B12-Homeostasis Flashcards
(24 cards)
What is homeostasis?
The maintenance of a constant internal environment in the body.
Why does temperature need to be controlled?
Many important enzyme-controlled reactions such as respiration would be affect as most enzymes work best at 37 °C.
What does the thermoregulatory centre in the hypothalamus in the brain do?
Thermoregulatory centre is sensitive to temperature of blood flowing
through it.
It also receives information about skin temperature from receptors in
skin and coordinates body’s responses to keep core temperature at 37 °C.
What happens when temperature is too high?
Blood flows through thermoregulatory centre in brain, which monitors temperature and sends impulses to lower body temperature.
Blood vessels supplying capillaries in skin vasodilate, increasing volume of blood in capillaries and increasing cooling by radiation from skin
surface.
More sweat produced by sweat glands, cooling skin surface as sweat evaporates.
Thermoregulatory centre monitors blood temperature and stops cooling mechanisms when it returns to normal.
What happens when body temperatures are too low?
Blood flows through thermoregulatory centre in brain, which monitors temperature and sends impulses to increases body temperature.
Blood vessels supplying capillaries in skin vasoconstrict, decreasing volume of blood in capillaries and decrease heat transfer to skin
surface.
Skeletal muscles contract rapidly and we shiver. These contractions need energy from
respiration, and some of this is released as heat.
The hairs on the skin also help to control body temperature. The hairs lie flat when we are warm, and rise when we are cold.
If we are too cold nerve impulses are sent to the hair erector muscles which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.
What are the 3 ways that water is removed from the body?
exhalation,(uncontrolled)
sweating,(uncontrolled)
excretion in urine(controlled
What is Urea and why does it have to be removed
Urea is nitrogenous waste product formed from breakdown of excess amino acids in liver. Urea is poisonous to body cells
in high concentrations.
How is the liver involved in the production of urea?
Excess amino acids carried to liver in bloodstream. Liver removes amino group from amino acids by deamination. This initially forms ammonia, which is converted into urea.
Why is it importance to maintain the balance of mineral ions and water in the body?
Balance of water, mineral ions, and nitrogenous waste (urea) in body important because of effect solute concentrations in cells, tissue fluid,
and blood have on osmosis. Balance enables body cells to retain shape and work efficiently.
What are the kidneys?
The kidneys are organs of the urinary system - which remove excess water, salts and urea.
Blood is transported to the kidney through the renal artery. The blood is filtered at a high pressure and the kidney selectively reabsorbs any useful materials such as glucose, salt ions and water. After it has been purified, the blood returns to the circulatory system through the renal vein.
The kidneys produce urine and this helps maintain water balance. The urine is taken from the kidneys to the bladder by the ureters. The bladder stores the urine until it is convenient to expel it from the body.
What is urine?
Urine contains water, urea and salts. Urea is produced in the liver when excess amino acids are broken down. Urea is the main waste product removed in the urine, as it is not reabsorbed in the kidney.
How does ADH stimulate water balance?
Too much water:
Blood would become diluted.
Receptor cells in brain would detect reduced blood concentration and pituitary gland would release less ADH into blood.
Kidney tubules would absorb less water, so you would produce lots of very dilute urine.
Too little water:
Receptor cells in brain would detect increased concentration of urea in blood (even with loss of mineral ions in sweat) and pituitary gland would release more ADH into blood.
ADH acts on the kidneys, increasing water reabsorption back into the bloodstream, which reduces urine volume and concentrates the urine. This helps to maintain fluid balance and prevent dehydration.
What is selective reabsorption?
Selective reabsorption in the kidneys is the process where useful substances, like glucose, water, and ions, are reabsorbed from the filtrate back into the blood. This happens in the nephron tubules. Waste products like urea are not reabsorbed and are excreted as urine. This process is vital for maintaining the correct water and ion balance in the body.
What is dialysis?
Medical treatment in which blood is removed from the body and filtered before being returned.
Disadvantages of dialysis?
Time-consuming: Hemodialysis typically requires multiple sessions per week, each lasting several hours.
Dietary restrictions: Dialysis patients often need to follow strict diets to limit the buildup of certain substances in the blood between treatments.
Infection risk: Hemodialysis requires access to the bloodstream, which can increase the risk of infection.
Cost: Dialysis can be expensive to the NHS.
How does the dialysis machine work?
Access: A surgical procedure creates an access point, usually in your arm, to allow easy access to your bloodstream.
Anticoagulation: An anticoagulant, is added to the blood to prevent clotting as it passes through the dialysis machine.
Filtration: Blood passes through the dialysis machine, where waste products like urea , as well as excess fluids and ions, are removed. The fluid works by creating a concentration gradient across a semi-permeable membrane where substances like ions, glucose and urea can move through.It contains the same amount of glucose and and dissolved ions as normal blood, so if blood is deficient then these substances can diffuse into the blood.
Return: The cleaned blood is returned to your body through an air trap to remove any air bubbles and prevents causing air embollisms.
Advantages of dialysis?
Life-saving: Dialysis keeps people alive when their kidneys fail, removing waste products and excess fluid from the blood.
Bridge to transplant: Dialysis can keep a patient stable while they wait for a kidney transplant.
Why does dialysis fluid contain no urea?
Dialysis fluid contains no urea to create a concentration gradient. This gradient allows urea and other waste products to diffuse from the patient’s blood, where their concentration is high, into the dialysis fluid, where their concentration is zero to help remove urea.
Why do people on dialysis have to have diet with less salts and proteins?
People with kidney failure cannot remove excess mineral ions such as salt or get rid of urea produced by the breakdown of excess amino acids from proteins, so they have to limit intake to keep levels in body as low as possible to remain feeling well between dialysis sessions.
How to reduce organ rejection in Kidney transplants?
Human Leukocyte Antigens
HLAs: Matching HLAs between donor and recipient to minimise immune reactions.
Antibody Screening: Detecting pre-existing antibodies in the recipient that could react against the donor kidney.
Immunosuppression: Using medications to suppress the recipient’s immune system and prevent rejection.
Advantages of transplants:
Patients can lead a more normal life without having to watch what they eat and drink
Cheaper for the NHS overall.
Disadvantages of transplants:
Must take immune-suppressant drugs which increase the risk of infection
Shortage of organ donors
Kidney only lasts 8-9 years on average
Any operation carries risks
How do kidney transplants work?
Transplanted kidney from a donor takes on functions of failed kidneys, balancing
blood chemistry and removing urea.
Parts of the Nephron
Bowman’s capsule: A cup-like structure that surrounds the glomerulus and collects the filtrate.
Glomerulus: A network of capillaries where filtration of blood occurs.
Proximal convoluted tubule: The first part of the tubule system where reabsorption of essential substances like glucose, amino acids, ions, and water begins.
Loop of Henle: A U-shaped structure responsible for creating a concentration gradient in the medulla of the kidney, facilitating water reabsorption.
