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physiology units 5-6
| Question | Answer |
|---|---|
| What are the main functions of the kidney? | Regulate ECF volume and blood pressure; regulate osmolarity; maintain ion balance; maintain blood pH; excrete wastes; produce hormones; perform gluconeogenesis |
| Which kidney functions are essential for survival? | Regulation of ECF volume, blood pressure, osmolarity, and ion balance |
| How do kidney functions contribute to homeostasis? | They control water and ion loss, regulate pH, and maintain internal balance while located in the retroperitoneal space |
| What is the function of the renal artery? | Carries oxygenated blood into the kidney |
| What is the function of the renal vein? | Carries filtered blood out of the kidney |
| What is the function of smaller kidney blood vessels? | Distribute blood to nephrons for filtration and reabsorption |
| What is the function of the renal cortex? | Outer layer containing corpuscles and most nephron segments |
| What is the function of the renal medulla? | Inner layer containing loops of Henle and collecting ducts |
| What are the calyces? | Chambers that collect urine from collecting ducts |
| What is the renal pelvis? | Funnel that collects urine from calyces and sends it to ureter |
| What is the function of the ureter? | Transports urine to the bladder |
| What is a nephron? | Functional unit of the kidney that filters blood and modifies filtrate |
| What are the two major structures of the nephron? | Renal corpuscle and tubule |
| What is Bowman’s capsule? | Outer part of renal corpuscle that collects filtrate |
| What is the glomerulus? | Leaky capillary bed inside corpuscle that produces filtrate |
| What is the function of the renal corpuscle? | Filter blood to produce filtrate |
| What is the function of the tubule? | Reabsorb ions and water; secrete substances into filtrate |
| What are the parts of the renal tubule? | Proximal tubule, descending limb, ascending limb, distal convoluted tubule, collecting duct |
| What does the collecting duct do? | Collects filtrate from multiple nephrons and carries urine to calyces |
| What are the three layers of the renal corpuscle? | Bowman’s capsule, glomerulus, juxtaglomerular apparatus |
| What are podocytes? | Specialized epithelial cells on Bowman’s capsule that form filtration slits |
| What is the juxtaglomerular apparatus? | Region where tubule contacts afferent/efferent arterioles and regulates renin release |
| What do macula densa cells detect? | Na+ and Cl- concentration in filtrate |
| What do juxtaglomerular (granular) cells release? | Renin |
| What are cortical nephrons? | Nephrons with short loops of Henle located high in cortex |
| What do cortical nephrons primarily do? | Reabsorb filtrate components like glucose and ions |
| What are juxtamedullary nephrons? | Nephrons with long loops of Henle near medulla |
| What is the function of juxtamedullary nephrons? | Reabsorb filtrate and concentrate urine |
| Where are all renal corpuscles located? | In the cortex |
| How is kidney blood flow unique? | Kidneys receive 20% of cardiac output and only 20% of glomerular blood is filtered |
| What is plasma composed of? | Gases, hormones, solutes, macromolecules, ions |
| What is the function of red blood cells? | Transport O2 and CO2 |
| What is the function of white blood cells? | Immunity |
| What is the blood vessel order in cortical nephrons? | Afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries → venule → renal vein |
| How many capillary beds does a nephron have? | Two: glomerulus and peritubular/vasa recta |
| What is the formula for excretion? | Excreted = Filtered – Reabsorbed + Secreted |
| Why is the glomerulus leaky? | Endothelial cells have fenestrations (pores) |
| What is the basal lamina composed of? | Collagens and negatively charged glycoproteins |
| What does the basal lamina do? | Prevents proteins from entering filtrate |
| What do podocyte slits do? | Regulate filtration by widening or narrowing |
| What are the three filtration barriers? | Endothelial pores, basal lamina fibers, podocyte slit spaces |
| What can filter into Bowman’s space? | Water, ions, glucose, amino acids, gases, small molecules |
