Textbook Question
Explain what would happen if depolarization of the trigger zone led to a negative feedback loop instead of a positive one.
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Ch. 11 Introduction to the Nervous System and Nervous Tissue
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814
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Table of contents
- Ch. 1 Introduction to Anatomy and Physiology24
- Ch. 2 The Chemistry of Life37
- Ch. 3 The Cell54
- Ch. 4 Histology46
- Ch. 5 The Integumentary System30
- Ch. 6 Bones and Bone Tissue36
- Ch. 7 The Skeletal System40
- Ch. 8 Articulations19
- Ch. 9 The Muscular System35
- Ch. 10 Muscle Tissue and Physiology29
- Ch. 11 Introduction to the Nervous System and Nervous Tissue28
- Ch. 12 The Central Nervous System41
- Ch. 13 The Peripheral Nervous System41
- Ch. 14 The Autonomic Nervous System and Homeostasis31
- Ch. 15 The Special Senses39
- Ch. 16 The Endocrine System42
- Ch. 17 The Cardiovascular System I: The Heart28
- Ch. 18 The Cardiovascular System II: The Blood Vessels43
- Ch. 19 Blood32
- Ch. 20 The Lymphatic System and Immunity41
- Ch. 21 The Respiratory System27
- Ch. 22 The Digestive System27
- Ch. 23 Metabolism and Nutrition7
- Ch. 24 The Urinary System39
- Ch. 25 Fluid, Electrolyte, and Acid-Base Homeostasis39
- Ch. 26 The Reproductive System10
- Ch. 27 Development and Heredity5
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook
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Amerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem L2.4
Amerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem L2.4Chapter 11, Problem L2.4
Explain why cardiac muscle cells and some smooth muscle cells will continue to contract even when their nerve supply has been removed
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Understand the concept of autorhythmicity: Cardiac muscle cells and some smooth muscle cells have the ability to generate their own action potentials without external nervous system input. This property is known as autorhythmicity, which is driven by specialized pacemaker cells.
Explain the role of pacemaker cells: In cardiac muscle, pacemaker cells located in the sinoatrial (SA) node spontaneously depolarize due to the presence of leaky ion channels. This depolarization triggers action potentials that spread through the heart, causing contraction.
Discuss the role of gap junctions: Cardiac muscle cells are connected by intercalated discs, which contain gap junctions. These gap junctions allow ions to flow directly between cells, enabling the action potential generated by pacemaker cells to propagate throughout the heart muscle, ensuring coordinated contraction.
Relate to smooth muscle: Some smooth muscle cells, such as those in the gastrointestinal tract, also exhibit autorhythmicity. These cells can generate slow waves of depolarization, which may reach threshold and trigger contraction, even in the absence of nervous system input.
Summarize the independence from nerve supply: While the nervous system can modulate the rate and strength of contractions (e.g., through sympathetic or parasympathetic input), the intrinsic ability of these muscle cells to generate action potentials ensures that they can continue to contract even when their nerve supply is removed.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Myogenic Activity
Myogenic activity refers to the ability of certain muscle cells, particularly cardiac muscle cells, to generate their own contractions without external nerve stimulation. This is due to the presence of specialized pacemaker cells in the heart, which initiate electrical impulses that trigger muscle contractions, allowing the heart to beat rhythmically and autonomously.
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Active Transport
Calcium Ion Role
Calcium ions play a crucial role in muscle contraction. In cardiac and smooth muscle cells, the influx of calcium ions from the extracellular space and the sarcoplasmic reticulum activates the contractile proteins, leading to muscle contraction. This process can occur independently of nerve signals, allowing these muscles to contract even when their nerve supply is compromised.
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Functional Syncytium
A functional syncytium is a group of cells that function as a single unit due to their interconnections. In cardiac muscle, cells are interconnected by intercalated discs, allowing for rapid transmission of electrical signals and coordinated contractions. This structural feature enables the heart to contract effectively even in the absence of nerve input, as the cells can still communicate and contract together.
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Related Practice
Textbook Question
Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?
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Textbook Question
During a surgical procedure, an anesthesiologist administers to the patient an inhaled anesthetic agent that opens Cl− channels in the postsynaptic membranes of neurons in the brain. Explain why this would put the patient 'to sleep' for the duration of the surgical procedure.
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Textbook Question
Albert, the patient in question 3, takes the drug lithium, which reduces the permeability of the neuronal axolemma to Na+ (that is, it allows fewer Na+ to enter the axon). Predict the effect this would normally have on his neuronal action potentials. Do you think this drug would be beneficial or harmful, considering his condition?
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Textbook Question
A hypothetical poison blocks K+ leak channels. How would this affect the resting membrane potential of skeletal muscle fibers? Explain your reasoning.
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Textbook Question
What would happen if the drug blocked K+ channels instead?