Cardiac Output And Its Regulation

Cardiac Output And Its Regulation

Question 1. Electrocardiograph.
Answer:

• The instrument or the ECG machine by which the electrical activities of the heart are recorded is called electrocardiograph.

Electrocardiographic grid [ECG grid]:

• Electrocardiograph records the electrical signals produced from the heart on a moving strip of paper.
• The markings on this paper is called ECG grid.
• It consists of horizontal and vertical lines at regular intervals of 1 mm.

“Understanding cardiac output and its regulation through FAQs: Mechanisms, functions, and uses explained”

Lines of ECG Grid:

1. Vertical lines:

• It indicates duration of different waves of ECG.
• Interval between two thin lines (1mm) = 0.04 sec.

2. Horizontal lines:

• It indicates amplitude of ECG waves.
• Interval between two thin lines (5 mm) = 0.5 MV
• Interval between two thin lines (1 mm) = 0.1 MV

Frank-Starling law and cardiac output

“Importance of studying cardiac output and its regulation for medical students: Questions explained”

Speed of the paper:

• The movement of paper is adjusted in 25 mm/sec and 50 mm/sec.
• Usually, it is 25 mm/sec.
• If heart rate is very high, the speed of the paper is changed to 50 mm/sec.

“Steps to explain cardiac output and its regulation: Stroke volume vs heart rate: Q&A guide”

Question 2. Regulation of cardiac output.
Answer:

Cardiac output is controlled by two main regulatory process:

1. Control of heart rate or extrinsic autoregulation:

• It is governed by vasomotor center located in the medulla.
• Vasomotor center

2. Control of stroke volume or intrinsic autoregulation:

• It is governed by
• Heterometeric regulations
• It is based on Frank Starling’s law.
• It states that the force of contraction of heart is directly proportional to the initial length of muscle fibres before the onset of contraction.

“Common challenges in mastering cardiac output and its regulation notes effectively: FAQs provided”

Preload:

• During diastole due to the ventricular filling, the muscle fibers are stretched.
• This increases the length of the fibers.
• This, in turn, increases the end diastolic pressure in the ventricle.
• This is called preload.

Afterload:

• At the end of isometric contraction period, the semilunar valves are opened.
• Blood is ejected into the aorta and pulmonary artery.
• Due to this, pressure in these vessels increases.
• This is called afterload.

“Factors influencing success with cardiac output and its regulation studies: Q&A”

Homometric regulation:

• Here myocardial contractibility increases without an increase in initial length of cardiac muscle fibers.