Lecture Quiz 6 Flashcards
Where is the heart located?
in the mediastinum superior to the diaphragm anterior to the vertebral column posterior to the sternum left to the midline
What is the pericardium?
a double walled sac around the heart
composed of a superficial fibrous pericardium and deep two-layer serous pericardium
What is the parietal layer?
pericardium
lines the internal surface of the fibrous pericardium
What is the visceral layer of the pericardium?
epicardium
lines the surface of the heart
How are the layers of the pericardium separated?
a fluid-filled pericardial cavity
What does the pericardium do?
protects and anchors the heart
prevents overfilling of the heart with blood
allows the heart to work in a friction-free environment
What are the layers of the heart wall?
epicardium
myocardium
endocardium
What is the epicardium?
visceral layer of the serous pericardium
What is the myocardium?
cardiac muscle layer forming the bulk of the heart
What is the endocardium?
endothelial layer of the inner myocardial surface
What are the atria?
the receiving chambers of the heart
each atrium has a protruding auricle
What are the pectinate muscles?
mark atrial walls
help atria contract more efficiently
What are the ventricles?
the discharging chambers of the heart
What are the papillary muscles?
line ventricular walls
prevent blood flowing back into atria
What are the trabeculae carnae muscles?
mark ventricular walls
make contraction more efficient
What difference do you find between the right and left ventricle?
both hold the same volume of blood, but the left ventricular wall is thicker
Of the four chambers, how do they relate in chamber size?
atria are smaller than the ventricles
right side = left side
Of the four chambers, how do they differ in wall thickness?
atria < ventricles
right ventricle < left ventricle
What percentage do the atria account for blood pumped?
at rest, 5%
exercise, 40%
What are the atrioventricular valves of the heart (general)?
valves between the atria and ventricles
prevent backflow into the atria when the ventricles contract
What are the chordae tendineae?
anchor atriventricular valves to papillary muscles
What is the mitral (bicuspid) valve?
AV valve between left atrium and left ventricle
What is the tricuspid valve?
AV valve found between the right atrium and right ventricle
What are the semilunar valves?
lie between the ventricle and the aorta
prevent the backflow of blood into the ventricles
What is the aortic valve?
semilunar valve leading from the left ventricle into the aorta
What is the pulmonary valve?
lies between the right ventricle and the pulmonary trunk
What are arteries?
vessels that take blood away from the heart
What are veins?
vessels that return vlood to the heart
Where does oxygenation of blood occur?
varies in arteries and veins
What does pulmonary circulation do?
enriches the blood with oxygen and removes excessive carbon dioxide
Describe the pathway of the pulmonary circulation
blood enters right ventricle through tricuspid valve
passes through pulmonary valve to pulmonary trunk
splits into left and right pulmonary arteries
travels through capillaries of the lungs for gas exchange
right and left pulmonary veins return blood to left atrium
What does systemic circulation do?
carries oxygenated blood to the entire body
Describe the pathway of systemic circulation
blood passes through mitral valve into left ventricle
travels through aortic valve into aorta and its branches
capillaries in peripheral tissues allow gas exchange
blood is returned to the right atrium through the superior and inferior venae cavae and the coronary sinus
What are cardiomyocytes?
large, branched cells
single central nucleus
striated
heavily vascularized
What do intercalated discs of cardiac cells do?
connect cardiomyocytes
allow free passage of ions between the cells
allows heart muscle to contract simultaneously as a functional system
How is the heart stimulated and what is that known as?
by nerves
also self-excitable
this is known as automaticity
What are the two types of cardiomyocytes?
contractile cells
pacemaker cells
What happens during phase 0 of action potential in contractile cardiomyocytes?
slow sodium channels leak until the muscle reaches the threshold of the fast sodium channels
sodium ions rush in until the membrane polarity is reversed
What happens during phase 1 of action potential in contractile cardiomyocytes?
polarity reversal causes the fast sodium channels to snap shut and the potassium channels to open
this causes the membrane potential to start to become more negative
What happens during phase 2 of action potential in contractile cardiomyocytes?
plateau
potassium ions continue leaking out
calcium channels open and positively charged calcium ions leak in, cancelling the effect of potassium ions leaking out
no net change for 100 milliseconds
calcium ions are used to form cross bridges
excitation-contraction coupling: calcium ions cause the plateau phase and bind to troponin and initiate cross bridge formation
What happens during phase 3 of action potential in contractile cardiomyocytes?
repolarization
calcium ions quit leaking in
passage of potassium ions out of the cell causes a return to the resting membrane potential
What happens during phase 4 of action potential in contractile cardiomyocytes?
resting potential
the only activity during this phase is the constant leakage of the slow sodium channels
What is unique about the refractory period in cardiomyocytes?
it is very long ~250 msec
premature stimulation does not cause tetanus for this reason
