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Cardiac Output (CO) (Heart Rate (HR) (Heart rate is how quickly the heart…

- - - - Examples: Adrenaline, Exercise and Heat
      - SNS responsible for increase heart rate
        
        Done by atrial (bainbridge) reflex, there's an increase in blood within the atria which stimulates the baroreceptors leading to the SA node to be stimulated.
        
        Norepinephrine released and binds to beta 1 adrenergic receptors. This causes the reduction of re-polarization allowing depolarization to occur easier.
    - - Examples: Cold and Rest
      - PNS responsible for reducing the heart to sinus rhythm (75 b/m)
        
        Alters the membrane potential to slow down the SA node (responsible for impulses of action potential) by hyper-polarizing pacemaker cells through the opening of K+ channels
  - - - Arial Fibrillation - Irregular Heart Beats; Can lead to blood clots. Ventricular Fibrillation - Rapid irregular Heart Beats; Can lead to cardiac arrest and death
- - - - Afterload: back pressure exerted on heart by arterial blood
        
        not normally a major factor
        
        Hypertension: increased ESV, decreases stroke volume
      - Venous Return: amount of blood returning to heart
        
        decreases-extreme rapid heartbeat, blood loss
        
        increases-slow heartbeat, exercise
      - Contractility: strength of cardiac muscle tissue
        
        Positive inotropic agents (increase contractility): sympathetic stimuli, hormones, Ca2+
        
        Negative inotropic factors: acidosis, increased extracellular K+, calcium channel blockers
- - - - First, small wave, lasts about 0.08 s and results from movement of the depolarization wave from the SA node through the atria. ~0.1s after the P wave begins, the atria contract.
    - - Large complex results from ventricular depolarization and precedes ventricular contraction. Paths of depolarization waves through ventricular walls change continuously which produces corresponding changes in current direction. Time required for each ventricle to depolarize depends on its size relative to the other ventricle. Average duration of complex is 0.08s.
    - - Caused by ventricular repolarization, typically lasts about 0.16s. Repolarization is slower than depolarization, so the T wave is more spread out and has a lower amplitude (height) than the QRS complex.
  - - - The time (~0.16 s) from the beginning of atrial excitation to the beginning of ventricular excitation. If the Q wave is visible, it marks the beginning of ventricular excitation (P-Q interval).
        
        Includes atrial depolarization (and contraction)and the passage of the depolarization wave through the rest of the conduction system.
    - - During this segment, when the action potentials of the ventricular myocytes are in their plateau phases, the entire ventricular myocardium is depolarized.
    - - Lasts ~0.38 s, is the period from the beginning of ventricular depolarization through ventricular repolarization.
- - - - Average resting CO is 5.25 L/min
      - Maximal CO: In nonathletic people is between 20-25 L/min meanwhile in trained athletes it can be up to 35 L/min
- - - - Right AV Valve (Tricuspid Valve): has three flexible cusps, flaps of endocardium reinforced by connective tissue cores.
      - Left AV Valve (Mitral Valve): bicuspid valve
      - Attached to each AV valve flap are tiny white collagen cords called chordae tendineae, aka heart strings which anchor cusps to the papillary muscles protruding from the ventricular walls.
    - - Aortic Valves
        
        Guard the bases of the large arteries
      - Pulmonary Valves
        
        Guard the bases of the large arteries
- - - - Receives oxygen-poor blood from body tissues and then pumps this blood to the lungs to pick up oxygen and dispel carbon dioxide.
        
        The blood vessels that carry blood to and from the lungs form the pulmonary circuit.
    - - Receives the oxygenated blood re- turning from the lungs and pumps this blood throughout the body to supply oxygen and nutrients to body tissues.
        
        The blood vessels that carry blood to and from all body tissues form the systemic circuit.
    - - The heart uses blood as the transport medium as it propels oxygen, nutrients, wastes, and other substances into the interconnecting blood vessels that service body cells.