CVS Flashcards
What is the primary function of the cardiovascular system (CVS)?
Transport of oxygen, carbon dioxide, nutrients, metabolites, hormones, and heat.
How are the two sides of the heart arranged in the circulation?
In series—ensures equal output from both sides.
Why are most vascular beds arranged in parallel?
To ensure all tissues receive oxygenated blood and allow regional redirection of blood flow.
What are arterioles, and what is their function?
Resistance vessels that control flow and allow redirection of blood.
What do venules and veins function as in the CVS?
Capacitance vessels—control fractional blood distribution.
What is meant by ‘pressure’, ‘resistance’, and ‘capacitance’ in the CVS?
Pressure = force driving flow, Resistance = opposition to flow (mainly by arterioles), Capacitance = ability to store blood (mainly in veins).
What forms the intercalated discs in cardiac muscle?
Desmosomes (physical connection) and gap junctions (electrical connection).
Why can cardiac muscle not undergo tetanic contraction?
Long refractory period due to prolonged action potential (~250 ms).
Describe the phases of a non-pacemaker action potential.
0 - Na⁺ influx, 1 - partial repolarization, 2 - Ca²⁺ plateau, 3 - K⁺ repolarization, 4 - resting potential.
What ions contribute to the pacemaker action potential?
Na⁺ (If), Ca²⁺ (T-type and L-type), K⁺ (decreasing permeability during pre-potential).
What is the role of the SA node?
Acts as the heart’s pacemaker, initiating action potentials.
What does the P wave represent in an ECG?
Atrial depolarization.
What do the QRS complex and T wave represent?
QRS = Ventricular depolarization, T = Ventricular repolarization.
How does the AV node help in coordination?
Delays the impulse to allow ventricular filling.
What are the phases of the cardiac cycle?
Isometric contraction, ejection (rapid & slow), isometric relaxation, filling (rapid & slow).
Define stroke volume (SV).
SV = EDV - ESV (End Diastolic Volume - End Systolic Volume).
What is ejection fraction?
EF = SV / EDV.
What causes the 1st and 2nd heart sounds?
1st = AV valves closing, 2nd = semilunar valves closing.
What is preload?
The initial stretching of cardiac myocytes (related to EDV).
What is afterload?
The pressure the heart must overcome to eject blood (related to TPR).
How does the sympathetic nervous system affect heart rate and contractility?
Increases both via β₁ receptor activation.
How does the parasympathetic nervous system affect the heart?
Decreases heart rate via vagus nerve (muscarinic receptors).
How is cardiac output calculated?
CO = Heart Rate × Stroke Volume.
