homeostasis and response - HOMEOSTASIS Flashcards
thermoregulation, body temperature, losing/gaining heat, sugar regulation, blood glucose + controlling it, diabetes, osmoregulation/ADH, kidney transplants, hormones/puberty in females
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core body temperature
vital organs deep in the body like liver, kidneys, heart are maintained at 37 degrees C
(70% of your energy is used to keep this up)
skin temperature at body extremities (toes, fingers) are usually lower than core body temp
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more or less tired on a cold day?
on a cold day, you’d be focusing your energy on generating more heat so you’d be more tired and hungry
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how can heat be gained
- movement and exercise
- shivering
- vasoconstriction (turning blue)
- wearing extra clothes
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how can heat be lost
- sweating
- vasodilation (turning red)
- removing extra clothing
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how is temperature controlled (receptors, hypothalamus)
body temp is monitored and controlled by temperature receptors in the skin & brain
–> they detect changes in the temperature of blood flowing through those areas
the thermoregulatory centre is in the brain
if body temp deviates from 37 degrees C:
the hypothalamus & skin receptors send out electrical signals
these trigger actions or behaviour that increase or decrease heat loss
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why do we shiver/get goosebumps
when core body temperature drops, muscles begin to twitch (rapidly contract and relax) –> shivering
shivering generates heat which raises body temperature
goosebumps involuntarily appear when someone becomes cold
they are caused by tiny muscles at the base of body hairs pulling the hairs erect
the upright hairs trap an insulating layer of air which helps reduce heat loss
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vasoconstriction/warming up
why do people go pale when cold?
when core body temperature falls, blood vessels in the skin get narrower - vasoconstriction
–> this reduces the volume of blood flowing near the skin surface so blood runs deeper and reduces the amount of heat loss from the body
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vasodilation/cooling down
why do people turn red when hot?
when core body temperature rises, blood vessels in the skin get wider - vasodilation
–> this allows a larger volume of blood to flow near the surface of the skin, transferring heat to the environment and cooling the body down
additional cooling occurs with production of sweat from sweat glands –> as sweat evaporates, it transfers heat away from the body
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negative feedback control of body temperature
BODY TEMP FALLS
skin sensory nerve endings stimulated
hypothalamus detects change in blood temperature
impulse sent to muscles and skin
shivering (muscle contraction, increased metabolism and relaxation) and vasoconstriction begin
BODY TEMP RISES
skin sensory nerve ending stimulated
hypothalamus detects change in blood temperature
impulse sent to muscles and skin
sweating (losing water through pores in skin to cool by evaporation) and vasodilation begin
BODY TEMP FALLS…..
homeostasis meaning
the process of keeping things the same
a series of automatic control systems ensures that the body maintains a constant temperature and steady levels of water, ions, and blood sugar.
homeostasis allows the body’s cells to work at their optimum
glucose
a type of sugar used by the body to provide energy
glycogen
a storage substance made of glucose stored in the liver
insulin
a hormone (chemical messenger) that tells your body to change glucose –> glycogen
made in the pancreas
glucagon
a hormone that tells your liver to change glycogen BACK –> glucose
made in the pancreas
what affects blood glucose
- eating - rise
- vigorous exercise - fall
dangers of high/low blood glucose
excess glucose - makes blood plasma and tissue fluid around cells TOO CONCENTRATED
–> this can severely damage cells e.g. causing crenation (collapsing) in red blood cells
low blood sugar can make cells swell up and burst - lysis
negative feedback controlling blood glucose levels
BLOOD GLUCOSE LEVELS RISE
Pancreas realises that glucose levels are too high
Pancreas releases insulin (chemical messenger) towards Liver through the bloodstream
Liver receives the message so decreases levels of glucose in blood by taking glucose molecules from the bloodstream and sticking it together* to create glycogen
Liver stores it
*takes a soluble molecule that affects osmosis - sticks it together - creates an insoluble molecule that doesn’t affect osmosis
BLOOD GLUCOSE LEVELS FALL
Pancreas realises that the glucose levels are now too low
Pancreas releases glucagon (chemical messenger) through the bloodstream to Liver
Liver receives the message so takes the stored glycogen and splits it up into glucose again and releases it into the bloodstream to increase the blood glucose levels
BLOOD GLUCOSE LEVELS RISE…
type 1 diabetes
- symptoms and treatment
pancreas unable to produce insulin
symptoms:
- frequent urination
- thirst
- fatigue
- confusion
- collapse
treatment
- control
- frequent blood sugar testing
- high sugar –> inject insulin
- stem cell transplant
type 2 diabetes
- treatment
liver/muscles no longer recognise insulin produced by pancreas
treatment:
- older people - treated with tablets
- metformin persuades liver/muscles to recognise insulin
- regular exercise + healthy diet
- lifestyle change
where do you gain and lose water
gain
- respiration in cells (350cm^3)
- drinks (1450cm^3)
- food (800cm^3)
loss
- faeces (100cm^3)
- exhaled air (400cm^3)
- sweat (600cm^3)
- urine (1500cm^3)
what is the job of the kidney
to balance the amount of water it takes in with the amount it gets rid of
what happens when you don’t drink enough water
in hot weather
- lose water as sweat to keep you cool
- kidney produces small amounts of concentrated urine using less water in the body
- you become thirsty to increase water consumption
- water levels then increase due to ADH and thirst
what happens when you drink too much water
- too much water in the body
- use the toilet a lot
- kidney produces a large volume of dilute urine
- water levels decrease due to lots of urine and ADH
what does the hormone ADH do
it controls the amount of water in your urine and is made by the pituitary gland in the brain when you need to keep water in your body
when you are dehydrated how much ADH is released
more ADH is released and concentrated urine is produced
when you are overhydrated how much ADH is released
less ADH is released and dilute urine is produced
what are the 3 kidney stages (no explanation)
filtration
selective reabsorption
urine formation
what is filtration in the kidneys (1)
the RENAL ARTERY branches and ends with lots of capillaries called the GLOMERULUS (inside the nephron).
