Cardiovascular 4 Flashcards
ESV vs EDV
ESV: end systolic volume
EDV: end diastolic volume
Pressure Volume Loop of Cardiac Cycle:
A-A’ Segment
Late Diastole
-starts at ESV (not all blood is pumped out after contraction)
-pressure in ventricle is lower than the atria and the AV valve opens causing the ventricle to passively fill with blood (80% is passive)
Pressure Volume Loop of Cardiac Cycle:
A’-B Segment
Atrial Systole
-atria contracts -forces more blood into ventricle, slightly increasing volume and pressure
-at the end, maximal amount of blood is in ventricles
-this is EDV
Pressure Volume Loop of Cardiac Cycle:
B-C Segment
Isovolumetric Contraction
-ventricle begins contracting -closes AV valve
-continued contraction causes a large increase in pressure within the ventricle
Pressure Volume Loop of Cardiac Cycle:
C-D Segment
Ventricular Ejection
-once pressure in ventricle rises above 80mmHg, exceeds the aorta
-aortic valve opens causing rapid ejection of blood
-pressure still rises as ventricle contracts
-part way through this segment the ventricle begins to relax and pressure begins to drop, but blood still flows in due to inertia
Pressure Volume Loop of Cardiac Cycle:
DA Segment
Isovolumetric Relaxation
-pressure in aorta begins to exceed ventricle
-causes semi lunar valve to close, ventricle continues to relax
Left Venticle Systemic circuit ranges mmHg from:
About 10mmHg in pressure to 120mmHg
-about 50-125mL
Right Ventricle Pulmonary Circuit mmHg ranges:
Around 15-35mmHg
-about 60-140mL
EDV
End Diastolic Volume -the maximal volume in the ventricle after ventricular filling
70kg man at rest is around 135mL
ESV
End Systolic Volume -the minimal amount of blood in the ventricles, blood left after ventricular contraction
-around 65mL for 70kg male
-provides safety margin, a more forceful contraction will cause larger SV, causing decrease in ESV
SV
Stroke Volume -the amount of blood ejected during a single ventricular contraction
-around 70mL in 70kg male
-can increase to as high as 100mL and is modulated by autonomic system, venous return, and certain drugs
SV=
EDV-ESV
Ex) 135mL- 65mL
=70mL
EF
Ejection Fraction -the percentage of EDV that is ejected fro the heart (SV)
=SV/ EDV
Ex) 70mL/ 135mL
=52%
CO
Cardiac Output
Heart rate x Stroke volume
-flow of blood delivered from one ventricle per minute
-about 4-5 L/min
-pulmonary and systemic outputs are usually identical
-can raise to 30-35 L/min during exercise
Cardiac output can be modified by adjusting
Heart rate or stroke volume
2 Factors that determine the amount of force generated by cardiac muscle:
Contractility of the heart and
Length of muscle fibers at the beginning of contraction
How does contractility affect the amount of force generated by cardiac muscle
The intrinsic ability of cardiac muscle fibres to contract at any given fiber length and is a function of Ca2+ entering and interacting with the contractile filaments
How does the length of the muscle fibres at the beginning of contraction affect the amount of force generated by cardiac muscle
This is determined by the volume of blood in the ventricle at the beginnning of contraction (EDV)
Inotropic agent
Any chemical that affects contractility
-influenced by an inotropic effect
Ionotropic effect
The influence to an inotropic agent
How does contractility increase in cardiac muscle
Catecholamines (NE and E) released from sympa neurons or adrenal medulla
-cause a positive inotropic effect regardless of EDV
-increases as the amount of Ca2+ available for contraction INCREASES
Chemicals increasing contractility have a what effect
A positive ionotropic effect
Chemicals decreasing contractility have a what effect
A negative inotropic effect
