Heart Rate and Arterial Pulse Overview
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Questions and Answers

Which part of the autonomic nervous system primarily inhibits heart rate?

  • Vagus nerve (correct)
  • Cervical spinal cord
  • Sympathetic nervous system
  • Intrinsic nervous system

What is the intrinsic heart rate of the SA node when the heart is completely denervated?

  • 120 beats per minute
  • 75 beats per minute
  • 60 beats per minute
  • 110 beats per minute (correct)

Which mechanism is primarily responsible for the normal heart rate being less than the intrinsic heart rate?

  • Higher center regulation
  • Reflex regulation
  • Sympathetic regulation
  • Autonomic regulation (correct)

What neurotransmitter is released at vagal nerve endings to decrease heart rate?

<p>Acetylcholine (A)</p> Signup and view all the answers

Which nerve predominantly supplies the SA node?

<p>Right vagus nerve (A)</p> Signup and view all the answers

Which enzyme hydrolyzes acetylcholine, affecting its duration of action on the SA node?

<p>Cholinesterase (D)</p> Signup and view all the answers

Which of the following best describes the effect of sympathetic stimulation on heart rate?

<p>Increases heart rate (A)</p> Signup and view all the answers

The neural regulating mechanisms of heart rate include all of the following EXCEPT:

<p>Metabolic regulation (C)</p> Signup and view all the answers

Which condition is most likely associated with an anacrotic pulse?

<p>Aortic stenosis (C)</p> Signup and view all the answers

What characterizes a water-hammer pulse?

<p>Rapid upstroke and rapid downstroke (A)</p> Signup and view all the answers

Which physiological factor can lead to bradycardia?

<p>Fear (D)</p> Signup and view all the answers

Pulsus paradoxus is often observed in which condition?

<p>Constrictive pericarditis (A)</p> Signup and view all the answers

Which pulse type is a combination of anacrotic and collapsing pulse?

<p>Pulsus bisferiens (A)</p> Signup and view all the answers

What feature is characteristic of a dicrotic pulse?

<p>Prominent dicrotic wave with two beats (A)</p> Signup and view all the answers

Which of the following conditions is least likely to cause tachycardia?

<p>Myxedema (D)</p> Signup and view all the answers

Which statement is true about pulsus alternans?

<p>It presents regular beats but varies in strength. (B)</p> Signup and view all the answers

What is classified as bradycardia in adults?

<p>Less than 60 beats/min (A)</p> Signup and view all the answers

Which factor can lead to an increase in heart rate during the day?

<p>Increased sympathetic discharge (D)</p> Signup and view all the answers

How does body temperature affect heart rate?

<p>It increases heart rate with increased temperature (B)</p> Signup and view all the answers

Which physiological factor is associated with higher heart rates in infants and children?

<p>Natural cardiac pacemaker activity (C)</p> Signup and view all the answers

What change occurs in heart rate upon change of posture from supine to standing?

<p>Increased heart rate due to decreased baroreceptor stimulation (A)</p> Signup and view all the answers

Which of the following statements about heart rate is false?

<p>Bradycardia is observed only in older adults. (A)</p> Signup and view all the answers

Which physiological mechanism explains sinus arrhythmia related to heart rate changes?

<p>Changes in vagal activity during respiration (B)</p> Signup and view all the answers

How does food intake affect heart rate?

<p>It increases heart rate by enhancing metabolic demand. (B)</p> Signup and view all the answers

What is the primary reason that the effect of sympathetic stimulation on heart rate lasts longer than that of parasympathetic stimulation?

<p>Norepinephrine is not degraded quickly. (D)</p> Signup and view all the answers

Which reflex primarily involves stimulation of the vagus nerve to decrease heart rate?

<p>Baroreceptor Reflex (D)</p> Signup and view all the answers

What initiates the Baroreceptor Reflex when blood pressure rises?

<p>Stimulation of baroreceptors in the carotid sinus. (D)</p> Signup and view all the answers

Which condition is associated with decreased stimulation of baroreceptors, resulting in increased heart rate?

<p>Hypotension (D)</p> Signup and view all the answers

The Bainbridge Reflex is most effective when the initial heart rate is:

<p>Low (A)</p> Signup and view all the answers

What primarily stimulates chemoreceptors to affect heart rate?

<p>Chemical composition of blood (D)</p> Signup and view all the answers

Cushing's Reflex is activated in response to:

<p>Hypovolemia and hypotension (C)</p> Signup and view all the answers

The effect of norepinephrine on heart rate is primarily mediated through which system?

<p>Adenylyl cyclase system (D)</p> Signup and view all the answers

What is the effect of direct stimulation of VMC on heart rate?

<p>It leads to vasoconstriction and tachycardia. (D)</p> Signup and view all the answers

Which system contributes to an increased heart rate during emotional states?

