USMLE World physiology 2 Flashcards

Terms Definitions
Normal GFR value
120 ml/min
Name the hormone—glucagon, insulin, or epinephrine:• Glycogenolytic, gluconeogenic, lipolytic, glycolytic, proteolytic, and stimulated by hypoglycemia and AAs
Skeletal muscle capillary pressure
30 mmHg
Stress hormones
GH, Glucagon, cortisol, epinephrine
What adrenal enzyme deficiency results in hypertension, hypernatremia, increased ECF volume, and decreased adrenal androgen production?
17-alpha-Hydroxylase deficiency
What hormone acts on Granulosa cells?
Serum concentration of what substance is used as a clinical measure of a patient's GFR?
How is plasma potassium concentration in alkalosis?
17α-OH deficiency
Excess 11-deoxycorticosterone and low aldosterone (no AII): Na and water retention, low-renin hypertension. No cortisol: skin hyperpigmentation (due to excess ACTH), adrenal hyperplasia; corticosterone partially compensates low cortisol levels. No 17-ketosteroids: male pseudohermaphrodite, no testosterone, no estrogen.
Sarcomere Z line
Within the A band.
Isovolumetric relaxation
Ventricular pressure decreases; volume is end-systolic volume; aortic and mitral valves are closed
↑ permeability of collecting ducts, ↓ urine, ↑ urine osmolarity, ↑ ECF, ↓ osmolarity
What type of muscle contraction occurs when the muscle shortens and lifts the load placed on it?
Isotonic contraction
What hormone is required for 1, 25-dihydroxy-vitamin D (1, 25-diOH-D) to have bone resorbing effects?
What presynaptic receptor does NE use to terminate further neurotransmitter release?
What cell converts androgens to estrogens?
Granulosa cell
What vessels have the largest total cross-sectional area in systemic circulation?
What hormone disorder is characterized by the following abnormalities in sex steroids↓, LH↓, and FSH↓?
• Sex steroids , LH , FSH
Pituitary hypogonadism
Lung mechanics during inspiration
Diaphragm contracts, intrapleural pressure becomes more negative. Expansion of alveoli makes alveolar pressure negative causing air to flow into the lungs.
Which factors affect PAO2?
Atmospheric pressure, oxygen concentration of inspired air and PACO2
Normal plasma anion gap value
PAG = 12
Due to excess GH in postpuberty. Enlargement of hands, feet and lower jaw, increased proteins, decreased fat, visceromegaly, cardiac insuficiency.
Sarcomere H zone
Contains thick myosin filaments. Shortens during contraction.
Mitral insufficiency
↑ atrial volume and pressure; systolic murmur
Cholesterol esterase
Hydrolizes cholesterol esters to yield cholesterol and free fatty acids
↓ permeability of collecting ducts, ↑ urine, ↓ urine osmolarity, ↓ ECF, ↑ osmolarity
Diabetes insipidus
Actions of CCK
Inhibits gastric emptying, stimulates pancreatic enzyme secretion, stimulates contraction of the gallbladder and relaxation of sphincter of Oddi.
What enzyme is needed to activate the following reactions?• Trypsinogen to trypsin
What thyroid abnormality has the following?
• TRH decreased, TSH decreased, T4 decreased
Tertiary hypothyroidism/hypothalamic (Low TRH causes all the rest to be decreased because of decreased stimulation.)
What equals the total tension on a muscle minus the preload?
Name the valve abnormality based on the following criteria:
• Back-filling into the left atrium during systole; increased v-wave, preload, left atrial volume, and left ventricular filling
Mitral insufficiency
Name the ventricular muscle membrane channel:
• Open at rest; depolarization is stimulus to close; begin to reopen during the plateau phase and during repolarization
Voltage-gated potassium channels
↑ T4, ↑ TSH, ↓ TRH
Pituitary (secondary) hyperthyroidism
Secretion of GH
Pulsatile during non-REM sleep; more frequent in puberty due to increased androgens; requires thyroid hormones; decreases in the elderly.
