Phisiology Flashcards
Why low estrogen state (postmenopausal, ovary dysfunction or surgical remove) favors development of osteoporosis?
⬇️ Estrogen ▶️ ⬇️ Osteoprotegerin ⬆️ RANK-L ▶️ (+) differentiation to active osteoclasts ▶️ bone resorption
⬇️ Estrogen ▶️ ⬆️ RANK in osteoclasts precursors
Pulmonary function test pattern in pulmonary fibrosis.
- Restrictive pattern: ⬇️ lung volumes
⬇️ FEV1, FVC
Normal or ⬆️ FEV1/FVC ratio
⬇️ Diffusion capacity (DLCO)
Excess copper (from senescence ceruloplasmin and not absorbed) is mainly excreted by which pathway?
Secreted into bile ▶️ excreted in stools
-Renal tubular secretion ▶️ 5-15% of excretion
Which component of surfactant rises in amniotic fluid at week 36 and which at week 30?
- Phosphatidylglycerol ▶️ 36 week
- Phosphatidylcholine (lecithin) ▶️ 30 week
Where is controlled the respiratory rate? How is it regulated based on oxygen content?
Medullary respiratory center based on input from:
- central chemoreceptors (medulla) ▶️ PaCO2 (mainly in healthy)
- peripheral chemoreceptors (carotid and aortic bodies) ▶️ PaO2 (mainly in severe hypoxia)
In a water deprivation state (ex, dehydration) which portion of the nephron has the most concentrated and the most diluted urine? why?
- Water deprivation state = ↑ADH levels →↑aquaporin-2 in principal cells at Collector ducts (V2R)→↑H2O reabsorption→most concentrated urine
- Ascending loop of Henle→↑NaCl reabsorption→dilution
- Distal convoluted tubule most diluted urine (even more reabsorption of electrolytes, impermeable to water - lowest osmolarity [hypotonic] - regardless ADH levels)
What is the Jervel and Lange-Nielsen syndrome? why does it occur?
- Sensorineural hearing loss and congenital QT long syndrome
- Mutations (autosomal recessive) - KCNQ1, KCNE1 genes (voltage-gated K+ channels)→↓ K+ current→↑ action potential and QT duration.
Cause and ECG changes of Brugada syndrome.
- Mutations in cardiac sodium or L-type clacium channels
- pseudo right bundle branch block. ST-segment elevation V1-V3
*↑Risk ventricular tachyarrhythmias and sudden death
Which volumes are elevated in COPD patient, mainly in emphysema?
- Residual volume
- Functional Residual Capacity
- Total Lung Capacity
Differences between myoglobin and hemoglobin respect O2-Hb dissociation curve and affinity.
- Myoglobin ▶️ ⬆️ affinity O2 ▶️ hyperbolic curve (P50=1 mmHg)
- Hb ▶️ less afinity than myoglobin (Affinity ⬆️ after binding of 1 O2 molecule heme-heme interaction) ▶️ sigmoid curve (P50=26mmHg)
*myoglobin is equivalent to a 1 subunit (alpha or beta) of the Hb
What is the mechanism by which CO poisoning causes headache, dizziness, seizures, respiratory arrest?
Competitive binding to Hb and with 200x greater affinity than O2
Why stimulation of B1 adrenergic receptor (mainly ⬆️ the heart rate) affect systolic blood pressure? what is the effect?
➕B1 ▶️ ⬆️ HR and contractility ⏩ BP=CO(cardiac output)xHR ▶️ ⬆️ BP (mainly systolic)
Which protein allows the transport of neurotransmitter-containing secretory vesicles in the neurons?
Kinesin ▶️ microtubule-associated, ATP-powered motor protein ▶️ anterograde transport down axons to synaptic terminals
Why is less the ventilation at the apex of the lungs?
