3) Corticotrophin Releasing Hormone is released by the paraventricular nucleus and taken up by the portal system where it has its action on the anterior lobe of the pituitary. A recent, interesting development is the finding of a direct projection from the eye to the suprachiasmatic nucleus of the supraoptic hypothalamic region.
4) The median eminence—the bulge from which the infundibulum extends to the anterior pituitary . In the median eminence, a dense network of capillaries arises from the superior hypophyseal arteries. These capillaries drain into portal vessels that traverse the pituitary stalk and then form a capillary network within the anterior pituitary gland. The primary direction of this hypophyseal portal system is from hypothalamus to pituitary, however, retrograde flow also exists. This creates an ultrashort feedback loop between the pituitary gland and hypothalamic neurons.
5) The mammillary or posterior region at the level of the mammillary bodies [What does it secrete?]
sexually dimorphic nucleus (SDN, intermediate nucleus, INAH-1),
suprachiasmatic nucleus (SCN)
tuberal lateral nucleus (NTL).
The hypothalamus regulates body functions that vary at different times of the day (e.g., body temperature, hormone secretion, hunger) or those that vary over a period of many days (e.g., menstrual cycle). A projection from the retina to the suprachiasmatic nucleus is thought to supply the clock with day-night information needed for synchronizing diurnal (daily) rhythms (also known as circadian rhythms). Lesions of the hypothalamus often disrupt the state of the sleep-waking cycle.
This neural region is associated with hormonally related behaviour (anger and sexual activity), homeostatic regulation (blood pressure, heart rate, appetite, and temperature) and functions that relate to both (puberty, reproductive cycles, and lactation). The hypothalamus is a small part of the diencephalon that is involved
in the mediation of endocrine, autonomic and behavioral functions.book whenever the specific hormone systems to which they belong are described. Several neuropeptides have been isolated from the hypothalamus, and many continue to be discovered. However, only those that have been demonstrated to control anterior pituitary function (hypophysiotropic hormones) and, therefore, play an important role in endocrine physiology will be discussed.
GnRH is a small peptide produced in the hypothalamus by specialized nerve cells; as such, GnRH is called a neurohormone, a class of hormones that include thyrotropin-releasing hormone, oxytocin (see below), antidiuretic hormone (Chapter 18), and corticotropin-releasing hormone. Release of GnRH results in activation of a specific GnRH receptor, located in the gonadotropes of the pituitary gland. This receptor is a membrane-bound G-protein-coupled stimulator of phospholipase C, which results in calcium release and protein kinase C activation via conversion of plasma membrane phosphatidylinositol into inositol triphosphate and diacylglycerol (Chapter 8). These signals result in production and release of FSH and LH, as will be described below. Regulation of this important signal is multifold. GnRH is degraded within minutes so it is constantly produced in pulses, and the size and frequency of these pulses is important in signaling. These GnRH pulses are constant in males but vary in females, depending on the menstrual cycle. Interestingly, the frequency of the GnRH pulses result in different expression of FSH (low frequency) and LH (high frequency). As a result FSH and LH are variably expressed during the female menstrual period (Figure 20-2). Levels of testosterone, estrogen, and prolactin (increased during pregnancy) as well as increased concentration of FSH and LH create a negative feedback loop, which can decrease GnRH pulses.
(2) involved in temperature regulation, homeostatic regulation (blood pressure, heart rate, appetite, and temperature
(3) control of food and water intake (thirst),
4) sexual behavior and reproduction
(5) control of daily cycles in physiological state and behavior
(6) mediation of emotional responses,such as anger
(7) controls functions that relate to both (puberty, reproductive cycles, and lactation).
[They are closely related because of the portal system of blood supply. The superior, medial, and inferior hypophyseal arteries provide arterial blood supply to the median eminence and the pituitary. ]
UPDATE as of June 27, 2020