Respiratory and Cardiovascular Systems Physiology

Comprehensive vocabulary flashcards covering anatomical terms, physiological mechanisms, gas exchange equations, heart conduction, ECG events, and hemodynamics from the Respiratory and Cardiovascular system lectures.

Pulmonary Ventilation

The mechanical movement of air into and out of the lungs (breathing) driven by volume and pressure changes in the thoracic cavity.

External Respiration

The diffusion of gases in a gas state across the respiratory membrane, where $\text{O}_2$ moves from the alveoli of the lungs into the blood and $\text{CO}_2$ moves from the blood into the alveoli.

Internal Respiration

The exchange of gases in a liquid state between systemic blood vessels and the active metabolizing tissues of the body.

Respiratory Zone

The actual microscopic site of gas exchange in the lungs, composed of respiratory bronchioles, alveolar ducts, and alveoli.

Conducting Zone

The rigid conduits that transport air to and from the respiratory zone; they cleanse, warm, and humidify incoming air and reclaim heat and moisture during exhalation.

Vibrissae

Coarse nasal hairs located within the nasal vestibule that act as physical filters to block incoming dust and debris.

Respiratory Mucosa

A lining made of pseudostratified ciliated columnar epithelium containing goblet cells and seromucous glands that secrete lysozyme and defensins to trap and destroy pathogens.

Nasal Conchae

Three pairs of scroll-like projections (superior, middle, and inferior turbinates) on the lateral walls of the nasal cavity that increase mucosal surface area and create turbulence to warm, moisten, and filter air.

Paranasal Sinuses

Mucosa-lined, air-filled cavities located in the frontal, sphenoid, ethmoid, and maxillary bones that lighten the skull, warm and moisten air, and resonate speech sounds.

Epiglottis

A spoon-shaped flap of elastic cartilage at the superior opening of the larynx that folds down to route food into the esophagus and prevent aspiration into the trachea during swallowing.

Vocal Folds

True vocal cords located within the larynx that vibrate with expelled air to produce sound and speech, with the size of the opening determining pitch.

Glottis

The vocal folds (true vocal cords) along with the medial slit-like opening between them through which air passes.

Type I Alveolar Cells

Single-layer squamous epithelial cells that form the primary structural walls of the alveoli across which rapid gas diffusion occurs.

Type II Alveolar Cells

Cuboidal epithelial cells scattered within the alveolar walls that secrete surfactant to lower surface tension of alveolar fluid.

Surfactant

A complex lipid and protein secretion produced by type II alveolar cells that disrupts water hydrogen bonding at the liquid-gas interface, preventing alveolar collapse during exhalation.

Tidal Volume (TV)

The volume of air inhaled or exhaled with each normal resting breath, averaging approximately $500\,\text{ml}$ in both adult males and females.

Inspiratory Reserve Volume (IRV)

The maximal volume of air that can be forcefully inspired beyond a normal tidal volume inspiration, averaging $3100\,\text{ml}$ in adult males and $1900\,\text{ml}$ in adult females.

Expiratory Reserve Volume (ERV)

The maximal volume of air that can be forcefully exhaled after a normal tidal volume expiration, averaging $1200\,\text{ml}$ in adult males and $700\,\text{ml}$ in adult females.

Residual Volume (RV)

The volume of air that remains trapped in the lungs even after a maximal forced exhalation, averaging $1200\,\text{ml}$ in adult males and $1100\,\text{ml}$ in adult females.

Vital Capacity (VC)

The total volume of exchangeable air in the lungs, calculated as the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume ($\text{VC} = \text{TV} + \text{IRV} + \text{ERV}$).

Anatomical Dead Space

The volume of inspired air occupying the conducting zone passages (~$150\,\text{ml}$) that does not participate in gas exchange.

Alveolar Dead Space

The volume of air in alveoli that are non-functional or non-perfused due to collapse or obstruction, contributing to total dead space without performing gas exchange.

Lung Compliance

The measure of the stretchability of the lungs and the openness of the alveoli; low compliance is caused by scar tissue or high surface tension, whereas high compliance occurs in emphysema.

Boyle's Law

A gas law stating that pressure is inversely related to volume ($P \propto 1/V$); decreasing alveolar volume increases alveolar pressure, driving air out of the lungs.

