Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
WEEK 18:
Red Cell Physiology:
| Question | Answer |
|---|---|
| erythropoietin | polypeptide hormone released by peritubular cells in kidney in response to increase stem cells for erythropoiesis (making more RBC to deliver more O2) in response to hypoxia |
| when is erythropoietin released | in response to hypoxic conditions eg in COPD or at altitude |
| what is recombinant erythropoietin (EPO) used clinically for | treat anaemias associated with renal failure |
| maturation of immature RBC into reticulocytes | immature RBC's nucleus is pushed out and taken up by bone marrow macrophages (to make space for haemoglobin) becoming a reticulocyte with enough mRNA to make haemoglobin. This reticulocyte can enter the blood stream making 0.5-2% of circulating RBCs |
| life span of a normal RBC | 120 days |
| how to measure RBC life span (in haemolytic anaemia) | patient RBC sample is labelled with 51Cr + put back in patient measuring how quickly radioactivity disappears + where radioactivity is (if RBC destroyed too quickly then radioactivity disappears faster + increased radioactivity in area destroying RBC) |
| degradation of RBCs | occurs in reticuloendothelial system (mononuclear phagocyte system) of spleen, liver, and bone marrow |
| what happens to degraded RBCs (3) | proteins are degraded and recycled, iron retained in stores, and porphyrin from haem is converted to bilirubin in liver |
| haemoglobin is made of (2) | haem and globin |
| tetrameric (4 parts) | 4 globin chains each made of polypeptide with haem prosthetic group (2 alpha and 2 beta) |
| haem | ferrous iron (Fe2+) in centre of protoporphyrin complex |
| globin chains are linked by | non covalent bonds |
| adult haemaglobin (HbA) contains | a2b2 subunits |
| fetal Hb contains | a2y2 subunits |
| explain transport and absorption of iron from diet to Hb | Fe3+ converted to Fe2+ in stomach then enters mucosal cells in duodenum where it binds to apoferritin to form ferritin (storage) or transported out as Fe3+. In the blood, Fe3+ binds to transferrin and delivers it to bone marrow where its inserted into Hb |
| where are RBCs broken down | liver and spleen |
| 1L of plasma holds how much O2 | 3ml of O2 |
| 1L blood holds how much O2 | 195ml of O2 |
| how is Hb an allosteric protein | binding of 1st O2 enhances binding of 2nd O2 due to conformational changes |
| Bohr effect | acidity (high CO2) decreases Hb affinity for O2 so less O2 readily given to tissues |
| Bohr effect on curve | shift to right |
| 2-3-diphosphoglycerate (DPG) | in RBC with same molar concentration as Hb and is responsible for binding to deoxyhaemoglobin to reduce O2 affinity and O2 binding to shift equilibrium |
| 2,3-diphosphoglycerate (DPG) in fetus | DPG cannot bind to fetal Hb (as it has different subunits) so there is a higher O2 affinity so O2 moves from mother to fetus via placenta more easily |
| carboxyhaemoglobin formation | formed because CO has a higher affinity to Hb than O2, so CO-Hb does not readily dissociate and tissue becomes starved of O2 (bad in smokers!) |
| methaemoglobinaemia | ferric state iron (Fe3+) cannot carry O2 |
| patient with methaemoglobinaemia may have | cyanosis and symptoms of anoxia (dizziness, respiratory distress, and tachycardia) |
| hereditary cause of methaemoglobinaemia | lack of glucose-6-phosphate dehydrogenase (G6PD) which keeps Hb in reduced state |
| function of G6PD | keeps Hb in reduced state |
| environmental cause of methaemoglobinaemia | drugs eg antimalarials, sulphonamides through oxidant stress |
| carbaminohaemoglobin | CO2 bound to haemoglobin |
| CO2 + H2O -> HCO3- + H+ reaction is catalysed by | carbonic anhydrase in RBC |
| what happens to the products of CO2 + H2O | Hb buffers H+ and HCO3- leaves cell causing Cl- to enter (chloride shift) |
| what can happen to CO2 in body (3) | dissolve, bound to Hb, or react with water vapour |
| reticulocyte | immature RBC that has lost their nucleus but still have RNA to make haemoglobin |
| when is the reticulocyte level increased | when erythropoiesis is increased eg bleeding or haemolysis |
| how are antacids a problem for the conversion of Fe3+ into Fe2+ | antacids decrease stomach acid so less Fe3+ is reduced into Fe2+ |
| why does tetracycline reduce iron absorption | tetracycline binds to iron via chelation to form a complex that cannot be absorbed |
| what detects iron deficiency (2) | erythroid regulator from bone marrow and iron stores regulator |
| what part of RBC binds to O2 | Fe2+ in haem |
| when does DPG increase | when arterial O2 is low (so that O2 affinity decreases and O2 can be more readily given to tissues) |
| increased 2,3-diphosphoglycerate (DPG) shifts curve | left |
| reflexes which modulate breathing (4) | chemoreceptors (monitor PCO2 and PO2), baroreceptors (monitor blood pressure), stretch reflexes in lungs (prevent overexpansion or too much deflation of lungs), and protective reflexes eg sneezing or coughing |
Created by:
kablooey
Popular Physiology sets