Deck XIII Flashcards Preview

USMLE World Missed Questions > Deck XIII > Flashcards

Flashcards in Deck XIII Deck (30):

What are the two principle factors that regulate coronary blood flow?

Adenosine and Nitric oxide (NO)


What is the difference in function of adenosine and NO in regulation of coronary blood flow?

NO mediates coronary vascular dilation in large arteries and pre-arteriolar vessels; adenosine acts as a vasodilator in small coronary arteries.


A holosystolic murmur that increases in intensity on inspiration most likely represents what pathology?

Tricuspid regurgitation (the other holosystolic murmurs- mitral regurgitation or VSD do not typically increase in intensity on inspiration)


How do you calculate total filtration rate of a substance?

(Inulin clearance)(Plasma concentration of substance X)


How do you calculate the net excretion rate of a substance?

(Inulin clearance)(plasma concentration of substance X)- (tubular reabsorption of substance A)


What is the difference between type I and type II muscle fibers?

Type I fibers- aeorbic metabolism with high myoglobin and mitochondrial concentrations; type II fibers- rapid, forceful movement (IIB- anerobic glycogenolysis and subsequent glycolysis, IIA- fast twitch generate ATP via aerobic metabolism)


How do you calculate renal plasma flow (RPF)?

(1-hematocrit)(renal blood flow)


What is an alternate equation for FF that uses RPF instead of RBF?

FF= GFR/ (1-Hct)(RBF)


Lesions of the macula cause what condition?

Central scotomas


Describe the changes in urea concentration along the proximal tubule of the nephron.

Urea is freely filtered from the glomerular capillaries and is poorly reabsorbed from the proximal tubule


Describe the changes in bicarbonate concentration along the proximal tubule of the nephron.

Bicarb is actively reabsorbed in the proximal tubule due to the activity of carbonic anhydrase within proximal tubule cells. Bicarb concentration decreases in the proximal tubule as it continues through.


What is the airway pressure at the FRC? What is the intrapleural pressure?

airway: 0 cm H2O; intraplural: -5 cm H2O due to the tendencies of the chest wall to expand and the lungs to collapse


List the following in order of fastest to slowest cardiac conduction velocity: atrial muscle, AV node, purkinje system, ventricular muscle.

Purkinje system, atrial muscle, ventricular muscle, AV node


How do transmembrane carrier proteins in the GLUT family transport glucose?

Facilitated diffusion


Where is GLUT 4 found?

Skeletal muscle and adipocytes. It is insulin sensitive


What is the function of GLUT2?

It facilitates the export of glucose from the liver, small intestine, and kidneys into circulation and helps to control insulin secretion in the pancreas.


What are the manifestations of osteodystrophy?

Increased bone turnover, resorptive bone lesions


What is osteitis fibrosa cystica?

The high bone turnover rate seen in hyperparathyroidism.


What is the role of progesterone in ovulation?

Its secretion increases following ovulation (day 14) with formation of the corpus luteum. It then maintains the endometrium to allow for implantation.


When do progesterone levels peak in the menstrual cycle?

In the mid-luteal phase


A patient with one testicle is found to have elevated serum FSH levels and a normal serum LH level. What substance is likely to be impaired in this patient?

Inhibin B


What is the role of LH in males?

To stimulate release of testosterone from leydig cells


What is the role of FSH in males?

To stimulate release of inhibin B from the sertoli cells of the testes


Describe the feedback loop between testosterone and LH and GnRH secretion in males.

Testosterone has negative feedback on LH and GnRH secretion


What is the relationship of feedback between Inhibin B and FSH?

Inhibin B supresses FSH secretion.


Where is inhibin B produced?

In the sertoli cells. It is the physiological inhibitor of FSH secretion (LH is primarily controlled by testosterone feedback)


What is the equation for cardiac output in terms of oxygen consumption?

O2 consumption/ A-V O2 difference


Describe the relationship between serum creatinine and GFR.

Nonlinear relationship where creatinine decreases as GFR increases. Approximately every time GFR halves, serum creatinine doubles.


Describe the EKG findings in a patient with a-fib.

Tachycardia, irregular rhythm, narrow QRS complexes, no P waves "irregularly-irregular R-R intervals".


How is A-fib initiated?

By aberrant electrical impulses that arise within regions of heightened atrial excitability (most often the pulmonary veins)