Homeostasis Flashcards

Question

Structures found within the nephron?

Answer 1

Structures found within the nephron: -Bowermans Capsule -Glomerulus -Proximal convoluted tubule -Loop of henle -Distal convulated tubule -Collecting duct

Answer 2

Bowermans capsule = a cup shaped structure containing the glomerulus where ultrafiltration takes place (filtering small molecules and ions out blood but keeping large molecules ie proteins)

Answer 3

Three filtering systems in the Bowman's Capsule that helps prevent cells and large molecules leaving out the blood: -Narrow gaps (fenestrations) between endothelium cells in capillaries -Basement membrane (mesh of collagen around glomerolus) -Podocytes (epithelial cells of the capsule that have finger-like pojections, which form filtration slits)

Answer 4

Glomerulus: a tangle of capillaries in which the pressure forces all solutes in the blood plasma to be forced through the capillary walls. This includes ions, amino acids, glucose, urea, water. Proteins and erythrocytes do not pass through as they are too large.

Answer 5

Proximal Convoluted Tubule: First coiled region of the tubule, where products needed in the blood (ions, glucose, amino acids etc) are reabsorbed into the blood.

Answer 6

Loop of Henle: Establishing a water potential gradient (

Answer 7

Distal Convoluted Tubule: Second coiled region of the tubule, where osmosis and diffusion of solutes occurs in order to fine tune the water potential and pH of the blood. Antidiuretic Hormone (ADH) affects the permeability of the distal convoluted tubule.

Answer 8

Collecting Duct: Urine travels through the collecting duct down to the pelvis. More fine tuning occurs, as ADH creates aquaporins to allow the exit of excess water.

Answer 9

Ultrafiltration in the glomerulus and Bowmans capsule: The glomerulus is supplied with blood from a comparatively wide afferent renal artery, but leaves through a narrower efferent renal artery. This means the blood in the glomerulus is under very high pressure. This causes the contents of the blood to be forced through the capillary wall, like a sieve, then through the basement membrane (a second 'sieve' made of collagen fibres and protein) into the nephron. These sieve like structures are important as they do not allow cells, large proteins or platelets to pass into the nephron. The cells in the wall of the bowman's capsule contain cells called podocytes, which have extensions called pedicels wrapped around the capillaries meaning any cells, large proteins or platelets which leave the capillary walls don't enter the tubule. Filtrates include water, amino acids, glucose, ions and importantly: urea and other nitrogenous waste products.

Answer 10

Reabsorption in the proximal convoluted tubule: Ultrafiltration removes nitrogenous waste, but it also removes glucose, ions and other useful substances in the plasma. The proximal convoluted tubule are covered with microvilli, which increase the surface area available for substances to be reabsorbed. There are many mitochondrial cells in the tubule wall, to provide the ATP required for active transport of substances back into the blood.

Answer 11

Loop of Henle = Establishing a water potential gradient (ie the water potential in the nephron filtrate becomes higher than what it is in the medulla, additional water can then be reabsorbed from the collecting duct)

Answer 12

Osmolarity - concentration of a solution expressed as total number of solute particles per litre

Answer 13

Ismotic - to have the same osmolarity as another fluid

Answer 14

Equilibrate - to bring into a state of equilibrium

Answer 15

Interstital fluid - fluid which surrounds tissue cells

Answer 16

Countercurrent multiplication in the loop of henle: Before moving into the loop of henle the filtrate in the nephron is isosmotic with the blood. Sodium and chloride ions are pumped out of the ascending limb to create a water potential gradient. The filtrate moves down the falling limb, and water osmoses out due to the water potential gradient. The ideal gradient is 200 mOsm. Water in the falling limb equilibrates with the interstitial fluid, by passively diffusing into the medulla. This does not change the osmolarity of the interstitial fluid. When the filtrate moves around the loop of henle, the ideal 200 mOsm gradient is lost, so steps 3 and 4 are repeated. After enough filtrate has passed through, the interstitial fluid at the bottom of the loop has reached a maximum osmolarity of ~1200 mOsm.

Answer 17

Osmoregulation is the control of water and salt levels in a fluid

Answer 18

Osmoregulation and the distal convulated tubule: High levels of ADH are released when you are dehydrated, and cause the distal convoluted tubule walls to become more permeable to water, meaning more returns to the blood and the urine becomes more concentrated. This way we conserve water. There are many mitochondria in the tubule cell walls, allowing salts to be actively transported out of the nephron into the blood when required. Sodium ions are actively pumped out, and chloride ions follow passively down an electrochemical gradient.

