Heart Rate Regulation Lecture Quiz

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37 Questions

What is the effect of increased intracranial pressure on the heart rate, as explained in the text?

Decrease heart rate due to compression of cerebral vessels

Which of the following conditions leads to an increase in heart rate by affecting blood gases and pH levels?

Hypoxia

How does thyroxin affect heart rate according to the text?

By increasing heart rate through direct SAN stimulation and increased body metabolism

In the context of physical regulation of heart rate, how does an increase in body temperature affect heart rate?

Increases heart rate by stimulating medullary CVCs

What is the effect of catecholamines on heart rate according to the text?

Increase heart rate by directly stimulating SAN

What is the term for a condition in which the heart rate is less than 50 bpm?

Bradycardia

Which physiological variation contributes to a higher heart rate in females compared to males?

Gender

During muscular exercise, what happens to the heart rate in athletes compared to non-trained individuals?

Increases

What effect does increased respiration have on the heart rate?

Increases heart rate

Which factor is NOT mentioned as influencing heart rate in the text?

Kidney function

Which of the following is a cause of increased heart rate?

Hyperkalemia

What is a potential cause of decreased heart rate?

Moderate hypoxia

Which of the following is a hormone that can increase heart rate?

Hyperkalemia

During which activity is the heart rate likely to decrease?

Muscular exercise

Which of the following is a cause of increased heart rate according to the text?

Severe pain or if applied to trigger areas

What is the main effect of the Baroreceptors reflexes on heart rate and force of contraction?

Decreased heart rate and force of contraction

In the context of Marey's Reflex, how is heart rate related to arterial blood pressure (ABP)?

Inversely proportional

What stimulates cardiac vagal neurons to decrease heart rate at normal mean ABP?

A burst of action potentials

Which cranial nerve supplies the carotid sinus with sensory nerves for baroreceptor function?

Glossopharyngeal nerve (IX)

How do baroreceptors respond to changes in blood pressure?

Rapidly

Which mechanism is responsible for the phenomenon of respiratory sinus arrhythmia?

Chemical regulation of HR

Which area of the brain plays a role in the CNS ischemic response related to cardiovascular control?

Vasoconstrictor area in medulla oblongata

Which of the following is involved in chemical regulation of heart rate?

Hormones like epinephrine and norepinephrine

What is the primary physiological role of Cushing's reflex in cardiovascular regulation?

Compensate for increased intracranial pressure with hypertension

How do hormones like epinephrine and norepinephrine affect heart rate?

By increasing heart rate and cardiac contraction through adrenergic effects

What is the main mechanism behind the development of Respiratory Sinus Arrhythmia (RSA)?

Central irradiation from the respiratory center to neighboring cardiovascular centers.

In Cushing's reflex, what happens to heart rate and blood pressure when painful stimuli are applied to trigger areas?

Heart rate increases and blood pressure decreases.

What is the response of the sympathetic nervous system in the CNS ischemic response when there is decreased blood pressure?

Increased local CO2 and lactic acid production.

Which of the following correctly explains the effect of emotions on heart rate and blood pressure?

Severe emotions like fear or grief cause increased heart rate and vasodilation.

What is the primary effect of hormones on heart rate regulation?

Increase in heart rate by stimulating the sympathetic nervous system.

What is the mechanism behind the phenomenon of respiratory sinus arrhythmia?

Stimulation of type B receptors leading to decreased sympathetic activity

How does Cushing's reflex affect heart rate?

Increased sympathetic tone leading to hypertension

What is the CNS ischemic response?

Vasodilation of renal arterioles

Which factor stimulates peripheral chemoreceptors to regulate heart rate?

Increased H+ in blood

How do hormones affect heart rate regulation?

By releasing ANP causing vasodilation

During respiratory sinus arrhythmia, what happens during atrial systole?

Type A receptors discharge impulses

What is the primary role of peripheral chemoreceptors in heart rate regulation?

Sensing decreased PaO2 and increased PaCO2

Study Notes

Heart Rate Regulation

  • Heart rate (HR) is regulated by the nervous system, chemical factors, and temperature.

Factors Affecting Heart Rate

  • Factors that increase HR:
    • Less stimulation of baroreceptors
    • Stimulation of atrial stretch receptors
    • Inspiration
    • Muscular exercise
    • Mild or moderate painful stimuli
    • Mild or moderate emotions (e.g., stress & anger)
    • Moderate hypoxia
    • Catecholamines
    • Thyroxin
    • Increased body temperature
  • Factors that decrease HR:
    • More stimulation of baroreceptors
    • Severe emotions (or fear & grief)
    • Expiration
    • Increased intracranial pressure
    • Severe premortal hypoxia & acidosis
    • Hyperkalemia
    • Severe pain or if applied to trigger areas

Cushing's Reflex

  • Increased intracranial pressure leads to compression of cerebral vessels, causing hypoxia, which activates RVLM neurons, leading to systemic vasoconstriction, elevating ABP, and reflexly decreasing HR.

Chemical Regulation of Heart Rate

  • Changes in blood gases & H+:
    • Decreased O2, increased CO2, and increased H+ increase HR (direct & indirect effects)
    • Severe premortal decrease HR (effect on SAN & CVCs)
  • Hormones:
    • Catecholamines increase HR
    • Thyroxin increases HR

Physical Regulation of Heart Rate

  • Increased body temperature (1°C) increases HR (by ≈ 10-15 bpm)

Normal Heart Rate

  • Average HR under resting conditions for an adult man: 70-75 bpm
  • Range: 50-100 bpm
  • Bradycardia: HR < 50 bpm
  • Tachycardia: HR > 100 bpm

Physiological Variations of Heart Rate

  • Gender: HR in females is more than in males
  • Age:
    • Fetus: 140-150 bpm
    • Newborn: 130-140 bpm
    • 1-3 years: 95-115 bpm
    • Elderly: 75-80 bpm
  • Circadian Rhythm: lowest in the early morning (65/min) and highest in the evening (85/min)
  • Rest (Physical & Mental) & Sleep: decrease HR (60 bpm)
  • Muscular Exercise: increases HR (up to ≈ 180 bpm)
  • Posture: standing → ↑ HR (by up to 25%)
  • Emotions: may increase or decrease HR
  • High Metabolic Rate: increases HR
  • Increased respiration: is associated with accelerated HR

Test your knowledge on the importance of cardiovascular regulation, central areas controlling the cardiovascular system, heart rate variations, and mechanisms involved in heart rate regulation. This quiz covers topics discussed in a lecture on heart rate and its regulation.

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