57 Questions
What is the typical resting heart rate?
60-100 beats per minute
What is the intrinsic firing rate of the SA node?
100-150 beats per minute
How does vagal tone normally affect the resting heart rate?
Decreases it
What is the heart rate range associated with maximum cardiac output?
90-110 beats per minute
Which receptors influence heart rate through the detection of blood pressure changes?
Baroreceptors
What is the effect of norepinephrine on heart rate?
Increases heart rate
What is the effect of potassium levels on heart rate?
Decreases heart rate
How does the Frank–Starling law match stroke volume to venous return?
By increasing stroke volume as venous return increases
What are the definitions and cardiac effects of positive and negative inotropic agents?
Positive inotropic agents increase contractility, while negative inotropic agents decrease contractility.
What is the term for abnormally fast resting heart rate?
Tachycardia
How are preload, contractility, and afterload related to stroke volume?
Preload and contractility both increase stroke volume
What is the mechanism of action of acetylcholine on heart rate?
Inhibiting SA node firing rate
What is the effect of well-conditioned athletes on resting heart rates?
They have unusually low resting heart rates
How does sympathetic nervous system affect heart rate?
By increasing the firing rate of the SA node
What do proprioceptors, baroreceptors, and chemoreceptors influence in relation to heart rate?
The rate and rhythm of the heartbeat
What is the effect of digitalis on contractility?
It increases contractility by stimulating calcium entry into myocardial cells
Which term refers to the maximum amount of blood that can be ejected from the ventricle?
Stroke volume
Which hormone affects heart rate by increasing the firing rate of the SA node?
Glucagon
What is the effect of certain diseases on cardiac output through afterload?
They reduce cardiac output by increasing afterload
What is the role of vagal tone in relation to the resting heart rate?
Vagal tone decreases the resting heart rate by inhibiting the parasympathetic nervous system
How do potassium levels affect heart rate?
High potassium levels decrease heart rate by inhibiting the parasympathetic nervous system
What is the mechanism of action of positive chronotropic agents on heart rate?
They increase heart rate by inhibiting the parasympathetic nervous system
How do well-conditioned athletes affect resting heart rates?
Well-conditioned athletes have lower resting heart rates due to increased parasympathetic nervous system activity
What is the effect of calcium on myocardial contractility?
Calcium increases contractility by increasing the firing rate of the SA node
How do certain diseases reduce cardiac output through afterload?
Certain diseases increase afterload, leading to a reduction in cardiac output
What is the role of baroreceptors in influencing heart rate?
Baroreceptors decrease heart rate by detecting high blood pressure and stimulating the parasympathetic nervous system
How does exercise increase cardiac output?
Exercise increases cardiac output by primarily increasing stroke volume
What is the mechanism of action of norepinephrine on heart rate?
Increases the firing rate of the SA node
How does vagal tone normally hold the resting heart rate below the intrinsic firing rate of the SA node?
By increasing the release of acetylcholine
What are the cardiac effects of negative inotropic agents?
Decrease myocardial contractility
How do certain diseases reduce cardiac output by increasing afterload?
By decreasing myocardial contractility
What is the effect of calcium on myocardial contractility?
Increases myocardial contractility
What is the effect of potassium levels on heart rate?
Increases heart rate
What is the normal mechanism by which exercise increases cardiac output?
By increasing sympathetic activity
What is the term for abnormally slow resting heart rate?
Bradycardia
What is the heart rate range associated with maximum cardiac output?
100-120 beats per minute
How does norepinephrine affect contractility?
Increases contractility by promoting the release of calcium from the sarcoplasmic reticulum
What is the typical resting heart rate?
60-100 beats per minute
What effect does the sympathetic nervous system have on heart rate?
Increases heart rate
What is the effect of norepinephrine on heart rate?
Increases heart rate
How does the Frank–Starling law of the heart match stroke volume to venous return?
By increasing stroke volume with increased venous return
What is the intrinsic firing rate of the SA node?
$100 beats per minute$
How do hormones affect heart rate?
By changing the firing rate of the SA node
What effect do certain diseases have on cardiac output through afterload?
Increase cardiac output by increasing afterload
How does exercise influence cardiac output?
By increasing cardiac output through increased heart rate and stroke volume
What is the effect of potassium levels on heart rate?
$Decreasing potassium levels increases heart rate$
What effects do positive inotropic agents have on the heart?
Increase contractility
What is the effect of well-conditioned athletes on resting heart rates?
Decreasing resting heart rates due to increased vagal tone
How does the sympathetic nervous system affect heart rate?
It increases heart rate by stimulating the SA node
What is the typical resting heart rate and how does it change with age?
60-100 bpm and decreases with age
How do hormones affect heart rate?
Their effect on heart rate varies depending on the hormone and its mechanism of action
What mechanisms by which exercise increases cardiac output?
By increasing contractility
What are the definitions and cardiac effects of negative inotropic agents?
They decrease contractility and stroke volume
How do certain diseases reduce cardiac output by increasing afterload?
By increasing the resistance to blood flow in the blood vessels
What is the intrinsic firing rate of the SA node and how does vagal tone normally hold the resting heart rate below this?
$100-150$ bpm and vagal tone decreases firing rate to $60-100$ bpm
What is the meaning of preload, contractility, and afterload, and how each one affects stroke volume?
They have distinct effects on stroke volume by influencing ventricular filling and ejection
How do norepinephrine, glucagon, and digitalis affect contractility?
They all increase contractility by stimulating myocardial cells
Test your knowledge of the pathways of sympathetic and parasympathetic innervation of the heart, the meaning of cardiac output, resting heart rates, chronotropic agents, and the effects of the sympathetic and parasympathetic nervous systems on heart rate.
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