Topic 5 - Homeostasis and Response - Homeostasis in action Flashcards
(20 cards)
1
Q
How is the body temperature kept constant?
A
- body has to balance amount of energy gained and lost to keep core body temperature constant
- this relies on thermoregulatory centre in the hypothalamus of your brain
- contains receptors sensitive to temperature of blood flowing through brain
2
Q
How does negative feedback control body temperature?
A
- temperature receptors detect that core body temperature too high
- thermoregulatory centre acts as a coordination centre - receives information from temperature receptors
- effectors e.g. sweat glands produce response to counteract change (vice versa)
3
Q
What happens when you are too hot?
A
- sweat produced by sweat glands - evaporates from skin - transfers energy to environment
- blood vessels supplying the surface skin capillaries dilate so more blood flows closer to surface of skin
- this is vasodilation - helps trasnsfer energy from skin to environment
4
Q
What happens when you are too cold?
A
- hairs stand up to trap insulating layer of air
- no sweat produced
- blood vessels supplying the surface skin capillaries constrict to close off skins bloody supply - vasoconstriction
- shiver - needs respiration - transfers some energy to warm body
5
Q
Why does CO2 need to be removed from the body?
A
- dissolved CO2 produces an acidic solution
- affects working of all enzymes in the body
6
Q
Why does urea need to be removed from the body?
A
is poisonous - if levels build up in body - could cause extensive damage to cells
7
Q
Urea and filtration?
A
- proteins and their amino acids can’t be stored by body - excess amino acids converted into fats + carbohydrates - can be stored
- occurs in liver and involves process called deamination
- ammonia produced as waste product from this process
- ammonia is toxic - converted into urea in liver- urea then transported to kidneys where it is filtered out of blood and excreted from body in urine
8
Q
Ions and filtration?
A
- ions such as sodium taken into body in food - absorbed into the blood
- if ion content of body is wrong - could upset balance between ions and water - too much or too little water drawn into cells by osmosis
- having wrong amount of water can damage cells or mean they don’t work as well as normal
- some ions are lost in sweat - this amount is not regulated - right balance of ions in body must be maintained by kidneys - right amount of ions reabsorbed into blood after filtration - rest is removed from body in urine
9
Q
Water and filtration?
A
- body has to constantly balance water coming in against water going out
- we lose water from skin in sweat and from lungs when breathing out
- can’t control how much we lose in those ways - amount of water is balanced by amount we consume and amount removed by kidneys in urine
9
Q
Very simply, what do the kidneys do?
A
act as filters to clean the blood
10
Q
What is the kidneys function?
A
- kidneys make urine by removing waste products from your blood
- substances are filtered out of blood as it passes through the kidneys - called filtration
- useful substances like glucose, some ions and right amount of water are absorbed back into blood
- processes called selective reabsorption
11
Q
How is the concentration of urine controlled?
A
- concentration of urine controlled by hormone called anti-diuretic hormone (ADH) - is released into bloodstream by pituitary gland
- brain monitors water content of blood - instructs pituitary gland to release ADH into blood according to how much is needed
- whole process is controlled by negative feedback.
12
Q
ADH four marker?
A
- ADH released by pituitary gland when the body water content too low
- makes kidney tubules more permeable to water
- means more water is reabsorbed from the tubules back into the bloodstream
- as a result, a smaller volume of more concentrated urine is produced
13
Q
What happens if the kidneys don’t work properly?
A
- waste products build up in blood - you lose your ability to control levels of ions and water in your body
- eventually this results in death
14
Q
How can people who have kidney failure be helped?
A
- can be kept alive by having dialysis treatment where machines do the job of the kidneys
- could have a kidney transplant.
15
Q
How does dialysis work?
A
- dialysis has to be done regularly to keep the concentrations of dissolved substances in the blood at normal levels + to remove waste substances
- in a dialysis machine - person’s blood flows between partially permeable membranes surrounded by dialysis fluid - permeable to things like ions and waste substances - not big molecules like proteins (just like the membranes from the kidney)
- dialysis fluid has same concentration of dissolved ions and glucose as healthy blood
- useful dissolved ions and glucose won’t be lost from blood during dialysis
- only waste substances and excess ions and water diffuse across the barrier
16
Q
Disadvantages of dialysis?
A
- many patients with kidney failure have to have a dialyis session 3 times a week - each session takes 3-4 hours
- may cause blood clots or infections
- not pleasant - expensive for the NHS to run
17
Q
How do kidney transplants work?
A
- currently - kidney transplants are only cure for kidney failure
- healthy kidneys usually transplanted from people who have died suddenly
- person who died has to be on organ donor register or carry donor card
- kidneys can also be transplanted from people who are still alive - small risk to person donating the kidney
18
Q
Disadvantages of kidney transplants?
A
- risk donor kidney can be rejected by patient’s immune system
- antigens on cell surface of donor organ can trigger your antibodies in immune system to attack the foreign antigens
- patient treated with immunosuppressants to prevent this
19
Q
Compare dialysis and kidney transplant?
A
transplants cheaper in long run than dialysis - people with a kidney transplant can live a more free life
