Page 759 - Atlas of Histology with Functional Correlations

Pars intermedia in humans is rudimentary and in lower vertebrates produces

melanocyte-stimulating hormone

Neurohypophysis

Does not have any secretory cells; secretory neurons are located in

hypothalamus of brain
Has a direct neural connection to hypothalamus via multitude of
unmyelinated axons
Contains axonal hypothalamohypophyseal tract and supportive cells,
pituicytes

Neurons of axons located in supraoptic and paraventricular nuclei of
hypothalamus
Neurons synthesize hormones that are transported in and stored at axon

terminals as Herring bodies
Carrier glycoprotein neurophysin binds to hormones for transport to axon
terminals
Releases two hormones from axon terminals, oxytocin and antidiuretic
hormone (vasopressin)

Oxytocin

Release stimulated by vaginal and cervical distension during labor and
nursing infant

Stimulates contraction of smooth uterine muscles during childbirth
Activates milk ejection in lactating glands by stimulating contraction of
myoepithelial cells

Antidiuretic Hormone

Increases permeability to water in distal convoluted tubules and collecting
ducts of kidney

Creates more concentrated urine after water is reabsorbed from glomerular
filtrate
Is also released during decreased blood volume and increase in blood tonicity
Increased osmotic pressure stimulates osmoreceptors to activate the release

of ADH

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