Kidney and Homeostasis Flashcards
define homeostasis
is the maintenance of a constant internal environment within a living organism, irrespective of the external condition
why is homeostasis important?
so that cells can function efficiently and independently of fluctuations in the conditions of the external environment
therefore cells are provided with constant conditions, even during different levels of activity of the organism
give three examples of homeostatic control
regulation of blood glucose levels
regulation of solute potential eg water is lost via excretion, sweating and expiration
regulation of core body temperature and pH
what effect might a change in temperature and pH have on enzyme-catalysed reactions? why is this important for life?
changing temp. and pH can affect the rate of reactions
if these factors were affected by the environment, we would be restricted to very specific environments
this would increase competition for food and shelter
describe homeostatic control
there is a set point which is the desired level or the norm at which the system operates.
nevertheless, changes in pH, temperature and solute potential still take place and will therefore fluctuate around the set point.
homeostasis uses negative feedback to return the body to the set point.
the set point is determined by a control centre and deviations from the set point are corrected by negative feedback so that he set point is restored
give the role of negative feedback
uses detector/receptor -> monitors condition -> provides input to control centre/coordinator -> evaluates the information -> provides output to effector -> makes a response designed to take away deviation i.e. restore the set point/norm
define negative feedback
a reaction to a change in a system that negates (reverses) the first change
what does positive feedback do?
an effector increases a change
give two examples of positive feedback
oxytocin stimulates the contraction of the uterus at the end of the pregnancy and the contractions stimulate the production of more oxytocin, which increases the stimulus
when the skin is cut, the first stage of clot formation is that platelets adhere to the cut surface and also they secrete signalling molecules which attract more platelets to the site
what is thermoregulation?
restoration of the core body temperature back to the norm
where is the control centre of thermoregulation?
the hypothalamus in the brain
explain why a tall, thin swimmer is more likely to suffer from hyperthermia than a short, stout swimmer of the same body mass?
larger surface area to volume ratio and less insulation so will lose more heat by conduction
give two functions of the kidney
nitrogenous excretion
osmoregulation
what is the difference between excretion and egestion?
excretion - the removal from the body of these waste products
egestion - defaecation which is the removal of unwanted material from the digestive system
what is nitrogenous excretion?
amino acids can’t be stored and surplus amino acids which are not used for the synthesis of proteins and other nitrogenous compounds are deaminated in the mammalian liver
give 4 steps simply describing how nitrogenous excretion works
1- amine group is removed from amino acid
2- the removed amine group is converted to ammonia which is highly toxic
3- with the addition of CO2, urea which is less toxic is formed and transported in the blood plasma to kidneys
4- urea is removed by the kidneys and excreted in the urine
what is osmoregulation?
the control of water content and solute composition of body fluids eg blood, tissue fluid and lymph
give two ways humans gain water and three ways they lose water
gain:
food and drinks
respiration (metabolic water)
lose:
urination and egestion of faeces
sweating
exhalation - to keep exchange surfaces moisture
give the different labels of the human urinary system
kidneys
ureters
bladder
sphincter
urethra
what is the function of the kidneys?
filter waste products from the blood
what is the function of the ureters?
carries urine to the bladder
what is the function of the bladders?
stores urine prior to elimination
what is the function of the sphincters?
it is a muscle that allows conscious control of urine release
what is the urethra?
it transports urine outside of the body for elimination
what are vasa recta?
blood cells that run parallel to the loop of Henle
give the labels of the kidney
cortex
medulla
pelvis
tough fibrous capsule
ureter
renal vein
renal artery
give labels for the structure of the nephron inside the kidney
glomerulus
bowman’s capsule - glomerular capsular space, glomerular capillary
afferent arteriole
efferent arteriole
proximal convoluted tubule
distal convoluted tubule
loop of Henle
collecting duct
what is ultrafiltration?
filtration under pressure that separates small soluble molecules from the blood plasma
the small molecules like water, glucose, urea and salts are filtered from the knot of capillaries (glomerulus) to form a filtrate in the Bowman’s capsule
high hydrostatic pressure is generated in the glomerulus because the afferent arteriole diameter is wider than the efferent arteriole
what does the proximal convoluted tubule contain in the Bowman’s capsule?
villi
what type of cells are surrounding the Bowman’s capsule?
squamous epithelial cells