Anatomy Final: Ch. 21
Events of Cardiac Cycle
1) SA node depolarizes and activation begins 2) depolarization spread across the atrial surfaces and AV node 3) Atrial contraction begins. The AV node delays the spread of electrical activity to the AV bundle by 100 msecs 4) Impulses travel along the AV bundle within the interventricular septum to the apex of the heart. Impulses also spread to the papillary muscles of the right ventricle by the moderator band. 5) The impulse is distributed by Purkinje fibers and relayed throughout the ventricular myocardium. Atrial contraction is completed and ventricular contraction begins
What valve is found between the left atrium and left ventricle? How many cusps does it have? What is another name for the valve?
Bicuspid valve, aka mitral valve, aka left AV valve. 2 cusps.
List the 4 chambers of the heart
Left & Right Atria and Left & Right Ventricles
Name the circuits.
Right Atrium & Ventricle: Pulmonary circuit Left Atrium and Ventricle: Systemic Circuit
What valve leads to the aorta?
aortic semilunar valve
How do the papillary muscles and chordae tendineae prevent valve inversion when the ventricles contract?
by attaching the cusps of the AV valves to papillary muscle
What type of cells coordinates cardiac contractions? How many types are there?
conducting cells. Nodal cells & conducting fibers.
Layers of the heart
epicardium: external surface myocardium: cardiac muscle cell layer endocardium: internal surface
What are 3 major veins that return deoxygenated blood from the heart?
great, middle, and small cardiac veins.
Which chamber has the thickest walls? What is the significance of the thick wall?
left ventricle. the left ventricle must be able to pump blood more strongly to complete the systemic circuit. the left ventricle pumps 6-7 times more strongly than the right ventricle.
Define Nodal cells and conducting fibers. Describe how a signal travels from the Cardiac Pacemaker to the myocardium.
nodal cells: SA node & AV node. establish rate of contraction. cell membranes automatically depolarize. conducting fibers: distribute contractile stimulus to myocardium.
Describe the ANS control of heart rate. How are Norepinephrine and Acetylcholine related to heart rate?
pacemaker sets heart rat, but impulses from the ANS modify pacemaker activity. Norepinephrine: increases heart rate and force of contraction, it is a sympathetic response, tachycardia: action potential speed up Acetylcholine: decreases heart rate and force of contraction, parasympathetic response, bradycardia: action potential slows down
Describe the pericardium
parietal pericardium: lines pericardial cavity visceral pericardium: lines the heart
What special features does the right atrium have?
pectinate musculature & fossa ovalis (fetal remnant of foramen ovale)
What valve leads to the pulmonary trunk?
pulmonary semilunar valve
Which vessels return oxygenated blood to the left atrium?
pulmonary veins
What are 2 major arteries that supply oxygenated blood to the heart?
right and left coronary arteries
Systole vs. Diastole
systole: contraction. blood is ejected into ventricles via AV valves or it is ejected into the semilunar valves
Where is the coronary sinus and which heart chamber does it empty into?
the coronary sinus is on the posterior aspect of the heart, it supplies blood to the right atrium.
Describe anatomical position of the heart
the heart is slightly left of the midline, located in the mediastinum. the heart sits at an oblique angle in the body; the right border is formed by the right atrium, and the inferior border is formed by the right ventricle. the heart is rotated slightly to the left, so the sternocostal (anterior) surface is formed by the right atrium & ventricle and the posterior surface is formed by the left atrium.
In which chamber can the moderator band be found? What is its function?
the moderator band is found in the right ventricle. it is a muscular band that extends from inter ventricular septum to ventricular wall. it prevents over expansion of the thin-walled right ventricle.
Which major vessels bring deoxygenated blood to the heart?
the superior and inferior vena cava and the coronary sinus. all enter the right atrium, the coronary sinus is on the posterior aspect of the heart
What causes valves to open? What keeps valves closed?
when atria contract, pressure in the atria causes the AV valves to open. when ventricles contract, the pressure causes semilunar valves to open. as the semilunar valves open, the AV valves close, forcing blood through the semilunar valves.