| What cannot filter into Bowman’s space? | Large proteins, red blood cells, white blood cells |
| What is net filtration pressure? | The sum of all forces in the renal corpuscle that determines filtration |
| What is the normal net filtration pressure? | 10 mmHg |
| What does positive net filtration pressure mean? | Filtration occurs into Bowman’s space |
| What does zero or negative net filtration pressure mean? | Filtration stops |
| What is the hydrostatic pressure of glomerular capillaries (PGC)? | Blood pressure pushing fluid into Bowman’s space |
| Does PGC favor or oppose filtration? | Favors filtration |
| What causes colloid osmotic pressure of glomerular capillaries (πGC)? | Plasma proteins pulling water back into capillaries |
| Does πGC favor or oppose filtration? | Opposes filtration |
| What is hydrostatic pressure of Bowman’s capsule (PBC)? | Back pressure from fluid already in the capsule |
| Does PBC favor or oppose filtration? | Opposes filtration |
| What is colloid osmotic pressure of Bowman’s capsule (πBC)? | Force created if proteins enter Bowman’s space |
| Does πBC favor or oppose filtration? | Favors filtration |
| Why is πBC normally zero? | Proteins do not filter into Bowman’s space |
| What is the formula for net filtration pressure? | (PGC + πBC) – (PBC + πGC) |
| How much filtrate is produced per day? | 180 L/day |
| How much urine is excreted per day? | 1.5–2 L/day |
| What is glomerular filtration rate (GFR)? | Amount of fluid and solutes filtered per unit time |
| How does heart rate affect GFR? | Higher HR increases GFR; lower HR decreases GFR |
| What is the filtration coefficient? | Measure of glomerular capillary leakiness |
| What determines the filtration coefficient? | Surface area and permeability of glomerular capillaries |
| What does high GFR mean? | More solutes and water excreted |
| What does low GFR mean? | Less solutes and water excreted |
| What is the myogenic response? | Afferent arteriole constricts when stretched by high BP |
| What does the myogenic response prevent? | Excessive filtration from high blood pressure |
| What is tubuloglomerular feedback? | Macula densa adjusts GFR based on filtrate salt content and flow |
| What paracrine factor is released when BP and filtrate NaCl are high? | Adenosine |
| What does adenosine do to the afferent arteriole? | Constriction |
| What is the effect of adenosine on GFR? | Decreases GFR |
| What paracrine factor is released when BP and filtrate NaCl are low? | Nitric oxide |
| What does nitric oxide do to the afferent arteriole? | Dilation |
| What is the effect of nitric oxide on GFR? | Increases GFR |
| What happens if the afferent arteriole constricts? | GFR decreases |
| What happens if the afferent arteriole dilates? | GFR increases |
| What happens if the efferent arteriole constricts? | GFR increases |
| What happens if the efferent arteriole dilates? | GFR decreases |
| How does angiotensin II affect renal arterioles? | Constriction of both afferent and efferent arterioles |
| What is the effect of angiotensin II on GFR? | Reduces GFR |
| What is creatinine used for clinically? | Estimating GFR |
| Why is creatinine not perfectly accurate? | It is filtered and secreted by tubules |
| What is inulin used for? | Gold‑standard measurement of GFR |
| Why is inulin rarely used clinically? | Requires IV infusion and constant monitoring |
| What is blood urea nitrogen (BUN)? | Measurement of nitrogen in urea in the blood |
| Why can BUN rise in kidney disease? | Urea is not filtered effectively and accumulates in blood |
| What does high serum creatinine indicate? | Low GFR and impaired kidney function |
| What does GFR tell us clinically? | Whether kidneys are filtering normally or are diseased |
| Why does low GFR indicate kidney disease? | Damaged nephrons cannot filter properly and cannot regenerate |
| What does filtered load tell you? | How much of a substance is filtered into the kidneys per unit time |
| What does filtered load help assess? | Tubule health and reabsorption capacity |
| How is filtered load calculated? | Plasma concentration of substance × GFR |
| What is the first step before calculating filtered load? | Measure GFR using creatinine |
| What is the percent excretion formula? | (Total excreted ÷ Filtered load) × 100 |
