The key chemical messenger responsible for increasing cardiac output when animals are exercising or under certain stresses is

Which respiratory surface lacks physical protection from the external environment?​

The ____ are the smallest vessels that carry blood in the body.​

BONUS In a resting human, a ventricle pump moves roughly ____ liter(s) of blood per minute.​

Choose the nephron structure that best matches the description. Some choices may be used more than once.​

Osmolarity is the ____.​

The QRS complex of an ECG corresponds to

In mammals, urine drains out of the ____ into a collecting duct.​

The primary organ where erythropoietin is produced is the

Plasma makes up approximately ____ percent of the total blood volume.​