Cardiac Emergencies | Electrophysiology


Automaticity: self-generate electrical activity
Excitability: respond to appropriate electrical stimulus
Conductivity: transmits stimulus from cell to cell
Contractility: Contract when stimulated by the appropriate electrical stimulus
Regulation of heart function: comes partially from the brain (autonomic), from hormones if the endocrine system and from the heart tissue

Barorecepters: sensory nerve endings that sense changes in BP from vasodilation/ constriction
Lower BP in response to increased arterial pressure

  • Inhibit medulla
  • Excite vagal center
  • Decrease force of cardiac contraction

Increase BP in response to decreased arterial pressure

  • Inhibit vagal center
  • Activate sympathetic nervous system >>> norepinephrine and epinephrine

Chemoreceptors: walls of atria of heart, vena cava, aortic arch and carotid sinus. Increase in CO2/decreases in O2 initiate a sympathetic response to increase rate and depth of respiration.

Chronotropic State: control of the heart rate

  • Less than 60 = bradycardia
  • More than 100 = tachycardia

Dromotropic State: rate of electrical conduction

Inotropic State: Strength of contraction

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