Physio Ch 09 Flashcards
pumps blood through the lungs
right heart
pumps blood through the peripheral organs
left heart
pulsatile two-chamber pump
heart
weak primer pump for the ventricle, helping to move blood into the ventricle
Atrium
Ventricles supply the main pumping force that propels the blood either
- through the pulmonary circulation by the right ventricle
- through peripheral circulation by the left ventricle
continuing succession of heart contractions transmitting action potentials throughout the cardiac muscle to cause the heart’s rhythmical beat
cardiac rhythm
Three major types of cardiac muscle
- atrial muscle
- ventricular muscle
- specialized excitatory and conductive muscle fibers
provide excitatory system that controls the
rhythmical beating of the heart
excitatory and conductive
fibers
dark areas crossing the cardiac muscle fibers
intercalated discs
cell membranes that separate individual cardiac muscle cells from one another
intercalated discs
At each intercalated disc the cell membranes fuse with one another and form this structure that allow rapid diffusion of ions
gap junctions
causes ventricular contraction to last as much as 15 times as long in cardiac muscle as in skeletal muscle
plateau
.
.
velocity of conduction in the specialized heart conductive system
4 m/sec
interval time which a normal cardiac impulse cannot reexcite an already excited area of cardiac muscle
refractory period
normal refractory period of the ventricle
0.25 to 0.30 secs
period which muscle is more difficult than normal to excite but can be excited by very strong excitatory signal
relative refractory period
refractory period of atrial muscle
0.15 seconds
refractory period of ventricular muscles
0.25 to 0.30 seconds
mechanism by which the action potential causes the myofibrils of muscle to contract
excitation-contraction coupling
velocity of conduction of the excitatory action potential signal along both atrial and ventricular muscle fibers
0.3 - 0.5 m/sec or 1/250 in large nerve fibers or 1/10 in skeletal muscle fibers
calcium entering the cell activates these channels to release calcium from sarcoplasmic reticulum
calcium release channels, ryanodine receptor channels
Inside is a large quantity of mucopolysaccharides that are electronegatively charged and bind an abundant store of calcium ions
T tubules
Transport of calcium back into
the sarcoplasmic reticulum is achieved with the help of a
calcium-ATPase pump
cardiac events that occur from the beginning of one heartbeat to the beginning of the next are called
cardiac cycle
Each cardiac cycle is initiated by spontaneous generation of an action potential in the?
sinus node
act as primer pumps for the ventricles
atria
period of relaxation during which the heart fills with blood
diastole
total duration of the cardiac cycle, including systole and diastole, is the reciprocal of the?
heart rate
At a normal heart rate of 72 beats/min, systole comprises about ____ of the entire cardiac cycle.
0.4
At three times the normal heart rate, systole is about ____ of the entire cardiac cycle.
0.65
a wave in the electrocardiogram caused by spread of depolarization through the atria
P wave
How many seconds will the QRS waves appear after the onset of the P wave?
0.16 sec
appear as a result of electrical depolarization
of the ventricles
QRS waves
this complex begins slightly before the onset of ventricular systole
QRS
represents the stage of repolarization of the ventricles when the ventricular muscle
fibers begin to relax
ventricular T wave