B12 Flashcards
Homeostasis in action
Where is internal body temperature controlled from ?
thermoregulatory centre in hypothalamus of brain
How does the thermoregulatory centre control and maintain a constant body temperature of 37 degrees celsius ?
- has receptors sensitive to the temperature of blood
- skin-based temperature receptors also send back information via impulses to the thermoregulatory centre
- sends impulses to body based on information from receptor cells
How does the body cool itself down in response to impulses from the thermoregulatory centre ?
- vasodilation
[] capillaries dilate, meaning blood flows closer to the surface of the skin
[] heat from the blood can thus transfer into the environment via the skin - sweating
[] evaporates off of the surface of the skin, taking heat energy with it into the environment and thus cooling the body down - body hairs lie flat
[] less insulation of skin so more heat can be lost efficiently
How does the body warm itself up in response to impulses from the thermoregulatory centre ?
- vasoconstriction
[] capillaries constrict so that blood flows away from the surface of the skin
[] heat in blood is not lost to the environment via the skin as much - hairs stand on end
[] create insulating layer of air, trapping heat to warm body - skeletal muscles contract repeatedly and rapidly (shivering)
[] energy produced by the respiration needed to rapidly contract muscles warms the body - sweat production stops/slows
[] stops evaporation of sweat and thus loss of heat into the environment from body
Why is carbon dioxide harmful to the body if allowed to build up, and how is it removed ?
- dissolved carbon dioxide produced an acidic solution which would change the pH of the body and affect enzyme action
- carbon dioxide diffuses into the blood and is carried to alveoli, where it again diffuses out of the blood and is exhaled
[] water vapour is lost from the body as a side effect of exhalation
Why is urea harmful to the body if allowed to build up, and how is it removed ?
- urea produced when excess proteins are broken down into amino acids, which are then deaminised in the liver to remove the amino group (can be used in respiration or to make other molecules)
[] produces ammonia, which is very toxic, and is then converted into urea immediately to be removed - nitrogenous; in excess is poisonous to body cells
- filtered out of body by kidneys and excreted in urine with excess water and mineral ions
What are the waste products your body has no control over the removal of ?
- water
[] lost through exhalation, sweating - mineral ions + urea
[] lost through sweat
What are the waste products your body has control over the removal of ?
- water
[] urine - urea
[] urine - mineral ions
[] urine - carbon dioxide
[] exhalation
Describe the functions of the parts of the body involved in the excretory system
- kidneys
[] contain nephrons in the renal cortex which filter the blood of urea, waste minerals and water + selectively reabsorb water + glucose, regulated by the renal medulla
[] produces urine - ureter
[] carries urine produced in the kidneys to the bladder - bladder
[] stores urine until excretion - renal artery
[] carries blood with waste products in it to the kidney to be filtered - renal vein
[] carries filtered blood towards the heart
What are the structures in a nephron (and what is a nephron) ?
- nephron = where blood is filtered and urine is produced
- glomerulus
[] inside of the weird tri-bulbous structure at the top of a nephron - bowman’s capsule
[] bulb surrounding the glomerulus - proximal (close to glomerulus) tubule
- loop of Henle
[] u-shaped loop after the proximal tubule - distal (far from glomerulus) tubule
- collecting duct
[] transports urine from the nephron to the renal pelvis
Explain the stages in blood filtration in the kidneys
- blood passes through the renal cortex of the kidney via capillaries
[] small molecules like urea, water, glucose and mineral ions are able to diffuse into the nephron, whilst bigger molecules like proteins are kept out and remain in the blood in capillaries - selective reabsorption
[] ALL glucose is reabsorbed into the blood
[] as much water as needed to maintain stable blood water and body water levels is reabsorbed, whilst excess remains in the urine
[] as many ions are needed to maintain stable levels in the blood and body are reabsorbed, whilst the excess remain in the urine - urine formed
[] molecules NOT selectively reabsorbed continue along the nephron and are passed down the ureter into the bladder
Describe the role of ADH in selective reabsorption of water in the kidneys
- ADH = anti-diuretic hormone
[] released into the bloodstream by the pituitary gland in response to information about low water levels in the body - more ADH = more selective reabsorption of water
- less ADH = less selective reabsorption of water
- ADH controls porosity of the nephrons in the kidney and thus the rate of absorption of water back into the blood
Describe the negative feedback loop of ADH release
pituitary gland receives information from receptors in the brain that water levels in the blood are too low
-> ADH released into the blood and travels to kidneys
-> in kidneys, stimulates selective reabsorption of water
-> water levels in blood rise
-> pituitary gland receives information from receptors in the brain that the blood is too dilute
-> pituitary gland stops or slows the release of ADH
-> cycle repeats
What are the two ways in which kidney failure can be treated ?
- dialysis
- kidney transplant
How does dialysis filter the blood ?
- has dialysis fluid surrounding a partially permeable membrane within which the patient’s blood is pumped through
[] dialysis fluid contains the same amount of mineral ions, water and glucose as a healthy person’s blood
[] thus, NO NET MOVEMENT of glucose (need to keep as much as possible in the blood)
[] as much diffusion of urea across the partially permeable membrane into the fluid as possible happens
[] only the excess mineral ions and water diffuse across the partially permeable membrane, down the concentration gradient
[] molecules too big to diffuse across the membrane remain in the blood - dialysis fluid is constantly replaced to maintain the concentration gradient and keep diffusion of all substances involved as efficient as possible
Describe the disadvantages and advantages of dialysis compared to kidney transplant in treating kidney failure
dialysis
- advantages:
[] no risk of rejection, so no immunosuppressant drugs needed
[] more readily available to people than donor kidneys
[] people can lead relatively normal lives between dialysis sessions
- disadvantages:
[] dialysis machines are bulky and expensive, meaning they are usually only available in hospital
[] dialysis takes around 4-8 hours to complete
[] patients have to spend long hours at hospital multiple times a week for dialysis procedures
[] between sessions, patients must eat carefully controlled amounts of protein to prevent build-up of urea in the blood (makes muscle gain harder)
transplant
- advantages:
[] no need to carefully control diet and drink intake once procedure is done
[] only need one kidney replaced to be able to restore most of normal function
[] no need for long inconvenient and expensive dialysis sessions
- disadvantages:
[] waiting lists for donors are long
[] high risk of rejection, so patient must take immunosuppressants for the rest of life - inconvenient, sometimes expensive and weaken immune system, so more susceptible to disease
[] risks associated with surgery (general anaesthesia, complications)
What is rejection ?
- transplanted organs that are not grown using therapeutic stem cell methods have different antigens (proteins on a cell surface) than the body’s own due to differences in genetic material
- because the immune system of the recipient doesn’t recognise the antigens on the donor organ, they produce antibodies to attack the organ and latch onto antigens, unravelling them and destroying the cells