Answer 19

Collecting duct in the kidneys: The urine enters the collecting duct which transports it down through the medulla to the pelvis. The urine becomes more concentrated as it passes through the medulla, as the salty conditions created by the loop of henle mean water osmoses out down a potential gradient. ADH also controls the permeability of the collecting duct, and creates aquaporins in the membrane which allow additional water to escape through, thus determining urine concentration and volume

Answer 20

Osmoregulation involves crontrolling the water potential of the blood within very narrow boundaries, regardless of the activities of the body

Answer 21

Water potential of the tissue fluid has to remain stable as possible, because if water moves into or out of cells by osmosis it can cause damage and even death

Answer 22

The amount of water lost in urine is controlled by ADH in a negative feedback system

Answer 23

ADH is produced by the hypothalamus and secreted into the posterior pituitary gland where it is stored -Increases permeability of the distal convulated tubule and the collecting duct to water

Answer 24

Hypertonic = blood with low water potential - too much water leaving by osmosis - cells shrivel

Answer 25

Hypotonic - blood with high water potential - too much water enting cell by osmosis - cells burst (lysis)

Answer 26

Hypertonic negative feedback response: more water reasborbed by osmosis into blood from nephron tubules -> urine more concentration -> less water lost in urine

Answer 27

Hypotonic negative feedback response: -less water reabsorbed by osmosis into blood from nephron tubules -> urine more dilute -> more water lost in urine

Answer 28

Blood water potential increases -> detected by osmoreceptors in hypothalamus -> they shrivel and stimulate hypothalamus to release less ADH -> DCT and collecting duct walls less permeable -> less water reabsorbed into blood and urine is more dilute

Answer 29

Water potential decreases: Detected by osmoreceptors and stimulates hypothalamus to release more ADH into blood by posterior pituitary gland -> DCT and collecting duct walls more permeable due to increased embedded aquaporins -> more water is reabsorbed into blood and less lost in urine (more concentrated)

Answer 30

Aquaprorins are protein channels for water to pass through - more embedded in membrane = more water leaves DCT + collecting tubule + resbsorbed into blood

Answer 31

ADH binds to cell membranes of DCT -> activates phosphorylate enzyme -> causes vesicles containing aquaporins to fuse with membrane and become embedded

Answer 32

Urine contains the breakdown of products of lots of chemicals including hormones and toxins - affected by disease = new substances show in urine ie glucose (diabetes), creatine (muscle damage)

Answer 33

Traditional pregnancy testing: blood of mother injected into toad - if pregnant, hCG triggered egg production in the toad

Answer 34

Modern pregnancy testing: Monoclonal antibodies are used to detect the presence of hCG hormone

Answer 35

Monoclonal antibodies = antibodies from a single clones of cells that are produced to target particular cells or chemicals in the body

Answer 36

Mouse injected with hCG to make appropiate antibody - Bcells removed from spleen and fused with myeloma (cancer cell) -> known as hybridoma - hybridoma replicates rapidly and antibodies are collected

Answer 37

Main stages in a pregnancy test: -Wick is soaked in the first urine (highest hCG) -Test contains monoclonal antibodies with beads attached - only binds to hCG - if pregnant, they bind forming hCG-Antibody complex (coloured bead) -Urine carries along test -Immbolised monoclonal antibodies arranged in line or pattern (ie +) that bind to hCG complex -Continues to second line that binds wether hCG present or not -Pregnant = 2 lines, not = 1 line

Answer 38

Anabolic steroids are drugs that mimic the action of testesterone and stimulates muscle growth

Answer 39

Urine sample used - first passed through imunoassay using monoclonal antibodies that bind to drug - then gas chromotraphy is positive

Answer 40

Kidney failure may happen due to: -Kidney infections -Raised blood pressure that damages epithelial cells of bowmans capsule -Damage from cyst pressure

Answer 41

Kidney infection/damage can cause: -Protein inurine - as bowmans capsule membrane damaged and can't filter properly so large plasma proteins pass through -Blood in urine due to affected filtering process

Answer 42

Effect of kidney failure where conc of urea and mineral ions build up in the body: -Loss of electrolyte balance -Build up of toxic urea in blood -High blood pressure -Weakened bones as calcium/phosphorus balance in blood lost -Pain and stiffness in joints due to protein build in blood -Anemia - reduced rbc

Answer 43

Measuring glomerular filtration rate: GFT widely used to indicate kidney disease = involves blood test measuring creatine level - increased creatine = kidneys not working properly

