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Which part of the autonomic nervous system primarily inhibits heart rate?
Which part of the autonomic nervous system primarily inhibits heart rate?
What is the intrinsic heart rate of the SA node when the heart is completely denervated?
What is the intrinsic heart rate of the SA node when the heart is completely denervated?
Which mechanism is primarily responsible for the normal heart rate being less than the intrinsic heart rate?
Which mechanism is primarily responsible for the normal heart rate being less than the intrinsic heart rate?
What neurotransmitter is released at vagal nerve endings to decrease heart rate?
What neurotransmitter is released at vagal nerve endings to decrease heart rate?
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Which nerve predominantly supplies the SA node?
Which nerve predominantly supplies the SA node?
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Which enzyme hydrolyzes acetylcholine, affecting its duration of action on the SA node?
Which enzyme hydrolyzes acetylcholine, affecting its duration of action on the SA node?
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Which of the following best describes the effect of sympathetic stimulation on heart rate?
Which of the following best describes the effect of sympathetic stimulation on heart rate?
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The neural regulating mechanisms of heart rate include all of the following EXCEPT:
The neural regulating mechanisms of heart rate include all of the following EXCEPT:
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Which condition is most likely associated with an anacrotic pulse?
Which condition is most likely associated with an anacrotic pulse?
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What characterizes a water-hammer pulse?
What characterizes a water-hammer pulse?
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Which physiological factor can lead to bradycardia?
Which physiological factor can lead to bradycardia?
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Pulsus paradoxus is often observed in which condition?
Pulsus paradoxus is often observed in which condition?
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Which pulse type is a combination of anacrotic and collapsing pulse?
Which pulse type is a combination of anacrotic and collapsing pulse?
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What feature is characteristic of a dicrotic pulse?
What feature is characteristic of a dicrotic pulse?
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Which of the following conditions is least likely to cause tachycardia?
Which of the following conditions is least likely to cause tachycardia?
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Which statement is true about pulsus alternans?
Which statement is true about pulsus alternans?
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What is classified as bradycardia in adults?
What is classified as bradycardia in adults?
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Which factor can lead to an increase in heart rate during the day?
Which factor can lead to an increase in heart rate during the day?
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How does body temperature affect heart rate?
How does body temperature affect heart rate?
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Which physiological factor is associated with higher heart rates in infants and children?
Which physiological factor is associated with higher heart rates in infants and children?
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What change occurs in heart rate upon change of posture from supine to standing?
What change occurs in heart rate upon change of posture from supine to standing?
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Which of the following statements about heart rate is false?
Which of the following statements about heart rate is false?
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Which physiological mechanism explains sinus arrhythmia related to heart rate changes?
Which physiological mechanism explains sinus arrhythmia related to heart rate changes?
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How does food intake affect heart rate?
How does food intake affect heart rate?
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What is the primary reason that the effect of sympathetic stimulation on heart rate lasts longer than that of parasympathetic stimulation?
What is the primary reason that the effect of sympathetic stimulation on heart rate lasts longer than that of parasympathetic stimulation?
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Which reflex primarily involves stimulation of the vagus nerve to decrease heart rate?
Which reflex primarily involves stimulation of the vagus nerve to decrease heart rate?
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What initiates the Baroreceptor Reflex when blood pressure rises?
What initiates the Baroreceptor Reflex when blood pressure rises?
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Which condition is associated with decreased stimulation of baroreceptors, resulting in increased heart rate?
Which condition is associated with decreased stimulation of baroreceptors, resulting in increased heart rate?
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The Bainbridge Reflex is most effective when the initial heart rate is:
The Bainbridge Reflex is most effective when the initial heart rate is:
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What primarily stimulates chemoreceptors to affect heart rate?
What primarily stimulates chemoreceptors to affect heart rate?
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Cushing's Reflex is activated in response to:
Cushing's Reflex is activated in response to:
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The effect of norepinephrine on heart rate is primarily mediated through which system?
The effect of norepinephrine on heart rate is primarily mediated through which system?
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What is the effect of direct stimulation of VMC on heart rate?
What is the effect of direct stimulation of VMC on heart rate?
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Which system contributes to an increased heart rate during emotional states?
Which system contributes to an increased heart rate during emotional states?
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What hormonal effect is associated with an increase in heart rate?
What hormonal effect is associated with an increase in heart rate?
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Which condition is known to decrease heart rate?
Which condition is known to decrease heart rate?
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What is a pulse deficit?
What is a pulse deficit?
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What mechanism explains the increased strength of the second beat in pulsus alternans?
What mechanism explains the increased strength of the second beat in pulsus alternans?
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Which of the following is the most common cause of pulsus alternans?
Which of the following is the most common cause of pulsus alternans?
