Chapter 18 Flashcards
Apex
points toward left hip
Apical impulse
palpated between fifth and sixth ribs, just below left nipple
Pericardium
double-walled sac that surrounds heart, made up of two layers
Parietal layer
lines internal surface of fibrous pericardium
Visceral layer (epicardium)
on external surface of heart
Fossa ovalis
remnant of foramen ovale of fetal heart
ligamentum arteriosum
is a small ligament that is the remnant of the ductus arteriosus formed within three weeks after birth.
Auricles
appendages that increase atrial volume
Left arterial appendage
place where clots form in A-fib
Coronary circulation
delivered when heart is relaxed
Coronary arteries
both left and right coronary arteries arise from base of aorta
Left Anterior Descending artery
part of left coronary artery and it is the widow maker
Intercalated discs
connecting junctions between cardiac cells that contain desmosomes and gap junctions
Desmosomes
hold cells together, prevent cells from separating during contraction
Gap junctions
allow ions to pass from cell to cell, electrically adjacent cells
Similarities with skeletal muscle
SR release Ca2+ and muscle contraction is preceded by depolarizing AP
Differences between cardiac and skeletal muscle
heart contacts as a unit and influx of Ca2+ from extracellular fluid triggers Ca2+ release from SR
Sequence of excitation
SA node, AV node, bundle of his, purkinje fibers
SA inherent rate
100x/minute
AV inherent rate
50x/minute
Purkinje fibers
depolarize 30x/minute
Benefit of longer AP and contraction
sustained contraction ensures efficient ejection of blood and longer refractory period prevents tetanic contractions
Positive inotropic
increase contractility
epinephrine and norepinephrine
Negative inotropic
decrease contractility
Positive chronotropic
increase heart rate
Negative chronotropic
decrease heart rate
