Chapter 14 Cardiovascular system Flashcards
pulmonary circulation
goes from the right side of the heart to the lungs and then back to the heart
systemic circulation
goes from the left side of the heart to the tissues and back to the heart
Pressure gradient (^P)
blood flows down the pressure gradient
from highest pressure (aorta) to the lowest pressure (venae cavae/pulmonary veins)
driving pressure
the pressure created when the ventricles contract
resistance
increases as the length of the tube and the viscosity (thickness) of the fluids increase, and the radius of the tube decreases.
Radius has the greatest effect on resistance
Relationship between resistance and flow rate
Resistance increases, flow rate decreases
inverse relationship
fluid flow and pressure gradient relationship
fluid flow through a tube is proportional to the pressure gradient
flow rate
the volume of blood that passes one point in the system per unit time
velocity
the distance a volume of blood travels in a given period of time
at a constant flow rate, the velocity of flow through a small tube is faster than the velocity through a larger tube
myocardium
cardiac muscle
striated muscle
autorhythmic cells
generate a signal for the contraction of the heart
they are non-contractile myocardium
intercalated disks
link myocardial cells that contain gap junctions
junctions allow depolarization to spread rapidly from cell to cell
pacemaker potential
the unstable membrane potential of autorhythmic cells
pacemaker potential is due to I^f channels that allow a net influx of positive charge
the sinoatrial node (SA node)
here actions potentials originate and spread rapidly from cell to cell in the heart
the potentials are followed by a wave of contraction
path of the electrical signal
SA node (using the internodal pathway) - AV node - AV bundle - bundle branches - terminal Purkinje fibers - myocardial cells
electrocardiogram (ECG)
surface recording of the electrical activity of the heart
readings include the P, QRS complex, and T waves
provides information on heart rate, rhythm, conduction velocity, and condition of cardiac tissues
P-wave
represents atrial depolarization
QRS complex
ventricular depolarization and incorporates atrial repolarization
T-wave
ventricular repolarization
cardiac cycle
one cycle of contraction and relaxation
systole
contraction phase
diastole
relaxation phase
end-diastolic volume (EDV)
majority blood enters the ventricles while the atria are relaxed
Only 20% of ventricular filling is due to atrial contraction
the volume of blood at the end of ventricular filling is EDV
AV valves
prevent backflow of blood into atria
Closure of AV valves during ventricular contraction set up vibrations that create the first heart sound
Isovolmic ventricular contraction
during this, the ventricular blood volume does not change but pressure increases
semilunar valves
when ventricular pressure exceeds arterial pressure these open and ejects blood into the arteries
when ventricles relax and ventricular pressure falls these valves close and create the second heart sound
end-systolic volume
the volume of blood in the ventricles at the end of the contraction
stroke volume (SV)
amount of blood pumped by one ventricle during one contraction
cardiac output
the volume of blood pumped per ventricle per unit of time
= HR x SV
average cardiac output at rest = 5L/min
changes in cardiac output are accomplished through changes in heart rate, stroke volume, or both
parasympathetic activity
slows HR down
sympathetic activity
increase HR