hypothalamus

Examples of hypothalamus in the following topics:

• 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.

• 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.

• Hormonal Regulation of the Reproductive System

  • Male and female gonads are regulated by FSH and LH from the pituitary; their production is stimulated by GnRH, secreted by the hypothalamus.
  • Oxytocin release is stimulated by the suckling of an infant, which triggers the synthesis of oxytocin in the hypothalamus and its release into circulation at the posterior pituitary.
  • GnRH, secreted by the hypothalamus, stimulates the production of FSH and LH from the pituitary gland.
  • Hormonal regulation of the female reproductive system involves hormones from the hypothalamus, pituitary, and ovaries.
  • GnRH secreted by the hypothalamus stimulates the release of FSH, which stimulates the growth of egg cells, and LH, which signals for the the ovulation of an egg from its follicle.

• Humoral, Hormonal, and Neural Stimuli

  • For example, the hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland.
  • As blood concentrations of T3 and T4 rise, they inhibit both the pituitary and the hypothalamus in a negative feedback loop.
  • The hypothalamus stimulates the anterior pituitary gland, via hormones, to release thyroid-stimulating hormone (TSH).

• Hormonal Regulation of the Excretory System

  • The water concentration of the body is monitored by osmoreceptors in the hypothalamus, which detect the concentration of electrolytes in the extracellular fluid.
  • The posterior pituitary is an extension of the hypothalamus.
  • It is composed largely of neurons that are continuous with the hypothalamus.
  • The hypothalamus controls the mechanisms of ADH secretion, either by regulating blood volume or the concentration of water in the blood.
  • As blood osmolarity decreases, a negative feedback mechanism reduces osmoreceptor activity in the hypothalamus; ADH secretion is reduced.

• Labor and Birth

  • This causes the cervix to stretch, sending nerve impulses to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary.
  • A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin.
  • When the baby begins suckling at the breast, signals are sent to the hypothalamus causing the release of prolactin from the anterior pituitary, which signals the mammary glands to produce milk.

• Female Hormones

  • The stages of the ovarian cycle in the female are regulated by hormones secreted by the hypothalamus, pituitary, and the ovaries.
  • The decrease in progesterone also allows the hypothalamus to send GnRH to the anterior pituitary, releasing FSH and LH to start the cycles again .
  • The ovarian and menstrual cycles of female reproduction are regulated by hormones produced by the hypothalamus, pituitary, and ovaries.

• Other Hormonal Controls for Osmoregulation

  • Angiotensin II also triggers the release of anti-diuretic hormone (ADH) from the hypothalamus, leading to water retention in the kidneys.
  • It is formed by the hypothalamus, but is stored and released from the posterior pituitary gland.

• Male Hormones

  • At the onset of puberty, the hypothalamus begins secreting high pulses of GnRH, or gonadotropin-releasing hormone.
  • A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus and anterior pituitary to inhibit the release of GnRH, FSH, and LH .

• Hormonal Regulation of Stress

  • The sympathetic nervous system regulates the stress response via the hypothalamus.
  • Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress responses via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary.
  • In a long-term stress response, the hypothalamus triggers the release of ACTH from the anterior pituitary gland.