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The Cortex
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The Cortex

The hypothalamus receives communications, either directly or indirectly, from various portions of the cerebral cortex. Both experimental and clinical evidence indicate that these cortical areas comprise a suprasegmental level for the integration of autonomic functions and the maintenance of a constant internal environment for the body. The term "visceral brain" has been applied to the limbic system. Authorities differ as to just how many structures are included in the so-called limbic system. The limbic lobe, or gyrus fornicatus, is composed of the cingulated gyrus, isthmus, hippocampal gyms, and uncus, but closely related are the subcallosal and retrosplenial gyri, pyriform area, hippocampus, and various subcortical structures including the amygdala and septal nuclei. The insula, medial portion of the temporal lobe, and medial and posterior orbital gyri are also closely allied, although not actually a part of the limbic system.

The hypothalamus receives discharges from all these structures, as well as from certain frontal and temporal lobe areas. No separate cortical centers for parasympathetic and sympathetic control have been established with certainty, and the character of the reaction that follows either stimulation or destruction of these areas is dependent upon the general physiologic state of the organism.

The anatomic pathways responsible for these reactions are not precisely known. For the most part, perhaps, the impulses are relayed to the hypothalamus, either directly or indirectly through the thalamus, but there may also be projection pathways to the autonomic centers in the brain stem and spinal cord that travel in the lateral columns in close relationship with the corticospinal pathways. The sensory portions of the cerebral cortex play a part in relaying impulses to the motor areas; it is well known that visual, auditory, and other stimuli that call forth emotional responses may cause variations in autonomic reactivity with changes in circulatory and respiratory function, bladder disturbances, either sweating or anhidrosis, and pupillary dilation.



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