Questions and Answers
What is the main function of the vasomotor center?
Where is the vasomotor center located?
What is the function of the vasoconstrictor area?
What nerve is involved in decreasing heart rate?
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What is the function of the vasodilator area?
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What controls the vasoconstrictor area?
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What is another name for the vasodilator area?
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What is the function of the sensory area in the vasomotor center?
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What is the location of the vasomotor center?
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Which nerves carry sensory impulses to the sensory area?
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What is the function of parasympathetic nerve fibers?
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Which area is stimulated to cause tachycardia?
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What carries sensations of stretch and pain from the heart to the brain?
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What is the origin of sympathetic nerve fibers?
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Which area is affected by emotional response?
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What is the function of the vasodilator area?
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What is the effect of stimulating the preoptic and anterior nuclei on heart rate?
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What is the name of the variation in heart rate that occurs during forced breathing?
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What responds to changes in chemical constituents of blood?
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What is the effect of hypoxia, hypercapnea, and increased hydrogen ions concentration on heart rate?
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What is the name of the reflex that increases heart rate when venous return is increased?
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What is the effect of Bainbridge reflex on vagal tone?
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Study Notes
Regulation of Heart Rate
- Heart rate is constantly regulated within the normal range despite variations during physiological conditions such as emotion and exercise.
- Regulatory mechanism in the body brings heart rate back to normal.
Nervous Mechanism of Heart Rate Regulation
- Consists of three components:
- Vasomotor center (cardiac center)
- Motor (efferent) nerve fibers to the heart
- Sensory (afferent) nerve fibers from the heart
Vasomotor Center (Cardiac Center)
- Bilaterally located in the reticular formation of medulla oblongata and the lower part of the pons.
- Divided into three major areas:
- Vasoconstrictor area (cardioaccelerator center)
- Vasodilator area (cardioinhibitory center)
- Sensory area
Vasoconstrictor Area (Cardioaccelerator Center)
- Located in the reticular formation of medulla in the floor of IV ventricle.
- Increases heart rate by sending accelerator impulses to the heart through sympathetic nerves.
- Causes constriction of blood vessels.
- Under the control of hypothalamus and cerebral cortex.
Vasodilator Area (Cardioinhibitory Center)
- Located in the reticular formation of medulla oblongata in the floor of IV ventricle.
- Decreases heart rate by sending inhibitory impulses to the heart through vagus nerve.
- Causes dilatation of blood vessels.
- Under the control of cerebral cortex and hypothalamus.
Sensory Area
- Forms the posterior part of vasomotor center, which lies in nucleus of tractus solitarius in medulla and pons.
- Receives sensory impulses via glossopharyngeal nerve and vagus nerve from periphery, particularly from baroreceptors.
- Controls vasoconstrictor and vasodilator areas.
Motor (Efferent) Nerve Fibers to Heart
- Heart is innervated by both parasympathetic and sympathetic nervous systems.
- Parasympathetic fibers originate from the medulla oblongata and pass through vagus nerve.
- Sympathetic fibers originate from upper thoracic (T1 to T4) segments of spinal cord.
Parasympathetic Nerve Fibers
- Cardioinhibitory nerve fibers that reach the heart through the cardiac branch of vagus nerve.
- Carry inhibitory impulses from vasodilator area to the heart.
Sympathetic Nerve Fibers
- Cardioacceleratory nerve fibers that supply the heart.
- Carry cardioaccelerator impulses from vasoconstrictor area to the heart.
Sensory (Afferent) Nerve Fibers from Heart
- Pass through inferior cervical sympathetic nerve.
- Carry sensations of stretch and pain from the heart to the brain via spinal cord.
Factors Affecting Vasomotor Center and Heart Rate Regulation
- Impulses from higher centers:
- Cerebral cortex (emotional response, area 13)
- Hypothalamus (stimulation of posterior and lateral nuclei causes tachycardia, stimulation of preoptic and anterior nuclei causes bradycardia)
- Impulses from respiratory centers:
- Respiratory sinus arrhythmia (heart rate increases during forced inspiration and decreases during expiration)
- Impulses from baroreceptors:
- Marey reflex (baroreceptors respond to changes in blood pressure)
- Impulses from chemoreceptors:
- Respond to changes in chemical constituents of blood, particularly oxygen, carbon dioxide, and hydrogen ion concentration
- Impulses from right atrium:
- Bainbridge reflex (cardioaccelerator reflex that increases heart rate when venous return is increased)
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Description
This quiz covers the regulation of heart rate within the normal range, including the nervous mechanism that controls it. Learn about the vasomotor center, motor and sensory nerve fibers, and how they work together to maintain a healthy heart rate.
