Chapter 14: Cardiac Output, Blood Flow, and Blood Pressure

Comprehensive vocabulary flashcards covering Chapter 14: Cardiac Output, Blood Flow, and Blood Pressure, including cardiac mechanics, capillary exchange, hemodynamics, reflex regulation, and clinical hypertension.

Cardiac Output (CO)

The total volume of blood pumped per minute by each ventricle, mathematically defined as $\text{Stroke Volume} \times \text{Cardiac Rate}$ and averaging approximately $5500\,\text{mL/min}$ ($5.5\,\text{L/min}$) at rest.

Stroke Volume (SV)

The volume of blood ejected per beat by each ventricle during contraction, normally averaging between $70\,\text{mL}$ and $80\,\text{mL}$ per beat ($0.07\text{--}0.08\,\text{L/beat}$).

Cardiac Rate (Heart Rate)

The frequency of ventricular contractions per minute, averaging between $70\,\text{beats/min}$ and $75\,\text{beats/min}$ at rest due to parasympathetic tone.

Pacemaker Potential

The spontaneous, rhythmic depolarization of the sinoatrial (SA) node cells toward threshold, which proceeds at an intrinsic baseline rate of approximately $100\,\text{beats/min}$ in the absence of neural inputs.

Autonomic Regulation of Pacemaker Potential

The modification of the SA node depolarization rate where sympathetic stimulation (norepinephrine and epinephrine) steepens the pacemaker potential to increase heart rate, while parasympathetic stimulation (acetylcholine) flattens the slope to reduce heart rate.

End-Diastolic Volume (EDV)

The volume of blood filling the ventricles at the completion of ventricular diastole, which sets the resting length and degree of stretch of cardiac muscle fibers prior to contraction.

Frank-Starling Law of the Heart

The intrinsic myocardial relationship stating that an increase in end-diastolic volume stretches ventricular muscle fibers, optimizing actin-myosin overlap and stimulating increased $\text{Ca}^{2+}$ release from the sarcoplasmic reticulum to produce greater contraction tension and stroke volume.

Sarcomere Length-Tension Relationship in Cardiac Muscle

The structural basis of the Frank-Starling law illustrated by progressive sarcomere stretching from $1.5\,\mu\text{m}$ up to optimal overlap at $2.4\,\mu\text{m}$, which yields progressively higher contractile tension over time.

Myocardial Contractility

The intrinsic strength of ventricular contraction at any given resting sarcomere length, enhanced via sympathetic stimulation (epinephrine and norepinephrine) to increase stroke volume and quicken both contraction and relaxation times.

Total Peripheral Resistance (TPR)

The overall impedance to arterial blood flow throughout the systemic vasculature, primarily governed by blood vessel diameter, where arteriolar vasoconstriction serves as the main cause of increased resistance.

Extracellular Fluid (ECF)

The body fluid compartment comprising approximately $1/3$ of total body water, subdivided into interstitial fluid ($80\%$) and circulating blood plasma ($20\%$).

Starling Forces

The opposing physical forces acting across capillary walls: blood pressure driving hydrostatic filtration out of the capillary into tissues, and colloid osmotic forces driving water absorption back into the capillary lumen.

Capillary Filtration

The hydrostatic pressure-driven transcapillary movement of fluid, water, and dissolved solutes out of blood vessels and into the surrounding interstitial fluid compartment.

Capillary Absorption

The osmotic movement of fluid and dissolved solutes from the interstitial fluid back across the vessel wall and into the vascular bloodstream.

Atrial Natriuretic Peptide (ANP)

A peptide hormone produced and secreted by atrial cardiac myocytes in response to atrial wall distension from elevated blood volume, which promotes renal sodium excretion and fluid loss in urine to decrease circulating blood volume.

Natriuresis

The physiological process of enhanced urinary sodium excretion by the kidneys, stimulated by hormones such as atrial natriuretic peptide (ANP).

Systemic Vascular Pressure Gradient

The driving pressure differential governing systemic blood flow, dropping from a mean pressure of approximately $100\,\text{mmHg}$ at the exit of the left ventricle to $0\,\text{mmHg}$ at the right atrium ($\Delta P = 100 - 0 = 100\,\text{mmHg}$).

Resistance Vessels

Small muscular arteries and arterioles whose small, highly regulable luminal diameters generate the primary systemic resistance, resulting in the largest drop in intravascular blood pressure.

Exchange Vessels

Capillaries that permit the selective microcirculatory exchange of nutrients, metabolic gases, fluid, and solutes between the bloodstream and the interstitial fluid.

Capacitance Vessels

Venules and large veins that possess high compliance and distensibility, holding a substantial proportion of systemic blood volume at low intravascular pressures.

