Learning Assessment Quizzes (4,6,7) Flashcards
(27 cards)
Under normal conditions, all cardiac electrical activity is initiated in the
SA Node
Propagation of an action potential across the intercalated disc is due to _____________ through gap junctions.
the electrostatic attraction of ions
The direct propagation of cardiac action potentials between atrial and ventricular myocytes is prevented by
the cardiac skeleton
The term _________________ is used to describe conduction velocity.
Dromotropic
Control of cardiac function can be regulated or modulated via (select all correct answers):
- The parasympathetic nervous system
- Autoregulation
- The sympathetic nervous system
- The somatic nervous system
1,2,3
Primary control of heart rate in an normal, healthy individual at rest is due to changes in _________________ input to the sinoatrial (SA) node.
Parasympathetic
Increased parasympathetic input to the sinoatrial (SA) node results in _______________ of the nodal cells due to an increased permeability of the cell membrane to ____________.
hyperpolarization; potassium
The cardiac sympathetic nerve innervates which of the following (select all correct answers):
- atria
- atrioventricular (AV) node
- ventricles
- sinoatrial (SA) node
All of the above
Sympathetic input has a positive chronotropic effect by increasing cell membrane permeability to
Na+/Ca+
Sympathetic input to ventricular myocytes has a _____________________ effect.
positive inotropic
When stimulated to contract, cardiac myocytes contract as a single unit due to the presence of gap junctions at the intercalated discs. This property is known as a/an:
functional syncytium
Propagation of a cardiac action potential down a transverse tubule results in the opening of ____________ channels.
voltage-gated L-type calcium
The influx of extracellular calcium following excitation acts as ______________ calcium to open calcium channels on the sarcoplasmic reticulum.
trigger
Relaxation of cardiac myocytes occurs with the majority of calcium
being actively pumped back into the sarcoplasmic reticulum.
The resting tension on a cardiac myocyte is influenced by
preload and EDV
The term used to describe the downstream pressure/resistance that has to be overcome in order for blood to be ejected from the ventricles is know as
afterload
In the heart, a positive inotropic effect results in ______________ in a myocyte’s ability to shorten.
increase
Cardiac myocyte relaxation is influenced by the re-uptake of calcium by the sarcoplasmic reticulum. Sympathetic input can ____________ relaxation by leading to the phosphorylation of __________________.
increase; phospholamban
In addition to increasing the relaxation rate of cardiac myoctes, sympathetic input can shorten the absolute refractory period
by increasing cell membrane permeability to potassium via delayed rectifier channels.
One complete cycle of the cardiac cycle includes (select all that apply)
- cardiac muscle excitation
- cardiac relaxation
- ejection of blood from ventricles
- cardiac filling
all of the above
Following the ejection phase, as a result of blood moving away from the heart:
aortic pressure decreases
During the majority of diastole, filling of the ventricles is
passive
Isovolumetric contraction of the left ventricle occurs until
the aortic valve opens