Gravity stretch downward the lungs from the apex - apex is fixed in pleural cavity by low intrapleural pressure (“pleural suction”) ▶️ Alveoli more stretched and expanded at apex than base during end-expiration ▶️ less air during inspiration (less compliance)
Why if ventilation and perfusion increases from apex to the base, the V/Q (ventilation/perfusion) ratio is greater in apex than base?
Perfusion (Q) ⬆️⬆️ > Ventilation (V) ⬆️
*“denominator is much greater and numerator is slighty increased in base”
Which are the changes on GFR, FF and RPF if selectively constrict efferent arteriole and afferent arteriole?
- Efferent arteriole constriction ▶️ ⬇️ glomerular blood outflow ▶️ ⬆️ glomerular capillary hydrostatic pressure ▶️ ⬆️ GFR; ⬇️ RPF (stasis) ⏩ FF=GFR⬆️/⬇️RPF=⬆️FF;
- If Efferent arteriole constriction continues ⬆️⬆️ ▶️ ⬆️ oncotic pressure more than hydrostatic in glomerulus ⏩ ⬇️ GFR
- Afferent arteriole constriction ▶️ ⬇️ plasma flow into glomerular capillaries ▶️ ⬇️ capillary hydrostatic pressure ▶️ ⬇️ GFR; ⬇️ RPF equal than GFR ⏩ FF unchanged
What happen when muscle make too much force, and what mediates that response?
Golgi tendous organ (GTO)▶️ interneuron ▶️ 🚫 alpha-motoneuron in spinal cord ⏩ sudden muscle relaxation
*GTO response to actively contraction of muscle to maintain muscle tension
Which regions of the sarcomere have only thick and only thin filaments? Which bands remain unchanged and which changes in length during contraction?
- Thick filaments (myosin) ▶️ band H
- Thin filaments (actin) ▶️ band I
- During contraction ▶️ band A not change, band I, H get shorter
Why during panic attack a patient can have drowsiness, dizziness, blurred vision, weakness (neurologic symptoms)?
Panic attack ▶️ hyperventilation ▶️ ⬇️ PaCO2 ▶️ hypocapnia ▶️ brain blodd vessel constriction (⬆️resistance) ▶️ ⬇️ cerebral blood flow
*CO2 ▶️ potent cerebral vasodilator (most powerful effect of the arterial blood gases on brain blood flow). PaO2<50mmHg (severe hypoxia) ▶️ vasodilation in brain vessels ▶️ ⬆️ cerebral blood flow and intracranial pressure
Which vitamins are lack in the newborn and must be supplemented and why?
- Vitamin K ▶️ immediately parenteral at delivery ▶️ prevent hemorrhagic disease of the newborn
- Vitamin D in exclusively breastfed, lack sunlight exposure, dark skin pigmentation ▶️prevent rickets
*Iron in preterm/low birthweight, breastfed >4 mo until initiate solid food
Which substances in excess can increase the resistance to insulin during pregnancy?
- Plancental growth hormone (PGH)→Placental maturation
- human Placental lactogen (hPL)→Fetal development
- TNF-α, leptin, adiponectin
What part of cardiac cycle is the sarcomere length of the left ventricular muscle fibers the greatest and the lowest?
- End diastolic volume→longest sarcomere length
- End systolic volume→shortest sarcomere length
When occur an intrapulmonary shunt?
When there is an area adequately perfused but poorly ventilated
What substances predominantly drive the angiogenesis?
- Vascular endothelial growth factor (VEGF)
- Fibroblast growth factor (FGF)
What is the approximate intrapleural pressure value at the functional residual capacity (FRC) point? Why?
- -5 mmHg
- Tendencies of chest wall to expand and lung to collapse oppose one another
- FRC point ▶️ positive alveolar transmural pressure and negative chest wall transmural pressure oppose one another equally ▶️ airway pressure of zero (different of intrapleural pressure) ▶️ no tendency of air to flow into or out the lungs ⏩ center of the airway pressure-volume curve
Where is the first site of electric activation of the heart?
