Flashcards in 5.1.2 excretion and homeostatic control NOT ON MOCK Deck (83)
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1
what is excretion
Process of removing metabolic wastes e.g. carbon dioxide and nitrogen based byproducts to maintain metabolism. Enables organisms to maintain pH balance and regulate osmotic pressure
2
Describe the gross structure of the mammalian liver
liver lobules: cylinders of hepatocytes arranged in rows and connected at the centre, are connected to:
hepatic vein: takes deoxygenated blood away from the liver and is attached to:
hepatic portal vein: contains products of digestion
hepatic artery: supplies oxygenated blood via sinusoid capillaries
And bile duct: transports pile to the gallbladder for storage
3
Outline the functions of the mammalian liver
site of gluconeogenesis, glycolysis, glycogenesis
stored glycogen
Deaminates excess amino acids, forming ammonia and organic acids. Acids can be respired or converted into glycogen. Ammonia is detoxified by addition of carbon dioxide in ornithine cycle
detoxifies chemicals e.g. converts alcohol to ethanal then acetic acid
4
How does the mammalian liver function
Blood flows from the hepatic artery and hepatic portal vein down sinusoids. Harmful substances and oxygen removed, broken down and harmful substances then re-enter the blood. Blood then flows into the central vein and enters the hepatic vein. Kupffer cells remove bacteria and breakdown red blood cells. Hepatocytes produce bile which is secreted into canaliculi , These drain into the bile duct, which joins up and leaves liver to deliver bile to the gallbladder
5
What does the hepatic vein do
Takes away Deoxygenated blood And harmful substances
6
What does the hepatic portal vein do
Brings blood from the small intestine
7
What does the bile duct do
Takes pile to the gallbladder for storage
8
What do Kupffer cells do
They are special white blood cells that breakdown bacteria and old red blood cells
9
what does the sinusoid do
blood goes along sinusoids from the hepatic vein and hepatic artery, picking up harmful substances. The sinusoids is where the vein and artery meet
10
Define detoxification
Many drugs/dangerous substances are broken down in the smooth endoplasmic reticulum by various specific enzymes of hepatocytes
11
How do our bodies metabolise alcohol
alcohol contains ethanol, it is lipid soluble, so move through cells very easily. Ethanol dehydrogenase catalyses the breakdown of ethanol to ethanal. Ethanal dehydrogenase then catalyses the breakdown of ethanol to ethanoate (acetate) . Ethanoate is then combined with coenzyme A to produce acetyl coenzyme A which can then enter the Krebs cycle to produce ATP (respiration)
12
Describe three functions of the mammalian kidney
excretion: the kidneys filter nitrogenous waste out of the body e.g. urea
Osmo regulation: the kidney maintains the water balance and pH of the blood and hence tissue fluid that surrounds all of the cells
selective reabsorption
ultrafiltration
13
Describe the gross structure of a mammalian kidney
fibrous capsule: protects kidney
Cortex: outer region consists of Bowmans capsules, convoluted tubules and blood vessels
Medulla: inner region consists of collecting ducts, loops of Henle, blood vessels
14
Describe how waste products in the urine move down to the bladder
The ureter Runs down from the kidney into the bladder and urethra through which we urinate, runs from the bladder to outside the body. Blood travels in through the renal artery. waste products are filtered out and nutrients are absorbed. The balance of water and solutes in the body is regulated. The renal vein takes the blood away. Waste products in urine move down to the bladder
15
what is a nephron
each kidney is made up of thousands of tiny tubes called nephrons.
