Heart Ch 18 Flashcards
2 Heart Circuits
Pulmonary Circuit
Systemic Circuit
Coverings of the Heart
Pericardium: Double walled sac
Fibrous pericardium:Loosely fitting superficial part
Serous pericardium: Deep to fibrous, thin slippery two-layer serous membrane that forms a closed sac around the heart
Parietal layer: lines the internal surfaces
Layers of the heart wall
Epicardium:on the heart also called visceral layer
Myocardium: heart muscle, forms the bulk of the heart
Endocardium:white sheet of epithelium that lines the inside surface of the heart
Pericardial cavity
Slitlike space between the visceral and parietal layers, lubercated with serous fluid allowing the heart to glide.
Cardiac skeleton
Dense network of fibrous connective tissue that reinforces the myocardium internally and anchors cardiac muscle fibers.
3 Sulci
Coronary: encircles junction of atria and ventricles
Anterior interventricular: marks septum separating right and left ventricles
Posterior interventricular: similar landmark on the hearts posterioinferior surface
3 veins blood enters the R Atria through
Superior vena cava
Inferior vena cava
Coronary sinus: collects blood draining from myocardium
L atria blood supply
4 Pulmonary veins
Papillary Muscles
Conelike muscle bundles that play a role in valve function and project into the ventricular cavity
AV valves
Atrioventricular valves: Located at each AV junction, prevent backflow
Mitral and tricuspid
Chordae tendineae
Tiny while collagen cords attached to each AV valve flap “heart strings” anchor cups to papillary muscles
SL valves
Semilunar (pulmonary and aortic) valves: guard aortic and pulmonary trunk from ventricles to prevent back flow
Coronary arteries
Left and right arise from the base of the aorta and full at diastole. Encircle the heart in the coronary sulcus.
Left coronary artery
Anterior interverntricular (left anterior descending artery): supplies septum and anterior walls of both ventricles. Circumflex: Supplies left atrium and posterior walls of left ventricle.
Right coronary artery
Right marginal artery: supplies lateral right side of the heart
Posterior interventrivular: runs to the apex and supplies the posterior ventricular walls.
(merges with anterior interventrical artery near the apex)
Coronary veins
Roughly follow the coronary arteries and merge into the coronary sinus which empties blood into the right atria.
Cardiac muscle anatomy
Short fat branched and interconnected.1-2 large centrally located nuclei.
Gap junctions and desmosomes
Functional Syncytium
Gap junctions electrically couple cardiac cells which allows ions to transmit across cells. A single coordinated unit.
2 heart fiber types
1% autoahythmic
the bulk are contractile muscle fibers
Action potential of contractile cardiac muscle
- Depolarization: Na+ influx through fast voltage gated Na+ channels.
- Plateau phase: due to Ca+ influx through slow Ca+ channels. Few K+ channels are open
- Repolarizaion: Due to Ca+2 channels inactivating and K+ channels opening. K+ efflus brings membrane back to resting
Extrinsic Innervation of the heart
Cardioacceleratory center
Cardioinhibitory center:
Cardioacceleratory center
Located in medulla oblingata projects sympathetic neurons fron T1-T5 run to cervical and upper thoracic trung. Innervate the SA & AV nodes and heart muscle and coronary arteries.
Cardioinhibitory center
Sends impulses to the parasympathetic dorsal vagus nucleus in the medulla, which sends inhibitory impulses to the heart via the vagus nerve.
Bipolar leads
3 electodes that measure the voltage differences either between two arms or an arm and a leg
Unipolar leads
9 chest leads
Heart sounds
1st occurs when the AV valves close, louder longer and more resilient than the second.
2nd occures when the SL valves snap shut, this is a short sharp sound.
Murmurs
Indicated an insufficient or incomplete valve closing.
EDV
End diastolic volume: The maximum volume of blood the ventricles will contain in a cycle.
Isovolumetric contraction phase
The split second the ventricles are full and contrace
ESV
End systolic volume: blood remaining in ventricles after contraction
Isovolumetric relaxation
Brief phase following the T wave when the ventricles relax and the back flow of blood closes the SL valves
Quiescent period
the 0.4 sec of total heart relaxation in each cardiac cycle
CO
Cardiac output: the amount of blood pumped out by each ventricle in 1 min
Stroke volume
The amount of blood pumped out by one ventricle by one beat
Cardiac reserve
The difference between resting and maximal CO
Preload
The degree to which cardiac muscle cells are stretched just before they contract
Frank-Sterlings Law
The greater the degree of stretch the greater the contraction
After load
The pressure the ventricles must overcome to eject blood
