Sympathetic nervous system segmentalization

The adrenal gland is located on the upper segment of the kidney (Fig. 42-1). It consists of an outer cortex and an inner medulla. The adrenal medulla secretes the catecholamines epinephrine (also called adrenaline) and norepineprhine (also called noradrenaline), which are involved in regulation of the sympathetic nervous system. The adrenal cortex consists of three histologically distinct zones zona glomerulosa, zona fasciculata, and an innermost layer called the zona reticularis. Each zone is responsible for production of different hormones (Fig. 42-2). 

Neurologic pathways in the sympathetic nervous system originate from the thoracic (T1 to T12) and the upper lumbar segments (LI and L2) of the spinal cord. Neurologic pathways in the parasympathetic nervous system originate from cranial nerves III, VII, IX, and X, from the brainstem, and the sacral segments S2, S3, and S4 from the spinal cord. This is why the parasympathetic nervous system is also known as the craniosacral division of the autonomic nervous system. 

The hypothalamus has two distinct segments, one concerning bodily activation to cope with environmental demands and the other concerned with the reduction of bodily activation to allow for recuperation. Continuous dominance of the arousal segment is associated with chronic anxiety dominance of the inhibitory segments is associated with depression. These two segments are associated with the two sections of the autonomic nervous system, arousal with the sympathetic section and inhibition with the parasympathetic section. Thus the hypothalamus forms the starting point of the two sections of the... 

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