CO

Cardiac output is defined as the volume of blood pumped every minute by each (left or right) ventricle of the heart. It is generally reported in L/min or mL/min.

Cardiac output (CO) is the product of heart rate (HR) and stroke volume (SV). Thus,

CO = HR × SV

Heart rate is defined as the number of heart contractions per minute. Stroke volume is the volume of blood pumped per ventricular contraction.

For a typical resting adult human being at rest, CO is approximately 5 L/min.

CO = 70 contractions/min × 70 mL/contraction = 4,900 mL/min

Thick connective tissue that separates the atria and the ventricles. It is also referred to as fibrous skeleton of the heart. Despite its name, it is important to note that there is no bone in this tissue.

Electrophysiology is the study of the electrical properties of biological macromolecules, cells, tissues, and organs. Electrical signals such as voltage and/or current are generally measured. Examples include measuring changes in the membrane voltage of excitable cells (e.g., neurons, muscle cells, and some endocrine cells) during an action potential. The current carrried by ions as they permeate the pore of ion channels can also be measured - both at the single-channel level (single-channel current), as well as the macroscopic current resulting from the activity of a population of channels. As another example, electrical measurements may involve recording voltage changes at the surface of the skin that result from the activity of skeletal muscles (electromyogram, EMG), cardiac myocytes (electrocardiogram, ECG), or neurons in the brain (electroencephalogram, EEG).

Refers to the ability of some cells to be electrically excited resulting in the generation of action potentials. Neurons, muscle cells (skeletal, cardiac, and smooth), and some endocrine cells (e.g., insulin-releasing pancreatic β cells) are excitable cells.

Resting Membrane Potential - Introduction

Hyperthyroidism refers to a pathophysiological condition in which the thyroid gland produces and releases abnormally high levels of the thyroid hormones (T₃ and T₄).

The symptoms of hyperthyroidism may include high metabolic rate, weight loss, nervousness, excess heat production, tachycardia, and tremor.

Two main forms of hyperthyroidism exist: (1) Primary hyperthyroidism, and (2) Secondary hyperthyroidism.

In primary hyperthyroidism, the thyroid gland produces high levels of the thyroid hormones, either as a result of a secretory tumor of the thyroid gland, or under the control of thyroid stimulating immunoglobulins (such as in Graves' disease).

Secondary hypothyroidism is caused by high levels of thyroid stimulating hormone (TSH) produced by the anterior pituitary gland. TSH then stimulates the thyroid gland to produce excessive amounts of the thyroid hormones.

Hypothyroidism
Euthyroidism

Lidocaine is a local anesthetic and an antiarrhythmic drug. It is a commonly used local anesthetic for minor surgery and in dental procedures. Lidocaine is also used topically to relieve itching, burning, and pain from skin inflammations.

Lidocaine's mechanism of action is to block fast voltage-gated Na⁺ channels of neurons and cardiac myocytes.

Other names used for lidocaine are xylocaine and lignocaine.

Pharmacological Inhibition of Na⁺ and K⁺ Channels

Lidocaine (Wikipedia)

Ouabain binds to and inhibits the transport activity of the Na⁺/K⁺/ATPase (i.e., sodium pump).

Ouabain is plant derived and belongs to the class of drugs referred to as cardiac glycosides. Similar to other cardiac glycosides, ouabain increase heart muscle contractility. However, ouabain is used only experimentally and not in humans (as for example digoxin is for the treatment of congestive heart failure).

There is some evidence that ouabain may be produced endogenously in humans.

Vanadate

Ouabain (Wikipedia)

PCG

A recording of the sounds produced by the heart during the cardiac cycle. The main sounds recorded are those associated with turbulent blood flow caused by the closure of heart valves.

The voltage difference across a cell plasma membrane in the resting or quiescent state. It is also simply referred to as the resting potential (V_rest). The value of the resting membrane potential varies from cell to cell. Depending on the cell type, it can range from −90 mV to −20 mV.

For example, V_rest is −90 mV in skeletal and cardiac muscle cells as well as in astrocytes. In a typical neuron, V_rest is approximately −70 mV. In many non-excitable cells, V_rest ranges from −60 to −50 mV. In photoreceptors, V_rest is about −20 mV.

Resting membrane potential

Refers to the rapid depolarization of the membrane early in the action potential. In neuronal, skeletal muscle, and cardiac muscle action potentials, the Hodgkin cycle is responsible for the spike phase of the action potential.

See figure.

Important Features of the Neuronal Action Potential