nephron : The filtering unit of the kidney which performs the job of filtering, and fluid balance jobs-each kidney is made up of many nephrons
16
describe the blood vessels associated with a nephron
wide afferent arteriolar from renal artery enters renal capsule and forms glomerulus : branches knot of capillarities which combine to form narrow efferent arteriole
efferent arteriole branches to form capillary network that surrounds tubules
17
describe the sections of a nephron
bowman’s capsule is at the start of nephron: cup-shaped, surrounds glomerulus, inner layer of podocytes
PCT: series of loops surrounded by capillaries, walls made of epithelial cells with microvilli
loop of henle: hairpin loops extends from cortex into medulla
DCT: similar to pct but fewer capillaries
collecting duct: dct from several nephrons empty into collecting duct, which leads into pelvis of kidney
18
describe the process of ultrafiltration
occurs in bowman’s capsule
high hydrostatic pressure in glomerulus forces small molecules (urea, water, glucose, mineral ions) out of capillary fenestrations against osmotic gradient
basement membrane acts as the filter. blood cells and large molecules eg proteins remain in capillary
19
how are cells of the bowman’s capsule adapted for ultrafiltration
fenestrations between epithelial cells of capillaries
fluid can pass between and under folded membrane of podocytes
20
state what happens during selective reabsorption and where it occurs
useful molecules from glomerular filtrate eg glucose are re absorbed into the blood
occurs in pct
21
outline the transport processes involved in selective reabsorption
glucose from glomerular filtrate (co-transport with Na+ ions) -> cells lining PCT (active transport) -> intercellular spaces (diffusion) -> blood capillary lining tubule
22
how does the kidney produce urine
after selective reabsorption, filtrate passes loop of henle, which acts as countercurrent multiplier and then through DCT, where water and mineral ions are re absorbed
more water is reabsorbed in collecting duct. remaining fluid (urine) contains only waste materials and water
23
what happens in the loop of henle
1. active transport of Na+ and Cl- out of ascending limb.
2. water potential of interstitial fluid decreases
3. osmosis of water out of descending limb (ascending limb is impermeable to water)
4. water potential of filtrate decreases going down descending limb: lowest in medullary region, highest at top of ascending limb
24
explain the role of the DCT
reabsorption:
A. of water via osmosis
B. of ions via active transport permeability of walls is determined by action of hormones
25
define osmoregulation
control of plasma water potential via negative feedback homeostatic mechanisms
26
explain the role of the hypothalamus in osmoregulation
1. osmosis of water out of osmoreceptors in hypothalamus causes them to shrink
2. this triggers hypothalamus to produce ADH (anti diuretic hormone)
27
explain the role of the posterior pituitary gland in osmoregulation
stores and secretes the ADH produced by the hypothalamus
28
explain the role of ADH in osmoregulation
forms hormone-receptor complex on surface membrane of cells in collecting duct. triggers activation of cAMP as secondary messenger
triggers cellular processes that increase reabsorption of water. urine becomes more concentrated
29
How does ADH increase reabsorption of water
1. makes cells lining collecting duct more permeable to water : binds to receptor -> activated phosphorylase -> vesicles with aquaporins on membrane fuse with cell surface membrane
2. makes cells lining collecting duct more permeable to urea: water potential in interstitial fluid decreases
30
what can cause kidney failure
kidney infections cause inflammatory damage = change in glomerular filtration rate (rate at which filtrate flows through kidney).
kidney stones
uncontrolled diabetes
high blood pressure damages capillaries of glomeruli = larger molecules pass into urine
31
describe the effects of kidney failure
build-up of toxic waste products eg urea causes symptoms such as vomiting
if kidneys cannot remove excess water from blood, fluid accumulation leads to swelling
disruption to electrolyte balance can make bones more brittle or increase water retention
32
name potential treatments for kidney failures
renal dialysis : haemodialysis / peritoneal dialysis (short-term solution repeated several times a week so toxic waste products do not accumulate
kidney transplant (long-term solution, but difficult to find suitable donor with same blood / tissue type and patient requires immunosuppressants
33
describe haemodialysis
removes blood from body and pumps it through a machine
blood runs countercurrent to dialysis fluid, artificial membrane separates fluids = diffusion gradient enables molecules to move
add blood thinning agent to avoid clotting outside body
34
describe peritoneal dialysis
dialysis fluid is put into body cavity
exchange of molecules happens across the body’s own peritoneal membrane
fluid must be drained and replaced
35
how can urine samples be used to test for pregnancy
monoclonal antibodies bind to the hormone human chorionic gonadotropin hCG in the urine of pregnant women
36
how can urine samples be used to test for drugs such as anabolic steroids
gas chromatography measures the time it takes for the urine sample to pass through the column compared to the time taken for a steroid to pass through
37
what are anabolic steroids
drugs used to build muscle mass
banned from sporting events due to their dangerous side effects and to ensure completion is fair
38
how is the structure of the PCT adapted for its function
PCT has a brush border, larger cells and fewer visible nuclei than DCT. therefore the cells lining this tubule are ciliates to ensure maximum surface area for selective reabsorption
39
ppq: suggest why ‘uncertain diagnosis’ occurs more often in the group of patients aged 65+ years compared with the group below 65 years of age
because older people may have more complex medical problems / older people may have more than one thing wrong with them
40
ppq: how might the peritoneum differ in its function from the artificial membrane in dialysis machine used in haemodialysis
it can perform active transport / facilitated diffusion
41
ppq: why does the dialysis fluid used in peritoneal dialysis contain dextrose solution rather than water alone?
