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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