tailieunhanh - Ebook Color atlas and textbook of human anatomy Vol.3 - Nervous system and sensory organs (5th edition): Part 2

(BQ) Part 2 book "Color atlas and textbook of human anatomy - Nervous system and sensory organs" presents the following contents: Telencephalon, cerebro vascular and ventricular systems, autonomic nervous system, autonomic nervous system, sensory organs, the ear. | 204 Diencephalon Hypothalamus and Hypophysis Diencephalon Neuroendocrine System continued Hypothalamohypophysial System A-D The hypothalamohypophysial tract D consists of the supraopticohypophysical tract and the paraventriculohypophysial tract which originate in the supraoptic nucleus D1 and in the paraventricular nucleus D2 respectively. The fibers run through the hypophysial stalk into the hypophysial posterior lobe where they terminate at the capillaries. The hormones produced by the neurons of both hypothalamic nuclei migrate along this pathway to the axon terminals and enter from here into the bloodstream. Electrical stimulation of the supraoptic nucleus C3 leads to an increased secretion of vasopressin antidiuretic hormone while stimulation of the paraventricular nucleus C4 leads to an increased secretion of oxytocin. In this system the neurons do not release stimulating substances that affect the secretion of a hormone by an endocrine gland such as the glandotropic hormones or releasing factors of the tuberoinfundibular system but they themselves produce hormones that have a direct effect on the target organs effector hormones . The carrier substances to which the hormones are bound during their migration in the axons can be demonstrated histologically. These Gomori-positive substances often cause swellings of the axons Herring bodies B5 . The neurosecretory substances in axons and swellings appear in the electron-microscopic image as granules that are much larger than synaptic vesicles. At the capillaries of the neurohypophysis the axons form club-shaped endings AD6 containing small clear synaptic vesicles in addition to the large granules. At the sites of contact with axon terminals the capillary walls lack the glial covering layer that in the central nervous system forms the boundary between ectodermal and mesodermal tissues and envelops all vessels p. 44 . It is here that the neurosecretory product enters the bloodstream. At the terminal bulbs of the .