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Name a condition characterized by a heart rate less than 60 bpm.
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Bradycardia
How do beta-blockers affect cardiac contractility?
Beta-blockers decrease contractility by acting as negative inotropic agents.
Which hormones are known to increase heart rate?
Thyroid hormones, specifically T3 and T4.
Identify positive inotropic agents and their effect on stroke volume.
Positive inotropic agents, like norepinephrine and glucagon, increase contractility and, hence, stroke volume.
Which part of the autonomic nervous system releases norepinephrine and increases heart rate?
The sympathetic nervous system.
Explain how increased afterload affects stroke volume.
Increased afterload increases the resistance the ventricles must overcome to eject blood, which can decrease stroke volume.
What effect does high calcium ion concentration have on heart rate?
High Ca²⁺ concentration increases heart rate.
How does the parasympathetic nervous system affect heart rate?
It releases acetylcholine, which decreases heart rate.
What is the significance of the Frank-Starling Law in relation to stroke volume?
It states that a greater stretch of cardiac muscle fibers results in a more forceful contraction, increasing stroke volume.
What mechanism underlies the Atrial Bainbridge Reflex?
The reflex increases heart rate in response to increased venous return.
What role do chemoreceptors play in regulating heart rate?
Chemoreceptors detect low O₂, high CO₂, and low pH, which can stimulate an increase in heart rate.
What is the equation to calculate cardiac output (CO)?
Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)
Which factor related to heart rate is particularly higher in fetuses compared to adults?
Heart rate is particularly higher in fetuses, ranging from 120-140 bpm.
What is the result on stroke volume if afterload decreases?
Stroke volume increases when afterload decreases.
What is stroke volume, and how is it calculated?
Stroke Volume (SV) is the volume of blood pumped by the ventricles per beat, calculated as SV = End Diastolic Volume (EDV) - End Systolic Volume (ESV).
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