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Ch. 13 The Peripheral Nervous System
All textbooksErin C. Amerman 2nd EditionCh. 13 The Peripheral Nervous SystemProblem 12.12a
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Chapter 13, Problem 12.12a

Fill in the blanks: The tracts of the posterior columns decussate in the_____, whereas the tracts of the anterolateral system decussate in the _____.

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Identify the two main sensory pathways mentioned: the posterior columns and the anterolateral system.
Understand that 'decussate' means to cross over to the opposite side of the central nervous system.
Recall that the posterior columns, also known as the dorsal columns, carry fine touch, vibration, and proprioceptive information.
Remember that the decussation of the posterior columns occurs in the medulla oblongata.
Recognize that the anterolateral system, which includes the spinothalamic tract, carries pain and temperature sensations and decussates at the level of the spinal cord.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Decussation

Decussation refers to the crossing over of nerve fibers from one side of the central nervous system to the other. This process is crucial for the integration of sensory and motor pathways, allowing the brain to process information from the opposite side of the body. Understanding where decussation occurs helps in localizing neurological functions and understanding the pathways of sensory information.

Posterior Columns

The posterior columns, also known as the dorsal columns, are a major sensory pathway in the spinal cord responsible for transmitting fine touch, vibration, and proprioceptive information. These tracts ascend to the brainstem, where they decussate at the medulla oblongata before reaching the thalamus and ultimately the sensory cortex. Knowledge of this pathway is essential for understanding how sensory information is processed and perceived.
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Anterolateral System

The anterolateral system, which includes the spinothalamic tract, is responsible for transmitting pain, temperature, and crude touch sensations. Unlike the posterior columns, the fibers of the anterolateral system decussate at the level of the spinal cord shortly after entering. This system is vital for understanding how the body perceives and responds to potentially harmful stimuli.
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Related Practice
Textbook Question

Match each type of neuroglial cell with its correct function.     ​​​​


____Schwann cells    ​​​​

____Ependymal cells     

____Microglial cells    ​​​​

____Oligodendrocytes     

____Satellite cells    ​​​​

____Astrocytes


a. Phagocytic cells of the CNS

b. Surround the cell bodies of neurons in the PNS

c. Create the myelin sheath in the PNS

d. Anchor neurons and blood vessels, maintain extracellular environment around neurons, assist in repair of damaged brain tissue

e. Create the myelin sheath in the CNS

f. Ciliated cells in the CNS that produce and circulate the fluid around the brain and spinal cord

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Textbook Question

Mark the following statements about the spinal cord as true or false. If a statement is false, correct it to make a true statement.


e. The corticospinal tracts are the main sensory tracts in the spinal cord.

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Textbook Question

Which parts of the body have the greatest amount of space dedicated to them in the primary somatosensory cortex? Why?

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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

Fill in the blanks: The cell bodies of upper motor neurons reside in the_____and function to_____, whereas the cell bodies of lower motor neurons reside in the_____and function to_______.

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