Fewell - Cardiac Cycle & Ventricular Performance 2021 Flashcards
Primary role of the Cardiovascular System
maintaining
homeostasis is the transport of nutrients and
dissolved gases to tissues as well as removal of
by-products of metabolism
Goal of transport
match supply to demand
>tissue regulate their blood flow to meet demand of organs
Why does The heart pumps blood into the
circulatory system?
to establish a
driving pressure for perfusion of the
various tissues
Circulatory System & cardiac filling during normal functions
the heart accepts
blood at low filling pressures during
DIASTOLE and then propels it forward at
higher pressures during SYSTOLE
What mechanisms help the heart pumps blood into the
circulatory system?
- Generation of Action Potentials
- Automaticity & Rhythmicity
- Conduction of Action Potentials
- Excitation – Contraction Coupling
- Muscle Contraction
- Mechanical Activity of the Heart
Circulatory System heart failure impact on cardiac filling
when the heart is unable to pump blood forward to meet the metabolic demands of the body or is able due so only if cardiac filling pressures are abnormally high
Systemic Transport Formula/Determinants of Systemic transport of Gas or Nurtrients
Systemic Transport = Gas or Nutrient Content x Cardiac Output
Systemic transport (Ex: Oxygen)
Systemic Oxygen Transport = CaO2 x CO
Cardiac Output Formula
Stroke Volume x Heart Rate
Cardiac Output definition
amount of blood that the heart pumps in 1 minute (L/min)
Cardiac Output: pulmonary artery vs aorta
measured in aorta or pulmonary artery because left and right side have same cardiac output
Why is cardiac output intermittent?
Output is intermittent, continuous flow to body tissues occurs by distension of the aorta and its branches during systole and elastic recoil of these structures during diastole..
Windkessel Reservoir
Winkessel (air chamber) converts pulsatile inflow
into a smoother outflow
>an air chamber used in past fire engines
Windkessel Reservoir and Cardiovascular System
Stephen Hales [1677-1761] drew the analogy between the resistance and compliance elements of the cardiovascular system to a Windkessel Reservoir
Determinants of Stoke Volume
+ contractility and preload
- afterload
determinants of cardiac output
+ stroke volume and heart rate
cardiac cycle definition
The sequence of
electrical and mechanical
events that repeats with
every heartbeat
phase of cardiac cycle
systole and diastole
cardiac cycle for 1 heart beat
total of 0.8 seconds
>0.3 seconds for systole (contraction)
>0.5 seconds for diastole (refilling)
roles of systole and diastole on heart rate increases
diastole shortens more than systole
Right & Left Ventricles - Contraction
The right ventricle contracts like a bellows whereas the left ventricle contracts like a hand squeezing a tube of
toothpaste
____ Events Precede
_____ Events
Electrical & Mechanical
Flow results from ___
Pressure Gradients
Valves open and close as results of ____
Pressure gradients
Opening and closing of valves produces ___
heart sounds
Fewell’s four phases of the cardiac cycle
- Inflow Phase
- Isovolumic Contraction
- Outflow Phase
- Isovolumic Relaxation
Inflow Phase Valves
Mitral Valve Open – Aortic Valve Closed
Isovolumic Contraction Valves
Both Valves Closed – No Flow
Outflow Phase Valves
Mitral Valve Closed – Aortic Valve Open
Isovolumic Relaxation Valves
Both Valves Closed – No Flow
Cardiac Cycle Wigger’s Diagram (Inflow)
LEFT HEART PHASE 1
• Rapid ventricular filling
• Decreased ventricular filling – Diastasis
• Atrial contraction – Additional ventricular
filling
>Diastole (Passive early & later Active DIFFERENT FROM TEXTBOOK HERE!!!!)
>Mitral Valve Open – Aortic Valve Closed
Cardiac Cycle Wigger’s Diagram (isovolumic contraction)
LEFT HEART PHASE 2
> Systole
>Mitral Valve Closed – Aortic Valve Closed
Cardiac Cycle Wigger’s Diagram (Outflow)
LEFT HEART PHASE 3
Systole
Mitral Valve Closed – Aortic Valve Open
• Rapid ventricular ejection
• Decreased ventricular ejection
Cardiac Cycle Wigger’s Diagram (Isovolumic Relaxation)
LEFT HEART PHASE 4
> Diastole
>Mitral Valve Closed – Aortic Valve Closed
Heart rate is determined by ____
the cardiac cycle???
Stroke volume formula
SV = End-Diastolic Volume (LVEDV) minus End-Systolic Volume (LVESV)
>around 70mL
Stroke volume definition
the amount of blood pumped by the left ventricle during one cardiac cycle
Ejection Fraction Formula
Ejection Fraction = stroke volume/ end-diastolic volume
>should be around 55%
Preload definition
Force that stretches the relaxed muscle fiber
end-diastolic volume
Contractility definition
Cardiac performance at a given preload & afterload
Afterload definition
Force again which the contracting muscle
must act
(aortic pressure)
Preload Formula
transmural end-diastolic left ventricular pressure = end-diastolic left ventricular pressure – Pericardial Pressure
Frank-Starling
stroke volume of the heart increases in response to an
increase in the volume of blood filling the heart when all other
factors remain constant.
preload systolic vs diasytolic
systolic has a larger preload than diastyolic
BUT increased pressure good because optimize myocardial fiber lenght
