Electrical Activity of the Heart and Hemodynamics Review

These flashcards cover key vocabulary and concepts regarding the electrical activity of the heart, hemodynamics, EKG fundamentals, and related physiological mechanisms.

Resting Membrane Potential

The electrical voltage difference across the membrane of a resting cardiac muscle cell, typically around -90mV.

Depolarization

The process where the cell's membrane potential becomes more positive due to a rapid influx of positive ions, primarily sodium (Na+).

Repolarization

The process of returning the cell's membrane potential to its negative resting state, driven by the outflow of potassium (K+).

Threshold Potential

The critical level of depolarization that must be reached to trigger a full action potential in cardiac cells.

Action Potential

A brief, rapid change in voltage across the cell membrane that propagates an electrical signal, initiating contraction.

Automaticity

The ability of certain cardiac cells to generate their own electrical impulses spontaneously.

Effective Refractory Period

The time interval during the action potential when a cardiac muscle cell cannot be re-excited by another electrical stimulus.

Arrhythmias

Irregularities in the heart's rhythm, which can manifest as tachycardia, bradycardia, or irregular heart rhythms.

SA Node

The natural pacemaker of the heart that initiates the electrical impulses driving heartbeats.

AV Node

A node that slows electrical impulse conduction to allow for proper atrial contraction before ventricular contraction.

Bundle of His

A collection of heart muscle cells that transmits impulses from the AV node to the ventricles.

Purkinje Fibers

Fibers that rapidly distribute electrical impulses throughout the ventricles to ensure coordinated contraction.

Cardiac Cycle

The sequence of events in the heart from the beginning of one heartbeat to the beginning of the next.

Frank-Starling Law

The principle that the force of ventricular contraction increases with the degree of muscle fiber stretch.

Preload

The degree of stretch of the ventricular muscle fibers at the end of diastole, corresponding to end-diastolic volume.

Afterload

The pressure or resistance that the ventricle must overcome to eject blood during systole.

Contractility

The intrinsic ability of the myocardium to contract at a given preload and afterload.

Ejection Fraction

The ratio of the volume of blood pumped out of a ventricle with each heartbeat to the volume of blood in the ventricle at the end of diastole.

Tachycardia

An abnormally fast heart rate, typically exceeding 100 beats per minute.

Bradycardia

An abnormally slow heart rate, typically below 60 beats per minute.

Heart Rate

The number of heartbeats per minute.

Stroke Volume

The amount of blood pumped by the heart with each beat.

Cardiac Output

The total amount of blood the heart pumps per minute, calculated as heart rate multiplied by stroke volume.

Mean Arterial Pressure (MAP)

The average pressure in a person's arteries during one cardiac cycle.

Baroreceptor Reflex

The reflex mechanism for regulating blood pressure through changes in heart rate and vascular tone in response to changes in blood pressure.

Vasodilation

The widening of blood vessels, which decreases vascular resistance and increases blood flow.

Vasoconstriction

The narrowing of blood vessels, which increases vascular resistance and decreases blood flow.

End Diastolic Volume (EDV)

The volume of blood in a ventricle at the end of filling (diastole).

End Systolic Volume (ESV)

The volume of blood remaining in a ventricle after contraction (systole).

Peripheral Resistance

The resistance to blood flow in the peripheral vessels, affecting blood pressure.

Coronary Circulation

The circulation of blood in the blood vessels supplying the heart muscle.

Cerebral Circulation

The blood flow in the brain's blood vessels, highly sensitive to changes in oxygen and carbon dioxide levels.

Renin-Angiotensin-Aldosterone System (RAAS)

A hormone system that regulates blood pressure and fluid balance.

Hypotension

Abnormally low blood pressure.

Hypertension

Abnormally high blood pressure, often leading to cardiovascular complications.

Calcium Channel Blockers

Drugs that inhibit the influx of calcium ions into cardiac and smooth muscle cells, affecting contractility and heart rate.

Diuretics

Medications that promote the excretion of water and electrolytes through urine, reducing blood volume.

ACE Inhibitors

Drugs that block the conversion of angiotensin I to angiotensin II, lowering blood pressure.

ANP (Atrial Natriuretic Peptide)

A hormone released by the heart that decreases blood volume and blood pressure.

ADH (Vasopressin)

A hormone that promotes water retention by the kidneys and increases blood pressure.

Oxygen Demand

The amount of oxygen that tissues require at any given time, influencing cardiac function.

Inotropic Effects

Effects that change the strength of heart muscle contraction.

Chronotropic Effects

Effects that influence heart rate.

Dromotropic Effects

Effects that influence the conduction speed of electrical impulses in the heart.

Systole

The phase of the cardiac cycle during which the heart muscle contracts and pumps blood.

Diastole

The phase of the cardiac cycle during which the heart muscle relaxes and fills with blood.

Electrical Conduction System

The network of specialized cardiac muscle cells that generates and conducts electrical impulses in the heart.

Electrocardiogram (ECG or EKG)

A graphical representation of the electrical activity of the heart.

