M5 CH15 excretion & homeostasis

Question 1

outline how nitrogenous waste is excreted from the body in mammals, with reference to the orthenine cycle

Answer 1

the orthenine cycle
1. excess amino acids are deaminated, and so are converted to ammonia
2. ammonia is highly toxic, and so it is converted to urea
3. urea is then excreted from the body

Question 2

state the 3 main waste products that need to be excreted from the body

Answer 2

1. carbon dioxide
2. nitrogenous waste: urea
3. bile pigments

Question 3

what nitrogenous waste do fish excrete?

Answer 3

ammonia

Question 4

explain how bile pigments are excreted from the body in the liver.

Answer 4

hepatocytes secrete the bile into canaliculi
bile passes into ductules where it then travels to gall bladder to be removed

Question 5

explain what the term detoxification means

Answer 5

the neutralisation or breakdown of unwanted chemicals

Question 6

outline the key structural features of hepatocytes, liver cells
(4 points)

Answer 6

large nuclei
prominent golgi apparatus
many mitochondria
contains catalase: involved in breakdown of hydrogen peroxide

Question 7

outline the role of hepatocytes (liver cells) in regulating blood glucose regulation

Answer 7

-In response to insulin they absorb excess glucose from the blood and convert it back to glycogen (glycogenesis)
(lowers BSLs)

-In response to glucagon, they hydrolyse glycogen back into glucose (glycogenolysis) and release it into the blood
(raises BSLs)

Question 8

state the blood vessel that delivers oxygenated blood to the hepatic vein in the liver.

Answer 8

hepatic artery

Question 9

state the blood vessel that delivers deoxygenated blood to the hepatic vein in the liver

Answer 9

hepatic portal vein

Question 10

state what sinusoids are
(liver)

Answer 10

spaces where oxygenated and deoxygenated blood mix

Question 11

explain the role of kupffer cells in the liver

Answer 11

act as macrophages, engulfing foreign particles to protect the liver from disease.

Question 12

state the structure found at the CENTER of the kidney, outline its role

Answer 12

pelvis
where urine collects before it leaves the kidney and travels to ureter

Question 13

state the structure found in the middle layer of the kidney, and its role

Answer 13

medulla
contains the nephrons: where the blood is filtered

Question 14

state the structure found in the outside layer of the kidney, and its role

Answer 14

cortex
carries blood from the renal arteries to the nephron (found in medulla)

Question 15

state the structures found in the medulla in the kidney

Answer 15

loop of henle
collecting ducts

Question 16

state the structures found in the cortex of the kidney

Answer 16

bowmans capsule
glomerulus
PCT
DCT

Question 17

state the order that the structures occur in during filtration in the nephron

Answer 17

1. glomerulus
2. proximal convoluted tubule
3. loop of Henle
4. distal convoluted tubule
5. collecting ducts

Question 18

explain the role of the Bowmans capsule

Answer 18

filters the blood before in can pass into glomerulus
its basement membrane acts as a filter

Question 19

explain what happens at the proximal convoluted tubule

Answer 19

selective reabsorption:
- glucose and amino acids are reabsorbed INTO the blood by active transport
- sodium ions are pumped OUT

Question 20

state the adaptations of the PCT

Answer 20

• lots of microvili: increases surface A
• lots of mitochondria: provides energy for active transport

Question 21

outline what happens at the loop of henle

Answer 21

water and salt are reabsorbed back into the blood

Question 22

state the structure in the nephron where water is reabsorbed, and name the hormone controls the structures membrane permeability

Answer 22

distal convoluted tubule

ADH

Question 23

what is the role of the collecting duct

Answer 23

takes the end product urine away to the pelvis and ureter

Question 24

outline the 2 components of the loop of henle, and what each is permeable to

Answer 24

descending limb: water

AsceNding limb: NA ions and CL ions
(tip+ ascending has N and A in)

Question 25

when observing a diagram of a kidney, which section is usually darker?

Answer 25

the cortex

Question 26

describe the term "homeostasis" and state the factors that contribute to homeostasis.

