Heart part 2
Cardiac output is
the amount of blood pumped out of each ventricle in one minute
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
The heart relies almost exclusively on what?
How are the cardiac and skeletal muscle the same?
Both are striated & contract by sliding filament mechanism
What is valvular stenosis?
The valve flaps become stiff and constrict the opening.
Can the heart valves function with leaky valves?
Yes, as long as the impairment is not too great
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
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.
Where are the autorhythmic cells located?
within the heart walls
What are auto rhythmic cells?
specialized cells that generate electrical impulses throughout the myocardium
During pulmonary circulation blood leaves what?
The right ventricle & moves to the lungs
During systemic circulation blood leaves the what?
left ventricle and goes directly to the aorta
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 inward influx of na causes what to happen to the membrane?
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.
What is attached to each AV valve flap?
Tiny white collagen cords called chordae tendineae
The endocardium is composed of what?
simple squamous epithelium
The coronary arteries arise from the what?
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
Mitochondria account for what percentage of volume of cardiac cells?
What do the gap junctions allow?
ions to pass from cell to cell transmitting current across the entire heart
What do desmosomes prevent?
adjacent cells from separating during contraction
What do intercalated discs contain?
anchoring desmosomes and gap junctions
Where are the two AV valves located?
one at each atrial-ventricular junction
What does the atrio ventricular valve do?
prevents backflow into the atria when the ventricles are contracting
Wwhat is the Rt atrioventricular valve called?
What is the mitral valve sometimes called?
What is automaticity or autorhythmicity?
The ability of the heart to self excite-can initiate their own depolarization
In cardiac muscle the heart either contracts as a unit or not at all?
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 prevents tetanic contractions?
the long cardiac refractory period
What is the bulk of the heart muscle composed of?
contractile muscle fibers
the tricuspid valve has what?
3 flexible cusps
What are the 3 flexible cusps on the AV made of?
flaps of endocardium reinforced by connective tissue cores
the cells of the myocardium behave as a single unit called what?
What does the cardiac conduction system do?
coordinates & synctronizes heart activity
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
The vagus nerve carries what impulses to the heart and other visceral organs?
The heart is enclosed in a doule-layered membrane called what?
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 tricuspid valve is located between what?
right atrium & left ventricle
the P-wave is a measure of what?
The left AV valve has how many flaps
The ability of some cardiac muscle cells to initiate their own depolarization & cause depolarization of the heart is called what?
What is an age related change of the heart that affects function?
fibrosis of cardiac muscle
What is one of the veins that drains blood directly from the myocardium?
middle cardiac vein
What is the cause of the plateau in cardiac muscle action potentials?
calcium ion influx
The duration of the action potential and contractile phase is much greater in what?
The vessels that carry oxygen to the myocardial cells are called what?