitary gland release and where is it found
releases many hormones
located beneath the hypothalamus in the brain
what does the pancreas release
insulin
what does the adrenal gland release
adrenaline
what does the testes release
testosterone
what is testosterone responsible for
responsible for male growth characteristics (puberty)
what do the ovaries release
oestrogen
difference between nerves and hormones
nerves - fast action - short lived response - act on a precise area - electrical signal hormones - slower action - act for a long time - act in a more general way - chemical signal
role of adrenaline
prepares the body for a fight or flight response that is needed when a threat or stressor is identified by the hypothalamus
what three areas does adrenaline affect
heart
liver
blood vessels
how does adrenaline affect the heart
binds to specific receptors
causing heart muscle cells to contract more frequently and more strongly which increases BLOOD PRESSURE and HEART RATE
- this in turn increases blood flow to the muscles so the cells receive more oxygen and glucose for increased respiration
how does adrenaline affect the blood vessels
blood vessels in the muscles widen to increase blood flow
blood vessels in the organs narrow so blood flow decreases and blood pressure increases
how does adrenaline affect the liver
binds to receptors in the liver
causes the liver to break down GLYCOGEN into GLUCOSE and release it into the blood for respiration ( increasing BLOOD SUGAR CONCENTRATION)
role of thyroxine
plays an important role in regulating metabolic rate
metabolic rate
the rate at which chemical reactions in the body occur
what are the 6 stages of the thyroxine negative feedback loop
- low thyroxine levels in the bloodstream
- stimulates hypothalamus to release TRH (thyrotropin releasing hormone)
- TRH stimulates the pituitary gland to release TSH (thyroid stimulating hormone)
- thyroid releases more thyroxine
- thyroxine levels in the blood return to normal
- when thyroxine levels are normal, thyroxine inhibits the release of TRH and the production of TSH
what happens on day 1 of the menstrual cycle
menstruation starts
lining of the uterus breaks down and is released
what happens on days 4-14 of the menstrual cycle
uterus lining builds up again to form a thick, spongy layer full of blood vessels, ready for the implantation of a fertilised egg
what happens around day 14 of the menstrual cycle
ovulation (egg develops and is released)
what happens on days 14-28 of the menstrual cycle
lining of the uterus is maintained
if no fertilised egg has implanted by day 28, lining starts to break down again and the cycle repeats
4 hormones involved in the regulation of the menstrual cycle
FSH (follicle stimulating hormone)
LH (luteinising hormone)
oestrogen
progesterone
FSH (released by, target organ, purpose)
released by pituitary gland at the start of menstruation
targets ovaries
stimulates follicles to mature and develop
oestrogen (released by, target organ, purpose)
produced by egg follicles in the ovaries, increasing in levels from day 1
targets the pituitary gland
stimulates the production of LH and inhibits FSH and causes uterus lining to thicken and grow
LH (released by, target organ, purpose)
released by pituitary gland in a surge after stimulation by oestrogen
targets ovaries
causes ovulation by causing the dominant follicle to rupture and release the mature egg into the fallopian tubes
progesterone (released by, target organ, purpose)
produced by the corpus luteum (empty follicle)
targets uterus
maintains the uterus lining and inhibits FSH AND LH
what happens if levels of progesterone fall
low progesterone levels allow FSH levels to rise and the whole cycle to start again
what happens to progesterone during pregnancy
levels of progesterone remain high (they keep FSH and LH inhibited so the menstrual cycle does not start again)
infertile
unable to reproduce naturally
ART (assisted reproductive technology)
a fertility treatment that involves eggs being handled outside of the body
give 2 examples of ART
clomifene therapy
in vitro fertilisation (IVF)
what situation causes clomifene therapy to be used
if women are infertile due to no or irregular ovulation
what happens in clomifene therapy
the drug clomifene causes more FSH and LH to be released, stimulating egg maturation and ovulation
this s good because if a couple knows when ovulation will occur, they can have intercourse during this time period to increase the likelihood of becoming pregnant
what happens in IVF (preparing the eggs)
- drug is given to stop the natural production of FSH and LH
- this stops the usual cycle of a single egg maturing in an ovary and being released
- a larger than usual dose of FSH is given to th ewoman for several days to cause many eggs to grow and mature in both ovaries
- a larger than usual dose of LH is given to complete egg cell maturation so that many are released at the same time
what happens in IVF (after egg collection)
egg cells are collected and fertilised with the man’s sperm and grown into embryos
the woman is given progesterone to prepare the uterus for implantation of an embryo by causing it to thicken
embryos are inserted into the woman to hopefully implant and grow into a baby
what two hormones can be used as contraceptives
oestrogen
progesterone
or both (the combined pill or contraceptive patch)
how does oestrogen work as a contraceptive
prevents ovulation by keeping levels high permanently, inhibiting FSH
after a while egg development and production stop
how does progesterone work as a contraceptive
progesterone reduces fertility
it stimulates the production of thick cervical mucus which prevents sperm from entering
what is a barrier method of contraception
methods of contraception that place a barrier between the sperm and the egg
give 2 examples of barrier methods
condoms
diaphragms
what must diaphragms must be used with
spermicide