Bronchoconstriction

The contraction of bronchiolar smooth muscle that reduces airway radius and increases airway resistance, stimulated by parasympathetic activation (ACh) or histamine.

Bronchodilation

The relaxation of bronchiolar smooth muscle that widens the airway radius and decreases resistance, triggered by sympathetic signaling (epinephrine) or carbon dioxide ($\text{CO}_2$).

Dalton's Law of Partial Pressures

A law stating that the total pressure of a gas mixture is equal to the sum of the partial pressures exerted by each individual gas ($P_{\text{total}} = P_1 + P_2 + P_3 + \dots + P_n$).

Henry's Law

A law stating that when a gas mixture contacts a liquid, each gas dissolves in proportion to its partial pressure and its solubility coefficient; $\text{CO}_2$ is $20\times$ more soluble in water than $\text{O}_2$.

Chloride Shift

The ionic balancing mechanism in systemic capillaries where bicarbonate ($\text{HCO}_3^-$) diffuses out of red blood cells into plasma in exchange for chloride ions ($\text{Cl}^-$) entering the cells.

Bohr Effect

The decrease in hemoglobin's affinity for oxygen caused by an increase in hydrogen ion concentration ($\text{H}^+$) or decreased pH, facilitating oxygen unloading in metabolically active tissues.

Peripheral Chemoreceptors

Sensory receptors located in the carotid bodies and aortic arch that detect decreases in arterial $\text{P}_{\text{O}_2}$ (below $60\,\text{mm}\,\text{Hg}$) as well as elevations in $\text{P}_{\text{CO}_2}$ and $\text{H}^+$.

Central Chemoreceptors

Sensory receptors located in the medulla oblongata that detect changes in cerebrospinal fluid $\text{H}^+$ derived from arterial $\text{P}_{\text{CO}_2}$, serving as the primary chemical driver of ventilation.

Pericardium

The double-walled fibroserous sac enclosing the heart, consisting of an outer fibrous layer and an inner serous pericardium (parietal layer and visceral layer/epicardium) separated by the pericardial cavity.

Epicardium

The visceral layer of the serous pericardium, forming the outermost anatomical layer of the heart wall.

Myocardium

The thick middle layer of the heart wall, composed predominantly of contractile cardiac muscle cells arranged spirally to pump blood.

Endocardium

The glistening sheet of simple squamous endothelium and thin connective tissue lining the internal heart chambers, valve surfaces, and continuous with the endothelial lining of blood vessels.

Cardiac Skeleton

A dense network of crisscrossing collagen and elastic connective tissue fibers that anchors muscle cells, supports heart valves, and acts as an electrical insulator between atria and ventricles.

Pulmonary Circuit

The low-pressure cardiovascular circuit driven by the right side of the heart that pumps oxygen-poor blood to the lungs to pick up $\text{O}_2$ and unload $\text{CO}_2$, and returns oxygenated blood to the left atrium.

Systemic Circuit

The high-pressure cardiovascular circuit driven by the thicker left ventricle that pumps oxygen-rich blood through the aorta to all organs and body tissues and returns deoxygenated blood to the right atrium.

Atrioventricular (AV) Valves

The two heart valves (tricuspid on the right, bicuspid/mitral on the left) that open when atrial pressure exceeds ventricular pressure and close during ventricular systole to prevent backflow into the atria.

Semilunar (SL) Valves

The two pocket-like valves (aortic and pulmonary) that are forced open by ventricular ejection during systole and snap closed during diastole as backflowing blood fills their cusps.

Intercalated Discs

Specialized microscopic membrane junctions between adjacent cardiomyocytes containing desmosomes for structural anchoring and gap junctions for electrical coupling.

Functional Syncytium

The coordinated physiological state wherein all cardiomyocytes contract together as a single synchronized functional unit due to ion transfer across gap junctions.

Sinoatrial (SA) Node

The primary physiological pacemaker of the intrinsic conduction system located in the right atrium that spontaneously depolarizes at an inherent rate of approximately $100\,\text{impulses/min}$.

Atrioventricular (AV) Node

A node of specialized conductive tissue in the interatrial septum that delays the electrical impulse by approximately $0.1\,\text{s}$, allowing the atria to finish contracting before ventricular excitation begins.

Purkinje Fibers

The subendocardial conducting network of large, modified cardiomyocytes that rapidly distribute action potentials through the ventricular myocardium from the apex upward.