| What must be done to total excreted before calculating percent excretion? | Multiply by urine output to convert mg/L to mg/day |
| What does it mean if excretion ≠ filtered load? | Substance was reabsorbed or secreted by tubules |
| What does hypo‑ mean? | Low levels of something |
| What does hyper‑ mean? | High levels of something |
| What is the main function of the proximal tubule? | Reabsorbs 65% of filtrate including water, ions, glucose, amino acids |
| What is reabsorbed in the descending loop of Henle? | Water and some sodium |
| How much volume is reabsorbed in the entire loop of Henle? | 20% |
| What is reabsorbed in the ascending loop of Henle? | Ions such as Na+, K+, Cl− |
| Does the ascending loop reabsorb water? | No |
| What is reabsorbed in the distal tubule? | Na+, K+, Cl− and Ca2+ under PTH control |
| How much volume is reabsorbed in the distal tubule and collecting duct? | 14% |
| What does the collecting duct do? | Variable water and sodium reabsorption; secretes potassium |
| Which transport mechanisms move substances from high to low concentration? | Channels, uniporters, symporters |
| Which transporter moves two molecules in opposite directions? | Antiporter |
| Which transport mechanism uses ATP? | Primary active transport |
| What is paracellular transport? | Movement between epithelial cells |
| What is transcellular transport? | Movement through epithelial cells using channels and transporters |
| What is required for transcellular transport? | Channels/transporters on both luminal and basolateral membranes |
| How does secretion occur in tubule cells? | Via transcellular transport from blood into tubule lumen |
| What is regulation at the level of cellular location? | Hormones move channels into or out of the membrane to control function |
| What is an example of location‑based regulation? | Aquaporin II removed from membrane stops water movement |
| What is regulation at the level of activity? | Hormones increase the speed or efficiency of existing transporters |
| What is an example of activity regulation? | Na+/H+ exchanger works faster when stimulated |
| What is regulation at the level of gene expression? | Hormones increase production of transport proteins via mRNA synthesis |
| What is an example of gene expression regulation? | More Na+/K+ ATPase produced to increase ion transport |
| How does the sodium gradient help reabsorb other molecules? | Na+ gradient drives reabsorption of glucose, amino acids, and ions via symporters |
| Why is filtrate composition important for Na+‑driven transport? | Filtrate resembles ECF, so most ions are higher in filtrate than in tubule cells |
| What transporters are found in the proximal tubule? | Many symporters on luminal side and uniporters on basolateral side |
| What is reabsorbed in the descending limb of Henle? | Water and some sodium |
| Why does water move out of the descending limb? | Medullary ECF becomes increasingly concentrated deeper into the medulla |
| Does the descending limb have paracellular transport? | No, tight junctions prevent it |
| Do hormones act on the descending limb? | No |
| What is reabsorbed in the ascending limb of Henle? | Ions such as Na+, K+, and Cl− |
| Is the ascending limb permeable to water? | No, not even paracellularly |
| Does the ascending limb have paracellular Na+ reabsorption? | Yes |
| What is reabsorbed in the distal convoluted tubule? | Na+, K+, Cl− and Ca2+ under PTH control |
| Which hormone regulates Ca2+ reabsorption in the distal tubule? | Parathyroid hormone (PTH) |
| What cells are found in the collecting duct? | Principal cells and intercalated cells |
| What do principal cells respond to? | Hormones regulating water and sodium balance |
| What do intercalated cells respond to? | Changes in plasma pH |
| How is the descending limb different from the ascending limb? | Descending reabsorbs water; ascending reabsorbs ions and is water‑impermeable |
| How are the ascending limb and distal tubule similar? | Both reabsorb ions and are water‑impermeable |
| Which tubule segments respond to hormones? | Distal tubule and collecting duct |
| What is obligatory urine loss? | Minimum urine volume needed to excrete wastes even when dehydrated |
