Cardiovascular Essentials
The cardiovascular system is composed of these three major components.
What are the heart, vasculature, and blood?
This variable is calculated as EDV minus ESV.
What is stroke volume?
These specialized junctions connect cardiac myocytes end-to-end.
What are intercalated discs?
The resting membrane potential of a myocardial cell is approximately this value.
What is -90 mV?
Blood flows through the circulation from areas of this pressure to areas of this pressure.
What is high pressure to low pressure?
This innermost vessel layer contains the endothelium.
What is the tunica intima?
These vessels contain approximately two-thirds of the body's blood volume at any given time.
What are capacitance vessels (veins and venules)?
During this phase of the cardiac cycle, the ventricles are contracting but ventricular volume does not change.
What is isovolumetric contraction?
This component of the intercalated disc provides a low-resistance pathway for ion current to travel from one myocyte to another.
What are gap junctions?
During Phase 0 of the myocardial action potential, rapid entry of this ion causes depolarization.
What is Na⁺?
Blood velocity is lowest in these vessels because they collectively have the greatest cross-sectional area.
What are capillaries?
This vessel-wall layer contains most of the vascular smooth muscle responsible for altering vessel diameter.
What is the tunica media?
This blood component is calculated as RBC volume divided by total blood volume and is an important determinant of blood viscosity.
What is hematocrit?
The more the ventricle fills during diastole, the greater the subsequent force of contraction. This principle describes that relationship.
What is the Frank-Starling law?
These structures primarily provide mechanical attachment between adjacent myocytes and prevent the cells from pulling apart during contraction.
What are desmosomes?
During this phase, Ca²⁺ influx is approximately balanced by K⁺ efflux, producing the characteristic plateau.
What is Phase 2?
In laminar flow, blood located here travels at the greatest velocity.
What is the center of the vessel?
This endothelial-derived substance is described in the lecture as the most potent vasodilator released by the endothelium.
What is nitric oxide?
These vessels are the primary site of resistance and regulate local blood flow through vasoconstriction and vasodilation.
What are resistance vessels?
A patient has an EDV of 140 mL and an ESV of 56 mL. Their ejection fraction is this.
What is 60%?
During cardiac excitation-contraction coupling, calcium entering through L-type calcium channels activates these SR calcium-release channels.
What are ryanodine receptors, or RyR2?
This prolonged characteristic of the cardiac action potential prevents another normal action potential from occurring immediately and helps prevent tetanic contractions.
What is the refractory period?
According to Poiseuille's law, changing this vessel characteristic has an especially large effect on blood flow because it is raised to the fourth power.
What is radius?
An increase in blood flow raises this mechanical force on the endothelium, stimulating eNOS and nitric oxide production.
What is shear stress?
As oxygen molecules bind to hemoglobin, the affinity of hemoglobin for additional oxygen does this.
What is increases?
A person's HR increases from 60 to 90 bpm while SV falls from 80 to 60 mL. Their cardiac output changes from this value to this value.
What is 4.8 L/min to 5.4 L/min?
Cardiac muscle differs from skeletal muscle because contraction requires this initial event before the SR can release a much larger amount of calcium.
What is extracellular Ca²⁺ entry through L-type calcium channels?
Vagal stimulation increases K⁺ permeability in pacemaker cells. Explain the resulting effect on membrane potential and heart rate.
What is hyperpolarization, a slower rate of spontaneous depolarization, and therefore a decreased heart rate?
An increase in blood viscosity would have what effect on resistance and blood flow, assuming pressure and vessel radius remain constant?
What is increased resistance and decreased blood flow?
This vessel type lacks a tunica media and is specialized for the exchange of gases, nutrients, and waste products between blood and tissues.
What are capillaries?