B12-Homeostasis Flashcards
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 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. If solute concentration outside body cells higher than cell contents, water will leave cells by osmosis and cells will shrink and stop working. If solute concentration outside body cells is lower than cell contents, water will enter cell by osmosis and cells will swell and may burst. 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.Kidney tubules would absorb more water, conserving both salt (being lost in sweat) and water, so you would produce small quantities of urine containing concentrated urea but a relatively low concentration of mineral ions.
What is selective reabsorption?
Having filtered out small essential molecules from the blood - the kidneys must reabsorb the molecules which are needed, while allowing those molecules which are not needed to pass out in the urine. Therefore, the kidneys selectively reabsorb only those molecules which the body needs back in the bloodstream.
The reabsorbed molecules include:
all of the glucose which was originally filtered out
as much water as the body needs to maintain a constant water level in the blood plasma
as many ions as the body needs to maintain a constant balance of mineral ions in the blood plasma
What is dialysis?
Medical treatment in which blood is removed from the body and filtered before being returned.
Disadvantages of dialysis?
they are expensive
the patient must have his or her blood connected to the machine for several hours every week
patients must follow a very rigid diet to avoid complications
they only work for a limited time for a patient
