Physiology Q 2
Put these phases of the cardiac cycle in the correct order. 1. opening of the semilunar valves 2. isovolumic contraction 3. beginning of atrial systole 4. closure of the AV valves 5. completion of ventricular filling 6. beginning of ventricular systole 7. ventricular relaxation8. ventricular ejection
3, 5, 6, 4, 2, 1, 8, 7
In the condition known as complete heart block, what happens?
Electrical signals from the SA node never reach the ventricles, so the contraction of the atria is not coordinated with the contraction of the ventricles
Which event results in the first heart sound?
The AV valves close
Sympathetic stimulation increases the heart rate by
increasing ion influx, thus increasing the rate of depolarization
Acetylcholine slows the heart rate by just
increasing the permeability to K+ and decreasing the permeability to Ca2+
A drug decreases heart rate by hyperpolarizing cardiac pacemaker cells. This drug probably binds to
muscarinic receptors
This protein is activated by the Ca2+-calmodulin complex to phosphorylate the myosin light chain protein.
myosin light chain kinase
An important difference between single-unit and multiunit smooth muscle is the
numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet
The AV node is important because it
slows the transmission of the electrical impulses to the ventricles in order for the atria to finish contracting
A patient is born with a mutation in her calmodulin gene. This could affect the contraction of ________ muscles.
smooth
The volume of blood ejected from each ventricle during a contraction is called the
stroke volume
During ventricular systole,
the AV valves are closed
In order for blood to enter the heart,
the atria must be in diastole but the atrial pressure must be lower than the veins
During the isovolumic phase of ventricular systole,
the atrioventricular valves and semilunar valves are closed
During ventricular ejection,
the ventricles are in systole
Smooth muscle cells do not have which protein(s)?
troponin only
Relative to skeletal muscle, smooth muscle
uses less energy to generate a given amount of force, can sustain contractile force without fatigue and uses calcium from the sarcoplasmic reticulum and extracellular space.
According to the Frank-Starling law of the heart, the cardiac output is directly related to the
venous return
In which situation would the stroke volume be the greatest?
when venous return is increased
Which is NOT a property of single-unit smooth muscles?
Each cell functions independent of its neighbor
Epinephrine and norepinephrine increase ion flow through ________ channels.
If and Ca2+
Which will increase the heart rate?
both sympathetic stimulation and epinephrine stimulation of the SA node
Manganese ions block the calcium channels in the cardiac muscle membrane. How would the presence of manganese ions in the extracellular fluid affect the contraction of the heart muscle?
The heart would beat less forcefully
Compared to skeletal muscle, contraction of smooth muscle cells is
a slower response to a stimulus and sustained without fatigue
The term that describes the volume of blood circulated by the heart in one minute is
cardiac output (CO)
Drugs known as beta blockers will
decrease heart rate
Drugs known as calcium channel blockers can be used to
decrease the force of cardiac contraction
The term used to describe the amount of blood in the ventricle available to be pumped out of the heart during the next contraction is
end-diastolic volume (EDV)
The fibrous skeleton of the heart is important because it
forces electrical activity to be conducted through the atrioventricular node
If the membranes of the cardiac muscle cells in the SA node become more permeable to potassium ions,
heart rate will decrease
The cardiac output is equal to the
product of heart rate and stroke volume
