Chapter 42 (2)

TRUE OR FALSE:
The timely delivery of O2 to the body's organs is critical.

Overall organization of the mammalian cardiovascular ssystem, beginning with the pulmonary circuit:
- contraction of the right __ pumps blood to the lungs via the __. As the blood flows through __ int he left and right lungs, it loads O2 and unloads CO2. Oxygen-rich blood returns from the lungs via the __ to the left __ of the heart. Next the oxygen rich blood flows into the left __, which pumps the oxygen rich blood out to body tissues throught he __. Blood leaves the left __ via the __, which conveys blood to arteries leading throughout the body. The first branches from the __ are the __, which supply blood to the heart muscle itself. Then branches lead to __ in the head and arms (forelimbs). The __ then descends into the abdomen, supplying oxygen-rich blood to arteries leading to __ in the abdominal organs and legs. Within the capillaries, there is a net diffusion of O2 from the blood to the tissues and of CO2 produced by cellular respiration into the blood. Capillaries rejoin, forming __, which convey blood to veins. Oxygen poor blood from the head, neck, and forelimbs is channeled into a large vein, the __. Another large vein, the __, drains blood from the trunk and hind limbs. The two __ empty their blood into the right__, from which the oxygen poor blood flows into teh right ventricle.

The Heart:
The two __ of the heart (cardiac muscle) ahve telatively thin walls and serve as collection chambers for blood returning to the heart. Much of the blood entering the __ flows into the __ while all heart chambers are relaxed.

Contraction of the __ transfers the remainder before the __ start to contract. The __ have thicker walls and contract much more forcefully than the __,e specially the left one, which pumps blood to all body organs through the systemic circuit. Althought the __ contracts with greater force than the __, it pumps the same volume of blood as the __ during each contraction.

The heeart contracts and relaxes in a rhythmic cycle. When it contracts, it pumps blood; when it relaxes, its chamb ers fill with blood. One complete sequence of pumping and filling is referred to as the __.

The contraction phase of the cycle is called __,a dn teh relaxation phase is called __. The volume of blood each ventricle pumps per minute is the __. Two factors determine this: __ and __.

Four valves in the heart prevent backflow and keep blood moving in the correct direction. Made of flaps of connective tissue, the valves open when pushed from one side and close when pushed from the other. An __ lies between each atrium and ventricle; they are anchored by strong fibers that prevent them from turning inside out. Pressure generated by the powerful contraction of the ventricles closes the __, keeping blood from flowing back into the atria.

__ are located at the two exits of the heart: where the aorta leaves the left ventricle and where the pulmonary artery leaves the right ventricle. These valves are pushed open by the pressure generated during contraction of the ventricles. TWhen the ventricles relax, presuure built up in the aorta closes the semilunar valves and prevents significant backflow.

If blood squirts backward through a defective valve, it may produce an abnormal sound called a __.

In vertebrates, the heartbeat originates in the heart itself. Some cardiac muscle cells are __, meaning they contract and relax repeatedly without any signal from the nervous system.
-Because each of these cells has its own intrinsic contraction rhythm, how are their contractions coordinated in the intact heart?
The answer lies in a group of autorhythmic cells located in the wall of the right atrium , near where the __ enters the heatrt.
- This cluster of cells is called the __ and it sets the rate and timing at which all cardiac muscle cells contract.

The __ generates electrical impulses much like those produced by nerve cells. Because cardiac muscle cells are electrically coupled through __, impulses from the __ spread rapidly within heart tissue.

In addition, these impulses generate currents that are conducted to the kin via boddy fluids. The medical test called __ uses electrodes placed on the skin to detect and record tehse currents. The resulting graph has a characteristic shape that represents the stages in the cardiac system.

Impulses from the __ first spread rapidly through the walls of the __,c ausing both __ to contract in unison. During atrial contraction, the impulses originating at the__ reach other autorhythmic cels that are located in the wall between the left and right __.
-- These cells for m a relay point called the __. Here the impulses are delayed for about .1 seconds before spreading to the walls of the ventricles. This delay allows the __ to empty completely befor ehte ventricles contract. Then, the signals from the __ are conducted throughout the ventricular walls by specialized muscle fibers called bundle branches and Purkinje fibers.

Physiological cues alter heart tempo by regulating the __. Two sets of nerves, the __ and __ nerves, are largely responsible for this regulation.
- One set speeds up the __ and the other set does what.

__ secreted into theblood alsoinfluence the pacemaker.
A third type of input that affects the pacemaker is __.