| Where is ADH produced? | Hypothalamus |
| Where is ADH released? | Posterior pituitary |
| Why is ADH also called vasopressin? | It also constricts blood vessels |
| What triggers ADH release? | Low blood pressure or high plasma osmolarity |
| What sensors detect blood pressure changes? | Baroreceptors in aortic arch and carotid sinus |
| How do baroreceptors signal ADH release? | Low BP reduces action potentials to brain, stimulating ADH release |
| What sensors detect osmolarity changes? | Osmoreceptors in and near the hypothalamus |
| How do osmoreceptors trigger ADH release? | Cells shrink when osmolarity increases, causing action potentials that stimulate ADH release |
| Why does low body water increase ADH release? | Low water decreases BP and increases osmolarity |
| How does ADH affect the collecting duct? | Inserts aquaporin II channels into luminal membrane of principal cells |
| What happens to aquaporin II without ADH? | Removed from membrane by endocytosis; collecting duct becomes water‑impermeable |
| Does the collecting duct ever have zero ADH? | No, usually some ADH is present so some water is reabsorbed |
| What behavioral response helps restore water balance? | Thirst triggered by osmoreceptors |
| Why can urine reach 1400 mOsm with ADH? | Medullary osmolarity is 1400 mOsm, allowing maximal water reabsorption |
| What is urine osmolarity without ADH? | About 100 mOsm |
| Why do juxtamedullary nephrons help concentrate urine? | Their long loops extend deep into the medulla, enhancing osmotic gradient |
| What is diuresis? | Increased urine production |
| How does alcohol act as a diuretic? | Inhibits ADH release from posterior pituitary |
| Is caffeine a diuretic? | No, it increases bladder smooth muscle contractility but not water loss |
| What is diabetes insipidus? | Condition where tubules fail to reabsorb enough water, causing large urine volumes |
| What hormone system is activated when sodium levels are low? | The renin‑angiotensin‑aldosterone system (RAAS) |
| What hormone is released when sodium levels are high? | Atrial natriuretic peptide (ANP) |
| How do sodium levels affect blood pressure? | High Na+ increases ECF volume and BP; low Na+ decreases both |
| Which molecules in RAAS are hormones? | Angiotensin II, aldosterone, ANP |
| Which RAAS hormone is a steroid? | Aldosterone |
| Which RAAS hormone requires extracellular receptors? | Angiotensin II and ANP |
| Which molecules in RAAS are enzymes? | Renin and ACE |
| Which molecules in RAAS are inactive precursors? | Angiotensinogen and angiotensin I |
| Where is renin produced? | Juxtaglomerular cells of the afferent arteriole |
| What does renin act on? | Angiotensinogen from the liver |
| What does renin convert angiotensinogen into? | Angiotensin I |
| What enzyme converts angiotensin I to angiotensin II? | ACE (angiotensin‑converting enzyme) |
| Where is ACE found in highest concentration? | Lung capillary endothelial cells |
| What is the rate‑limiting step of RAAS? | Renin production and release |
| What stimulates renin release? | Low Na+ or low blood pressure |
| What cells detect Na+ levels in filtrate? | Macula densa cells |
| How do macula densa cells stimulate renin release? | Release paracrine signals to juxtaglomerular cells |
| How do baroreceptors stimulate renin release? | Low BP reduces firing to kidneys, increasing renin secretion |
| Where is aldosterone produced? | Adrenal cortex (on top of each kidney) |
| What stimulates aldosterone release? | Angiotensin II and high plasma K+ |
| What does angiotensin II do in the proximal tubule? | Increases Na+ reabsorption via Na+/H+ exchanger and Na+/K+ ATPase |
| What effect does angiotensin II have on blood vessels? | Potent vasoconstriction of afferent and efferent arterioles |
| How does angiotensin II affect GFR? | Decreases GFR due to reduced renal blood flow |
| What cells does aldosterone act on? | Principal cells of the collecting duct |
| What are the genomic effects of aldosterone? | Increased production of Na+ channels, Na+/K+ ATPase, and K+ channels |
| What are the rapid effects of aldosterone? | Increases activity of existing channels and pumps |
| What stimulates ANP release? | Atrial stretch from high blood volume and high Na+ |