P Wave

The wave on an ECG that represents atrial depolarization.

QRS Complex

The section of an ECG that represents ventricular depolarization.

T Wave

The wave on an ECG that represents ventricular repolarization.

QT Interval

The time from the beginning of the QRS complex to the end of the T wave, reflecting both depolarization and repolarization of the ventricles.

PR Interval

The time from the beginning of the P wave to the beginning of the QRS complex, indicating conduction through the AV node.

ST Segment

The segment on an ECG between the end of the QRS complex and the beginning of the T wave, reflecting the period when the ventricles are depolarized.

Electrical Activity Initiation

The process that begins the heart's contraction cycle through the SA node's spontaneous depolarization.

Cardiac Reserve

The ability of the heart to increase its output during increased activity or stress.

Atrial Kick

The contribution of atrial contraction to ventricular filling during late diastole.

Ectopic Pacemaker

An abnormal pacemaker site in the heart generating electrical impulses outside of the SA node.

Overdrive Suppression

The phenomenon where faster pacemaking activity suppressed slower pacemakers.

Reentry Circuits

Abnormal loops of electrical activity that can lead to arrhythmias.

Ventricular Fibrillation

A life-threatening condition where the ventricles quiver ineffectively instead of contracting.

Atrial Flutter

A type of arrhythmia characterized by rapid, organized contractions of the atria.

Blood Flow Regulation

The mechanisms that ensure adequate blood supply to tissues under varying conditions.

Hemodynamics

The dynamics of blood flow in the cardiovascular system.

Cardiac Output Regulation

The physiological mechanisms that adjust cardiac output in response to demand.

Venous Return Regulation

The mechanisms that control the volume of blood flowing back to the heart.

Stroke Work

The mechanical work done by the heart to eject blood, calculated as pressure times volume.

Capillary Exchange

The process that allows the transfer of oxygen, nutrients, and waste products between blood and tissues.

Interstitial Fluid Balance

The equilibrium between fluid in blood vessels and fluid in surrounding tissues.

Starling Equation

An equation that describes fluid movement across capillary membranes based on hydrostatic and oncotic pressures.

Lymphatic System

The network of vessels responsible for returning excess interstitial fluid to the bloodstream.

Adaptations to Exercise

Physiological adjustments made by the cardiovascular system in response to increased physical activity.

Velocity of Blood Flow

The speed at which blood travels through the circulatory system, inversely related to the cross-sectional area.

Cross-Sectional Area

The total area of all blood vessels in a segment, affecting the velocity of blood flow.

Reynolds Number

A dimensionless quantity used to predict flow patterns in different fluid flow situations.

Turbulence in Blood Flow

Chaotic flow patterns that can occur under certain conditions, influenced by factors such as vessel diameter and blood velocity.

Mean Electrical Axis

The average direction of electrical activity during ventricular depolarization.

Left Axis Deviation

A condition indicative of conditions like left ventricular hypertrophy, occurring when the mean electrical axis shifts leftward.

Right Axis Deviation

A condition that can suggest right ventricular hypertrophy or other cardiac anomalies.

Ischemia

Insufficient blood supply to tissues, commonly leading to tissue damage or dysfunction.

Acute Myocardial Infarction

A heart attack resulting from blocked blood flow to the heart muscle.

Vascular Resistance

The resistance that blood vessels offer to the flow of blood.

Vascular Compliance

The ability of blood vessels to stretch in response to pressure changes.

Sympathetic Nervous System

Part of the autonomic nervous system that triggers the fight-or-flight response, affecting heart rate and vascular tone.

Parasympathetic Nervous System

Part of the autonomic nervous system that promotes the rest-and-digest response, slowing heart rate.

Baroreflex

An automatic response to changes in blood pressure that alters heart rate and vascular resistance.

Catecholamines

Hormones (epinephrine and norepinephrine) released by the adrenal glands that act to increase heart rate and blood pressure.

Centrifugal Blood Flow

The pattern in which blood is ejected from the heart to the systemic circulation.

Centripetal Blood Flow

The pattern in which blood returns to the heart after circulating through the body.

Fluid Dynamics

The study of fluids (liquids and gases) in motion, applied to blood flow in the circulatory system.

Stress Test

An exercise test used to measure the heart's ability to respond to induced stress.

Cardiac Rehabilitation

A medically supervised program to improve cardiovascular health after events like a heart attack.

Vascular Health

The state of the blood vessels and their ability to function correctly.

Myocyte Remodeling

Changes in cardiac muscle cells in response to heart disease, injury, or stress.

Cardiac Index

Cardiac output normalized to body surface area, providing a better comparison of heart performance across individuals.

Volume Overload

A condition where too much blood enters the heart, leading to potential heart failure.

Pressure Overload

A condition where the heart must work harder than normal to pump blood against increased resistance.

Clinical Guidelines for Cardiovascular Health

Recommendations for maintaining heart health and preventing cardiovascular diseases.

Lifestyle Modifications for Heart Health

Changes in diet, exercise, and behaviors aimed at improving cardiovascular health.