S1 heart sound
Closure of mitral and tricuspid valves; terminates ventricular filling, starts isovolumetric contraction
Changes in respiratory acidosis
Hypoventilation --> ↑ PaCO2 --> ↑ H and slight ↑ in HCO3 --> ↓ pH
Force that must be generated to eject blood into aorta. ↑ afterload in hypertension, ↓ afterload in hypotension. Acute ↑ in afterload --> ↓ stroke volume, ↑ EDV, ↑ preload
Factors that decrease slope of cardiac function curve
From the fourth month of fetal life to term, what secretes the progesterone and estrogen to maintains the uterus?
The placenta
What wave is the cause of the following venous pulse deflections?• The bulging of the tricuspid valve into the right atrium
C wave
What type of circuit is described when the total resistance is always greater than the sums of the individual resistors?
Series circuit
What acid form of H+ in the urine cannot be titrated?
How many carbons do androgens have?
Androgens are 19-carbon steroids.
What four factors affect diffusion rate?
1. Concentration (greater concentration gradient, greater diffusion rate)
2. Surface area (greater surface area, greater diffusion rate)
3. Solubility (greater solubility, greater diffusion rate)
4. Membrane thickness (thicker the membrane, slower the diffusion rate)

Molecular weight is clinically unimportant
What wave is the cause of the following venous pulse deflections?
• The contraction of the right atrium
A wave
↑ PTH, ↑ Ca, ↓ phosphate
Primary hyperparathyroidism. Causes: parathyroid adenoma (MEN I and II), ectopic PTH tumor (lung squamous CA)
Dead space
Regions that contain air but do not exchange O2 and CO2
↓pH, ↓PCO2, ↓HCO3, normal PO2, acid urine
Partially compensated metabolic acidosis
↑ glucose, ↓ insulin, ↓ C peptide
Type 1 diabetes
Parietal cells
Located in the middle part of the gastric glands. Secrete HCl and intrinsic factor.
Effects of hypothyroidism in newborns
↓ dendritic branching and myelination lead to mental retardation.
What form of renal tubular reabsorption is characterized by low back leaks, high affinity of a substance, and easy saturation? It is surmised that the entire filtered load is reabsorbed until the carriers are saturated, and then the rest is excreted.
A transport maximum (Tm) system
What hormone is secreted by the placenta late in pregnancy, stimulates mammary growth during pregnancy, mobilizes energy stores from the mother so that the fetus can use them, and has an amino acid sequence like GH?
Human chorionic somatomammotropin (hCS) or human placental lactogen (hPL)
What primary acid-base disturbance is caused by an increase in alveolar ventilation (decreasing CO2 levels) resulting in the reaction shifting to the left and decreasing both H+ and HCO3- levels?
Respiratory alkalosis (summary: low CO2, low H+, slightly low HCO3-)
How are resistance and viscosity related regarding flow?
Viscosity and resistance are proportionally related. The greater the viscosity, the greater the resistance is on the vessel.
What event signifies the first day of the menstrual cycle?
Onset of bleeding
What forms of fatty acids are absorbed from the small intestine mucosa by simple diffusion?
Short-chain fatty acids
What two stress hormones are under the permissive action of cortisol?
Glucagon and epinephrine
Where is ADH synthesized?
In the supraoptic nuclei of the hypothalamus; it is stored in the posterior pituitary gland.
Characteristics of cardiac muscle
Actin and myosin form sarcomeres, gap junctions, electrical syncytium, troponin binds calcium, intermediate ATPase activity, dyadic contacts by T-tubules near Z-lines, voltage-gated calcium channels.
Layers of the adrenal cortex
From external to internal: glomerulosa (aldosterone), fasciculata (cortisol), reticularis (androgens). "Salt, Sugar and Sex; the deeper it goes the sweeter it gets"
Tracer to measure plasma volume
Not permeable to capillaries - albumin
How is potassium balance in chronic acidosis?
Negative (potassium is excreted)
Ventilatory response to chronic hypoventilation
Peripheral chemoreceptors are the main drive for ventilation eventhough PaCO2 is increased.
