Cardiovascular\Respiratory Flashcards
Contraction of a Cardiac Muscle Cell
- Vagus nerve transmits impulses to heart muscle, Na+ diffuses into cardiac cells.
- Electrochemical impulse travels along the sarcolemma of the cells.
- Impulse triggers Ca+2 outside the sell to diffuse in which then causes sarcoplasmic reticulum to release Ca+2
- Ca+2 interacts with contractile proteins causing the cell to contract and shrink in size.
Cardiac Cycle
- SA node depolarizes
- Wave of depolarization spreads through atria, atria contract = ATRIAL SYSTOLE, AV valves are open, blood is forced into ventricles
- Atria repolarize and relax = ATRIAL DIASTOLE, wave of depolarization hits AV node, delay at AV node allows ventricles to fill with blood
- After delay AV node depolarizes and impulse travels through the rest of the conduction system (bundle of his, r/l bundle branches, and purkinje fibers), ventricles contract = VENTRICULAR SYSTOLE, blood is pumped into aorta and pulmonary trunk, AV valves close, SL valves are open
- Ventricles repolarize and relax = VENTRICULAR DIASTOLE, SL valves close, blood returns back to atria from the body
Frank-Starling Law
States that the force of the cardiac muscle contraction is proportional to the of stretch on the fibers.
Sinus Bradycardia
Slower than normal HR,
Sinus Tachycardia
Faster than normal HR, b/w 100-180bpm, normal under strenuous exercise.
Preload
Amount of stretch on the cardiac muscle fibers d/t returning blood.
Afterload
Amount of force required to open SL valves.
Sinus Arrhythmia
Speeds up/slows down, normal ECG but rate varies, normal esp. in children.
Paroxysmal Atrial Tachycardia
B/w 180-250 bpm, atrial and cardiac efficiency decrease, usually due to drug use etc.
Atrial Flutter
B/w 250-350bpm, atria contracting rapidly, ventricles keep at their normal pace due to refractory period of AV node, saw-tooth P waves.
Atrial Fibrillation
> 350bpm, atria are spazming, most common heart arrhythmia, loss of organized signal from SA to AV, no distinct P waves.
Ventricular Tachycardia
Ventricles are contracting rapidly which disables them from filling with sufficient amounts of blood per pump, poor circulation, ex. scarring d/t prior MI, impulse has to move around scarred V cells which stimulates the purkinje fibers more rapidly.
Ventricular Fibrillation
No blood getting to the body, no identifiable ECG waves, ventricles are spazming.
First Degree Heart Block
Longer than normal P-R interval, longer delay at AV node, due to minor damage to the conduction system.
Second Degree Heart Block
Occasional skipped beats, AV node cannot keep up to the sinus rhythm, ventricles don’t contract due to severe blockage of conduction system.
Third Degree Heart Block
No signal from atria to ventricles, ventricles must set up their own slower rhythm of 40-60bpm.
PAC
Ectopic focus in atria causing the atria to depolarize, not abnormal unless persistent.
PVC
Ectopic focus in ventricles causing ventricles to contract before atria have the chance to, also not abnormal unless persistent.
Bi/geminal
Every second beat is a PVC
Tri/geminal
Every third beat is a PVC
Cardiac Center-BP Too High
Stretch (Baro) receptors in either the carotid sinus reflex or the aortic reflex detect and send and impulse via sensory neurons to the medulla oblongata’s cardioinhibitory center which sends motor impulses via the vagus (parasympathetic) nerve to the heart to slow the HR. Uses acetylcholine via cholergic fibers.
Cardiac Center- BP Too Low
Stretch (Baro) receptors in either the carotid sinus reflex or the aortic reflex detect and send an impulse via sensory neurons to the medulla oblongata’s cardioacceleratory center which sends motor impulses via sympathetic nerves to the heart to increase HR. Uses norepinephrine via adrenergic fibers.
Atrial Reflex
Stretch (Baro) receptors in the aortic reflex detect high BP due to high amounts of returning venous blood, info is sent to the cardiac center to increase HR so that more blood is pumped out of the heart.
Ischemic Heart Disease
When the cardiac cells are receiving insufficient amounts of oxygen due to partial blockage of the coronary arteries as a result of atherosclerosis.
Atherosclerosis
Due to atheroma- plaque like structure forms on arterial walls in damaged endothelium, damage can be a result of hypertension.
Plaque
Mainly lipid (fatty) in nature but deposits of calcium salts follow (causes hardening of arteries=arteriosclerosis), may involves cell proliferation from artery wall.
Thrombosis
Stationary clot, partial blockage causing ischemia. May result in MI.
Embolism
Moving clot from heart may get caught downstream in coronary arteries. May result in MI.
Chronic Ischemic Heart Disease
Heart muscle is not getting sufficient O2, angina pectoris (chest pain upon exertion), contributing factor is hyperlipidemia ( high blood lipid levels)
HDL’s and VLDL’s
Good cholesterol, travelling to liver to be broken down.
LDL’s
Bad cholesterol, travelling to cells, may eventually form plaque on damaged endothelium and result in atherosclerosis.
Congestive Heart Failure
Not enough CO to respond to tissue demand, therefore preload and afterload increases= congestion, causes edema (not enough force to pump blood back to the heart, results in excess fluid in tissues.)
Causes of Congestive Heart Failure
Myocardial weakness (aging, ischemia, MI’s), valve problems, lung disease, hypertension.
Blood Flow %’s
Heart and Lungs=100% Brain=15% Digestive Organs=varies Kidneys=20% Muscles= at rest:20% active:75% Storage Areas=5%
Pre Capillary Sphincters
Shunt blood from one area to maximize flow to another.
What does BP do further away from the heart?
Drops due to an increase in the total cross sectional area.
Venous Blood Return
Aided by skeletal muscle contractions and one way valves.
Phlebitis
Inflammation of veins causing roughened endothelium where clots can form. Results in thrombophlebitis. Further along causes deep vein thrombosis where clot can dislodge resulting in a pulmonary embolism.
Predisposing Factors of a Pulmonary Embolism
- Pooling of venous blood (Static blood clots more easily due to muscle inactivity)
- Endothelial damage
- Varicose veins (Valvular incompetence= swelling in veins)
Determining Factors of BP
- Volume of blood
2. Resistance of vessel walls against flow
Factors that Effect BP
- Elasticity of arterial walls
- Viscosity
- Peripheral resistance=Vasomotor Center
- Kidneys
Viscosity
Thickness of the blood, polycythemia=increases RBC count means thicker blood which is harder to pump, erythropoietin is a kidney hormone that controls RBC synthesis, at high altitudes kidney detects low O2 levels which causes it to release EPO which causes red bone marrow to undergo RBC synthesis= acclimatization.