heart Flashcards
Two circuits of the heart
Pulmonary circuit: to lungs (rids CO2 and gets O2)
Systemic circuit: oxygenated blood to body
Heart location
- in mediastinum (paricardium)
- bt 2nd and 5th intercostal space
- 2/3 to the left of midsternal line
- anterior to vertebral column
- posterior to the sternum
Base and Apex
Base = posterior surface towards right
Apex = inferior, left–> points towards hip
Apex pulse bt 5th and 6th ribs (mid clavicular) –> Point of Maximal Impulse
Pericardium layers
- Fibrous pericardium: protects and anchors to surrounding structures and prevents overfilling
- Serous pericardium = parietal and visceral
- Parietal lines internal surface of fibrous pericardium
- visceral (epicardium) on external surface of heart
- Pericardial cavity filled with fluid to reduce friction
Pericarditis
- inflammation of pericardium
- roughens membrane surfaces -> pericardial friction rub (creaking sound)
Cardiac tamponade
excessive fluid sometimes compresses heart
-limits pumping ability
layers of heart wall
Epicardium: visceral layer of serous pericardium
Myocardium: spiral bundles of contractile cardiac muscle cells –> cardiac skeleton = interlacing CT that ancors muscle fibers, supports vessels/valves, and limits APs to specific areas)
Endocardium: continuous with endothelial lining of blood vessels –> lines heart chambers and covers cardiac skeleton of valves
fossa ovalis
in interatrial septum
-remnant of foramen ovale of fetal heart
Sulci
Coronary sulcus encircles junction of atria and ventricles
Anterior interventricular sulcus
Posterior interventricular sulcus
Auricles
appendages that increase atrial volume
Right atrium features vs left
pectinate muscles in both
right has crista terminalis which separates posterior from anterior
right has tricuspid valve
left has mitral/bicuspid valve
Which blood vessels enter into each atria?
superior/inferior vena cava and coronary sinus empty into right
four pulmonary veins empty into left
location of right vs left ventricle
right is most of anterior surface
left is posteroinferior surface
trabeculae carneae and papillary muscle
- irregular ridges of muscle on walls of ventricles
- anchor chordae tendineae
do atria or ventricles contribute more to the pumping of the heart
VENTRICLES!
atria barely pump anthing
purpose of heart valves
- ensure unidirectional bloodflow
- open and close in response to pressure changes
AV valves
prevent backflow when ventricles contract
chordae tendinea anchor cusps to papillary muscles and hold valve flaps in closed position
semilunar valves
prevent backflow when ventricles relax
aortic and pulmonary
Incompetent valve
-blood backflows so heart repumps the same blood over and over
valvular stenosis
stiff flaps constrict openeing
-heart has to exert more force to pump blood
pulmonary circuit
right atrium tricuspid valve right ventricle pulmonary semiluar valve pulmonary trunk pulmonary arteries lungs pulmonary veins left atrium
systemic circuit
left atrium mitral valve left ventricle aortic semilunar valve aorta tissues
ratio of blood in systemic circulation to pulmonary circulation
they’re equal
pulmonary = short, low pressure
systemic = long, high friction
coronary circulation
- part of systemic circulation
- functional blood supply to heart muscles
- delivered when heart is relaxed
- left ventricle receives most blood
- has many anastosomes (junctions)
Arteries of coronary circulation
Left coronary artery branches
- anterior interventricular artery
- circumflex artery
- supply interventricular septum, anterior ventricular walls, left atrium, and posterior left ventricle walls
Right coronary artery branches
- right marginal artery
- posterior interventricular artery
- supplie right atrium and most of right ventricle
Angina pectoris
thoracic pain caused by fleeting deficiency in blood delivery to myocardium
-weakens cells
Myocardial infarction
- prolonged coronary blockage
- areas of cell death repaired with noncontractile scar tissue
Cardiac muscle cells
- short, striated, branched, fat, interconnected
- 1-2 nuclei
- t tubules wide and less numerous
- SR simpler than skeletal muscle
- 25-35% of cell volume is mitochondria
Intercalated discs
- junctions between cells, anchoring them
- desmosomes prevent cells from separating during contraction
- gap junctions allow ions to pass from cell to cell; electrically couple adjacent cells –> allow heart to be functional synctium
Difference in cardiac muscle contraction from skeletal muscle contraction
- 1% of cells have autorhythmicity (don’t nees NS and can depolarize entire heart)
- All cardiomyocytes contract as a unit (all or none)
- long absolute refractory period (250 ms) preventing tetanic contractions
- Depolarization wave opens slow Ca channels in sarcolemma (Ca surge prolongs depolarization phase)
- AP and contraction last longer so blood can be ejected
- repolarization results in inactivation of Ca channels and opening of voltage K channels (Ca returns to SR)
Similarities between cardiac muscle contractions and skeletal muscle contractions
- Depolarization opens few voltage gated fast Na channels in sarcolemma (RMP foes from -90 to +30) –> close fast
- Depolarization wave down T tubules –> SR to release Ca
- Excitation contraction coupling occurs –> Ca binds troponin and filaments slide
summary of electrical activity of muscle contraction
- Depolarization: fast voltage-gated Na channels open and are quickly inactivated (pos feedback)
- Plateau phase: Ca influx through slow Ca channels keep the cell depolarized
- Repolarization due to Ca channels inactivating, allowing a K efflux
cardiac energy requirements
lots of mitochondria for aerobic respiration
-will switch to lactic acid from skeletal muscles if it needs a fuel source
Does the nervous system control heart contraction?
Nah
BUT AND can impact heart rate
How does the heart beat all at the same time?
- Gap junctions
- Intrinsic cardiac conduction system = network of noncontractile (autorhythmic) cells which initiate and distribute impulses
Pacemaker cells
- have unstable RMP due to slow opening of Na channels (always depolarizing)
- @ threshold, ca channels open
- explosive Ca influx = “rising phase” of AP
- Repolarization = inactivation of Ca channels and opening of voltage gated K channels
Summary of AP initiation by pacemaker cells
- Pacemaker potential –> repolarization closes K channels and opens slow Na channels, creating an ion imbalance
- Depolarization –> Ca channels open and a ton of Ca comes in (“rising phase”)
- Repolarization –> K channels open and K goes out of cell
