A & P Exam 2 Chapter 17 Flashcards

Gap junctions

Gap junctions

Signaling function from pores connecting adjacent cells

Desmosomes

Form links between cells and provide a connection between intermediate filaments of the cells cytoskeletons of adjacent cells. Prevents cells from separating during contraction

Sinoatrial node

in upper right atrium, slightly inferior and lateral to opening of superior vena cava

Atrioventricular node

Posterior and medial to tricuspid valve. Slower than SA node, intrinsic rate of only about 40 action potentials per minute

Atrioventricular bundle

Penetrates hearts fibrous skeleton in inferior interatrial septum and intraventricular septum

Right & left bundle branches

Course along right and left sides of the intraventricular septum

Terminal branches

Penetrate ventricles and finally come into contract with contractile cardiac muscle cells (purkinje fibers)

P-wave

Atrial depolarization

QRS complex

Ventricular depolarization

T wave

Ventricular repolarization

R-R interval

One heartbeat, full cardiac action potential

S-T segment

Interval between de and repolarization of ventricles / plateau phase

Q-T interval

Full action potentials of ventricles

P-R interval

Duration of atrial depolarization and AV node delay

Electrocardiography

A graph of the changes in electrical activity occurring in all of the contractile cardiac muscle cells over a period of time

Atrial fibrillation

Generally not life-threatening because atrial contraction is not necessary for ventricular filling, irregular heartbeat that lacks p waves

Ventricular fibrillation

Immediately life-threatening and has chaotic activity

Defibrillation

Stopping of fibrillation of the heart by administering a controlled electrical shock in order to restore normal rhythm, SA node will resume correct pacing

Building pressure

When the ventricles contract, their pressure surpasses those in the right and left atria and pulmonary trunk/aorta… both semilunar valves are forced shut by pushing against them, both valves are forced open by outgoing blood

Systolic

Measures the pressure in your arteries when your heart beats

Diastolic

Measures pressure in your arteries when your heart rests between beats

Cardiac cycle first phase

Ventricular filling phase

• Ventricles fill with blood in diastole

• Atrioventricular valves open

• Atrial systole occurs

• Semilunar valves are closed

Cardiac cycle second phase

Isovolumetric conraction phase

• Ventricular systole occurs

• Atrioventricular and semilunar valves close when enough pressure builds in ventricles

• Atrial diastole occurs

Cardiac cycle third phase

Ventricular ejection phase

• Ventricular systole continues

• AV valves still closed

• Atrial diastole continues

• Pressure opens semilunar valves and blood is ejected to pulmonary artery and aorta

Cardiac cycle fourth phase

Isovolumetric relaxation phase

• Ventricular diastole occurs

• AV valves still closed

• Atrial disatole continues

• Semilunar valves closed

Contractility

Forcefulness of a contraction, regardless of preload

Cardiac output

Amount pumped from ventricle each minute (mL/min), CO = SV x HR

Stroke volume

Amount of blood ejected from the ventricle with each beat. Influenced by preload, afterload, and contractility. SV = EDV - ESV

Preload

Initial stretching of cardiac monocytes, related to ventricular filling, influenced by the length of time ventricles are in diastole and the amount of blood returning to heart at one time

Afterload

Force against which the heart has to contract to eject blood

Frank-starling law

The more the muscle is stretched, the stronger it contracts

Factors that influence HR - positive chronotropic drugs

• Atropine

• Dopamine

• Epinephrine

• Isoproterenol

Factors that influence HR - negative chronotropic agents

• Beta-blockers

• Acetylcholine

Inotropic regulation increases

Contractility

Chronotropic regulation increases

Heart rate

Regulation of CO by sympathetic pathway

Cardiac acceleratory nerves innervate SA node and myocardium, increase rate/force of contraction

Regulation of CO by parasympathetic pathway

Vagus nerve innervates SA node and decreases rate of contraction

Heart failure

Chronic condition where the heart fails to supply required amount of O2 and blood, results in fatigue, SOB, and increased HR

Left-sided heart failure

Pulmonary edema

Right-sided heart failure

Peripheral edema