Sinoatrial node (dominant pacemaker) ▶️ junction of the right atrium and superior vena cava
Which study can you order in a patient that suspect pulmonary embolism but has a contraindication to use contrast? What would be the result?
- Contrast contraindication ▶️ can not make CT angiography
- Ventilation/perfusion scan (V/Q) ▶️ area of perfusion defect without ventilation defect (mismatched perfusion defect) ⏩ V/Q mismatch
What wave of the jugular venous tracing is absent in atrial fibrilation? why? and when this wave can be prominent?
- a wave→atrial contraction
- A fib→no atrial contraction, no p wave on ECG, it is “fibrilating”
- Hypertrophic cardiomyopathy
Transient holosystolic murmur in a patient with congestive heart failure, dissapear with treatment.
Functional mitral regurgitation
- ↑Preload→Acute dilatation of LV→separate normal mitral valve leaflets
- Tx→↓preload and afterload
Why mature RBC can not synthesize Heme, even though they have cytoplasmic enzymes involved in Heme synthesis?
- Normally lack of Mitochondria→need to first and final 3 steps of Heme synthesis→no Heme→no Hb.
- Heme synthesis (every organ, but mainly)→RBC precursors in BM, hepatocytes (microsomal cytochrome P450)
*Mature RBCs don’t synthesize Hb, survive for 120 days
Functions of von Willebrand factor (vWF).
- Endothelial damage→vWF binds glycoprotein Ib receptors (GpIb) on platelet→platelet aggregation and adhesion to subendothelial collagen
- Carrier for factor VIII→prolongs its half-life
Effect of the vasopressin on urea clearance.
- Vasopressin→(+)V2 receptors in collecting ducts→↑permeability of urea in medullary collecting ducts→↓urea clearance
- Passive reabsorption of urea into medullary interstitium→↑medullary osmotic gradient→maximally concentrated urine
At which point of the lung volumes we find the lowest pulmonary vascular resistance, and why?
FRC→point when don’t have maximal expiration nor maximal inspiration→equilibrium point
- Maximal inspiration→expand alveoli→↑length, ↓diameter of alverolar vessels→ collapse the alveolar blood vessels→↑alveolar vessel resistance
- Maximal expiration→↓lung volumes→↓radial traction, ↑compression by positive intrathoracic pressure on extra-alveolar veins and arteries→narrow extra-alveolar blood vessels→↑extra-alveolar vessel resistance
Source and effect of secretin at the pancreas.
- S cells of duodenum→in response to ↑H+ duodenal due acidic gastric contents arriving→Secretin→(+) pancreatic ductal cells→↑HCO3, ↓Cl in pancreatic secretions (exchange for one another at the apical surfaces of pancreatic ductal cells), Na, K remains equal.
What is the fastest and slowest cardiac tissue conduction?
- Fastest→Purkinje fibers
- Slowest→AV node
*Atrial muscle is faster than ventricular muscle
Concentration of PAH is lowest in what segment of the nephron?
Bowman’s space
*Primarily secreted in proximal tubule, freely filtered by glomerulus, no reabsorbed
In proximal tubule what substances are in high, equal and low concentrations in the tubular fluid and why?
In descendent order
- ⬆️concentration▶️PAH (90% secreted), Inulin, creatinine (20% secreted), urea▶️poorly reabsorbed, active secreted, freely filtered
- “Equal” or minimum change▶️Na, K (reflecxt osmolarity of tubular fluid)▶️equal reabsorption with the water
- ⬇️concentration▶️bicarbonate, Amino acids, glucose
Function and location of enteropeptidase
Jejunal brush border enzyme►trypsinogen→trypsin
In what portion of the nephron is the highest and lowest osmolarity in absence of ADH?