↓ sex steroids, ↑ LH, ↑ FSH
Primary hypogonadism or postmenopause.
Actions of 1,25 di-OH cholecalciferol
Increases Ca binding proteins by intestinal cells which increases intestinal reabsorption of Ca and phosphate. Also increases reabsorption of Ca in the distal tubules. Increased serum Ca promotes bone deposition.
Effects of parasympathetics on pacemaker cells
↑ gK causing hyperpolarization and ↓ sodium funny current decreasing slope of phase 4. Effect via M2 receptors.
↑ resistance, ↓ capillary flow, ↑ capillary pressure
Venous constriction - physical compression, ↑ sympathetic
Phase 4 of SA nodal cells
Gradually depolarizes cell towards treshold due to funny current - ↑ gNa
Which CHO is independently absorbed from the small intestine?
Fructose; both glucose and galactose are actively absorbed via secondary active transport.
What is the relationship between preload and the passive tension in a muscle?
They are directly related; the greater the preload, the greater the passive tension in the muscle and the greater the prestretch of a sarcomere.
What is the best measure of total body vitamin D if you suspect a deficiency?
Serum 25-hydroxy-vitamin D (25-OH-D)
What form of diabetes insipidus is due to an insufficient amount of ADH for the renal collecting ducts?
Central/neurogenic diabetes insipidus; in the nephrogenic form there is sufficient ADH available, but the renal collecting ducts are impermeable to its actions.
What is the renal compensation mechanism for acidosis?
Production of HCO3-, shifting the reaction to the left and thereby decreasing H+
What two factors lead to the development of the bends (caisson disease)?
Breathing high-pressure nitrogen over a long time and sudden decompression result in the bends.
What happens to capillary oncotic pressure with dehydration?
Oncotic pressure increases because of the removal of water.
Why is hypothyroidism associated with night blindness?
Thyroid hormones are necessary for conversion of carotene to vitamin A.
Where does CHO digestion begin?
In the mouth with salivary α-amylase (ptyalin)
Actions of thyroid hormones
↑ metabolic rate by ↑ Na/K ATPase except in brain, uterus and testes; essential for brain maturation and menstrual cycle; permissive for bone growth; permissive for GH synthesis and secretion; ↑ clearance of cholesterol; required for activation of carotene; ↑ intestinal glucose absorption; ↑ affinity and number of β1 receptros in the heart.
Factors that decrease systolic pressure
↓ stroke volume, ↑ HR, ↑ compliance
Factors that increase systolic pressure
↑ stroke volume, ↓ HR, ↓ compliance
Acute reflex changes in volume overload
↑ afferent baroreceptors --> ↑ parasympathetic, ↓ sympathetic, ↓ blood pressure, ↓ heart rate
↑ capillary flow, ↓ capillary pressure, no change in resistance
↓ venous pressure - hemorrhage, dehydration
Site 2 of hemoglobin
Oxygen is attached at 26mmHg which is p50. More affinity, second site to be saturated.
When a person goes from supine to standing, what happens to the following?• Dependent venous pressure
IncreasesRemember, the carotid sinus reflex attempts to compensate by increasing both TPR and heart rate.--------------------------------------------------------------------------------
Does the oncotic pressure of plasma promote filtration or reabsorption?
The oncotic pressure of plasma promotes reabsorption and is directly proportional to the filtration fraction.
What percentage of cardiac output flows through the pulmonary circuit?
100%; the percentage of blood flow through the pulmonary and systemic circulations are equal.
What causes a skeletal muscle contraction to terminate?
When calcium is removed from troponin and pumped back into the SR, skeletal muscle contraction stops.
What is the major hormone produced in the following areas of the adrenal cortex?• Zona reticularis
DHEA (androgens)Remember, from the outer cortex to the inner layer, Salt, Sugar, Sex. The adrenal cortex gets sweeter as you go deeper.
How many days prior to ovulation does LH surge occur in the menstrual cycle?
