Physiology Flashcards
When is the LV at its fullest?
At the end of diastole
When is the LV at its emptiest?
At the aortic valve closure
During the ventricular diastole, the proper filling of the ventricles depends on 3 conditions:
- The filling pressure of blood returning to the heart and atria (to push blood into the heart)
- The ability of the Atrio-ventricular valves to open fully (i.e. no stenosis)
- The ability of the ventricular wall to expand passively with little resistance (compliance)
What is stroke volume?
The amount of blood ejected with each beat =
End diastolic volume – End systolic volume
What is the ejection fraction?
Stroke Volume / End-diastolic volume
Normal range = 55-70%
What is pulse pressure?
Systolic BP – Diastolic BP
Ex. 120/80mmHg; Pulse pressure = 120-80 = 40mmHg
What is Mean arterial pressure (MAP)?
Diastolic BP + 1/3 Pulse pressure
Ex. B/P = 125/80mmHg;
Pulse pressure = 45mmHg;
MAP = 80mmHg + 45/3 = 95mmHg
What is the Windkessel effect?
The aorta distends during systole as more blood enters the aorta than leaves it. During diastole, the arterial pressure is maintained by the elastic recoil of walls of the aorta and other large arteries. The aorta kid of acts life a pump.
What are the 3 compartments of the total body water?
- INTRACELLULAR COMPARTMENT (2/3 of TBW) = 30 Liters
- EXTRACELLULAR FLUID (1/3 of TBW) = 15 Liters
A) INTERSTITIAL COMPARTMENT (12 L)
B) CIRCULATING PLASMA COMPARTMENT (3L)
What are the 2 types of circulation in the body and their advantages?
- Pulmonary and systemic circulation in series (all the blood that passes in one passes in another)
- Organs and in parallel
Advantages
- Systemic organs receive arterial blood of identical composition
- Flow through any of the systemic organs can be controlled independently
Equation of Flow (Q)?
FLOW (Q) = Pressure difference (Δ P)
Resistance (R)
Poisseuille’s Equation ?
Factors determine the resistance: R4 = Inside radius of tube / L = Tube length / η = Fluid viscosity.
Since the ΔP is nearly identical across all systemic organs, cardiac output is distributed among the various organs primarily on the basis of individual resistances to flow.
Describe how are the valves when during systole and diastole
Systole
- When the ventricular pressure exceeds the pressure in the pulmonary artery (right pump) or aorta (left pump), blood is forced out of the chamber through the outlet valve
- The inlet (AV valve) is closed
Diastole
- When the ventricular muscles cells relax, the pressure in the ventricle falls below than in the atrium, the AV valve opens, and the ventricle fills
- The outlet valve is closed
What is cardiac output and how do you calculate it?
Cardiac output: The amount of blood pumped out by the heart per minute
- HR = Heart rate = number of heartbeats per minute
- SV = Stroke volume = Volume of blood ejected per heart beat = EDV – ESV (end of diastolic – systolic)
CO = HR x SV
Describe the electrical conduction system of the heart
- Sinoatrial node: The heart’s pacemaker; Initiates the action potential that is conducted through the heart; Controls heart rate
- Atrioventricular node: Contains s l o w l y conducting cells that function to create a slight delay between atrial and ventricular contraction
- Purkinje fibers: specialized for rapid conduction to ensure that all ventricular cells contract at the same instant
+ Participation of the autonomic nervous system via ß2 (SE) and vagus nerve (PSE)
Name 1 to 6 in this Wiggers Diagram
- Isovolumic contraction
- Isovolumic relaxation
- A-V valve opens
- A-V valve closes
- Aortic valve closes
- Aortic valve opens
Bruh, what is the pressure-volume loop?
The pressure-volume loop is a graphical representation of the changes in intraventricular pressure which occur during the cardiac cycle as the ventricle fills and empties
- On the x axis is the intraventricular volume
- On the y axis is the intraventricular pressure
What are the 2 curves of the pressure-volume loop?
- EDPVR = End- diastolic pressure volume relation
Indicates the pressure volume relationship during cardiac filling - ESPVR = End-systolic pressure-volume relation
Indicates the pressure-volume relationship at END SYSTOLE (at aortic valve closure)
What is Startling’s law?
When you ↑ demand of the heart, the heart will follow the demande and the end systemic volume will be the same. In other words, it will work harder to acheive the demand. With all other factors equal, stroke volume increases as cardiac filling increases, until a plateau effect or heart failure.
What happends when there is an increase in the preload in the pressure-volume loop?
- An increased end-diastolic volume
- An unchanged end-systolic volume
- An increased stroke volume
On the contrary, a decrease in the preload results in:
- A decrease in the end-diastolic volume
- An unchanged end-systolic volume
- A reduced stroke volume
What happens to the pressure-volume loop when you increase afterload?
- An unchanged end-diastolic volume
- An increased end-systolic volume
- A decreased stroke volume
On the contrary, a decrease in the afterload results in:
- An unchanged end-diastolic volume
- A decreased end-systolic volume
- An increased stroke volume
What happens in the pressure-volume loop when you increase ventricular contracibility?
- An unchanged end-diastolic volume
- A reduced end-systolic volume
- An increased stroke volume
On the contrary, a decrease in the contractility results in:
- An unchanged end-diastolic volume
- An increased end-systolic volume
- A decreased stroke volume
What are the determinants of cardiac output?
A positive chronotropic effect is one in which the HEART RATE is INCREASED (and inversely)
A positive inotropic effect is one in which the CONTRACTILITY is INCREASED (and inversely)
