The Heart and Circulatory System Overview

Plasma

Aqueous solution of proteins, ions, and gases.

Erythrocytes

Red blood cells that carry oxygen.

Leukocytes

White blood cells defending against pathogens.

Platelets

Cell fragments that induce blood clotting.

Hematocrit

Volume percentage of red blood cells in blood.

Anemia

Condition of abnormally low hematocrit.

Cardiac Muscle

Muscle tissue making up the heart.

Systole

Phase of ventricle contraction.

Diastole

Phase of ventricle relaxation.

Cardiac Cycle

Sequence of systole and diastole.

Stroke Volume

Amount of blood ejected per heartbeat.

Cardiac Output

Blood pumped by the heart per minute.

Preload

Ventricular stretch at end of diastole.

Afterload

Resistance heart must overcome to eject blood.

Pulmonary Circuit

Circuit transporting blood to and from lungs.

Systemic Circuit

Circuit transporting blood to and from body.

AV Valves

Valves between atria and ventricles.

SL Valves

Valves between ventricles and arteries.

Blood Pressure

Pressure exerted by circulating blood.

Erythrocyte Lifespan

Approximately 4 months in circulation.

Blood Volume

Average 4-5 liters in humans.

Multi-potent Stem Cells

Cells that differentiate into blood cell types.

Cardiac Muscle Stretch

Influences strength of contraction.

Cardiac Cycle Phases

Includes systole and diastole phases.

Blood Flow Equation

F = DP/R, where F is flow.

Resistance in Blood Vessels

Impacts blood flow based on vessel diameter.

Normal Systolic Pressure

Ranges from 110-140 mmHg at rest.

Normal Diastolic Pressure

Ranges from 60-90 mmHg at rest.

Heart Rate

Number of heartbeats per minute.

CO Formula

CO = SV x HR for cardiac output.

Frank-Starling Mechanism

Increased stretch leads to increased contraction force.

Sympathetic Activity

Increases heart rate and contraction force.

Parasympathetic Activity

Decreases heart rate via vagus nerve stimulation.

Acetylcholine (ACh)

Neurotransmitter that slows heart rate.

M2 Receptors

Muscarinic receptors that slow heart rate.

Catecholamines

Hormones like norepinephrine and epinephrine.

Norepinephrine

Neurotransmitter that increases heart rate and contraction.

Epinephrine

Hormone that enhances cardiac output and glucose levels.

Adrenergic Receptors

Receptors for catecholamines affecting heart function.

Homeostasis

Maintaining stable internal conditions in the body.

Vagus Nerve

Carries parasympathetic signals to the heart.

Ionotropic Receptors

Receptors that form ion channel pores.

Metabotropic Receptors

Receptors linked to ion channels via G proteins.

Baroreceptor Reflex

Regulates blood pressure through heart rate adjustments.

Force of Contraction

Strength of heart muscle contraction during systole.

Sympathetic Nerves

Nerves that stimulate heart from spinal cord.

Norepinephrine Secretion

Released by sympathetic neurons to increase heart function.

Cardiac Muscle Depolarization

Process that triggers heart muscle contraction.

Action Potential

Electrical impulse that initiates heart contraction.

Cyclic AMP (cAMP)

Molecule that mediates sympathetic effects on heart.

Blood Volume Return

Amount of blood returning to the heart influences stroke volume.

β-adrenergic receptors

Receptors that bind epinephrine and norepinephrine.

Fight or flight response

Physiological reaction to perceived threat.

Calcium release

Increased calcium entry enhances heart contraction.

Sarcoplasmic reticulum

Organelle that stores calcium in muscle cells.

Troponin

Protein that interacts with calcium to trigger contraction.

Contractility

Strength of heart contraction for given blood volume.

Cardiac output

Volume of blood pumped by heart per minute.

Sympathetic stimulation

Increases heart rate and contractility.

Parasympathetic activity

Reduces heart rate via vagus nerve.

Sinoatrial (SA) node

Pacemaker of the heart generating action potentials.

Auto-rhythmicity

Ability of heart to contract independently.

Atrioventricular (AV) node

Delays signals from atria to ventricles.

Bundle of His

Conducts electrical signals from AV node.

Purkinje fibers

Rapidly spread action potentials in ventricles.

Action potential

Electrical impulse triggering heart muscle contraction.

Calcium channels

Regulate calcium flow into cardiac cells.

L-type calcium channel

Long-lasting channel sustaining action potentials.

T-type calcium channel

Transient channel initiating action potentials.

Funny channels

Mixed sodium-potassium channels activating heart rhythm.

Membrane potential

Electrical charge difference across cell membrane.

Repolarization

Return of membrane potential after depolarization.

Depolarization

Membrane potential becomes less negative, triggers contraction.

Ventricular contraction

Pumping action of ventricles to circulate blood.

Atrial contraction

Filling ventricles with blood before ventricular contraction.

Cardiac muscle cells

Branched cells connected by intercalated discs.

Intercalated discs

Structures allowing ion passage between cardiac cells.

Gap junctions

Connections permitting action potential spread in heart.

cAMP

Cyclic adenosine monophosphate; increases f-channel opening.

Pacemaker Potentials

Electrical signals generated by SA node.

PNa

Permeability to sodium ions in cardiac cells.

PCa

Permeability to calcium ions in cardiac cells.

PK

Permeability to potassium ions in cardiac cells.

Sympathetic Effect

Norepinephrine increases PNa and PCa, speeding depolarization.

Parasympathetic Effect

ACh decreases PNa and PCa, slowing depolarization.

Action Potential (AP)

Electrical impulse in cardiac muscle cells.

Refractory Period

Time during which cardiac cells cannot re-excite.

Tetanus

Sustained muscle contraction not possible in heart.

Excitation-Contraction Coupling

Process linking electrical signals to muscle contraction.

T-tubules

Extensions of plasma membrane in muscle cells.

Sarcoplasmic Reticulum

Calcium storage organelle in muscle cells.

Electrocardiogram (ECG)

Measure of heart's electrical activity on skin.

Electrode Placement

Pads that detect electrical signals from heart.

ECG Leads

Different angles measuring heart's electrical activity.

P Wave

Atrial depolarization lasting 0.08-0.10 seconds.

P-R Interval

Time from atrial to ventricular depolarization, 0.12-0.20 seconds.

QRS Complex

Ventricular depolarization, short duration 0.06-0.10 seconds.

S-T Segment

Plateau phase of ventricular action potentials.

T Wave

Ventricular repolarization phase in ECG.

Q-T Interval

Time for ventricular depolarization and repolarization, 0.20-0.40 seconds.