Because the heart does not depend on the nervous system, what would happen if all nerve connections to the heart are severed?
The heart continues to beat rhythmically
The inner lining of the fibrous pericardium is formed by the what?
Parietal layer of the serous pericardium
How are the cardiac and skeletal muscle the same?
Both are striated & contract by sliding filament mechanism
There are no valves guarding the entrances of the vena cava & the pulmonary veins into the rt & L atria?
What do the chordae tendineae & the papillary muscles do?
serve as guywires to anchor the valve flaps in their closed position
What happens when the ventricles contract?
They compress the blood in their chambers, so the intraventricular pressure rises, forcing the blood against the valve flaps, forcing them to close.
When the heart is completely relaxed what do the AV valve flaps do?
Hang limply into the ventricular chambers below
The cardiac muscle can use what for fuel?
Whatever nutrient supply is available including lactic acid.
What are auto rhythmic cells?
specialized cells that generate electrical impulses throughout the myocardium
During the spike of an action potential in a cardiac muscle cell what happens?
There is a rapid influx of NA into the cell
The inferior vena cava brings blood from the lower regions of the body and empties into the what?
What do the chordae tendineae that are attached to each AV valve do?
Anchor the cusps to the papillary muscles protruding from the ventricular walls.
The absolute refractory period refers to the time during which what happens?
the muscle cell is not in a position to respond to a stimulus of any strength
What do the gap junctions allow?
ions to pass from cell to cell transmitting current across the entire heart
What does the atrio ventricular valve do?
prevents backflow into the atria when the ventricles are contracting
What is automaticity or autorhythmicity?
The ability of the heart to self excite-can initiate their own depolarization
How does the entire heart contract together?
by the transmission of the depolarization wave across the heart cell to cell via ion passage through gap junctions
What are the 3 flexible cusps on the AV made of?
flaps of endocardium reinforced by connective tissue cores
Why does the myocardium behave as a single coordinated unit or functional syncytium?
Because cardiac cells are electrically coupled by the gap junctions
Autorhythmic cells do not contribute to what?
the contractile force of the heart & are anatomically different from the contractile cells
What is the correct sequence of layers in the heart wall, starting with the outer layer?
epicardium, myocardium, endocardium
When the mitral valve closes it prevents the backflow of blood from the what?
left ventricl into the left atrium
The ability of some cardiac muscle cells to initiate their own depolarization & cause depolarization of the heart is called what?