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How is a normal pulse defined?
How is a normal pulse defined?
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What is represented by the dicrotic notch in arterial pulse tracing?
What is represented by the dicrotic notch in arterial pulse tracing?
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What physiological change occurs in left ventricular failure that leads to a low volume pulse?
What physiological change occurs in left ventricular failure that leads to a low volume pulse?
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Which pulse rate indicates tachycardia?
Which pulse rate indicates tachycardia?
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What is a key characteristic of water-hammer pulse?
What is a key characteristic of water-hammer pulse?
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What condition is typically indicated by a pulse deficit?
What condition is typically indicated by a pulse deficit?
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What is the primary function of the parasympathetic nervous system regarding heart rate?
What is the primary function of the parasympathetic nervous system regarding heart rate?
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What physiological adaptation causes pulsus paradoxus?
What physiological adaptation causes pulsus paradoxus?
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Which term describes the condition of alternating strong and weak heartbeats?
Which term describes the condition of alternating strong and weak heartbeats?
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Study Notes
Heart Rate and Arterial Pulse
- Normal heart rate: 60-100 beats per minute in adults. Bradycardia is <60 bpm, tachycardia is >100 bpm.
- Heart rate varies with age, higher in infants and children, decreasing after 60 years.
- Heart rate is higher in males, due to lower metabolism.
- Diurnal variation: Higher heart rate during the day, especially in the afternoon, and lower at night, specifically during sleep.
- Body temperature: Higher temperature increases heart rate; lower temperature decreases heart rate.
- Environmental temperature: Higher temperatures (summer) lead to higher heart rates; lower temperatures (winter) lead to lower heart rates.
- Food intake: Increased food intake leads to higher heart rates.
- Posture: Standing increases heart rate compared to lying down
- Exercise: Exercise causes increased heart rate. This can occur before the exercise begins due to psychological factors.
Regulation of Heart Rate
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Autonomic nervous system primarily regulates heart rate:
- Vagus (parasympathetic) nerve slows the heart rate.
- Sympathetic nerves speed up the heart rate.
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Respiration: Heart rate is higher during inspiration and lower during expiration (sinus arrhythmia).
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- Baroreceptors are specialized sensory receptors located in blood vessels, particularly in the carotid sinus and the aortic arch.
- They are crucial for detecting changes in blood pressure and play a significant role in maintaining hemodynamic stability.
- When blood pressure rises, baroreceptors are stretched, sending signals to the central nervous system, primarily the medulla oblongata, to trigger a response that lowers heart rate and dilates blood vessels, effectively reducing blood pressure.
- Conversely, when blood pressure drops, baroreceptors decrease their discharge rate, prompting the body to increase heart rate and constrict blood vessels to stabilize blood pressure levels.
- This feedback mechanism is essential for homeostasis and helps the body respond to various physiological demands, such as changes in posture or physical activity.
: Respond to blood pressure changes, influencing heart rate indirectly.
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Chemoreceptors: Respond to changes in blood chemistry (hypoxia, hypercapnia), influencing heart rate.
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Bainbridge reflex: Increased venous return stimulates the heart to speed up.
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Higher brain centers: Thoughts, emotions, and stress can influence heart rate.
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Humoral control: Hormones like thyroid hormone impact heart rate
Arterial Pulse
- Definition: Rhythmic expansion of arterial walls caused by pressure waves during systole.
- Clinical importance: Essential for assessing heart and circulatory functioning.
- Normal pulse rate coincides with heart rate (60-100 beats per minute).
- Tachycardia: >100 bpm
- Bradycardia: <60 bpm
- Pulse tracing: Includes percussion (p) wave, dicrotic wave, and dicrotic notch.
- Variations in pulse: Anacrotic, dicrotic, water hammer (collapsing), pulsus bisferiens, pulsus paradoxus. and pulsus alternans, each have different characteristics.
Abnormal Pulses
- Anacrotic pulse: Slow, sloping upstroke. Often associated with aortic stenosis.
- Dicrotic pulse: Prominent dicrotic wave, frequently seen in fever.
- Water-Hammer (collapsing) pulse: Rapid upstroke and descent due to high volume and low resistance. Seen in aortic regurgitation.
- Pulsus bisferiens: Two distinct pulses felt per beat, seen in aortic regurgitation combined with aortic stenosis.
- Pulsus Paradoxus: Pulse amplitude decreases during inspiration, seen in constrictive pericarditis or pericardial effusion.
- Pulsus alternans: Alternating strong and weak beats indicating ventricular failure.
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Description
This quiz covers the key concepts related to heart rate and arterial pulse, including normal ranges, factors affecting heart rate, and the role of the autonomic nervous system in its regulation. Test your understanding of how age, temperature, and other factors influence heart rate variations.
