Textbook Question
The lower motor neurons that innervate contractile skeletal muscle fibers are called:
a. α-motor neurons
b. β-motor neurons
c. upper motor neurons
d. γ-motor neurons
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Ch. 13 The Peripheral Nervous System
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822
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Table of contents
- Ch. 1 Introduction to Anatomy and Physiology26
- Ch. 2 The Chemistry of Life38
- Ch. 3 The Cell55
- Ch. 4 Histology47
- Ch. 5 The Integumentary System30
- Ch. 6 Bones and Bone Tissue36
- Ch. 7 The Skeletal System40
- Ch. 8 Articulations19
- Ch. 9 The Muscular System36
- Ch. 10 Muscle Tissue and Physiology29
- Ch. 11 Introduction to the Nervous System and Nervous Tissue28
- Ch. 12 The Central Nervous System42
- 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 Heart30
- Ch. 18 The Cardiovascular System II: The Blood Vessels43
- Ch. 19 Blood32
- Ch. 20 The Lymphatic System and Immunity45
- 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
Chapter 13, Problem 13
Which parts of the body have the greatest amount of space dedicated to them in the primary somatosensory cortex? Why?
Verified step by step guidance1
Understand the primary somatosensory cortex: It is located in the postcentral gyrus of the brain and is responsible for processing sensory information from the body, such as touch, pressure, pain, and temperature.
Learn about the sensory homunculus: The primary somatosensory cortex is organized in a way that reflects the sensory input from different parts of the body. This organization is represented by the sensory homunculus, a distorted map of the body where the size of each body part corresponds to the amount of cortical space dedicated to it.
Identify the body parts with the greatest cortical representation: The hands, fingers, lips, and tongue have the largest areas dedicated to them in the primary somatosensory cortex. This is because these parts are highly sensitive and require fine sensory discrimination.
Understand the reason for this distribution: The amount of cortical space is proportional to the density of sensory receptors in a body part. Areas like the hands and lips have a high concentration of mechanoreceptors, which are specialized for detecting fine touch and texture, necessitating more cortical processing power.
Relate this to functional importance: The hands and lips are crucial for tasks requiring precision, such as manipulating objects or speaking. The brain allocates more resources to these areas to ensure accurate sensory input and control, which is vital for survival and interaction with the environment.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Primary Somatosensory Cortex
The primary somatosensory cortex (S1) is a region of the brain located in the postcentral gyrus, responsible for processing sensory information from the body. It receives input from the thalamus and is organized in a topographical manner, meaning different body parts are represented in specific areas. This organization allows for the perception of touch, temperature, pain, and proprioception.
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Primary Motor Cortex & Primary Somatosensory Cortex
Somatotopic Organization
Somatotopic organization refers to the mapping of the body's surface onto the brain, particularly in the somatosensory cortex. This means that areas of the cortex correspond to specific body parts, with larger areas allocated to regions with higher sensory acuity, such as the hands and face. This organization is often illustrated by the 'homunculus,' a visual representation showing the relative size of cortical areas dedicated to different body parts.
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05:04The Levels of Organization
Sensory Acuity
Sensory acuity is the ability to perceive and discriminate sensory stimuli with precision. Body parts with higher sensory acuity, like the fingertips and lips, have more sensory receptors and thus require more cortical space in the primary somatosensory cortex. This increased representation allows for finer tactile discrimination and greater sensitivity in these areas, which is crucial for tasks requiring detailed sensory feedback.
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Related Practice
Textbook Question
______detect the degree to which a muscle is stretched, whereas______detect the force of a muscle contraction.
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Textbook Question
How do upper and lower motor neurons differ?
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Textbook Question
The tracts of the posterior columns decussate in the ________, whereas the tracts of the anterolateral system decussate in the ________.
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Textbook Question
Which of the following statements is false?
a. The spinothalamic tracts are part of the anterolateral system.
b. Pain, temperature, and crude touch stimuli are carried by the anterolateral system.
c. Descending pathways from the brain and spinal cord can make the spinal cord less receptive to pain stimuli.
d. The thalamus serves as the 'gateway' for entry of all special sensory stimuli into the cerebral cortex, with the exception of audition (hearing).
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Textbook Question
List and describe the basic steps involved in producing movement, beginning with the upper motor neurons in the cerebral cortex.
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