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Homeostatic imbalances

Homeostatic imbalances. Pericarditis  inflammation of the pericardium Endocarditis  bacterial infection of the endocardium can lead to valvular stenosis Myocardial infarction heart attack/coronary Heart block any damage to the AV node results in irregular beating of ventricles

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Homeostatic imbalances

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  1. Homeostatic imbalances • Pericarditis inflammation of the pericardium • Endocarditis bacterial infection of the endocardium can lead to valvular stenosis • Myocardial infarction heart attack/coronary • Heart block any damage to the AV node results in irregular beating of ventricles • Murmurs abnormal or unusual hearts sounds

  2. ECG: normal and abnormal

  3. Alterations in Electrocardiogram Clinical Cardiology Concepts for Vets

  4. Cardiac Output • Cardiac Output - the amount of blood pumped by a ventricle per minute. Units may be in milliliters or Liters per minute. • Heart Rate - number of cardiac cycles per minute. Average for males = 64-72/min. Average for females = 72-80/min. • Stroke Volume - amount of blood pumped out of a ventricle each beat. Average resting stroke volume = 70 ml.

  5. Cardiac Output • CO (mL/min) =SV (70 mL/beat) X HR (75 beat/min) • Cardiac output = stroke volume X heart rate = 5250ml/min • SV= EDV - ESV • Stroke volume = end diastolic volume – end systolic volume • Cardiac reserve is the difference between a person’s maximum cardiac output and cardiac output at rest.

  6. Frank Starling Law of the Heart • The more cardiac muscle is stretched within physiological limits, the more forcibly it will contract. • Rubber band analogy • Increasing volumes of blood in ventricles increase the stretch & thus the force generated by ventricular wall contraction. • Greater stretch means more blood volume is pumped out, up to physical limits.

  7. Regulation of stroke volume • Preload is the degree of stretch on the heart. • Contractility is the force of ventricular contractions. • Afterload is the pressure that must be exceeded to eject blood from the ventricles. • The Frank-Starling law of the heart—preload is the critical factor controlling SV (stroke volume).

  8. Regulation of heart rate • When blood volume drops or the heart is weakened, SV drops and the HR increases. • Positive chronotropic factors increase HR. • Negative chronotropic factors decrease HR. • Extrinsic regulation by the ANS • Sympathetic nervous system increases firing of the pacemaker and enhances Ca2+ entry into heart cells. • Parasympathetic nervous system reduces heart rate through ACh which opens K+ channels. • Under resting conditions the PNS is dominant

  9. Chemical Regulation • Hormones • Epinephrine enhances HR and contractility • Thyroxine enhances effects of Epi and NE and leads to slower more sustained increase in HR • Ions • Hypocalcemia (Ca2+)depresses the heart; • Hypercalcemia prolongs the plateau phase and lead to heart irritability • Hyperkalemia (K+) may lead to heart block and cardiac arrest; hypokalemia leads to arrhythmia and weakened contractions. • Excess Na+ blocks Ca2+ inflow, decreasing contractile strength

  10. Other Factors • Exercise leads to a reduced HR when at rest. • Working large body muscles for at least 20 minutes elevates cardiac output and accelerates metabolism. • Athletes have a larger heart and a resting HR of 40-60 beats per minute • Increased temperature increases heart rate; decreased temperatures reduce heart rate and oxygen needs.

  11. Homeostatic imbalances • Congestive heart failure • Caused by Coronary artherosclerosis • Caused by  Persistent high blood pressure • Caused by Multiple myocardial infarcts • Left side failure Pulmonary congestion • Rights side failure Peripheral congestion

  12. Angina Pectoris • Medical term for chest pain due to coronary heart disease. • It occurs when the myocardium doesn’t get as much blood (Oxygen) as it needs. • Insufficient blood supply is called ischemia. • May initially occur during physical exercise, stress, or extreme temperatures. • It is a sign of increased risk of heart attack.

  13. Cardiac Arrhythmias • Arrhythmias irregular heart rhythms that may lead to fibrillation • Tachycardia: Heart rate in excess of 100bpm • Bradycardia: Heart rate less than 60 bpm • Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration • Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

  14. Aneurysm • Weakness of the wall of an artery causing an abnormal enlargment or bulge. • The aorta or the arteries that supply the heart, brain, legs or kindeys are most commonly affected.

  15. Atherosclerosis (Arteriosclerosis) • Narrowing and hardening of arteries and impairment of blood flow due to the deposition of fatty materials and calcium in their walls. • Risk factors include: • smoking • inactivity • diabetes • high blood cholesterol • personal or family history of heart disease • Atherosclerosis Animation

  16. Resources • Heart Sounds & Cardiac Arrhythmias • Live Cardiac Exam Video • Anatomy Links • Cardiac Cycle • Cardiac Cycle Graphics • Interactive Physiology Review • AP II Notes Homepage

  17. Conducting System of Heart

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