Autonomic Nervous System Dysfunction After Spinal Cord Injury

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The autonomic nervous system (ANS) plays a key role in the regulation of many physiologic processes, mediated by supraspinal control from centers in the central nervous system. The role of autonomic dysfunction in persons with spinal cord injuries is crucial to understand because many aspects of the altered physiology seen in these individuals are directly caused by ANS dysregulation.

Section snippets

Autonomic nervous system anatomy

The ANS has two components or divisions that may be disrupted as a result of damage to the spinal cord, the parasympathetic nervous system (PNS) and the sympathetic nervous system (SNS). The enteric nervous system, also considered a division of the ANS, is not directly disrupted after SCI. The level and extent of injury to the spinal cord determines the dysfunction that occurs. A thorough understanding of the anatomy is important in predicting the types of alterations in function that will

Autonomic nervous system physiology

The autonomic nervous system regulates all essential physiologic components of circulation including heart rate, stroke volume, and vascular resistance, which, in turn, determine arterial blood pressure and cardiac output. The autonomic nervous system regulates these functions in response to feedback from afferent pathways by affecting the force and frequency of cardiac contraction and vasodilation or vasoconstriction. Other influences have a role in the final physiologic state, including

Autonomic nervous system control of thermoregulation

Thermoregulatory responses depend on cold and warm sensors in the hypothalamus and the skin but also on input from mesencephalic, medullary, spinal, and intra-abdominal temperature sensors [2], [10]. Afferent fibers from the peripheral receptors with cell bodies in the dorsal root ganglia enter the spinal cord and ascend contralaterally to the medial lemniscus and the thalamus and then project further to the hypothalamus [2], [11]. The preoptic area of the hypothalamus controls the thermal

Alterations in autonomic nervous system function after spinal cord injury

Spinal cord injury results in a reduction or lack of autonomic control that is directly related to the level of injury. Spinal cord injury interrupts the connections between the supraspinal regulatory centers and the effector organs and interferes with both afferent and efferent signal transmission. Many of the major cardiovascular functions are associated with segmental outflow from several levels, such as the outflow to the heart or the splanchnic outflow. Sympathetic control of blood vessels

Cardiovascular alterations immediately after spinal cord injury

In the first few minutes after SCI, there is a disruption in central sympathetic control caused by interruption of the descending pathways that travel in the spinal cord. Animal studies have found that within seconds to minutes after injury, there is a systemic pressor response that results from a burst of sympathetic activity and outflow of adrenaline from the adrenal glands [25]. In the feline model of SCI, compression of the cervical spinal cord causes a brief increase in both systolic and

Summary

The autonomic nervous system plays a key role in the regulation of many physiologic processes mediated by supraspinal control from centers in the CNS. Spinal cord injury is associated with alterations in autonomic regulation, with level of injury playing a key role in the subsequent derangements that occur. Above T1, SCI causes a complete disruption of the sympathetic pathways and results in a variety of problems including bradycardia, neurogenic pulmonary edema, arrhythmias, and hypotension.

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