5.1.2 excretion and homeostatic control NOT ON MOCK Flashcards Preview

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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

ppq: name the liver cells that can lead to regeneration and the type of cell division they carry out

hepatocytes

mitosis