Brain regions brainstem

Figure 1.8 Some basic neuronal systems. The three different brain areas shown (I, II and III) are hypothetical but could correspond to cortex, brainstem and cord while the neurons and pathways are intended to represent broad generalisations rather than recognisable tracts. A represents large neurons which have long axons that pass directly from one brain region to another, as in the cortico spinal or cortico striatal tracts. Such axons have a restricted influence often only synapsing on one or a few distal neurons. B are smaller inter or intrinsic neurons that have their cell bodies, axons and terminals in the same brain area. They can occur in any region and control (depress or sensitise) adjacent neurons. C are neurons that cluster in specific nuclei and although their axons can form distinct pathways their influence is a modulating one, often on numerous neurons rather than directly controlling activity, as with A . Each type of neuron and system uses neurotransmitters with properties that facilitate their role...

Orexin neurons innervate all the major brain regions implicated in the generation of wakefulness including the aminergic and cholinergic brainstem... 

The brain, like the seminal vesicles, is able to reduce testosterone to 5a-dihydrotestosterone (DHT) and, like the placenta, the brain aromatizes testosterone to estradiol (Fig. 52-4). Neither conversion occurs equally in all brain regions. The aromatization reaction is discussed below. Regional distribution of 5a-reductase activity toward testosterone in rat brain reveals that the highest activity is found in the midbrain and brainstem, intermediate activity is found in the hypothalamus and thalamus, and the lowest activity is found in the cerebral cortex [1]. The pituitary has higher 5a-reductase activity than any region of the brain, and its activity is subject to changes as... 

A global view of consciousness is that it is generated throughout the entire brain, as a result of synchronisation of relevant neural networks. Specific systems or regions—for example the cerebral cortex, brainstem reticular formation and thalamic nuclei—may be key anatomical integrators. Areas with the most widespread interconnections are pivotal, and on this basis the cortex and thalamus are more relevant than cerebellum and striatum for example. Frontal cortex for example connects with every other brain region, both in terms of input and output, with 80% of such connections accounted for by cortico-cortical connections. Thalamic intralaminar nuclei are, in conjunction with the reticular nucleus, reciprocally connected to all cortical areas. By contrast the cerebellum has very few output pathways and striatal-cortical input is (via the thalamus) confined to frontal lobe. 

The main source of serotonin (5-HT) is the enterochromaffin cells, which release it as tissue hormone either into the gut lumen or the portal vein circulation. In the CNS, cell bodies of 5-HT-containing neurons are concentrated along the raphe nuclei of the brainstem and are also found in more lateral regions and in the reticular formation. The neurons terminate in almost all brain regions and in the spinal cord. 

---