dialysis is replicating function of kidney and part of kidney’s function is to remove excess water from blood;
dextrose reduces water potential of dialysis fluid
water moves from blood into dialysis fluid by osmosis
if it was water alone cells would burst
42
ppq: suggest why patients receiving peritoneal dialysis usually need to have the peritoneal dialysis fluid replaced 4x a day, but those receiving haemodialysis only need treatment 3x a week
peritoneal dialysis can remove less waste than haemodialysis
in haemodialysis fluid is constantly refreshed / changed but not in peritoneal dialysis
haemodialysis uses counter- current flow
haemodialysis maintains concentration gradient
in peritoneal dialysis the fluid reaches equilibrium with the blood
43
ppq: One function of healthy kidneys is to make the hormone erythropoietin (EPO), Which stimulates the production of red blood cells. Patients with kidney failure may need to be given supplements of EPO. State the type of cell from which red blood cells are formed and where this type of cell is located
Stem cells and found in the bone marrow
44
ppq: figure 6.1 is a diagram that represents the nephron in a mammalian kidney
use the letters from figure 6.1 to identify:
A) I. The region or regions where glucose is selectively reabsorbed into the blood capillaries
II. The region or region is present in the cortex
III. The region or regions where podocytes are located
I= Q
II = Q.J.K.L
III= J
45
ppq: the desert kangaroo rat, dipodomys desert i, lives in dry and hot conditions. it excretes a very small volume of urine relative to its size . the loops of henle in the kidneys of these mammals are longer than those found in mammals of a similar size that do not live in desert conditions
explain how the longer loop of henle is able to assist the desert kangaroo rat in preventing excessive water loss
more sodium and chloride ions pumped out of ascending limb / into medulla
builds up greater water potential gradient
allows reabsorption/ removal of more water from collecting duct
46
ppq: urine can be tested to detect a persons misuse of certain drugs in body-building
state the type of drug that can be misused in this way
anabolic steroids
47
ppq: explain the changes in fluid composition in table 3.1 and table 3.2
large molecules cannot enter the filtrate
endothelium / fenestrations / basement membrane prevent the large molecules reaching bowman’s capsule
all glucose is reabsorbed at the PCT
all amino acids are reabsorbed at the PCT
not all ions reabsorbed
urea concentration increases between filtrate and urine because movement of urea into tubule / water removed
48
ppq: suggest what a high concentration of creating in the blood plasma indicated about kidney function
high creatinine concentration indicated reduced function because less filtration (low GFR) but
49
ppq: discuss, with reference to the information (newspaper articles on kidney transplants), whether it is ethical for live donors to be used as a source of kidneys for transplantation
people should have a right to choose freely what to do with their kidney
perceived donor advantages : donors can benefit from money raised by selling a kidney, people can donate a kidney to family member, people can donate without payment
perceived donor disadvantages: exploiting people’s poverty (ethical it not doing it just for money they receive), and illegality of child donors
recipient issues : people should receive transplants irrespective of wealth, it is wrong that recipients are being charged excessively
50
ppq: complete the passage, using the most suitable term in each case
the blood in the glomerulus has a high ____ pressure, which forces small molecules, such as glucose and _____ out of the glomerulus and into the lumen of the bowman’s capsule. this process is known as ____
in the PCT, the glucose, most of the ___ and some of the salts are reabsorbed into blood ___ that surround the nephron at this point
the blood in the glomerulus has a high HYDROSTATIC pressure, which forces small molecules, such as glucose and AMINO ACIDS out of the glomerulus and into the lumen of the bowman’s capsule. this process is known as ULTRAFILTRATION
in the PCT, the glucose, most of the WATER and some of the salts are reabsorbed into blood CAPILLARIES that surround the nephron at this point
51
ppq: state precisely where the cells that detect a decrease in the water potential of the blood plasma are found
and name the cells that detect this decrease
walls of blood vessels in hypothalamus
