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Would you expect to find larger motor units in the postural muscles of the back or the muscles of the hand? Explain your answer.
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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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TOC.tableOfContents
- 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, 9780138201814Non è quello che usi tu?Cambia libro di testo
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Amerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblema L2.4
Amerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblema L2.4Capitolo 11, Problema L2.4
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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Understand that an action potential is a rapid change in membrane potential that travels along the axon of a neuron. Continuous conduction occurs in unmyelinated axons, where the action potential is propagated step-by-step along the entire length of the axon.
In continuous conduction, the action potential begins at the axon hillock. Sodium (Na⁺) channels open in response to a stimulus, allowing Na⁺ ions to enter the neuron, causing depolarization. This depolarization triggers adjacent voltage-gated Na⁺ channels to open, propagating the action potential down the axon.
As the action potential moves, the previously depolarized region undergoes repolarization. Voltage-gated potassium (K⁺) channels open, allowing K⁺ ions to exit the neuron, restoring the resting membrane potential. This ensures the action potential moves in one direction.
Saltatory conduction, in contrast, occurs in myelinated axons. The myelin sheath insulates the axon, preventing ion exchange along the myelinated segments. Action potentials 'jump' between the nodes of Ranvier, which are gaps in the myelin sheath where voltage-gated Na⁺ and K⁺ channels are concentrated.
Saltatory conduction is faster than continuous conduction because the action potential only needs to be regenerated at the nodes of Ranvier, rather than along the entire axon. This reduces the time and energy required for ion exchange and propagation, making the process more efficient.
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Action Potential
An action potential is a rapid, temporary change in the electrical membrane potential of a neuron, allowing it to transmit signals. It occurs when a neuron reaches a threshold potential, leading to the opening of voltage-gated sodium channels, resulting in depolarization. This is followed by repolarization as potassium channels open, restoring the resting membrane potential.
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03:53
Action Potential
Continuous Conduction
Continuous conduction refers to the slow propagation of action potentials along unmyelinated axons. In this process, the action potential is regenerated at every segment of the axon, leading to a gradual wave of depolarization. This method is less efficient and slower compared to saltatory conduction, as it requires more time for the ion channels to open and close along the entire length of the axon.
Video consigliato:
03:50Types of Propagation: Continuous Conduction
Saltatory Conduction
Saltatory conduction is the rapid transmission of action potentials along myelinated axons, where the action potential jumps between nodes of Ranvier. This occurs because myelin sheaths insulate the axon, preventing ion flow except at these nodes. As a result, saltatory conduction is significantly faster than continuous conduction, as it reduces the time and energy required for the action potential to propagate.
Video consigliato:
03:11Types of Propagation: Saltatory Conduction
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