Ch2. Hypothalamus

• The hypothalamus and pituitary are responsible for the central control of diverse hormone systems.
• The hypothalamus is a forebrain region that mediates nervous system control of hormone systems.
• Tropic hormone axes in the hypothalamus include hypothalamus => pituitary => peripheral glands.
• Neuroendocrine cells in the hypothalamus direct the release of hormones from hypothalamic neurons.
• Hypothalamic hormones control the function of the adenohypophysis by releasing hormones/factors and releasing inhibiting hormones/factors.
• Hypothalamic hormones are released in the pars nervosa.
• Releasing and release inhibiting hormones are all released into the portal system.
• The Hypothalamus-pituitary axis consists of 14 hypothalamic and pituitary areas.
• ADENO, adenohypophysis; MB, mammillary body; ME, median eminence; OC, optic chiasm; OT, optic tract; PN, pars nervosa are hypothalamic areas involved in endocrine control.
• Different cell types in the pars distalis express different receptors.
• A mixture of releasing hormones controls the release of tropic hormones.
• The suprachiasmatic nucleus is involved in circadian rhythms.
• Endocrine systems serve at least three general functions: control of growth, metabolism and development, broadcasting acute signals from the nervous system, and homeostasis -- maintaining body fluids within appropriate ranges.
• The mammalian pituitary consists of two major parts: Adenohypophysis (Anterior pituary) and Neurohypophysis (posterior pituitary).
• Vasopressin increases thirst.
• High doses of vasopressin cause contraction of arterioles and increase blood pressure.
• Release of vasopressin is inhibited by atrial natriuretic peptide (ANP) and ethyl alcohol.
• When osmolarity declines, osmosensors in the collecting duct no longer active, leading to a decrease in vasopressin release.
• Vasopressin increases water reabsorption in collecting ducts of kidney, a process known as tubular antidiuresis, by activation of aquaporins by phosphorylation and increased synthesis of aquaporins.
• ADH/vasopressin acts on the cells of the collecting duct to increase water permeability, leading to more concentrated urine and more water retention.
• A nose spray of oxytocin was shown to make lions more tolerant and less aggressive toward other lions.
• ADH/vasopressin also acts on the brain to increase thirst, leading to more water intake.
• Oxytocin causes rhythmic contractions of the reproductive tract, including uterus, fallopian tubes, and ovaries, leading to labor and birth.
• Oxytocin induces contraction of the mammary gland, stimulated by neuroendocrine reflex triggered by suckling, leading to milk ejection.
• Nonapeptides can also affect behavior, with prairie voles being monogamous and forming lifelong pair bonds, while meadow voles do not form stable pair bonds.
• Oxytocin even makes fierce lions friendlier.
• Oxytocin is implicated in pair bonding between mates, parents and offspring, and conspecifics.
• Vasopressin is involved in water homeostasis.
• Adenohypophysis (Anterior pituary) is derived from neural ridge (neuroectoderm) and Neurohypophysis (posterior pituitary) is derived from diencephalon (brain).
• Vasopressin, also known as antidiuretic hormone, acts to lower osmolatity by increasing water intake and retention.
• The nonapeptide hormones are neutral and basic.
• Vasopressin, also known as antidiuretic hormone, is synthesized in the supraoptic nucleus (SON) of the hypothalamus.
• The molecular weight of Oxytocin and antidiuretic hormone is ±1000, and they bind to G-protein coupled receptors.
• Water homeostasis is regulated by vasopressin, also known as antidiuretic hormone.
• The nonapeptide hormones include Oxytocin and antidiuretic hormone, also known as vasopressin.
• Oxytocin and antidiuretic hormone are synthesized in the SON and PVN hypothalamus.
• There are two genes that encode for Oxytocin and antidiuretic hormone, one is prepropressophysin and the other is preprooxyphysin.
• Melanotropin (MSH) reduces food intake.
• The Rosine kinase pathway, a key effector of which is PI3 kinase, plays a role in the regulation of growth hormone (GH) excess and deficiency.
• GH deficiency can cause dwarfism in childhood and primary pituitary dwarfism in adulthood.