osmoreceptors
52
ppq: name the part of the adrenal gland that releases aldosterone
cortex
53
ppq: suggest and explain what effect the action of aldosterone will have on the secretion of ADH
water potential of plasma will decrease (become more negative) and ADH secretion will increase
54
ppq: as the action of aldosterone takes effect, this is detected by receptors in the body and secretion of aldosterone decreases
state the name of the mechanism that results in this decrease in aldosterone secretion
negative feedback
55
ppq: which part(s) of the nephron corresponds to each of the statements below
walls are impermeable to water
glucose is reabsorbed into the blood
ADH acts on the walls
contains podocytes
most of the water is reabsorbed into the blood
walls are impermeable to water = ascending limb of loop of henle
glucose is reabsorbed into the blood= PCT
ADH acts on the walls = collecting duct/ DCT
contains podocytes= bowman’s capsule/ renal capsule
most of the water is reabsorbed into the blood = PCT
56
ppq: explain the role of the loop of henle in the production of urine
the role of the loop of henle is to cause a decrease in water potential in the medulla
as in ascending limb active transport outwards of ions
walls of descending limb permeable to water and water removed from descending limb
water potential of tissues surrounding collecting duct is lower than the fluid inside it
water is removed from the filtrate / urine in collecting duct.
eg: the drier the habitat the longer the loop and urea contributes to low water potential in medulla and facilitates diffusion of ions out of the loop at the bottom
57
ppq: name the organ that produces urea
liver
58
ppq: suggest why a high intake of protein in the diet will be likely to result in a high concentration of urea in urine
high intake of protein leads to a large amounts of amino acids
excess amino acids cannot be stored
amino acids deaminated
59
ppq: suggest what condition is indicated by the presence of glucose in a persons urine
diabetes
60
ppq: state the substance that is being tested for in urine when a pregnancy test is carried out
hCG (human chorionic gonadotrophin)
61
ppq: using your knowledge of how a pregnancy test stick works, suggest how the test stick can be used to indicate a positive result for LH in urine
LH binds to anti-LH
this antibody complex moved along (test stick together with urine)
this LH-anti-LH antibody complex binds only with immobilised antibodies specific to them
only control antibodies bind with immobilised antibodies specific to them
the binding of antibody produces coloured line
2 lines indicate positive result
62
ppq: explain how the glomerulus is able to perform its function
afferent arteriole has diameter greater than that of efferent arteriole
build up of high hydrostatic pressure
endothelium wall of glomerulus has small pores
which allow ultrafiltration
63
ppq: name the specialised cells present in bowman’s capsule that assist in the function
podocytes
64
ppq: suggest the effects of complete kidney failure on the composition of the blood
if kidney cannot filter, substances remain in blood
so there will be an increase in urea and increase in water and increase in ions and salts
65
ppq: explain the need for close matching of the donated kidney to the recipient
if not closely matched the donated kidney will be recognised as foreign
antigens on the donated kidney will be different
causing rejection
66
ppq: describe the features of the glomerulus and bowman’s capsule that allow them to perform their function effectively
ultrafiltration :
afferent arteriole is wider than efferent arteriole
high blood and hydrostatic pressure in glomerulus
endothelium has gaps to allow passage of substances
basement membrane stops removal of large molecules
podocytes / epithelial cells of bowman’s capsule have finger-like projections
67
ppq: suggest 2 differences in the composition of the urine of a person with nephritis when compared to the urine of a person with heathy kidneys
large proteins / amino acids present
blood cells present
glucose present
more water present / more dilute
more ions present
more vitamins present
68
ppq: suggest two ways in which the structure of this aquaporin prevents the passage of ions
the ions in the solution are too large to pass through the channel
shapes not compatible
positive charge in the channel repels the positively charged ions
69
ppq: explain the likely effect on the blood cells if the water potential of the plasma was allowed to increase significantly