| How does ANP reduce Na+ reabsorption? | Inhibits aldosterone release from adrenal gland |
| How does ANP affect GFR? | Dilates afferent arteriole to increase GFR and reduce Na+ reabsorption |
| What is the overall effect of ANP? | Increases Na+ and water excretion to lower blood volume and BP |
| What are the basic functions of the respiratory system? | Gas exchange, blood pH regulation, speech, host defense, dissolving small clots, modifying chemical messengers |
| Where are the lungs located? | Thoracic cavity above the diaphragm |
| How many lobes does each lung have? | Right lung has 3 lobes; left lung has 2 |
| What marks the beginning of the respiratory zone? | Presence of respiratory bronchioles and alveoli |
| How do O2 and CO2 cross the blood‑gas barrier? | Simple diffusion |
| Which direction does oxygen diffuse? | From air into blood |
| Which direction does carbon dioxide diffuse? | From blood into air |
| What is the function of Type I alveolar cells? | Form the blood‑gas barrier |
| What is the function of Type II alveolar cells? | Produce surfactant |
| What is the function of alveolar macrophages? | Remove debris and pathogens |
| What is pulmonary ventilation (VE)? | Total air moved in and out of lungs per minute |
| How is pulmonary ventilation calculated? | Tidal volume × respiratory rate |
| What is dead space ventilation (VD)? | Air in conducting zone that does not participate in gas exchange |
| How is dead space ventilation calculated? | Body weight in lbs × respiratory rate |
| What is alveolar ventilation (VA)? | Air reaching alveoli per minute |
| How is alveolar ventilation calculated? | VE − VD or (VT × RR) − (body weight × RR) |
| Where is the parietal pleura located? | Lining inside rib cage and top of diaphragm |
| Where is the visceral pleura located? | Covering the surface of the lungs |
| What is found in the intrapleural space? | Fluid (not air) |
| What law explains breathing mechanics? | Boyle’s law (pressure inversely related to volume) |
| What happens to intrapulmonary pressure during inhalation? | It decreases below atmospheric pressure |
| Which muscles drive inhalation at rest? | Diaphragm and external intercostals |
| What happens to intrapulmonary pressure during exhalation? | It increases above atmospheric pressure |
| Which muscles relax during exhalation at rest? | Diaphragm and external intercostals |
| What changes during exercise breathing? | Stronger contractions and use of internal intercostals and abdominal muscles for forced exhalation |
| What is intrapleural pressure? | Pressure in pleural cavity, always ~3 mmHg below intrapulmonary pressure |
| What is transpulmonary pressure? | Intrapulmonary pressure − intrapleural pressure |
| Why is transpulmonary pressure important? | Keeps lungs inflated; if zero, lungs collapse |
| What causes transpulmonary pressure to become zero? | Puncture of parietal or visceral pleura allowing air to enter pleural space |
| What happens during a pneumothorax? | Air enters pleural space, transpulmonary pressure becomes zero, lung collapses |
| What two factors create lung recoil? | Elastin fibers and surface tension |
| What produces surfactant? | Type II alveolar cells |
| What does surfactant do? | Reduces surface tension to prevent alveolar collapse |
| What is lung compliance? | Ease with which lungs stretch during inhalation |
| How is lung compliance calculated? | Change in lung volume ÷ change in lung pressure |
| What does low lung compliance mean? | Lungs are stiff and harder to inflate |
| What does high lung compliance mean? | Lungs stretch easily but recoil poorly |
| What causes low compliance in newborns? | Neonatal respiratory distress syndrome due to low surfactant |
| What happens to compliance in COPD/emphysema? | Compliance increases due to loss of elastin, making exhalation difficult |
| How does a traditional spirometer work? | Measures lung volumes and airflow to assess lung function |
| Which lung volumes can a spirometer measure? | Tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity, forced vital capacity |
| Which lung volume cannot be measured by spirometry? | Residual volume |
| What is tidal volume? | Air inhaled or exhaled during normal breathing (~500 mL) |
