BIOL 222 Lecture Notes - Lecture 8: Tachycardia, Bradycardia, Parasympathetic Nervous System
Document Summary
Control of cardiac output: co = sv * hr. Bradycardia - slow heart rate < 60 bpm (decreases co) Tachycardia - fast heart rate > 100 bpm (increases co) Opens k+ channels on sa and av nodes. Thyroid hormone - stimulate up regulation if adrenergic receptors on the heart (sympathetic more sensitive to epi, ne,) increases the heart rate. Hyperkalemia- membrane of the contractile cell is depolarized, difficult to repolarize (too much k+) Hypokalemia- membrane of contractile cells is hyperpolarized, harder to stimulate (too low k+) Preload: tension or stretch in ventricle myocardium before contraction. Venous return: amount of blood returned to the heart. Increase venous return = increase preload = increase sv= increase co. Stroke volume is directly related to edv. If more blood is in chamber, more will be pushed out. Contractility: strength of contraction after a given preload. Positive inotropic agents (increase contraction of strength) More ca2+ can enter cardiac muscle cells which entend contractions.
