Introduction:
Countercurrents exist when fluids flow in opposite directions in parallel and adjacent tubes. There are 2 countercurrent systems and an osmotic equilibrating device:

Countercurrent multiplier (Loop of Henle): Establishes gradient of osmolarity from cortex (300mOsm/L) to the papilla (1200mOsm/L) aided by Urea recycling
Countercurrent exchanger (Vasa recta): Maintains the corticopapillary osmotic gradient established by Countercurrent multiplier
Osmotic equilibrating device (Collecting duct): Depending on …

Definition: Cardiac cycle refers to the cardiac events that occur from the beginning of one heart beat by spontaneous generation of action potential in SA node to the beginning of the next. When the heart rate is 75/min, the period of one cardiac cycle is 0.8 sec.
Important terms:

Diastole: a period of relaxation during which heart fills with blood
Systole: a period …

Juxtaglomerular Apparatus or Complex is a specialized region of a nephron where the afferent arteriole and Distal Convoluted Tubule (DCT) come in direct contact with each other. Juxtaglomeruar Apparatus (JGA) consists of:
1) Juxtaglomerular cells (modified smooth muscle cells) of afferent arteriole including renin containing (synthesizes and stores renin) and sympathetically innervated granulated cells which function as mechanoreceptors to sense blood …

Sometimes during manual blood pressure measurement by auscultatory method, after a few initial tapping sounds, no sound is heard for a variable duration and then the sounds are heard again. This period when no sound is heard is called as auscultatory gap.
Korotkoff sounds:
When the cuff pressure is great enough to close the artery during part of the arterial pressure cycle, …