A&P Unit 2 Chapter 19 Heart

Pericardium

double walled sac that surrounds heart

has two layers fibrous and serous

fibrous pericardium

superficial; protects the heart to surrounding structures and prevents overfill

serous pericardium

deep two layered; visceral and parietal

parietal layer

part of serous pericardium

lines the internal surface of fibrous pericardium

visceral layer (epicardium)

on external surface of heart

pericardial cavity

fluid filled that decreases friction

myocardium

circular of spiral bundles of contractile cardiac muscle

cardiac muscle

one or two nuclei, sarcomeres, voluntary, striated

self excitable

coronary sinus

blood returning from coronary veins

cardiac ischemia

elevated or depressed ST segment

SA Node 1st

pacemaker in right atrial wall; sinus rhythm

impulses spread to atria and AV node

AV Node 2nd

allows atrial contraction before ventricle contraction

AV Bundle 3rd

only connection between atria and ventricles

Bundle Branches 4th

carry impulses toward the apex of the heart

Purkinje Fibers 5th

ventricular contraction immediately follows from apex toward atria

p wave

depolarization of sa node and atria

qrs complex

ventricular depolarization and atrial repolarization

t wave

ventricular repolarization

p-r interval

beginning of atrial exciattion to beginning of ventricular excitation

qt interval

beginning of ventricular depolarization thru ventricular repolarization

pq segment

atrial cells plateau/contract

st segment

ventricular plateau/ contract

lub sound

AV valves closing meaning beginning of ventricular contraction (systole)

dub sound

closing of SL valves at beginning of ventricular relaxatation (diastole)

cardiac output

amount of blood pumped out by each ventricle in one minute

equal to heart rate and stroke volume

stroke volume

volume of blood pumped out by one ventricle in one beat

Frank Starling Law

relationship between preload and stroke volume

relationship between blood filling of the heart and blood being pumped out of the heart

pre load

regulates stroke volume

degree of stretch of the heart muscle aka amount of blood returned to the heart

venous return

contractility

regulated stroke volume

force of contraction (Ca2+)

epi, glucagon, norepi

afterload

regulates stroke volume

back pressure exerted by arterial blood - resistance

increased by hypertension equlas lower SV

cardioacceleratory center

sends signal thru sympathetic trunk to increase rate and force

Stimulates SA and AV nodes, heart muscle, and coronary arteries

cardioinhibitory center

parasympathetic signals via the vagus nerve decrease rate

inhibits SA and AV nodes

bainbridge reflex

sympathetic reflex initiated by increased venous return equals atrial filling