Blood Hemodynamics & Blood Pressure

This set covers the fundamental concepts of blood pressure, factors influencing vascular resistance, mechanisms of venous return, and the homeostatic regulation of the cardiovascular system.

Systemic blood pressure

The pressure exerted by blood on the walls of the vessels through which it travels, generated by the pumping action of the heart.

Systolic blood pressure

The pressure emitted when the heart contracts and forces blood out into the major vessels.

Diastolic blood pressure

The pressure exerted within the vessels when the heart is in its relaxed or non-contracting phase.

$$mmHg$$

Abbreviation for millimeters of mercury, the standard unit of measurement for blood pressure.

Aorta

The largest blood vessel in the body where systemic pressure is at its highest, approximately $100\,mmHg$.

Brachial artery

The superficial artery in the upper arm commonly used to measure systemic arterial blood pressure due to its accessibility and proximity to heart level.

Occlusion

The process of closing off an artery, such as when inflating a blood pressure cuff to monitor flow.

Pulse pressure

The numerical difference between systolic and diastolic blood pressure measurements.

Hypertension

A condition characterized by chronically high blood pressure, often linked to cardiovascular disease.

Hypertensive crisis

A medical emergency occurring when systolic blood pressure exceeds $180\,mmHg$ and diastolic exceeds $120\,mmHg$.

Mean arterial pressure ($MAP$)

The pressure that propels blood to the tissues, calculated as diastolic blood pressure plus one-third of the pulse pressure.

Vascular resistance

The opposition to blood flow, influenced by the size of the vessel lumen, blood viscosity, and total vessel length.

Lumen

The open internal space of a blood vessel through which blood flows.

Blood viscosity

The thickness or stickiness of blood, primarily determined by the ratio of red blood cells to plasma and the presence of proteins like fibrinogen.

Fibrinogen

A plasma glycoprotein synthesized by the liver that acts as a structural component for clotting and increases blood viscosity.

Respiratory pump

A mechanism that aids venous return via pressure changes in the thoracic and abdominal cavities during breathing.

Skeletal muscle pump

The process where contracting muscles compress veins to milk blood toward the heart, with valves preventing backflow.

Cardiac output ($CO$)

The volume of blood pumped by each ventricle per minute, calculated as $\text{Heart Rate (HR)} \times \text{Stroke Volume (SV)}$.

Tachycardia

A heart rate that exceeds the normal resting rate, typically over $100\,beats\,per\,minute$.

Bradycardia

A heart rate that is slower than the normal resting range, typically below $60\,beats\,per\,minute$.

Ohm's law (hemodynamics)

A formula stating that blood flow ($F$) is equal to the pressure difference ($P$) divided by resistance ($R$), expressed as $F = \frac{P}{R}$.

Baroreceptors

Mechanoreceptors located in the carotid sinuses and aortic arch that monitor the stretch of vessel walls to relay blood pressure information to the brain.

Medulla oblongata

The part of the brain stem containing the cardiovascular center responsible for regulating heart rate and blood vessel diameter.

Negative feedback loop

The homeostatic process where a stimulus (change in blood pressure) triggers a response that counteracts the change to return the body to a set point.