1 day prior to ovulation
What is the term that refers to the number of channels open in a cell membrane?
Membrane conductance (think conductance = channels open)
During puberty, what is the main drive for the increased GH secretion?
Increased androgen secretion at puberty drives the increased GH secretion.
What is the term for days 15 to 28 in the female cycle?
Luteal phase
↓ T4, ↑ TSH, ↑ TRH
Primary hypothyroidism; ↑ TSH is the more sensible index
Effect of intracerebral hemorrhage in ECG
Inverted T waves with prolonged QT interval
Actions of principal cells of the distal tubule and collecting duct
Aldosterone increases Na receptors in the membrane and increases primary transport by Na/K ATPase. Secondary transport of Na and secretion of K.
↓ capillary flow, ↓ capillary pressure, no change in resistance
↓ arterial pressure - ↓ CO, hemorrhage, dehydration
Vessel with the most turbulent flow
Aorta - has large diameter, high velocity. In anemia (↓ viscosity) --> aortic murmur
The opening of what valve indicates the termination of isovolumetric relaxation phase of the cardiac cycle?
Opening of the mitral valve indicates the termination of the isovolumetric relaxation phase and the beginning of the ventricular filling phase.
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:• ECF, increase; ICF, increase; body, decrease
Gain of hypotonic fluid (water intoxication or hypotonic saline)
Where is most of the airway resistance in the respiratory system?
In the first and second bronchi
Is excretion greater than or less than filtration for net secretion to occur?
Excretion is greater than filtration for net secretion to occur.
Why is the cell's resting membrane potential negative?
The resting membrane potential of the cell is -90 mV because of the intracellular proteins.
What happens to intracellular volume when there is an increase in osmolarity?
ICF volume decreases when there is an increase in osmolarity and vice versa.
What are two causes of diffusion impairment in the lungs?
Decrease in surface area and increase in membrane thickness (Palv O2 > PaO2)
How is potassium affected by acidosis?
High concentration of ECF H --> H diffuses to ICF --> K diffuses to ECF --> hyperkalemia
Sarcomere length in skeletal muscle Vs. heart muscle
In skeletal muscle it's close to L0. In heart muscle, sarcomere legth is below optimal, therefore increased preload moves sarcomere legth towards optimal for maximal cross-bridge linking
True or false? Enterokinase is a brush border enzyme.
False. It is an enzyme secreted by the lining of the small intestine.
What percentage of CO2 is carried in the plasma as HCO3- ?
90% as HCO3-, 5% as carbamino compounds, and 5% as dissolved CO2
What does a loss of afferent activity from the carotid sinus onto the medulla signal?
A loss of afferent activity indicates a decrease in BP, and an increase in afferent activity indicates an increase in BP.
On a graphical representation of filtration, reabsorption, and excretion, when does glucose first appear in the urine?
At the beginning of splay is when the renal threshold for glucose occurs and the excess begins to spill over into the urine.
What happens to cardiac output and TPR if mean arterial pressure decreases?
TPR decreases, CO decreases but then increases to compensate and maintain blood pressure
Why is the apex of the lung hypoventilated when a person is standing upright?
The alveoli at the apex are almost completely inflated prior to inflation, and although they are large, they receive low levels of alveolar ventilation.
Why is there an increase in FF if the GFR is decreased under sympathetic stimulation?
Because RPF is markedly decreased, while GFR is only minimally diminished; this results in an increase in FF (remember FF = GFR/RPF).
Where in the kidney are the long loops of Henle and the terminal regions of the collecting ducts?
In the medulla; all the other structures are cortical.
Why is there a minimal change in BP during exercise if there is a large drop in TPR?
Because the large drop in TPR is accompanied by a large increase in cardiac output, resulting in a minimal change in BP.
What is the name of the force that develops in the wall of the lungs as they expand?
Lung recoil, being a force to collapse the lung, increases as the lung enlarges during inspiration.
What is the term for the load on a muscle in the relaxed state?
Preload. It is the load on a muscle Prior to contraction.
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