hypothalamus

Examples of hypothalamus in the following topics:

• Control of the Pituitary Gland by the Hypothalamus

  • The pituitary gland consists of two components: the anterior pituitary and the posterior pituitary, and is functionally linked to the hypothalamus by the pituitary stalk (also named the infundibular stem, or simply the infundibulum).
  • Whilst the pituitary gland is known as the master endocrine gland, both of the lobes are under the control of the hypothalamus: the anterior pituitary receives its signals from the parvocellular neurons, and the posterior pituitary receives its signals from magnocellular neurons.
  • The anterior lobe of the pituitary receives hypothalamic-releasing hormones from the hypothalamus that bind with receptors on endocrine cells in the anterior pituitary that regulate the release of adrenal hormones into the circulatory system.
  • Hormones from the hypothalamus are rapidly degraded in the anterior pituitary, which prevents them from entering the circulatory system.
  • The posterior lobe of the pituitary gland develops as an extension of the hypothalamus.

• Hypothalamus

  • The hypothalamus serves as a gateway between the nervous system and endocrine system.
  • The hypothalamus is located below the thalamus just above the brain stem.
  • All vertebrate brains contain a hypothalamus.
  • The hypothalamus functions as a type of thermostat for the body.
  • Also, the hypothalamus of homosexual men and heterosexual women both respond to testosterone.

• Hypothalamic-Pituitary Axis

  • The hypothalamus in vertebrates integrates the endocrine and nervous systems.
  • The hypothalamus is an endocrine organ located in the diencephalon of the brain.
  • It is attached to the hypothalamus via a stalk called the pituitary stalk (or infundibulum) .
  • It is a part of the brain, extending down from the hypothalamus, and contains mostly nerve fibers and neuroglial cells which support axons that extend from the hypothalamus to the posterior pituitary.
  • They are released into the circulatory system via neural signaling from the hypothalamus.

• Overview of the Pituitary Gland

  • The pituitary gland is connected to the hypothalamus and secretes nine hormones that regulate body homeostasis.
  • It protrudes off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity.
  • The pituitary is functionally connected to the hypothalamus by a small tube called the infundibular stem, or, pituitary stalk.
  • The anterior pituitary receives signaling molecules from the hypothalamus, and in response, synthesizes and secretes seven important hormones including thyroid-stimulating hormone and growth hormone.
  • The posterior pituitary does not produce any hormones of its own, rather, it stores and secretes two hormones made in the hypothalamus—oxytocin and anti-diuretic hormone.

• The Endocrine System and Hunger

  • Hunger is controlled by the hypothalamus and hormones.
  • The hypothalamus regulates the body's physiological homeostasis.
  • In the 1940s, the "dual-center" model, which divided the hypothalamus into hunger (lateral hypothalamus) and satiety (ventromedial hypothalamus) centers, was popular.
  • This theory developed from the findings that bilateral lesions of the lateral hypothalamus can cause anorexia, a severely diminished appetite for food, while bilateral lesions on the ventromedial hypothalamus can cause overeating and obesity.
  • When blood sugar levels fall, the hypothalamus is stimulated.

• The Posterior Pituitary

  • The posterior pituitary consists mainly of neuronal projections (axons) extending from the supraoptic and paraventricular nuclei of the hypothalamus.
  • The posterior pituitary is derived from the hypothalamus and is distinct from the more fleshy, vascularized anterior lobe.
  • The posterior pituitary stores two hormones secreted by the hypothalamus for later release:
  • Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus.
  • Antidiuretic hormone (ADH, also known as vasopressin), the majority of which is released from the supraoptic nucleus in the hypothalamus.

• Regulation of Water Intake

  • Thirst is a sensation created by the hypothalamus, the "Thirst Center" of the human body.
  • An osmoreceptor is a sensory receptor, primarily found in the hypothalamus of most homeothermic organisms, that detects changes in osmotic pressure.
  • When the osmoreceptors detect high plasma osmolarity (often reperesenting a low blood volume), they send signals to the hypothalamus, which creates the biological sensation of thirst, and also stimulates vasopressin (ADH) secretion, which starts the events that will reduce plasma osmolarity to normal levels.
  • The macula densa cells in the walls of the ascending loop of henle of the nephron is another type of osmoreceptor, however it stimulates the juxtaglomerular apparatus (JGA) instead of the hypothalamus.
  • Angiotensin II acts on the hypothalamus to cause the sensation of thirst.

• Control of Thyroid Hormone Release

  • TSH release, in turn, stimulates the hypothalamus to secrete thyrotropin-releasing hormone (TRH).
  • Thyroid hormones also provide negative feedback to the hypothalamus and anterior pituitary gland.
  • Thyroid hormones are produced from the thyroid under the influence of thyroid-stimulating hormone (TSH) from the anterior pituitary gland, which is itself under the control of thyroptropin-releasing hormone (TRH) secreted by the hypothalamus.

• Control of Hormone Secretion

  • Briefly, neurons in the hypothalamus secrete thyroid-releasing hormone that stimulate cells in the anterior pituitary to secrete thyroid-stimulating hormone.
  • When the blood concentration of thyroxine rises above the ideal value as detected by sensory neurons, the hypothalamus is signaled to stop thyroid-releasing hormone production, which eventually lowers the levels of thyroxine in the blood.
  • When these drop below the ideal value the hypothalamus is signaled to begin secreting thyroid-releasing hormone again.
  • During birth, as the baby moves through the birth canal, pressure receptors within the cervix signal the hypothalamus to stimulate the pituitary to secrete oxytocin.

• Brain: Midbrain and Brain Stem

  • Below the thalamus is the hypothalamus.
  • This relationship means that the hypothalamus regulates important behaviors that are controlled by these hormones.
  • The hypothalamus is the body's thermostat: it makes sure key functions like food and water intake, energy expenditure, and body temperature are kept at appropriate levels.
  • Neurons within the hypothalamus also regulate circadian rhythms, sometimes called sleep cycles.
  • It plays a role in memory formation and includes parts of the thalamus and hypothalamus as well as the hippocampus.