Central Autonomic Connections. There probably are no purely autonomic or somatic centers of integration, and extensive overlap occurs. Somatic responses always are accompanied by visceral responses, and vice versa. Autonomic reflexes can be elicited at the level of the spinal cord. They clearly are demonstrable in experimental animals or humans with spinal cord transection and are manifested by sweating, blood pressure alterations, vasomotor responses to temperature changes, and reflex emptying of the urinary bladder, rectum, and seminal vesicles. Extensive central ramifications of the autonomic nervous system exist above the level of the spinal cord. For example, integration of the control of respiration in the medulla oblongata is well known. The hypothalamus and the STN generally are regarded as principal loci of integration of autonomic nervous system functions, which include regulation of body temperature, water balance, carbohydrate and fat metabolism, blood pressure, emotions, sleep, respiration, and reproduction. Signals are received through ascending spinobulbar pathways, the limbic system, neostriatum, cortex, and to a lesser extent other higher brain centers. Stimulation of the STN and the hypothalamus activates bulbospinal pathways and hormonal output to mediate autonomic and motor responses The hypothalamic nuclei that lie posteriorly and laterally are sympathetic in their main connections, whereas parasympathetic functions evidently are integrated by the midline nuclei in the region of the tuber cinereum and by nuclei lying anteriorly.
The CNS can produce a wide range of patterned autonomic and somatic responses from discrete activation of sympathetic or parasympathetic neurons to more generalized activation of these nerves with highly integrated patterns of response. There are highly differentiated patterns of activity during a wide range of physiological conditions consistent with the need for modulation of different organ functions. There is evidence for organotropical organization of neuronal pools at multiple levels of the CNS that generate these various patterns of sympathetic and parasympathetic responses. The pattern generators at these different levels of the neuroaxis are often organized in a hierarchical manner that allows individual response or larger responses made up of multiple individual units.
As mentioned earlier, highly integrated patterns of response generally are organized at a hypothalamic level. These integrated patterns of response involve autonomic, endocrine, and behavioral components. On the other hand, more limited patterned responses are organized at other levels of basal forebrain, brainstem, and spinal cord.
The CNS can produce a wide range of patterned autonomic and somatic responses from discrete activation of sympathetic or parasympathetic neurons to more generalized activation of these nerves with highly integrated patterns of response. There are highly differentiated patterns of activity during a wide range of physiological conditions consistent with the need for modulation of different organ functions. There is evidence for organotropical organization of neuronal pools at multiple levels of the CNS that generate these various patterns of sympathetic and parasympathetic responses. The pattern generators at these different levels of the neuroaxis are often organized in a hierarchical manner that allows individual response or larger responses made up of multiple individual units.
As mentioned earlier, highly integrated patterns of response generally are organized at a hypothalamic level. These integrated patterns of response involve autonomic, endocrine, and behavioral components. On the other hand, more limited patterned responses are organized at other levels of basal forebrain, brainstem, and spinal cord.
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