Questions and Answers
What is the most likely source of a specimen with numerous GFAP-positive cells?
Which structure transports water from capillaries directly into the cerebrospinal fluid within the choroid plexus?
What term is used to describe collections of neuronal cell bodies within the central nervous system?
Which of the following structures is primarily involved in cerebrospinal fluid production?
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Which type of matter is primarily found in the outer layer of the brain and contains myelinated axons?
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What type of connective tissue layer surrounds Schwann cells in peripheral nerves?
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What is the role of the epineurium in peripheral nerves?
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What structure provides a blood-nerve barrier in peripheral nerves?
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What is the function of the anterior root of spinal nerves?
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Which type of fibers do afferent fibers represent in peripheral nerves?
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Which of the following best describes the function of the posterior root in spinal nerves?
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What defines nerves that possess only sensory fibers?
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What is the composition of peripheral nerves primarily made of?
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What is the outermost layer of connective tissue surrounding a large peripheral nerve called?
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What is the main function of the peripheral nervous system?
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What is meant by the term 'fascicle' in the context of peripheral nerves?
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In relation to peripheral nerves, what happens to major dense lines in Lanterman clefts?
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Where are peripheral nerves primarily located?
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What role do intrafusal muscle fibers play in relation to muscle spindles?
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Which of the following statements about muscular spindles is true?
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What is the function of the annulospiral and flower spray endings associated with muscle spindles?
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What type of muscle fibers are involved in the contraction process after the impulse reaches the spinal cord?
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Which characteristic of muscle spindles is most crucial for their function as mechanoreceptors?
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How do physiological reflexes differ from pathological reflexes?
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Which of the following is most accurate regarding the response mediated by muscle spindles?
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What is the primary reason that reflexes exist during intrauterine life?
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What structure interrupts the Myelin sheath at regular intervals?
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What is the approximate length of each segment of the Myelin sheath?
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How many axons can one Schwann cell myelinate?
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What is the primary composition of the Myelin sheath?
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What characteristic of the Myelin sheath is revealed by high-magnification Transmission Electron Microscopy (TEM)?
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Which of the following is a unique feature of Schwann cells compared to oligodendrocytes?
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Which part of the Schwann cell is responsible for fusing the layers of the Myelin sheath?
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What do the major dense lines of the Myelin sheath represent?
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Study Notes
Peripheral Nervous System (PNS) Structure
- Peripheral nerves are covered by a dense, irregular fibrous coat known as the epineurium, which fills the space between fascicles.
- Very small nerves consist of a single fascicle, while small nerves exhibit a winding disposition within connective tissue.
- Peripheral nerves connect different ganglia, facilitating communication between the central nervous system (CNS) and sense organs or effectors (muscles and glands).
- Contain both afferent (sensory) and efferent (motor) fibers, allowing transmission of signals to and from the CNS.
Myelin Sheath and Axonal Structure
- Myelinated nerve fibers are surrounded by a segmented myelin sheath, which is interrupted by Nodes of Ranvier, measuring 0.5 to 1.0 mm each.
- Each Schwann cell produces a myelin sheath for only one axon, in contrast to oligodendrocytes in the CNS.
- Myelin is a lipoprotein complex composed mainly of lipid bilayers and membrane proteins, important for efficient signal conduction.
- Endoneurium, a thin connective tissue layer, surrounds Schwann cells, while perineurium encases groups of axons creating a blood-nerve barrier.
- Epineurium is the outermost dense connective tissue layer surrounding the entire nerve.
Spinal Nerves and Functions
- Humans have 31 pairs of spinal nerves, each connecting to the spinal cord via anterior (efferent) and posterior (afferent) roots.
- Anterior root conducts motor impulses, while the posterior root contains sensory fibers conveying information to the CNS with cell bodies in the dorsal root ganglion (DRG).
Neuromuscular Spindles
- Muscular spindles, located in skeletal muscles, vary in size from 1 to 4 mm and are surrounded by a fusiform capsule of connective tissue.
- Comprised of intrafusal muscle fibers within the capsule and extrafusal muscle fibers outside.
- Trigger reflex responses by synapsing with alpha motor neurons in the spinal cord; important for muscle contraction.
- Two types of reflexes exist: physiological (normal) and pathological (abnormal).
Cerebrospinal Fluid (CSF) Circulation
- The arachnoid mater contains trabeculae that support the flow of cerebrospinal fluid (CSF).
- Ependymal cells in the choroid plexus assist in the transport of water from capillaries to form CSF.
Neuronal Structures
- Collections of neuronal cell bodies in the central nervous system are referred to as nuclei, while similar structures in the peripheral nervous system are called ganglia.
- AGFAP-positive cells indicate a region of gray matter, highlighting glial cell presence in neural tissue.
Study Questions Overview
- Each question provides insight into the understanding of structure functions within the CNS and PNS, including definitions of tissue types and roles of specific structures regarding fluid transport and neuronal organization.
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Description
This quiz covers the structure and role of the peripheral nervous system (PNS), focusing on its protective and mediating functions. Understand key terms such as epineurium and fascicles while exploring how the PNS connects the outside environment to the central nervous system.