- Descending limb of loop of henle→permeable to water but not solutes►more hypertonic tubular fluid
- Thin and thick ascending limb of henle→impermeable to water►passive absorption of NaCl (thin) and active transport out of the lumen by Na/K/Cl cotransporter (thick)→↓osmolarity, formation of corticomedullary concentration gradient
*Collecting ducts→permeability to water depends of ADH→water impermeable and absorbs more solutes if ↓ADH►hypotonic tubular fluid
Changes of arterial and venous pH, pO2, pCO2 during moderate (aerobic) exercise?
*Change of arterial pH during strenuous exercise.
- Arterial▶️near normal resting values▶️⬆️O2 consumption and CO2 production▶️equilibrated▶️⬆️cardiac output/skeletal muscle perfusion ventilation
- Venous▶️⬆️O2 extraction, ⬆️CO2 production⏩⬇️pH, ⬇️pO2, ⬆️pCO2
*Lactic acidosis▶️⬇️arterial pH
Effect of epinephrine on Beta cell of pancreatic islets and insulin secretion
- Alpha-2 adrenergic receptor→↓insulin→predominates
- Beta-2 adrenergic receptor→↑insulin
Which molecule interact with K channel at beta pancreatic cell to regulate insulin secretion? How is the regulation?
Glucose▶️glycolysis▶️⬆️ATP▶️binds and close K channel▶️depolarization▶️open voltage-dependent Ca channel▶️⬆️intraceullar Ca▶️insulin secretion
What cells secretes a substance that control the storage and release of iron by other cells?
Hepatic parenchyma cells▶️hepcidin (acute phase reactant)▶️bind ferroportin (transport intracellular Fe to circulation)▶️internalize and degrade
- Inflammation and ⬆️Fe▶️⬆️Hepcidin
- Hypoxia▶️erythropoiesis▶️⬇️Hepcidin▶️favors Fe absorption and accumulation in the body (Fe release by M🚫)
Which are the most important acid buffers in urine during metabolic acidosis and do they allow?
-NH3▶️trap H+▶️NH4 (most important - kidney ⬆️⬆️
Effect of CO poisoning on Hb, SatO2, PaO2, O2 content and methemoglobin.
No effect on PaO2 (amount of O2 dissolved in plasma), ↓SatO2, ↓O2 content, ↑carboxyhemoglobin, No methemoglobin
Causes of methemoglobin formation
- Nitrites→dietary intake, or polluted/high altitude H2O
- Benzocaine poisoning
*Oxidizing Fe2+ (normally in Hb)→Fe3+►does not bind O2 as readily, ↑affinity for cyanide.
If fertilization and implantation occur, when would be detected the B-hCG first in serum?
8 days after fertilization
*Urinary B-hCG is detected at 14 days after fertilization
What substance can be used as a marker of osteoblasts activity?
Serum level of bone specific alkaline phosphatase
*Differentiated by electrophoresis, specific monoclonal antibodies, heat desaturation (ex, bone specific easy desaturated by heat)
Uses and source of calcitonin
- Marker for medullary thyroid cancer▶️produced by parafollicular C cells of thyroid gland
- Tx of hypercalcemia
Most commonly method used to assess osteoclast activity
Deoxypyridinoline urinary excretion▶️pyridinoline covalently cross-link collagen fibers
In the setting of water deprivation (high ADH serum level) which segment of the nephron allow absorption of specific solute that is very important to the high medullary concentration gradient?
ADH▶️⬆️H2O reabsorption in medullary collecting ducts▶️conentrate urine in duct▶️⬆️⬆️urea▶️⬆️passive urea transporters▶️urea pass down gradient to medullary interstitium and thin loop of henle⏩50% of the medullary Osm
Principal autoregulation of coronary blood flow
- Adenosine▶️vasodilator in small coronary arterioles
- Nitric Oxide (NO)▶️coronary vascular dilation in large arteries and pre-arteriolar vessels
Cause of secondary polycythemia and increase hematocrit in obstructive sleep apnea. What others disease may be associated?