give two strengths of hormonal contraceptives
+ when used correctly, they are more effective at preventing pregnancy than barrier contraceptives
+ couple doesn’t have to think about contraception each time they have intercourse
give two weaknesses of hormonal contraceptives
- can have unpleasant side effects
- don’t protect against STI’s, only condoms do this
homeostasis
keeping internal conditions constant
this involves the body responding to both internal and external changes whilst balancing inputs and outputs
what is negative feedback
if a condition changed away from the normal level, a response is triggered that counteracts that change
3 examples of homeostasis
blood glucose regulation
thermoregulation
osmoregulation
why is thermoregulation important
it is vital to control body temperature in order to keep enzymes working at their optimum temperature
(this is typically 37’C)
describe the thermoregulatory centre
the centre is the hypothalamus
receptors there are sensitive to blood temperature and receives impulses from receptors in the epidermis and dermis
what happens in terms of thermoregulation when you are too hot (3)
erector muscles relax, so hairs lie flat
lots of sweat is produced and released through pores in the epidermis onto the surface of the skin (once evaporated, it transfers energy from the skin to the environment)
vasodilation - blood vessels near the surface of the skin widen so more blood can flow there and transfer energy to surroundings via radiation - shunt valve has restricted blood flow
what happens in terms of thermoregulation when you are too cold
erector muscles contract, so hairs stand on end, trapping an insulating layer of air near the surface of the skin to keep you warm
little sweat produced
vasoconstriction - blood vessels near the surface of the skin constrict so less blood can flow there and transfer energy to surroundings via radiation- shunt valve has increased blood flow
you shiver (muscles contract automatically), this increases rate of respiration which releases more energy to warm the body
what monitors blood glucose levels
the pancreas
describe the 5 stages of what happens if there is a high blood glucose concentration
- high levels of glucose in the blood detected
- INSULIN is secreted by the pancreas
- insulin causes the liver to turn glucose into glycogen (a storage molecule)
- glucose moves out from the blood therefore and into the liver and muscle cells
- blood glucose level is reduced
describe the 5 stages of what happens if there is a low blood glucose concentration
- low levels of glucose in blood detected
- GLUCAGON is secreted by pancreas
- glucagon makes liver turn glycogen back into glucose
- glucose is released into the blood from the liver
- blood glucose level is increased
what causes type 1 diabetes
the pancreas producing little or no insulin
how can type 1 diabetes be controlled
insulin therapy
typically by injection into the subcutaneous tissue
quantity injected depends on diet and activity
they should regularly exercise and limit their consumption of foods high in simple carbohydrates
what causes type 2 diabetes
the pancreas doesn’t produce enough insulin or is resistant to insulin
how can type 2 diabetes be controlled
controlled by eating a healthy diet, doing regular exercise and losing weight if necessary
(some people have medication and insulin injections)
what increases your chance of having type 2 diabetes
waist to hip ratio of over 1.0 for men or over 0.85 for women
BMI of over 30
waist to hip ratio
hip circumference
bmi (formula)
height ^2 (m)
osmoregulation
controlling the water content of the blood
what happens to cells if the water concentration is too high or low
too high:
water will move into the cells via osmosis, they become turgid, burst/ go through lysis
too low:
water leaves the cells by osmosis and they become flaccid
role of kidneys in regulating water concentration
control how much water is reabsorbed
control how much water is lost in urine
role of kidneys (3)
removal of urea from the blood
adjustment of ion levels in the blood
adjustment of water content in the blood
renal vein
carries deoxygenated blood away from the kidneys
renal artery
carries oxygenated blood to the kidneys
ureter
carries urine from the kidneys to the bladder
what are the parts of the nephron
the glomerulus Bowman's capsule proximal convoluted tubule distal convoluted tubule loop of Henle collecting duct
role of the glomerulus and Bowman’s capsule
filtration
- the liquid part of the bloods if forced into the Bowman’s capsule, leaving large molecules behind
role of the proximal and distal convoluted tubules
selective reabsorption of all glucose (using active transport) and sufficient mineral ions
role of the loop of henle
reabsorption of water
role of the collecting duct
waste products pass into the ureter and then into the bladder as urine
how is water concentration levels monitored and regulated in the blood
the amount of water reabsorbed is controlled by ADH
the hypothalamus monitors water content in the blood and instructs the pituitary gland to produce more or less ADH depending on whether levels are too low or high
what happens if there is water gain
hypothalamus detects water gain
less ADH is released
the collecting ducts are less permeable so less water is reabsorbed
what happens if there is water loss
hypothalamus detects water loss
more ADH is released
the collecting ducts are more permeable so more water is reabsorbed
what are two ways of treating kidey failure
dialysis
kidney transplant
dialysis
filters the bloods for patients who can’ d it themselves
dialysis fluid is personalised to contain the same concentration of glucose and salts in the blood plasms so they aren’t removed form the bloods
what is a weakness of having a kidney transplant
the patient has to take immunosuppressants for the rest of their life so that the kidney isn’t attacked by their immune system for being a foreign body