water potential of plasma would be higher than that of the blood cells
water would enter blood cells
blood cells swell and burst
70
ppq: name the type of monomer that makes up a molecule of ADH and the bond that joins the monomers together
type of monomer
amino acids
name of bond
peptide
71
ppq: ADH is a hormone that is produced by specialised nerve cells known as ____ cells. these cells detect changes in the water potential of the blood flowing through the ___. if the water potential of the blood is too low then ADH is released
ADH is not secreted immediately into the blood but passes along the ___ of the specialised nerve cells to the ____ ____ gland, from where it is released into the blood
ADH acts on the cells of the ____ ___ . The ADH molecule attaches to receptions on the ___ of these cells and causes protein channels known as ____ to insert themselves into the membrane. water passes through these channels by ____ and a smaller volume of more concentrated urine is produced
ADH is a hormone that is produced by specialised nerve cells known as OSMORECEPTOR cells. these cells detect changes in the water potential of the blood flowing through the HYPOTHALAMUS. if the water potential of the blood is too low then ADH is released
ADH is not secreted immediately into the blood but passes along the AXON of the specialised nerve cells to the POSTERIOR PITUITARY gland, from where it is released into the blood
ADH acts on the cells of the COLLECTING DUCT. The ADH molecule attaches to receptors on the PLASMA MEMBRANE of these cells and causes protein channels known as AQUAPORINS to insert themselves into the membrane. water passes through these channels by OSMOSIS and a smaller volume of more concentrated urine is produced
72
ppq: suggest where ADH is removed from the blood and describe what then happens to the ADH molecule
how adh is dealt with as a protein
in liver / hepatocytes
hydrolysis acted on by protease
deamination = formation of ammonia
ornithine cycle = formation of urea
amino acids used in gluconeogenesis
how ADH or urea is dealt with as a small molecule in kidney :
ultrafiltered from blood moves from blood into nephron
became small molecule, not all the urea is reabsorbed so urea present in urine is excreted
73
ppq: name the cells that make up the lobule
hepatocytes
74
ppq: explain how the pregnancy testing stick detects a pregnancy hormone
it tests for hCG
hormone small so can pass from blood into filtrate at bowman’s capsule
monoclonal antibodies on the stick
antibodies attached to marker
hormone binds complementary to antibody
which triggers appearance of colour / line becomes invisible
75
ppq: comment on whether the use of steroids should be permitted in sport
steroids gives an unfair advantage
there are many heath risks and side effects to taking steroids
eg depression and liver damage
steroids also do not reflect the athletes natural talent
76
ppq:
one difference of excretion and secretion
one example of a product of excretion and secretion
one similarly of excretion and secretion
one difference of excretion and secretion= excretion : substance is to be removed from body whereas secretion is released from glands
one example of a product of excretion and secretion. excretion : urea, secretion : hormone
one similarly of excretion and secretion. both require ATP
77
ppq: name the process by which the fluid passes from the glomerulus into the renal tube
ultrafiltration
78
ppq: with reference to table 4.1, explain how these observed changes in concentration are brought about by the PCT
selective reabsorption
of glucose and amino acids
direct uptake of glucose and amino acids by active transport
water follows by osmosis so concentration of urea and remaining substances increases
micro villi on the PCT provide the large surface area for uptake
79
ppq: in haemodialysis suggest why it is necessary to add an anticoagulant to the blood in stage 2 (when the blood blow in the machine related by a pump and anticoagulant is added)
so that clots do not form while in the dialysis machine
80
ppq: during haemodialysis suggest why NO anticoagulant is added to the blood towards the end of a dialysis session
to allow the blood to clot normally after treatment
81
ppq: state the process by which molecules and ions, other than water, will move from the blood into the dialysate
simple diffusion
82
ppq: suggest a reason for the accumulation of high concentration of NAPQI in the liver cells
because there is not enough glutathione
83