- Peritubular renal cells in renal cortex sense hypoxia▶️⬆️Erythropoeitin▶️⬆️RBC by bone marrow
- COPD, Right-left shunt, high altitude
Which type of RBC do you expect to find in a blood smear of a patient with iron supplementation by iron deficiency anemia? Why do they have that aspect?
- ↑Iron→↑Hb→↑erythropoiesis→↑both mature RBC and retyculocytes (immature RBC)
- Retyculocytes→↑ribosomal RNA (basophilic, reticular) [lack nucleus]►Blue and large in Wright-giemsa stain
What hormone stimulates the bicarbonate rich and chloride poor fluid secretion from pancreas, which cells produce it, its function and main stimulus?
- Duodenal mucosa→Intestinal S cells→Secretin►neutralizes hydrochloric acid from gastric contents
- Secretion begin with duodenal pH<5, rises with pH<3
What is the effect of the demyelination on the signal tansmission?
- Decrease lenght constant (space constant - How far along an axon an electrical impulse can propagate)→impaired stimulus transmission
- Increase time constant→slower impulse conduction
What is the function of myelin?
- ↑Membrane resistance→↓charge dissipation→↑Length constant→more effective transmission (insulation)
- ↓Membrane capacitance→↓Time constant→↑axonal conduction speed
What is the length constant and time constant of the signal neuronal transmission?
- Length constant→how far along an axon an electrical impulse can propagate
- Time constant→time that takes for a change in membrane potential to achieve 63% of the new value
Why and for what do the F hemoglobin have high oxygen affinity?
- Replacement of Hys by Ser in F Hb→↓positive charge of binding pocket for 2,3 BPG►limit attach of 2,3 BPG, better affinity to O2
- Facilitates transplacental O2 delivery from the maternal circulation to the fetus
What is the segment of the nehpron that is more permeable to water?
Proximal tubule reabsorb>60% of the water filtered by the glomeruli regardless patient hydration status
- Descending loop oh Henle→20% filtered water
- Late distal tubules and collecting ducts (variable according ADH level)→up to 20% filtered water
How is the diffusing capacity for carbon monoxide (DLCO) in emphysema and why?
Decreased due to destruction of alveoli and adjoining capillary beds
In which type of obstructive pulmonar disease may you have a increased diffusing lung capacity for carbon monoxide? How are the other important parameters?
- Asthma→↑pulmonary capillary blood volumes►↑DLCO
- ↓FEV1/FVC, ↑TLC
How can you differentiate the types of restrictive pulmonar disease?
- Extrinsic (Obesity, neuromuscular disease)→↑DLCO
- Intrinsic (interstitial lung diseases)→↓DLCO
Which stimulus down regulate gastric acid secretion after meal?
- Intestinal influences→ileum and colon→peptide YY→enterochromaffin like-cells (ECL) histamine-containing►inhibit histamine release (normally + inderectly acid secretion)
- ECL are + by Gastrin
What proteins mediate the decrease concentration of calcium inside de myocyte after excitation and contraction (myocyte relaxation)?
- Na+/Ca2+ exchange pump (NCX)→out 1 Ca2+ by in 3 Na+
- Ca2+-ATPase pump (SERCA)→hydrolysis ATP to put in Ca2+ in SER
What protein is required to activate RAS proteins?, What is the pathway and its consequence?
GTP→active RAS→(+)RAF→(+)MAP kinase kinase→(+) MAP kinase→(+) transcription factor and gene activation►cell proliferation, etc
Which substance is greater in pulmonary veins than pulmonary artery in a patient with heart failure? why?
Small pulmonary vessels→endothelial-bound angiotensin-converting enzyme►↑Angiotensin II in pulmonary vein compared to pulmonary artery
Functions and source of prostacyclin
- Prostacyclin synthase at capillary endothelium→prostaglandin H2►prostacyclin (prostaglandin I2)
- Inhibit platelet aggregation, adhesion to vascular endothelium, vasodilation, ↑vascular permeability, ↑leukocyte chemotaxis
On which situation may be low or decreased prostacyclin and its consequence?