Answer 44

Creatine is a breakdown product of muscles and it is used to give an estimated glomerular filtration rate which indicates kidney damage

Answer 45

Treating kidney failure with dialysis: -Haemodialysis -Peritoneal dialysis

Answer 46

Haemodialysis: Blood flows into machine -> through partially permeable dialysis membrane (mimics bowmans capsule membrane) -> dialysis fluid on other side of machine > large proteins and blood cells cannot pass through

Answer 47

-Dialysis fluid contains normal plasma levels of glucose to ensure no net movement of glucose out of the blood as well as mineral ions -Dialysis fluid also contains no urea to create steep conc gradient so urea leaves blood

Answer 48

Weaknesses of dialysis: -Depends on diffusion down conc gradients -takes 8 hrs and has to be repeated -people attached to the machines many hrs a week -carefully managed diets

Answer 49

Peritoneal dialysis: inside body - natural dialysis memebranes formed from abdomen lining - dialysis fluid inserted using catheter and left for several hrs

Answer 50

-Alternative to dialysis, can function for many years -Risk of rejection due to differing antigens - can be overcome by matching tissue type -Immunosupressant drugs for rest of their lives -Donor shortage

Answer 51

Urine is useful in diagnostic tests because: -Urine samples are easy to get -Non-invasive -Chemicals remain sometime after use - good for drug testing

Answer 52

Drug testing is split into two because: -Passed through immunoessay involving monoclonal antibodies -> then at the same time, gas chromotography used right after -> confirms findings

Answer 53

False negatives in pregnancy tests arise due to: -If test is done on day period is missed, woman may be pregnant but not produced enough hCG to produce strong enough coloured response -> hormone would've increased days later

Answer 54

Kidney failure is such a threat to life because: --Kidneys filter out dangerous chemicals - > these at high conc in ur blood lead to cell damage (osmotic damage)

Answer 55

Flow chart to show how dialysis works: Blood enters dialysis machine from artery -> filters through partially permeable membrane where urea filters into dialysis fluid -> dialysis fluid is moving in opposite direction

Answer 56

Countercurrent flow results in maximum concentration gradient can be achieved

Answer 57

PCT cells are adapted for reabsorption in the following ways: -Microvilli that increases surface area for reabsorption -Plasma membranes have many pumps and transporter proteins for active transport and facillitated diffusion -Many mitochondria to produce ATP for active transport

Answer 58

Limbs of the Loop of Henle: -Descending limb (permeable to water) -Ascending limb (impermeable to water, but sodium and chloride ion actively transported from filtrate into medulla, which raises water potential of the filtrate)

Answer 59

HCG property: B hCG has a molecular mass of less than 69,000

Answer 60

3 factors that would need to be controlled: -Initial glucose concentration on both sides of the membrane -Length/diameter of dialysis tubing -Type/brand of dialysis tubing

Answer 61

-Carbonic anhydrase in the PCT catalyses reaction between carbon dioxide and water to form hydrogen carbonate which allows ion reabsorption: -Less sodium ions enter PCT by facilliated diffusion, and no active transport of sodium ions into blood -> less ion excretion in urine

Answer 62

PCT and DCT comparison: -Both involves selective reabsorption -Both involve sodium ions -Both involve co-transport of ions and active transport -However, PCT involves glucose, amino acids, etc (molecules) rather than DCT which is primarily ion reabsorption (less selective)

Answer 63

Homeostasis is the maintenance of metabolic so to keep them functioning at regular conditions - within narrow regions in the body

Answer 64

Peripheral - found in skin - detects change in skin/responses to skin stimuli Hypothalamus - detects change of temperature in body

Answer 65

-Excretion = removal of metabolic waste from the body - some excretion takes place as bile produced from the breakdown of haemoglobin of old red blood cells removed in faeces -Defecation - involves removal of undigested food and dead cells

Answer 66

Hepatocyte features: -Large nuclei = suggests lots of DNA transcription -Lots of golgi = lots of lipid and protein processing -Many mitochondria - requires lots of ATP / they are metabolicaly active

Answer 67

Excess drinking = ethanoate produced as ethanol is detoxified in the liver -> fed into pathway synthesising fatty acids - and so lipids - if there is a lot of fatty acids there is a built up of tissue

Answer 68

3 Adaptations of the kidney: -Layer of fat - protects against mechanical damage -Good blood supply - maintains concentration gradients -Different sized blood vessels into and out of glomerolus to give high pressure for ultrafiltration