Heart Physiology 1 Flashcards
Cardiac Output of Heart per minute
5 L/min
Drug that increases the strength of heart contraction - mechanism involves pump, exchangers, contractile protein control
DIGITALIS
Drug that increases heart contraction and heart rate; is agonist for sympathetic receptors in heart (G-protein coupled receptors); modulate ionic channels through cAMP
Sympathomimetic amines (dopamine and dobutamine)
Drug that increases heart contraction and heart rate; Inhibits break-down of cAMP
Phosphodiesterase Inhibitors
Drug to treat angina, hypertension, arrythmias; partially blocks ionic channels important to heart and smooth muscle function
Calcium-channel Blocker
Drug that decreases heart rate and contraction; blocks sympathetic nervous system action on heart
Beta-blocker (adrenergic antagonist)
Drug that treats arrhytmias; work at changing ionic channels and autonomic receptors in cardiac cell membrane
Anti-arrhytmic drugs
What are approximate rates of death due to cardiovascular disease in different age groups?
Around 45 = 40%
Around 65 = 50%
Over 74 = 64%
Label this external heart
Label this internal heart
Label the heart valves
When do tricuspid and mitral valves open?
During ventricular diastole; When pressure in atrium is greater than pressure in ventricle
When do tricuspid and mitral valves close?
During ventricular systole; When pressure in ventricle greater than pressure in atrium because of ventricular contraction
What structure prevents valve eversion during ventricular systole (ventricular pressure is high)?
Chordae Tendineae attached to Papillary muscles
When are the semilunar valves closed?
During ventricular diastole (when pressure in aorta and pulmonary artery is greater than pressure in ventricles)
When are the semilunar valves open?
During ventricular systole (pressure in ventricles greater than pressure in aorta and pulmonary artery)
What is the name for the heart condition where blood flows abnormally between aorta and pulmonary artery (ductus arteriosus blood vessel from fetus stays open instead of closing)?
Patent Ductus Arteriosis
Narrowing of valve that often causes heart to pump much harder; has decreased cardiac reserve for exercise (because already contracting close to max); leads to left ventricular hypertrophy
Valve Stenosis
This disease often causes mitral or tricuspid valve stenosis
Rheumatic fever
Name for leaky valve that allows regurgitation; mitral regurgitation often leads to elevated atrial pressure, left ventricular dilation, reduced cardiac reserve, increased workload on heart
Valve Insufficiency
Define timeline of left ventricular systole
Starts with left ventricular contraction, continues with ejection of blood from left ventricle into aorta, ends with closing of aortic semilunar valve
Define timeline of left ventricular diastole
Starts with closing of aortic semilunar valve; continues with filling of ventricle; ends with ventricular contraction
Mitral regurgitation results from what? (simple answer)
Mitral valve insufficiency
How does the systolic pressure of the right heart (pulmonary circulation) compare to the systolic pressure of the left heart (systemic circulation)?
Right ventricular systolic pressure only reaches about 25mmHg (1/5 of normal systolic 120 BP in systemic circulation)
Define Cardiac Output
Amount of blood leaving each ventricle per minute
Define the formula for cardiac output
CO = HR x SV
Provide the range for Heart Rate
Ranges 60-180; ~70 (resting)
Provide rangel for Stroke Volume
70-120 mL; resting ~ 70-75mL
What variables influence stroke volume?
1) Heart Contractility (inotropic state)
2) Filling of heart (preload)
3) Pressure against heart must work (afterload)
Cellularly, what determines contractility of the heart?
1) Amount of Calcium that enters the myoplasm during each heartbeat
2) Number of functional myocytes
3) Coronary blood supply
What determines heart preload?
Central Venous Pressure
Label this diagram
Label this diagram
Define tidal volume (Vt)
Amount of (fresh) air inspired per breath
Define functional residual capacity (FRC)
Resting volume of the lung; point at which the force of chest wall expansion balances the force of lung collapse
Define minute ventilation
Amount of air that enters the lung per minute
Provide the formula for minute ventilation
Minute ventilation = frequency of breaths x tidal volume (increase minute ventilation by either taking bigger breaths or more breaths)
Where are chemoreceptors located that sense arterial blood oxygen and carbon dioxide to regulate ventilation?
Bifurcation of carotid artery in neck and aortic arch have receptors to sense oxygen; brainstem has receptors to sense CO2
What is the formula for caculating partial pressure?
Partial Pressure = total pressure x fraction of gas component
What is the partial pressure of oxygen entering the lungs at sea level? in alveoli?
160 mmHg; 102 mmHg
How is partial pressure of oxygen decreased in the body so that oxygen travels from atmosphere into bloodstream?
**1) Air is humidified **
2) Oxygen is being removed into bloodstream
What is the partial pressure of CO2 entering the lungs at sea level? at alveoli?
Almost 0mmHg; 40mmHg in circulation and alveoli
Provide bicarbonate buffering system equation.
CO2 + H20 = H2C03 = H+ + HC03-
**(carbon dioxide combines with water to form carbonic acid, which in turn rapidly dissociates to form hydrogen ions (H+) and bicarbonate) **
**All catalyzed by carbonic anhydrase **
Explain the resultant pathologies of mitral valve insufficiency (regurgitation).
When left ventricle contracts, some blood goes the wrong direction up into the left atrium
Atrial pressure is thus increased, backing up to cause pulmonary hypertension and pulmonary congestion; the left atrium adapts by enlarging
The left ventricle will hypertrophy to compensate for increased preload
Cardiac reserve is decreased because ventricle is already working harder than normal
Eventually, left ventricle begins to fail; ventricle dilates and weakens; ejection fraction decreases dramatically and patient experiences chronic heart failure
Explain resultant pathologies of aortic valve stenosis.
Heart must pump much harder and create more pressure at ventricle to maintain normal downstream areterial flow and pressure
**Cardiac reserve for exercise greatly decreases because the heart is already contracting close to max **
**The heart adapts by hypertrophy of the left ventricular **
In later stages, the left ventricle dilates and thins: muscle dissapears and systolic function deteriorates leading to chronic heart failure