Plateau Phase

The prolonged depolarization phase of a contractile cardiomyocyte action potential caused by slow influx of $\text{Ca}^{2+}$ balancing outward $\text{K}^+$ efflux, extending the absolute refractory period.

Pacemaker Potential

The slow, spontaneous depolarization toward threshold in autorhythmic cardiac cells, initiated by slow sodium ($\text{Na}^+$) influx through funny channels and decreased potassium ($\text{K}^+$) permeability.

Electrocardiogram (ECG)

A composite clinical tracing of all electrical currents (action potentials) generated throughout the nodal and contractile tissues of the heart over time.

P Wave

The first deflection on a standard electrocardiogram tracing, produced by atrial depolarization as the electrical impulse travels from the SA node across the atria.

QRS Complex

The large spike deflection on an electrocardiogram resulting from ventricular depolarization prior to ventricular contraction, which also masks atrial repolarization.

T Wave

The rounded wave on an electrocardiogram tracing produced by ventricular repolarization just prior to ventricular diastole.

Sinoatrial (SA) Block

A conduction defect on an ECG where the SA node impulse fails to excite the atria, visible as absent P waves and missing QRS complexes.

Ventricular Fibrillation

A life-threatening, chaotic cardiac electrical rhythm displaying disorganized waveforms without identifiable P, QRS, or T deflections, completely abolishing coordinated pumping.

Systole

The active contraction phase of the cardiac cycle, occurring during myocardial chamber depolarization when blood is under high pressure and pumped out.

Diastole

The relaxation phase of the cardiac cycle, occurring during myocardial repolarization when the heart chambers expand and refill with blood under low pressure.

End Diastolic Volume (EDV)

The total volume of blood collected inside each ventricle at the very end of ventricular diastole, representing the maximum resting chamber fullness before contraction.

End Systolic Volume (ESV)

The residual volume of blood that remains inside each ventricle at the end of ventricular systole after ejection is complete.

Cardiac Output (CO)

The volume of blood pumped out by each ventricle per minute, calculated as heart rate multiplied by stroke volume ($\text{CO} = \text{HR} \times \text{SV}$), normally averaging $5.25\,\text{L/min}$.

Stroke Volume (SV)

The volume of blood pumped out by one ventricle during each contraction, determined by the difference between end diastolic volume and end systolic volume ($\text{SV} = \text{EDV} - \text{ESV}$).

Preload

The degree of stretch of cardiac muscle cells before contraction; governed by the Frank-Starling law, where increased venous return stretches the ventricles, raising stroke volume.

Afterload

The backpressure exerted by arterial blood that the ventricular myocardium must overcome to push open the semilunar valves and eject blood.

Tachycardia

An abnormally rapid resting heart rate exceeding $100\,\text{beats/min}$, which if uncorrected can lead to ventricular fibrillation.

Bradycardia

An abnormally slow resting heart rate below $60\,\text{beats/min}$, which may result in inadequate systemic perfusion.

Tunica Intima

The innermost blood vessel tunic consisting of an endothelium of simple squamous epithelial cells supported by a delicate basement membrane and subendothelial layer.

Tunica Media

The middle tunic of blood vessel walls, composed of circularly arranged smooth muscle cells and elastin sheets that modulate vascular diameter, blood pressure, and flow.

Tunica Externa

The outermost blood vessel tunic, composed of woven collagen fibers that provide mechanical strength, anchor the vessel to surrounding structures, and protect it.

Precapillary Sphincters

Smooth muscle cuffs surrounding the entrance to true capillaries that contract or relax to control the microvascular route of blood entering a capillary bed.

Capacitance Vessels

A functional term for systemic veins, referring to their large lumens, thin walls, and high distensibility that allow them to accommodate up to $65\%$ of total blood volume as blood reservoirs.

Mean Arterial Pressure (MAP)

The calculated average pressure driving blood through the systemic arterial circulation, computed as: $\text{MAP} = \frac{1}{3}\text{Systolic Pressure} + \frac{2}{3}\text{Diastolic Pressure}$.

Poiseuille's Law

A physiological principle indicating that fluid flow through a tube is directly proportional to the pressure gradient and the fourth power of vessel radius ($\text{Flow} \propto r^4$), meaning doubling vessel radius increases flow by $16\times$ ($2^4$).