<p>Limbic system (D)</p> Signup and view all the answers

What hormonal effect is associated with an increase in heart rate?

<p>Release of catecholamines (B)</p> Signup and view all the answers

Which condition is known to decrease heart rate?

<p>Acidosis (C)</p> Signup and view all the answers

What is a pulse deficit?

<p>The difference between pulse rate and heart rate. (A)</p> Signup and view all the answers

What mechanism explains the increased strength of the second beat in pulsus alternans?

<p>Frank-Starling mechanism (A)</p> Signup and view all the answers

Which of the following is the most common cause of pulsus alternans?

<p>Left ventricular failure (C)</p> Signup and view all the answers

How is a normal pulse defined?

<p>60-100 beats/min (B)</p> Signup and view all the answers

What is represented by the dicrotic notch in arterial pulse tracing?

<p>Closure of the aortic valve (C)</p> Signup and view all the answers

What physiological change occurs in left ventricular failure that leads to a low volume pulse?

<p>Decreased stroke volume (C)</p> Signup and view all the answers

Which pulse rate indicates tachycardia?

<p>Greater than 100 beats/min (A)</p> Signup and view all the answers

What is a key characteristic of water-hammer pulse?

<p>Rapid rise and fall with a strong pulse (C)</p> Signup and view all the answers

What condition is typically indicated by a pulse deficit?

<p>Atrial fibrillation (A)</p> Signup and view all the answers

What is the primary function of the parasympathetic nervous system regarding heart rate?

<p>Decrease heart rate directly (C)</p> Signup and view all the answers

What physiological adaptation causes pulsus paradoxus?

<p>Decreased systolic pressure during inhalation (A)</p> Signup and view all the answers

Which term describes the condition of alternating strong and weak heartbeats?

<p>Pulsus alternans (C)</p> Signup and view all the answers

Flashcards

Tachycardia

A heart rate over 100 beats per minute (bpm).

Bradycardia

A heart rate under 60 beats per minute (bpm).

Sinoatrial (SA) node

The natural pacemaker of the heart, located in the right atrium. It sets the rhythm for heart contractions.

Normal Heart Rate

The normal range for heart rate in adults, from 60 to 100 beats per minute.

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Sinus Arrhythmia

The variation in heart rate that occurs during breathing, higher during inspiration and lower during expiration.

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Physiological Variations of Heart Rate

The influence of factors like age, gender, exercise, and body temperature on heart rate.

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Regulation of Heart Rate

The process of regulating heart rate by the nervous system and other factors.

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Arterial Pulse Tracing

The graphic representation of the pressure wave generated by the heart's contraction as it travels through the arteries.

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What regulates heart rate?

The autonomic nervous system controls heart rate. The vagus nerve (parasympathetic) slows down heart rate, while the sympathetic nerves speed it up.

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What's the intrinsic heart rate?

The intrinsic heart rate is the heart rate when completely denervated (no nerve input). It's around 110 beats per minute. However, our normal heart rate is lower due to the vagus nerve's influence.

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Which vagus nerve affects the SA node?

The right vagus nerve primarily affects the SA (sinoatrial) node, the heart's natural pacemaker, while the left vagus nerve mainly influences the AV (atrioventricular) node.

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How does the vagus nerve slow down heart rate?

The parasympathetic nervous system releases acetylcholine, which slows down the SA node, leading to a decrease in heart rate.

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How does the sympathetic nervous system speed up heart rate?

The sympathetic nervous system releases norepinephrine, increasing the SA node's activity, leading to a faster heart rate.

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What is the main influence on heart rate?

The parasympathetic system primarily controls the SA node, influencing the resting heart rate. It's like the 'brakes' of your heart rhythm.

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What are reflex mechanisms for heart rate control?

Reflex mechanisms, like the baroreceptor reflex, sense blood pressure changes. This information triggers the vagal or sympathetic nervous system to adjust heart rate.

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How do higher brain centers control heart rate?

Higher brain centers, like the cerebral cortex, can consciously or subconsciously influence heart rate in response to fear, stress, or excitement.

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Why does sympathetic stimulation of the heart last longer?

Sympathetic stimulation of the SA node leads to a longer-lasting increase in heart rate compared to parasympathetic stimulation (vagal nerve).

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How does norepinephrine contribute to the longer duration of sympathetic stimulation?

Norepinephrine, the neurotransmitter released by sympathetic nerves, isn't quickly broken down by a specific enzyme. It's mainly reabsorbed by nerve terminals and slowly enters circulation, prolonging its effect.

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What role does adenylyl cyclase play in the duration of sympathetic stimulation?

The signaling pathway activated by norepinephrine involves adenylyl cyclase, which takes time to produce its effects, further contributing to the prolonged action of sympathetic stimulation.

