Cardiac Output, Blood Pressure Regulation, and Coronary Circulation

Flashcards covering cardiovascular physiology, blood pressure regulation mechanisms, anatomical structures, and energy metabolism during exercise.

Frank-Starling Law of the Heart

The principle stating that stroke volume increases in response to an increase in end-diastolic volume (EDV) before contraction, as stretching cardiac muscle increases its force of contraction.

Cardiac Output (CO) Formula

The mathematical relationship where cardiac output equals heart rate multiplied by stroke volume: $\text{CO} = \text{HR} \times \text{SV}$.

Stroke Volume (SV) Formula

The volume of blood pumped per beat, calculated as end-diastolic volume minus end-systolic volume: $\text{SV} = \text{EDV} - \text{ESV}$.

Blood Pressure (BP) Formula

The equation defining systemic arterial pressure as cardiac output multiplied by peripheral resistance: $\text{BP} = \text{CO} \times \text{PR}$.

Tunica Intima

The innermost layer of a blood vessel, composed of endothelium and loose connective tissue.

Tunica Media

The middle layer of a blood vessel, consisting primarily of smooth muscle and elastic fibers.

Tunica Externa

The outermost layer of a blood vessel wall, composed predominantly of collagen fibers.

Baroreceptors

Pressure-sensitive sensory receptors located in the carotid arteries, aortic arch, and kidneys that initiate nervous system responses to changes in blood pressure.

$\beta$ Receptors (SA Node)

Receptors on the sinoatrial node that bind epinephrine and norepinephrine, causing $K^+$ leak gates to close more frequently per minute and increasing heart rate.

$\alpha$ Receptors (Smooth Muscle)

Receptors on arterial smooth muscle that bind epinephrine and norepinephrine to open membrane Ca2+ gates, causing vasoconstriction.

Vasoconstriction (Arterial Resistance)

The narrowing of arterial lumen diameter to $1/2$ its original size, which increases peripheral resistance by a factor of $4$.

Peripheral Resistance

The friction generated as blood pushes against the walls of the arterial blood vessels.

Contractility

The force of contraction in ventricular myocardium, enhanced when excess intracellular Ca2+ enables greater binding between actin and myosin.

End-Diastolic Volume (EDV)

The total volume of blood contained within a ventricle at the end of filling, right before contraction.

End-Systolic Volume (ESV)

The residual volume of blood remaining in a ventricle following contraction.

Juxtaglomerular (JG) Cells

Specialized renal cells that respond to sympathetic stimulation by releasing the enzyme renin into the bloodstream.

Renin

An enzyme secreted by juxtaglomerular cells in the kidneys that converts circulating angiotensinogen into angiotensin I.

Angiotensin Converting Enzyme (ACE)

An enzyme primarily in the lungs that converts angiotensin I into active angiotensin II.

Angiotensin II

A peptide hormone that induces arterial vasoconstriction to elevate peripheral resistance and triggers the adrenal cortex to release aldosterone.

Aldosterone

A steroid hormone secreted by the adrenal cortex that acts on the kidneys to increase sodium ($\text{Na}^+$) reabsorption.

Osmoreceptors (Hypothalamus)

Sensory receptors in the hypothalamus stimulated by elevated sodium levels in the blood, triggering unquenchable thirst and antidiuretic hormone secretion.

Antidiuretic Hormone (ADH)

A hormone released from the hypothalamus that acts on the kidneys to reduce urine output and preserve fluid volume.

Erythropoietin (EPO)

A hormone released by renal chemoreceptors in response to low oxygen levels that stimulates red blood cell production in bone marrow.

Erythropoiesis

The physiological process of creating new red blood cells within the bone marrow.

Blood Viscosity

The physical thickness or internal friction of blood, directly governed by red blood cell count, affecting peripheral resistance.

Orthostatic Hypotension

A sudden reduction in blood pressure occurring when a person moves to a standing position from sitting or lying down.

Mean Systemic Filling Pressure

The uniform pressure existing throughout the circulatory system when all blood flow stops, normally measuring approximately $7\,\text{mmHg}$.

Anastomosis

A vascular connection or opening between two divergent coronary arteries that provides collateral circulation if one vessel becomes slowly blocked.

Coronary Blood Flow (Rest)

The baseline rate of blood delivery to the heart muscle, averaging $225\,\text{mL/min}$ or roughly $4\text{--}5\%$ of total cardiac output.

Coronary Blood Flow Timing

The physiological occurrence where myocardial blood flow takes place primarily during diastole due to reduced mechanical pressure on coronary vessels.

Circumflex Artery

A major branch of the coronary circulation that establishes a functional connection between the left and right coronary arteries.

Sympathetic Effect on Coronary Arteries

Nervous stimulation that directly constricts coronary vessels but elevates cardiac metabolic activity, yielding net coronary artery dilation during exercise.

Parasympathetic Effect on Coronary Arteries

Nervous stimulation that directly dilates coronary vessels but reduces cardiac metabolic rate, yielding net coronary artery constriction.

Carbohydrate Burning Zone

Exercise intensity maintained between $60\%$ and $90\%$ of maximum heart rate, during which muscle glycogen stores are heavily utilized.

Fat Burning Zone

Cardiovascular exercise intensity performed between $50\%$ and $70\%$ of maximum heart rate, promoting lipid oxidation over longer durations.

Maximum Heart Rate Formula

An estimation calculated by subtracting age from $220$ ($\text{Max HR} = 220 - \text{age}$).

Carb Loading

A dietary protocol involving consumption of $8\text{--}12\,\text{g/kg}$ of carbohydrates $24\,\text{hours}$ before endurance events lasting over $90\,\text{minutes}$.

Heart Anatomy Diagram

Anatomical map showing cardiac chambers, major systemic and pulmonary blood vessels, and heart valves.

Artery vs. Vein Cross-Section

Structural comparison diagram illustrating the three tunica layers, elastic laminae, capillary network, and internal valve arrangement.

Renin-Angiotensin-Aldosterone System (RAAS) Pathway

Organ pathway detailing renal renin production, pulmonary ACE conversion, adrenal aldosterone release, and systemic vascular responses.

Blood Pressure Classification Chart

Diagnostic reference chart categorizing systolic ($40\text{--}180+\,\text{mmHg}$) and diastolic ($40\text{--}120+\,\text{mmHg}$) pressure zones.

Prehypertension

A clinical classification for blood pressure ranging from $120$ to $139\,\text{mmHg}$ systolic or $80$ to $89\,\text{mmHg}$ diastolic.

Stage 1 Hypertension

A clinical classification for blood pressure ranging from $140$ to $159\,\text{mmHg}$ systolic or $90$ to $99\,\text{mmHg}$ diastolic.

Stage 2 Hypertension

A clinical classification for blood pressure measuring $160\,\text{mmHg}$ or higher systolic or $100\,\text{mmHg}$ or higher diastolic.

Hypereffective Heart

A cardiac condition where maximum pumping capacity increases substantially above normal (reaching up to $\sim 25\,\text{L/min}$) due to factors like intense sympathetic drive or hypertrophy.