Textbook Question
Compare the effects of the cardioacceleratory and cardioinhibitory centers on cardiac output and blood pressure.
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Ch. 21 Blood Vessels and Circulation
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011
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Table of contents
- Ch. 1 An Introduction to Anatomy and Physiology25
- Ch. 2 The Chemical Level of Organization34
- Ch. 3 The Cellular Level of Organization29
- Ch. 4 The Tissue Level of Organization24
- Ch. 5 The Integumentary System17
- Ch. 6 Bones and Bone Structure33
- Ch. 7 The Axial Skeleton11
- Ch. 8 The Appendicular Skeleton17
- Ch. 9 Joints13
- Ch. 10 Muscle Tissue12
- Ch. 11 The Muscular System28
- Ch. 12 Nervous Tissue18
- Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes22
- Ch. 14 The Brain and Cranial Nerves20
- Ch. 15 Sensory Pathways and the Somatic Nervous System17
- Ch. 16 The Autonomic Nervous System and Higher-Order Functions30
- Ch. 17 The Special Senses15
- Ch. 18 The Endocrine System21
- Ch. 19 Blood31
- Ch. 20 The Heart31
- Ch. 21 Blood Vessels and Circulation26
- Ch. 22 The Lymphatic System and Immunity25
- Ch. 23 The Respiratory System4
- Ch. 24 The Digestive System18
- Ch. 26 The Urinary System31
- Ch. 27 Fluids & Electrolytes30
- Ch. 28 The Reproductive System12
- Ch. 29 Development and Inheritance17
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
Chapter 21, Problem 30
Jolene awakens suddenly to the sound of her alarm clock. Realizing that she is late for class, she jumps to her feet, feels light-headed, and falls back on her bed. What probably caused this reaction? Why doesn't this happen all the time?
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Step 1: Understand the physiological context. Jolene's sudden standing causes a rapid change in her body's position, which affects blood flow and blood pressure, particularly to the brain.
Step 2: Identify the likely cause. The light-headedness and fainting are probably due to orthostatic hypotension, a temporary drop in blood pressure when standing up quickly, leading to reduced cerebral blood flow.
Step 3: Explain the body's normal response. Normally, baroreceptors in the carotid arteries and aorta detect the drop in blood pressure and trigger a reflex to increase heart rate and constrict blood vessels, stabilizing blood pressure.
Step 4: Discuss why this doesn't happen all the time. The reflex response usually acts quickly and effectively, preventing symptoms. However, if standing is too sudden or if the reflex is delayed or impaired, symptoms like light-headedness can occur.
Step 5: Summarize the mechanism. Jolene's sudden movement caused a temporary mismatch between blood pressure regulation and gravity's effect on blood flow, leading to transient cerebral hypoperfusion and her symptoms.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Orthostatic Hypotension
Orthostatic hypotension is a sudden drop in blood pressure that occurs when a person stands up quickly from a lying or sitting position. This causes reduced blood flow to the brain, leading to dizziness or light-headedness, as experienced by Jolene.
Autonomic Nervous System Regulation
The autonomic nervous system controls involuntary functions like blood pressure regulation. It quickly adjusts heart rate and vessel constriction upon standing to maintain blood flow to the brain, preventing symptoms like dizziness under normal conditions.
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Somatic vs. Autonomic Nervous System
Baroreceptor Reflex
Baroreceptors are pressure sensors in blood vessels that detect changes in blood pressure. When standing up, they trigger reflexes to increase heart rate and constrict blood vessels, stabilizing blood pressure and preventing frequent episodes of light-headedness.
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Related Practice
Textbook Question
People with allergies commonly take antihistamines with decongestants to relieve their symptoms. The container warns that individuals who are being treated for high blood pressure should not take the medication. Why not?
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Textbook Question
Bob is sitting outside on a warm day and is sweating profusely. Mary wants to practice taking blood pressures, and he agrees to play the patient. Mary finds that Bob's blood pressure is elevated, even though he is resting and has lost fluid from sweating. (She reasons that fluid loss should lower blood volume and, thus, blood pressure.) Why is Bob's blood pressure high instead of low?
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