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Describe the baroreceptor reflex and its effect on heart rate.

Baroreceptors, located in the carotid sinus and aortic arch, sense changes in blood pressure. When pressure rises, they activate the nucleus tractus solitarius (NTS) in the medulla, which inhibits sympathetic activity and reduces heart rate.

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How does the baroreceptor reflex affect the vagus nerve?

The NTS also directly stimulates the vagus nerve, causing bradycardia (slowing of heart rate). So, the baroreceptor reflex has a double whammy effect on heart rate: decreasing sympathetic output and increasing parasympathetic output.

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What is the role of chemoreceptors in heart rate regulation?

Chemoreceptors, sensitive to changes in blood chemistry (like oxygen levels, CO2, and acidity), are primarily involved in regulating breathing. Their activation can also lead to bradycardia, but other factors might result in unchanged or slightly increased heart rate.

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Explain the Bainbridge reflex and its effect on heart rate.

The Bainbridge reflex, observed when blood or saline is rapidly infused, leads to an increase in heart rate, particularly if the initial heart rate is low. This is mediated by receptors in the atria (tachycardia-producing receptors) that respond to increased blood volume.

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Describe Cushing's reflex and its activation.

Cushing's reflex gets triggered in situations of severe blood loss (hypovolemia) and low blood pressure. This reduces blood flow to the medulla, leading to a complex response that may include an increase in heart rate and blood pressure.

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Anacrotic Pulse

A type of pulse with a slow rising upstroke and a secondary wave, often seen in aortic stenosis.

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Dicrotic Pulse

Also known as 'twice-beating pulse,' this pulse has a prominent dicrotic wave, giving the impression of two beats.

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Water-Hammer Pulse

A pulse with a rapid upstroke and a rapid downstroke, commonly associated with aortic regurgitation.

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Pulsus Bisferiens

Combines the slow rising pulse of anacrotic pulse with the collapsing pulse, commonly seen in aortic stenosis with aortic incompetence.

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Pulsus Paradoxus

A decrease in pulse volume during inspiration, often a sign of constrictive pericarditis or pericardial effusion.

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Pulsus Alternans

A regular pulse with alternating strong and weak beats, often seen in heart failure.

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VMC Stimulation: Vasoconstriction & Tachycardia -> Bradycardia

Direct stimulation of the Vasomotor Center (VMC) causes blood vessels to constrict and the heart to beat faster (tachycardia). This leads to a rise in blood pressure, which stimulates the baroreceptors, leading to a decrease in heart rate (bradycardia). It's a balancing act to maintain stable blood pressure.

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Higher Centers: Heart Rate Control

Stimulation of the motor cortex, frontal lobe, and thalamus increases heart rate. The limbic system is responsible for heart rate increases during emotions like anxiety and excitement.

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Hormonal Control of Heart Rate

Hormones like thyroxine and catecholamines influence the heart rate by causing it to increase.

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Chemical Control of Heart Rate

Low oxygen levels (hypoxia) increase heart rate, partly due to the adrenal medulla releasing catecholamines. High carbon dioxide levels (hypercapnia) and acidic conditions (acidosis) decrease heart rate.

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What is the arterial pulse?

Arterial pulse is the rhythmic expansion of an artery's wall caused by pressure waves from each heartbeat. It's a measure of the heart's effectiveness in pumping blood.

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Why is the arterial pulse clinically important?

Checking the radial pulse is important for assessing heart function, blood pressure, and blood vessel health. It's one of the vital signs, along with blood pressure, respiration, and temperature.

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Normal Pulse Rate

The pulse rate normally matches the heart rate, ranging from 60 to 100 beats per minute. A pulse rate above 100 is called tachycardia, and below 60 is bradycardia. Children have faster heart rates, and the elderly slower.

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Arterial Pulse Graph

Arterial pulse tracing shows two waves and a notch. The percussion wave (p) represents blood ejection during systole, the dicrotic wave (d) is the blood rebound against the closed aortic valve during diastole, and the dicrotic notch (n) marks aortic valve closure.

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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

  • Autonomic nervous system primarily regulates heart rate:

    • Vagus (parasympathetic) nerve slows the heart rate.
    • Sympathetic nerves speed up the heart rate.

  • Respiration: Heart rate is higher during inspiration and lower during expiration (sinus arrhythmia).

    • 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.

  • Chemoreceptors: Respond to changes in blood chemistry (hypoxia, hypercapnia), influencing heart rate.

  • Bainbridge reflex: Increased venous return stimulates the heart to speed up.

  • Higher brain centers: Thoughts, emotions, and stress can influence heart rate.

  • 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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Heart Rate and Arterial Pulse PDF

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.

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