Metabolic Vasodilation

Local arteriolar dilation in active skeletal muscle, myocardium, and skin induced by increased tissue metabolism during exercise, facilitating an elevation of skeletal muscle blood flow up to $80\%\text{--}85\%$ of cardiac output.

Baroreceptors

Specialized stretch-sensitive mechanoreceptors located in the carotid sinus, aortic arch, and heart that alter afferent sensory action potential firing in direct proportion to changes in arterial blood pressure.

Baroreceptor Firing Rate Response

The direct frequency relationship in which elevated mean arterial pressures from $60\,\text{mmHg}$ up to $180\,\text{mmHg}$ stimulate progressively higher action potential discharge frequencies in afferent baroreceptor sensory fibers.

Orthostatic Baroreceptor Reflex

The compensatory autonomic reflex arc initiated upon moving from lying to standing, where gravity-induced venous pooling decreases venous return, EDV, SV, CO, and arterial pressure, triggering medulla-mediated sympathetic stimulation to restore blood pressure.

Medulla Oblongata (Cardiovascular Center)

The brainstem integrating center that receives sensory baroreceptor afferents and regulates autonomic efferent outputs (sympathetic and parasympathetic) to control heart rate, contractility, and vasomotor tone.

Mean Arterial Pressure (MAP)

The average pressure throughout the arterial system across an entire cardiac cycle, calculated as $\text{Cardiac Output} \times \text{Total Peripheral Resistance}$ or $\text{Diastolic Pressure} + \left(\frac{1}{3} \times \text{Pulse Pressure}\right)$.

Pulse Pressure

The clinical measure of the arterial pressure wave excursion, defined arithmetically as $\text{Systolic Blood Pressure} - \text{Diastolic Blood Pressure}$.

Hypotension

An abnormally low blood pressure state that reduces blood flow and oxygen delivery to vital tissues such as the brain and cardiac muscle, caused by hemorrhage, severe dehydration, or cardiovascular defects.

Primary (Essential) Hypertension

The most common form of chronic elevated blood pressure, having an unknown direct etiology but linked to complex interactions of genetic predispositions and environmental or dietary factors.

Secondary Hypertension

Elevated blood pressure that results directly from a recognized, distinct underlying clinical pathology, such as kidney disease, renal artery disease, or endocrine disorders.

Left Ventricular Hypertrophy

Pathological enlargement and muscular thickening of the left ventricle caused by chronic pumping against elevated arterial afterload and total peripheral resistance, which can progress to heart failure.

Congestive Heart Failure

A clinical condition where cardiac output becomes insufficient to satisfy the body's perfusion requirements, resulting in compensatory fluid retention, increased blood volume, elevated EDV, and circulatory congestion.

Diuretics

A class of antihypertensive medications (e.g., thiazides and furosemide) that increase the volume of urine excreted by the kidneys, thereby reducing circulating blood volume and blood pressure.

Beta-Adrenergic Blockers

Cardiovascular drugs (e.g., atenolol) that block beta-adrenergic receptors, reducing cardiac rate, stroke volume, cardiac output, and renal renin secretion.

Alpha-Adrenergic Blockers

Vascular drugs (e.g., phentolamine) that selectively block alpha-adrenergic receptors to alleviate sympathetic vasoconstriction in systemic arterioles.

Calcium Channel Blockers

Antihypertensive agents (e.g., verapamil and diltiazem) that inhibit $\text{Ca}^{2+}$ influx into vascular smooth muscle cells, promoting vasodilation and reducing total peripheral resistance.

Direct Vasodilators

Antihypertensive compounds (e.g., hydralazine and minoxidil sodium nitroprusside) that cause vasodilation by acting directly on vascular smooth muscle.

Normal Blood Pressure (Adult Classification)

A blood pressure status defined by a systolic blood pressure under $120\,\text{mmHg}$ AND a diastolic blood pressure under $80\,\text{mmHg}$, requiring no drug therapy.

Elevated Blood Pressure (Adult Classification)

A clinical classification defined by a systolic blood pressure of $120\text{--}129\,\text{mmHg}$ AND a diastolic blood pressure less than $80\,\text{mmHg}$, managed via lifestyle modification without drugs.

Stage 1 Hypertension

A clinical classification defined by a systolic blood pressure of $130\text{--}139\,\text{mmHg}$ OR a diastolic blood pressure of $80\text{--}89\,\text{mmHg}$, treated with lifestyle modification and possible antihypertensive drugs.

Stage 2 Hypertension

A clinical classification defined by a systolic blood pressure of $140\,\text{mmHg}$ or greater OR a diastolic blood pressure of $90\,\text{mmHg}$ or greater, indicated for lifestyle modification and antihypertensive pharmacotherapy.