BIOS 252 Week 3 Case Study: CNS-PNS

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Chamberlain University

BIOS-252: Anatomy & Physiology II with Lab

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Date

Overview of Paraplegia

Definition of Paraplegia

Paraplegia is a medical condition characterized by the inability to voluntarily move the lower parts of the body. This paralysis can impact the trunk, legs, and pelvic organs. The loss of motor function is typically due to damage in the spinal cord or associated neural pathways.

Reflex Pathway: Components and Function

Parts of a Basic Reflex Pathway

The reflex pathway is a neural circuit responsible for automatic responses to stimuli. It comprises the following components:

Component	Description
Sensor	Somatic receptors in the skin, muscles, and tendons that detect stimuli.
Sensory Neuron	Afferent nerve fibers transmit signals from somatic receptors to the posterior horn of the spinal cord or brainstem.
Control Center	Integrating center in the spinal cord or brainstem where neurons in gray matter synapse.
Motor Neuron	Efferent nerve fibers carry motor nerve signals from the anterior horn to target muscles.
Effector Muscle	Muscle innervated by the efferent nerve fiber executes the response.

Babinski’s Sign: Implications and Diagnostic Use

Description of Babinski’s Sign

Babinski’s sign is a diagnostic tool used to assess the integrity of the corticospinal tract (CST). It is elicited by stimulating the sole of the foot with a blunt instrument. A normal response involves downward flexion of the hallux (big toe). However, an upward extension of the hallux is indicative of Babinski’s sign, which can signal damage to the CST.

Comparison to Normal Response

In healthy individuals, the plantar reflex leads to the downward motion of the hallux. Conversely, Babinski’s sign is typically associated with CNS pathology, such as upper motor neuron lesions. While this reflex is a normal primitive response in infants, its presence in adults suggests abnormal neural function.

Clinical Implications of Babinski’s Sign

The Babinski reflex serves as an early indicator of CST damage, which can result from conditions such as spinal cord injury or stroke. The presence of this reflex often necessitates advanced diagnostic imaging, including CT or MRI, and may warrant further studies, such as cerebrospinal fluid analysis, to identify the underlying cause.

Significance in Neurological Assessments

Distinction from First-Order Neuron Damage

Babinski’s sign specifically tests the CST, a descending pathway that connects the cerebral cortex to the spinal cord. Damage to the CST disrupts this tract’s ability to coordinate motor function. This reflex is distinct from first-order neuron damage, which would result in different clinical manifestations, such as diminished reflexes or muscle atrophy.

BIOS 252 Week 3 Case Study: CNS-PNS

Potential Locations of CST Lesions

Lesions associated with Babinski’s sign are typically found in the descending CST fibers. These fibers originate in the cerebral cortex and travel through the brainstem and spinal cord before synapsing with alpha motor neurons. Damage in this pathway disrupts motor coordination, leading to the pathological reflex.

References

Acharya AB, Jamil RT, Dewey JJ. Babinski Reflex. [Updated 2022 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: NIH

CK-12. (2014, November 13). Reflexes: Neurons in Action. Retrieved from CK-12 Human Biology

Wikipedia contributors. (2022, June 12). Reflex arc. Wikipedia, The Free Encyclopedia. Retrieved from Wikipedia