as blood passes through each glomerulus, it is filtered.
due to HIGH PRESSURES, SMALL MOLECULES are filtered out of the glomerulus and blood and passed into the nephron
what is selective reabsorption in the kidneys (2)
the kidneys SELECTIVELY REABSORBS molecules, only those which the body needs, back into the blood stream from the nephron.
this happens by active transport (energy from respiration is needed for reabsorption)
what is urine formation in the kidneys (3)
the molecules which are NOT selectively reabsorbed (urea, excess water, ions) form your urine
normal blood water levels increase… what happens next
receptors detect and pituitary gland releases less ADH
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kidney reabsorbs less water. urine is more dilute
-
blood water levels reduce. decreased ADH secretion stops
normal blood water levels decrease… what happens next
receptors detect and pituitary gland releases more ADH
-
kidney reabsorbs more water. urine is less dilute and more concentrated
-
blood water levels increase. increased ADH secretion stops
where is a replacement kidney usually attached
it is usually placed in the groin and attached to the blood vessels and the bladder - the ureter carries urine from the new kidney to bladder
what has to be special about the donor kidney and why
the kidney has to be very similar to to the patient’s tissue type because rejection is a major problem with transplantation.
the recipients immune system could recognise it as nonself and try to destroy it.
how do you choose a patient for a kidney transplant
your tissue type is determined the antigens on the surface of every cell
the antigens on every kidney donor are analysed and matched with a similar recipient
how do you reduce infection risk during kidney transplantation
immunosuppressant to prevent rejection however is weakens your immune system
advantages/disadvantages of dialysis and transplantation
dialysis
DISADVANATAGE
- each session takes 6 - 10 hours and 3 times a week
- patients have to strictly restrict diet and fluids
transplant
ADVANTAGE
- majority of UK supports organ donation
- person can survive well with 1 kidney
DISADVANTAGE
- shortage of donors
- kidney must be transplanted within 12 hours
- rejection possibility
- have to:
imitate recipient’s bone marrow
do drug treatment
keep in sterile conditions
to minimise rejection risk
when does puberty happen in males and females
testes make testosterone and this stimulates produce of sperm in boys
ovaries make oestrogen and start to release eggs in girls
what changes happens to males and females during puberty
males
broader shoulders
hair on face/legs/genitals
enlarged genitalia
voice deepens
skin changes
girls
breasts develop
hips widen
hair
skin changes
what are the 2 main things hormones do
stimulate egg release
inhibit egg release
4 stages of menstruation
1 - lining of uterus breaks down and bleeding begins
2 - stretches from day 4 to 14, when lining is repaired
3 - on day 14, the egg is released from the ovary
4 - the maintenance stage where the uterus is maintained in case the egg is fertilised
what are the 4 sets of hormones
follicle stimulating hormone (FSH)
oestrogen
luteinizing hormone (LH)
progesterone
what is the hormone
- follicle stimulating hormone (FSH)
responsible for
- it is made by the pituitary
- stimulates the development of an ovum
- stimulates ovaries to produce oestrogen
what is the hormone
- oestrogen
responsible for
- thickens the lining of the uterus
- inhibits production of FSH
- stimulates pituitary to produce LH
what is the hormone
- luteinizing hormone (LH)
responsible for
- produced by pituitary
- stimulates the release of an egg
what is the hormone
- progesterone
responsible for
- carries on maintaining the endometrial lining of the uterus for a potential pregnancy
- stops a new follicle developing
negative feedback loop of the puberty hormones
FSH made by pituitary
–>
eggs GROW inside follicle
–>
oestrogen made by ovary stimulates the pituitary to make LH
–> oestrogen stops making FSH and the cycle restarts
OR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
–> lining of uterus thickens
LH made by pituitary
–>
progesterone made by ovary
- if pregnant, progesterone and oestrogen continue to be produces
- if not pregnant, progesterone production stops and menstruation occurs
cycle starts again
