Page 155 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)
2) Relation between stroke & cardiac output & venous return

Stroke volume Definition  Volume of blood pumped by the ventricle / beat.
(SV) SV = End diastolic Volume (EDV) - End systolic volume (ESU) = 135ml - 65ml = 70ml
Cardiac Definition  The rate at which blood is pumped from ventricle. /Min [i.e. CO = the volume of blood pumped/min by each

Output ventricle.
(CO) C0 = SV X HR = 70 X 70 = [4900 ml] 5 liter/min
In Steady State COP of left Heart (The systemic blood flow) = Cardiac Output of the right heart (the Pulmonary blood
flow)
 SV or  HR   CO &  SV or  HR   C0

Definition  The rate at which blood is returned to the atria/ min [The greater the VR  The greater the CO]
Venous
 VR   EDV   Ventricular muscle length = stretch   Contractility   SV   CO
Return
 An  of TPR cause  a  in both CO & VR
(VR)
In Steady State VR to right atrium = VR to left atrium = COP from Left ventricle

.
Factors affecting cardiac output مهم
Factor Definition & Relation
1. Contractility (directly) ↑contractility ➔ ↑ SV ➔ ↑ COP
 It is the load on heart before contraction & equals to EDV.
2. Preload (EDV)
 SA is directly proportional to preload. [↑ EDV ➔ ↑ COP]
directly proportional
 EDV   Stretches ventricular muscle fibers  Strength of
ضابقنلاا لبق دوهجملا
ventricular contraction

 load on heart after contraction ➔
3. Afterload  Or pressure against which the ventricle pumps blood
و نيطبلا لباقيب يللا طغضلا  After load = total Peripheral Resistance =(arterial pressure)

ضبقني وه  SV is inversely proportional to after load.
 An  after load [↑ arterial pressure or ↑ TPR] ➔  in SV ➔ ↓
CO
4. Venous return  Venous return ➔  EDV ➔  ventricular muscle length ➔  contractility➔ SV ➔  CO

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