- Damaged endothelial cells→↓prostacyclin→↑risk thrombi and hemostasis
- Loss normal dynamic balance with TXA2 (platelet aggregation and vasoconstriction)
Major receptors involved in stimulating the vomiting reflex, where is it coordinated?
- M1, D2, H1, 5HT3, Neurokinin 1 (NK1)
- Area postrema→sense neurotransmitters, drugs or toxins
- Nucleus tractus solitarius (medulla)→recieve from area postrema, GI tract via X CN, vestibular system, CNS (meninges, hypothalamus); project to other medullary nuclei
What process allow the elastin to get a rubber like property?
Lysyl oxidase (requires Cu)→oxidatively deaminates lysine residues of tropoelastin at extracellular space→desmosine cross-link between neighboring polypeptides
Compensatory mechanism to maintain GFR and RPF if mean arterial pressure rises.
- Afferent arteriole constricts→regulates blood flow to glomerular capillaries→maintain steady flow►Myogenic mechanism of autoregulation (vasoconstriction that occurs when perfusion pressure increases)
- Metabolic mechanism - vasodilation in response to ↑metabolic waste products
- Efferent arteriole dilates→dissipates pressure► ↑outfllow from glomerulus
- EA constricts when MAP is low→↓outflow→sustain filtration pressure
Increasing which variable is more effective to improve alveolar ventilation?
- ↑Tidal Volume (VT)→more effective
- ↑Respiration rate→less effective
Why does anion gap occur? For example in diabetes ketoacidosis (DKA).
Unmeasured anionic ketoacids (ex, beta-hydroxybutyrate, acetoacetate) bind and lower HCO3
Coagulation factor with the shortest half-life
Factor VII
Unique organ that dilate (or decrease vascular resistance) their arteries when tissue oxygen content is elevated
Lungs
- ↓Vascular resistance in well-aerated alveoli
- Hypoxic vasoconstriction→blood flow is diverted away from underventilated regions toward better ventilated
*Reverse in peripheral circulation→hypoxic tissue→vasodilation►ensure ↑blood flow
What hormone of the hypothalamic-pituitary axis is elevated in menopause women?
FSH→may be used if clinical Dx is unclear
- Resistant ovarian follicle
- Lack negative feedback inhibition from inhibin
Why verapamil doesn’t affect the skeletal muscle contraction?
Mechanical coupling between L-type Ca+2 channel and RyR from sarcoplasmic reticumul→release of Ca+2 without extracellular entrance of Ca+2 that is blocked by verapamil
*Contraction of cardiac and smooth muscle is dependent of extracellular calcium→block L-type Ca+2 channel→blocks contraction
How can TNF-alpha, catecholamines, glucagon glucocorticoids induce to insulin resistance?
Activation of serine or threonine kinases→Phosphorylation serine or threonine residues of B-subunits of insulin receptor and insulin receptor substrate-1
What is the Böhr-Haldane effect?
- Haldane→binding of O2 to Hb drives the release of H+►plus HCO3 IN RBC changed by Cl [carbonic anhidrase]→CO2 + H2O (Lungs)
- Böhr→↑CO2 in RBC [carbonic anhidrase]►H+ (bind Hb, ↓affinity by O2), HCO3 (OUT changed by Cl)→unloading O2 from Hb (Peripheral tissues)
Effect of increase estrogen activity (pregnancy, post-menopausal hormone replacement tx, ACO use) on free and total thyroid hormones.
- ↑Thyroxine binding globulin (TBG)→binds more free T4, T3→initial ↓of free T3, T4
- In response normal hypothalamic-pituitary-thyroid axis→transient ↑T4, T3 until new TBG saturates►↑Total T3, T4→free T3, T4 remains normal→Euthyroid►Normal TSH