| What is inspiratory reserve volume? | Extra air inhaled beyond tidal volume |
| What is expiratory reserve volume? | Extra air exhaled beyond tidal volume |
| Which is usually larger: inspiratory or expiratory reserve volume? | Inspiratory reserve volume |
| What is residual volume? | Air remaining in lungs after maximal exhalation |
| What is total lung capacity? | Sum of tidal volume, inspiratory reserve, expiratory reserve, and residual volume |
| What is vital capacity? | Maximum air exhaled after a deep inhalation |
| What is forced vital capacity (FVC)? | Vital capacity measured during a forceful, rapid exhalation |
| What is FEV1? | Volume of air exhaled in the first second of a forced exhalation |
| How do you calculate the FEV1/FVC ratio? | FEV1 ÷ FVC × 100 |
| What is a normal FEV1/FVC ratio? | About 80% |
| What does a low FEV1/FVC ratio indicate? | Obstructive lung disease |
| What does a normal or high FEV1/FVC ratio with low lung volumes indicate? | Restrictive lung disease |
| What type of disease is asthma? | Obstructive lung disease |
| What causes airway obstruction in asthma? | Hyperresponsive smooth muscle causing bronchoconstriction and inflammation |
| Where is smooth muscle located in the lungs? | Throughout the conducting zone from trachea to terminal bronchioles |
| What triggers asthma symptoms? | Allergens, viruses, cold air, pollution |
| What type of disease is emphysema? | Obstructive lung disease |
| What structural change occurs in emphysema? | Loss of elastin and destruction of alveolar walls |
| How does emphysema affect lung compliance? | Increases compliance, making lungs easy to inflate but hard to deflate |
| How does emphysema affect exhalation? | Reduces recoil, making exhalation difficult |
| What type of disease is pulmonary fibrosis? | Restrictive lung disease |
| What causes pulmonary fibrosis? | Scarring of lung tissue from asbestos, coal dust, pollution, or unknown causes |
| How does pulmonary fibrosis affect lung compliance? | Decreases compliance, making lungs stiff and hard to expand |
| How does pulmonary fibrosis affect spirometry results? | Low lung volumes but normal or high FEV1/FVC ratio |
| How do obstructive and restrictive diseases differ in spirometry? | Obstructive: low FEV1/FVC; Restrictive: low volumes but normal ratio |
| How do you calculate atmospheric PO2? | Multiply total pressure (760 mmHg) by fraction of O2 (0.21) to get ~160 mmHg |
| Why is alveolar PO2 lower than atmospheric PO2? | Fresh air mixes with residual low‑O2, high‑CO2 air in the lungs |
| Why is the blood‑gas barrier efficient? | Large pressure gradients, huge surface area, and extremely thin membranes |
| What creates the pressure gradient for O2 diffusion? | High PO2 in alveoli and low PO2 in pulmonary capillary blood |
| Where does gas exchange occur? | Only at capillaries surrounding alveoli |
| What is atmospheric PO2? | 160 mmHg |
| What is alveolar PO2? | 100 mmHg |
| What is pulmonary venous PO2? | 100 mmHg |
| What is systemic arterial PO2? | 100 mmHg |
| What is PO2 in resting body tissues? | 40 mmHg |
| What is systemic venous PO2? | 40 mmHg |
| What is pulmonary arterial PO2? | 40 mmHg |
| How does increased alveolar ventilation affect systemic arterial PO2? | Increases arterial PO2 |
| How does decreased alveolar ventilation affect systemic arterial PO2? | Decreases arterial PO2 |
| Where is hemoglobin found? | Inside red blood cells |
| What is the structure of hemoglobin? | Protein with 4 heme groups, each binding 1 O2 (4 total) |
| What is on the X‑axis of the oxyhemoglobin dissociation curve? | PO2 (mmHg) |
| What is on the Y‑axis of the oxyhemoglobin dissociation curve? | Percent hemoglobin saturation |
| What does hemoglobin saturation mean? | Percentage of heme sites occupied by O2 |
| What is hemoglobin saturation leaving the lungs? | ~98% |
| What is hemoglobin saturation returning to the lungs at rest? | ~75% |
| Why is carbon monoxide dangerous? | Binds hemoglobin with higher affinity than O2 and prevents O2 binding |
| Where is PCO2 highest in the body? | Systemic tissues, systemic veins, and pulmonary arteries |
| Where is PCO2 lowest? | Alveoli after gas exchange |
| Why does CO2 diffuse out of blood into alveoli? | Moves from high PCO2 in blood to low PCO2 in alveolar air |