Answer 26

the maintenance of stable internal conditions of the body, with only small fluctuations - temperature - glucose levels - ion levels - water

Question 27

explain how the release of oxytocin during labour is an example of positive feedback

Answer 27

oxytocin is a hormone that triggers uterus contractions. when the uterus contracts, oxytocin is released, causing more contractions

Question 28

explain what an ectotherm is and provide examples

Answer 28

animals that use their surroundings to heat their body up e.g. fish/reptiles/invertebrates

Question 29

outline ways that ectotherms thermoregulate

Answer 29

WARM UP: basking in sun press body against warm ground colour variations: darker to absorb more heat COOL DOWN: finding shade colour variations: lighter to reflect the heat

Question 30

explain what an endotherm is and provide examples:

Answer 30

animals that thermoregulate through their internal metabolic reactions. humans mammals

Question 31

outline the ways that endotherms thermoregulate

Answer 31

WARM UP: - vasoconstriction: reduces radiation of heat off the surface of skin - raising body hair/feathers: traps a layer of air, providing insulation - shivering: rapid contraction/relaxation of voluntary muscles increases metabolic heat COOL DOWN: - vasodilation: enabling heat to radiate off surface of the skin - sweating: uses heat from metabolic reactions to evaporate the sweat off skin surface. - hair/feathers flat against skin: prevents layer of air being trapped/less insulation

Question 32

outline what monoclonal antibodies are

Answer 32

antibodies from a single clone of cells that are produced to target particular cells/ chemicals in the body

Question 33

outline the use of HCG to create monoclonal antibodies in the treatment of cancer

Answer 33

1. A mouse is injected with HCG so that it makes the appropriate antibody 2. the B cells that make the required antibody are removed (from spleen of mouse\) and fused with a myeloma ( type of cancer cell) 3. creates a hybridoma- which reproduces rapidly 4. these antibodies are collected

Question 34

outline the steps of a pregnancy test, and the role of monoclonal antibodies in the test.

Answer 34

1. the wick is soaked with urine (usually first in morning as has highest HCG levels) 2. test contains mobile monoclonal antibodies that have very small coloured beads attached that ONLY bind to HCG 3. if woman is pregnant the HCG in her urine binds to the mobile monoclonal antibodies and forms a HCG/antibody complex 4. urine reaches first "window" on the test. this is the result window. it has immobilised monoclonal antibodies usually arranged in a line. only HCG/antibody complexes can bind to these. therefore, if the woman is pregnant the complexes will bind and create a coloured line in the result window. (if she isn't= no colour) 5. urine carries on to 2nd window, where there is a line of immobilised antibodies that bind to only mobile antibodies (regardless of presence of HCG) coloured line forms regardless of result, to confirm that the test it working

Question 35

outline the effects of kidney failure

Answer 35

1. loss of electrolyte balance- osmotic imbalances 2. build up of urea in blood (toxic) can poison cells 3. high blood pressure (kidneys play role in b.p by maintaining water balance of blood) 4. weakened bones: calcium/phosphorous balance in blood is lost 5. pain/stiffness- build up of abnormal proteins 6. anaemia: kidneys are involved in production of epo- forms RBCS. :. RBC count decreases

Question 36

explain what the glomerular filtration rate is, and how it is estimated.

Answer 36

- A test used to estimate the volume of blood filtered by the glomeruli each minute, used to indicate a loss of function in the kidneys - blood test measures level of creatinine in the blood. if levels go up= kidney not working properly

Question 37

explain what haemodialysis is and how it works

Answer 37

- a dialysis machine is used to carry out the function of the kidney artificially - all by diffusion - usually carried out in hospital - blood leaves patients body from artery and enters machine- flows between partially permeable dialysis membranes (mimicking basement membrane of bowman's capsule. - removal of unwanted substances in blood --> urea/mineral ions - counter current exchange system (dialysis fluid & blood) : opposite directions, dialysis fluid contains NO urea, steep concN gradient created- so almost all urea diffuses from blood into dialysis fluid

Question 38

explain what peritoneal dialysis is and how it works.

Answer 38

- done at home - done in the body - dialysis fluid is introduced into abdomen via catheter - dialysis takes place across peritoneal membranes (urea diffuses into dialysis fluid,etc) - fluid drained off and discarded

Question 39

outline how a kidney transplant takes place, and the + and -ves.

Answer 39

- single healthy kidney placed in the body, BVs joined and ureter of new kidney is inserted into bladder - risk of rejection: antigens on donor differ from antigens on cells of recipient- immune system will recognise this (can result in rejection/destruction + if successful, kidney will function normally for many years + dialysis has serious long term side effects