Cardiac Cycle Flashcards
Why is there a signal delay at the AV node?
delay time allows time for atria to contract and ventricles to fill
Know that the heart is two separate pumps that are isovolumetric. Know the role of Frank-Starling law of the heart.
Both left and right sides of heart pump equal volume of blood w/ every heartbeat
Know normal ventricular pressures. Know the SL valve pressures that must be overcome before the SL valves will open for systemic and pulmonary circulation.
Systemic circulation: >120 mmHg
Pulmonary circulation: >30 mmHg
Be able to define systole and diastole. Know the valves open and close in response to blood pressure in the heart.
Systole: Squeeze/contraction of the heart
Diastole: Relaxation of the heart
Valves open and close in response to blood pressure in heart
List the two normal heart sounds and when and why they occur.
Lubb Dupp
Occurs when blood rushes into the chambers of the heart and the SL or AV valves snap shut.
ESSAY QUESTION: Understand and be able to describe the phases of the cardiac cycle to includes electrical events (ECG), pressure changes based on heart muscle contraction, heart sounds, changes in blood volume in the atria and ventricles, and the mechanical events of the valves opening and closing. This includes knowing what the atria and ventricles are doing. Know the pressure and volume changes during the cardiac cycle. Know what each valve is doing during the cardiac cycle and where the blood is going and why. Apply the ECG to the Cardiac Cycle.
Phases: Atrial Contraction, Isovolumetric Contraction (Ventricular Systole), Ventricular Ejection, Isovolumetric Relaxation, Ventricular Filling
Be able to use the terms ESV and EDV as they relate to the cardiac cycle.
ESV (End Systole Volume): Blood remaining in ventricle after the squeeze
EDV (End Diastolic Volume): Blood in the ventricle at complete relaxation
Be able to list and define the three types of arrythmia.
Bradycardia: Heartbeat is too slow
Trachycardia: Heartbeat is too fast
Fibrillation: when the heart won’t beat as one unit
Be able to explain the relationship between heart function and blood pressure in terms of cardiac output (C0) and stroke volume (SV) and heart rate (HR) and be able to explain cardiac reserve. Know how much blood is in your body. Know normal heartrate and blood pressures.
Cardiac Ouput: Volume of blood ejected from left/right ventricle into aorta and pulmonary trunk each minute
CO=SV x HR
~5L
Normal HR= 72 Beats/minute
Normal BP= 110/70 mmHg
Cardiac reserve- Max % that CO can increase above normal
Know the influences on stroke volume (SV) in terms of preload, contractility, and afterload.
preload: degree of stretch on heart before is contracts
Contractility: force of contraction of ventricular muscle fibers to push out blood
Afterload: pressure exerted before ejaculation of blood from ventricles can occur, this pressure is from blood that is already in aorta and pulmonary trunk
Know factors that increase cardiac output.
Increased preload, increased contractility, decreased afterload= increased stroke volume= increased CO
increased body temp, decreased physical fitness, chemicals increased sympathetic stimulation and decreased parasympathetic stimulation= increased HR= increased CO
Be able to describe the factors that regulate heart rate. Be able to describe nervous system regulation of the heart and chemical regulation of the heart.
Nervous system regulation: control from CV center in medulla- baroreceptors (detect BP changes and send info to CV center), proprioceptors (body muscles telling heart what they’re doing), chemoreceptors (levels of CO2, O2, H+), ANS- sympathetic (nor/epinephrine), parasympathetic (ACH decreases HR, slows depolarization of SA node)
Chemical Regulation: Hormones-nor/epinephrine & thyroxine increase heart pumping effectiveness (increase HR, SV, CO); relative concentration of Na+, K+, Ca+2 (blood electrolytes);
Other factors: age, gender, physical fitness, temperature
ESSAY QUESTION: Explain Phase 1- Atrial Contraction
SA node fires across both atria, depolarizing the atria and initiating Atrial Systole (contraction). Increasing blood pressure in the atria opens the AV valves to fill the ventricles with blood. The SL valves remain shut as the ventricles are in Ventricular Diastole (relaxation). This is Ventricular End Diastolic Volume (EDV) at 130 mlof blood in the ventricles. Blood in the aorta and pulmonary trunk
hold the SL valves shut.
At the end of Atrial Systole, the SA node fires the AV node which slows so that the atria can finish contraction. The action potential then speeds up as it fires to the Bundle of His, Bundle Branches and Perkinje Fibers for Ventricular Systole that goes through Isovolumetric Contraction and Ventricular Ejection.
ESSAY QUESTION: Explain Phase 2-Isovolumetric Contraction (Ventricular Systole)
_QRS Complex Fires: Atrial repolarization and Ventricular depolarization occurs. The atria begin to fill with blood coming into the heart from the inferior and superior vena cava and coronary sinus to the right atria (deoxygenated blood) and the pulmonary veins (oxygenated blood) to the left ventricle. The AV valves are snapped closed as the ventricles begin Ventricular Systole for the 1st Heart Sound
The Ventricles begin Systole (contraction) which continues through the S-T segment. Systole
(contracting) and increasing pressure on the blood in the ventricles but the pressure is not enough to override the afterload in the aorta and pulmonary trunk or the design of the aortic and pulmonary semilunar valves so the SL valves remain shut. The increasing pressure of blood in the ventricles keeps the AV valves shut. The volume of blood is unchanging.
ESSAY QUESTION: Expain Phase 3- Ventricular Ejection
ST Segment: Continuing Ventricular Systole (contraction) increases blood pressure enough to open the aortic (120 mmHg) and pulmonary (30 mm Hg) semilunar valves forcing blood into the aorta (systemic circulation) and the pulmonary trunk (pulmonary circulation). AV valves stay shut due to ventricular pressure. Volume of blood decreases to End Systolic Volume (ESV at 60 ml) as blood leaves the ventricles in ejection.
