Anatomy Unit 4: Circulatory System (Heart + Cardiac Cycle)

Atria

upper Chambers, thin walled, deliver blood to ventricles

Ventricles

lower Chambers, thicker walled and more muscular; left ventricle thickest (pumps blood further and experiences greater resistance)

pulmonary and aortic valves

semilunar valves; allow ejection of blood into arteries

tricuspid valve

atrioventricular valve found between right atrium and right ventricle

Bicuspid Valve

atrioventricular valve found between left atrium and left ventricle

pericardium

outer membrane that surrounds and protects the heart, secretes pericardial fluid

myocardium

thick layer of cardiac muscle making up the walls of the heart (muscular walls of chambers of the heart)

chordae tendineae

tendon like chords found within the ventricles that help prevent the backflow of blood through the valve (prevents valve prolapse since valves open into the ventricles)

Trabeculae carneae

series of ridges caused by raised bundles of cardiac muscles

Papillary muscles

cone-shaped trabeculae carneae to which the chordae tendineae are attached

auricles

wrinkled, pouch-like structure found on anterior surface of the atria; increases capacity of atria slightly (goal: enlarge volume of atria)

apex

inferior portion of the heart that comes to a point

base

broad, superior portion of the heart

septum

muscular partition that prevents blood on two sides from mixing

pericardial fluid

slippery secretion produced by pericardial cells; reduces friction as heart moves when it contracts

pulmonary trunk

large vessel from the right ventricle, which splits into the pulmonary arteries

coronary artery

branches from ascending aorta that bring oxygenated blood to the heart

diastole

begins at the end of a cardiac cycle; all 4 chambers in period at the same time; initiated by repolarization of ventricles (resting and refilling); ventricular pressure decreases, atrioventricular valves open, ventricles fill

Atrial Systole

action potential from SA node causes atrial depolarization; atria contract and complete filling of the ventricles (“LUB”); AV valves remain open, SL valves remain closed

Ventricular Systole

contraction of ventricles; pushes blood against AV valves forcing them shut (“DUB”); ventricular pressure increases, both SL valves open; ejection of blood

systemic circulation

left side of the heart pumps blood through vessels to the tissues of the body and back to the right side of the heart

pulmonary circulation

right side of the heart pumps blood through vessels to lungs and back to the left side of the heart

one square = 0.04 seconds, 5 squares = 0.2 seconds, 25 squares = 1 sec

length of time of one small box on ECG? one large box?

P wave

atrial depolarization → atria contract and the electrical current spreads from the pacemaker (SA node) throughout the atria

QRS Complex

ventricular depolarization → electrical impulse caused by purkinje fibers causes ventricles to contract

T Wave

repolarization of ventricles (ventricles relax, atria and ventricles fill with blood)

cardiac output

volume of blood pumped from heart per minute (milliliters per minute) → CO = SV * HR

stroke volume

amount of blood pumped per ventricle per contraction

heart rate

number of beats/contractions of ventricles per minute

sympathetic nervous system

nervous stimulation to increase SV/HR

parasympathetic nervous system

nervous system stimulation to decrease SV/HR

sinoatrial node

in right atrial wall → initiates each heartbeat (pacemaker). sends action potential to both atria causing them to contract (causes atrial systole

Atrioventricular node

in interatrial septum → picks up action potential from SA node and passes it to the atrioventricular bundle

Atrioventricular Bundle (Bundle of His)

in interventricular septum → picks up action potential from AV node and passes it to the right and left bundle branches

AV Right and Left Bundle Branches

in interventricular septum → picks up action potential and passes it to conduction myofibers

Conduction Myofibers (purkinjie Fibers)

ventricular myocardium → picks up action potential from bundle of his and passes it to ventricular myocardial cells, causing ventricles to contract (causes ventrical systole)

tachycardia 

rapid, resting heart rate over 100 bpm

bradycardia

slow, resting heart rate under 60 bpm

arrhythmia

irregularity in heart rhythm caused by problem in conduction system of the heart

atrial fibrillation

uncoordinated contraction of atrial muscles; muscle fibers quiver individually rather than contracting together → P wave not visible

ventricular fibrillation

asynchronous ventricular muscle contractions. Ventricular ejection ceases (death imminent) → must shock heart in order for SA node to begin in regular fashion → scrambled ECG

depolarization

excitement/contraction of heart

polarization

resting state, prepared to contract, atria fill with blood, must occur in order for heart to beat again

acetycholine

neurotransmitter which hyperpolarizes SA node and reduces HR

norepinephrine

neurotransmitter which increases HR

adrenal glands

releases hormones involved in endocrine regulation of heart rate

epinenphrine and noreponephrine

hormones released by endocrine system which regulate heart rate

atrial systole = 0.1 sec, ventricular systole = 0.3 sec, diastole = 0.5 sec, cardiac cycle = 0.9 sec

time for atrial systole, ventricular systole, diastole, and cardiac cycle

LUB sound

closing of the atrioventricular valves during atrial systole

DUB sound

closing of the semilunar valves during ventricular systole