| How are O2 and CO2 transport similar? | Both dissolve in plasma and bind hemoglobin |
| How do O2 and CO2 binding differ? | O2 binds heme; CO2 binds globin (carbamino form) |
| Why is bicarbonate important? | Main form of CO2 transport in blood |
| Where is bicarbonate produced? | Inside red blood cells |
| What enzyme converts CO2 to bicarbonate? | Carbonic anhydrase |
| When does the bicarbonate reaction shift right? | In systemic tissues when picking up CO2 |
| When does the bicarbonate reaction shift left? | In lungs when unloading CO2 |
| Why is a transporter needed in RBC membranes? | To move bicarbonate out so reaction continues forward |
| How does CO2 affect blood pH? | More CO2 increases H+ and makes blood more acidic |
| What factors cause a right shift in the dissociation curve? | Increased temperature, increased PCO2, decreased pH |
| What is the Bohr effect? | High CO2 and low pH reduce hemoglobin’s affinity for O2, increasing O2 delivery |
| What does a right shift of the dissociation curve mean? | Hemoglobin releases more O2; lower affinity for O2 |
| What does a left shift of the dissociation curve mean? | Hemoglobin holds onto O2 more tightly; higher affinity |
| What is the control center for blood gas homeostasis? | The medulla oblongata (respiratory center) |
| What are the receptors in blood gas homeostasis? | Chemoreceptors |
| What are the effectors in blood gas homeostasis? | Diaphragm and intercostal muscles |
| What triggers increased alveolar ventilation? | Chemoreceptors detect high PCO2, low pH, or low PO2 and increase action potentials to medulla |
| Which chemoreceptors sense pH? | Central chemoreceptors |
| Where are central chemoreceptors located? | Medulla oblongata in the CNS |
| How do central chemoreceptors detect blood pH? | CO2 crosses BBB, forms H+ in CSF, and H+ is sensed |
| Which chemoreceptors sense PCO2, pH, and PO2? | Peripheral chemoreceptors |
| Where are peripheral chemoreceptors located? | Aortic arch and carotid sinus |
| How do peripheral chemoreceptors respond to abnormal gases? | Increase action potentials to medulla when PCO2 high, pH low, or PO2 low |
| What happens during hyperventilation in terms of feedback? | Chemoreceptors detect high pH, low PCO2, high PO2 and reduce action potentials to slow ventilation |
| What role do kidneys play in acid‑base balance? | Excrete H+ and conserve HCO3– when acidic; excrete HCO3– when alkaline |
| How does the proximal tubule handle H+ and HCO3–? | Uses carbonic anhydrase to convert filtered HCO3– to CO2 and H2O, reabsorbs CO2, reforms HCO3–, and secretes H+ |
| What transporter secretes H+ in the proximal tubule? | Na+/H+ antiporter |
| How is bicarbonate returned to the blood from the proximal tubule? | Basolateral HCO3– transporters move it into blood |
| What is the purpose of converting HCO3– to CO2 in the filtrate? | CO2 diffuses easily into tubule cells for reabsorption |
| What do type A intercalated cells do? | Secrete H+ into tubule lumen when blood is acidic |
| What transporter do type A cells use to secrete H+? | ATP‑driven proton pump |
| What do type B intercalated cells do? | Secrete HCO3– into tubule lumen when blood is alkaline |
| What transporter do type B cells use? | HCO3–/Cl– exchanger |
| What causes respiratory acidosis? | Hypoventilation or lung disease causing CO2 retention |
| What lung conditions cause respiratory acidosis? | Pulmonary fibrosis, emphysema, hypoventilation |
| Why does respiratory acidosis occur? | High PCO2 increases H+ via bicarbonate reaction |
| What causes respiratory alkalosis? | Hyperventilation causing excessive CO2 loss |
| Why does hyperventilation cause alkalosis? | Low PCO2 reduces H+ production, raising pH |
| What is a consequence of respiratory alkalosis? | Vasoconstriction due to reduced vasodilator metabolites |
| What causes metabolic acidosis? | Non‑respiratory causes like kidney disease or prolonged diarrhea |
| How do lungs compensate for metabolic acidosis? | Increase alveolar ventilation to blow off CO2 |
| What causes metabolic alkalosis? | Loss of H+ or excess HCO3– (e.g., vomiting) |
| How do lungs compensate for metabolic alkalosis? | Decrease alveolar ventilation to retain CO2 |
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