Lab 6A: ECG and Pulse

The ECG and the Heart

• The heart's mechanical activity (contraction and relaxation) is controlled by electrical activity (depolarization and repolarization events).
• An electrocardiogram (ECG) records electrical changes in cardiac muscle during the cardiac cycle.
• The P wave indicates depolarization of the atria, which leads to their contraction.
• The QRS complex indicates depolarization of the ventricles right before they contract to pump blood out of the heart.
• The T wave represents repolarization of the ventricles as they relax, allowing the heart to refill with blood.

Regulation of Heart Rate

• The heart has its own built-in pacemaker, the SA node.
• The autonomic division and hormones can influence the rate of depolarization at the SA node.
• Norepinephrine and epinephrine increase the rate of depolarization at the SA node, increasing heart rate under stress.
• Acetylcholine slows down the rate of depolarization at the SA node, resulting in a drop in heart rate.

Measuring Changes in Blood Volume

• Plethysmography records volume changes in the body.
• The volume of blood in tissues changes with the cardiac cycle, creating a pulse.
• A pulse transducer measures changes in blood volume in a body part, such as the finger.
• The pulse transducer shines a beam of light through the skin and measures the light reflected by the heme pigment in the blood.

Regulation of Blood Flow

• The amount of blood flowing to a particular body part depends on the diameter of the arterioles leading into that tissue.
• Vasoconstriction and vasodilation occur when the smooth muscle in the arteriole walls contracts and relaxes, respectively.
• External factors, such as the sympathetic division, and local factors, such as temperature and changes in metabolites, influence the smooth muscle of the arteries.
• Vasoconstriction and vasodilation can be influenced by various hormones, such as vasopressin (ADH) and aldosterone.
• Local factors, such as cold temperatures, can cause vasoconstriction to divert blood away from the cold skin or extremities.
• During exercise, local factors, such as carbon dioxide and metabolic acids, can cause vasodilation in active skeletal muscle.

The ECG and the Heart

• The heart's mechanical activity (contraction and relaxation) is controlled by electrical activity (depolarization and repolarization events).
• An electrocardiogram (ECG) records electrical changes in cardiac muscle during the cardiac cycle.
• The P wave indicates depolarization of the atria, which leads to their contraction.
• The QRS complex indicates depolarization of the ventricles right before they contract to pump blood out of the heart.
• The T wave represents repolarization of the ventricles as they relax, allowing the heart to refill with blood.

Regulation of Heart Rate

• The heart has its own built-in pacemaker, the SA node.
• The autonomic division and hormones can influence the rate of depolarization at the SA node.
• Norepinephrine and epinephrine increase the rate of depolarization at the SA node, increasing heart rate under stress.
• Acetylcholine slows down the rate of depolarization at the SA node, resulting in a drop in heart rate.

Measuring Changes in Blood Volume

• Plethysmography records volume changes in the body.
• The volume of blood in tissues changes with the cardiac cycle, creating a pulse.
• A pulse transducer measures changes in blood volume in a body part, such as the finger.
• The pulse transducer shines a beam of light through the skin and measures the light reflected by the heme pigment in the blood.

Regulation of Blood Flow

• The amount of blood flowing to a particular body part depends on the diameter of the arterioles leading into that tissue.
• Vasoconstriction and vasodilation occur when the smooth muscle in the arteriole walls contracts and relaxes, respectively.
• External factors, such as the sympathetic division, and local factors, such as temperature and changes in metabolites, influence the smooth muscle of the arteries.
• Vasoconstriction and vasodilation can be influenced by various hormones, such as vasopressin (ADH) and aldosterone.
• Local factors, such as cold temperatures, can cause vasoconstriction to divert blood away from the cold skin or extremities.
• During exercise, local factors, such as carbon dioxide and metabolic acids, can cause vasodilation in active skeletal muscle.

This quiz covers the mechanical activity of the heart, including contraction and relaxation, and how it is controlled by electrical activity. It also explores the electrocardiogram (ECG) and its relation to the cardiac cycle.