Hypothalamus

Aka: Hypothalamus, Hypothalamus Gland, Anterior Hypothalamus, Medial Hypothalamus, Posterior Hypothalamus, Paraventricular Hypothalamic Nucleus, Gonadotropin Releasing Hormone, GnRH

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II. Definitions

  1. Thalamus
    1. Master control of the Autonomic System (analogous to a thermostat)
    2. Coordinates complex, related reflexive actions (e.g. fight or flight, Body Temperature, increased appetite)

III. Physiology

  1. Images
    1. hypothalamusPituitaryHormones.png
  2. Master control of the Autonomic System (analogous to a thermostat)
  3. Coordinates complex, related reflexive actions
    1. Fight or flight response (Sympathetic Nervous System)
    2. Increased appetite (Parasympathetic Nervous System)
    3. Body Temperature Regulation

IV. Anatomy

  1. Small organ in the Diencephalon
  2. Anterior Hypothalamus
    1. Supraoptic nucleus
      1. Neurons project into the posterior pituitary where they release Vasopressin (Antidiuretic Hormone, ADH)
    2. Paraventricular Hypothalamic Nucleus
      1. Neurons project into the posterior pituitary where they release Oxytocin or Vasopressin (ADH)
  3. Posterior Hypothalamus
    1. Produces and secretes releasing factors for anterior pituitary Hormones (ACTH, TSH, GH, LH, FSH)

V. Physiology: Hypothalamus and Pituitary Hormones

  1. Hypothalamus
    1. Corticotropin Releasing Hormone (CRH, CRF)
      1. Stimulates anterior pituitary release of Adrenocorticotropic Hormone (ACTH)
    2. Gonadotropin Releasing Hormone (GnRH, LHRH)
      1. GnRH is generated within hypothalamic Neurons (infundibular nucleus, arcuate nucleus)
      2. GnRH is released typically in pulses in men and women
        1. GnRH is also released in a surge before Ovulation
      3. GnRH binds receptors on the Pituitary Gland triggering release of gonadotropins from anterior pituitary
        1. Luteinizing Hormone (LH)
        2. Follicle Stimulating Hormone (FSH)
    3. Growth Hormone Releasing Hormone (GHRH)
      1. Stimulates anterior pituitary release of Growth Hormone
    4. Thyrotropin Releasing Hormone (TRH, TRF)
      1. Stimulates anterior pituitary release of Thyroid Stimulating Hormone (TSH)
      2. Stimulates anterior pituitary release of Prolactin
    5. Somatostatin
      1. Inhibits anterior pituitary release of Growth Hormone
      2. Inhibits anterior pituitary release of Thyroid Stimulating Hormone (TSH)
    6. Neurotransmitters
      1. Dopamine released from Hypothalamus inhibits anterior pituitary release of Prolactin
  2. Posterior Pituitary Gland (Hormones produced in the Hypothalamus, released from pituitary)
    1. Oxytocin
      1. Stimulates uterine contractions
      2. Stimulates milk let-down in Lactation
    2. Antidiuretic Hormone (ADH, Vasopressin)
      1. Increases renal water reaborption
  3. Anterior Pituitary Gland
    1. Prolactin
      1. Protein synthesized and secreted by Lactotrophs (acidophil cells) in the anterior pituitary
      2. Prolactin stimulates milk secretion into the Breast alveoli in pregnancy and Lactation
      3. Oxytocin stimulates myoepithelial cells to contract, expressing Breast Milk from the nipple
      4. Stimulated by Estrogen, vasoactive intestinal polypeptide (VIP), Thyroid Releasing Hormone (TRH)
      5. Inhibition by hypothalamic Dopamine (Prolactin Inhibiting Factor or PIF)
    2. Human Growth Hormone
      1. Polypeptide produced in the acidophil cells of the anterior pituitary
      2. Triggered by Hypoglycemia (or low Amino Acids) via hypothalamic release of GHRH
      3. Promotes bone and cartilage growth, Protein synthesis, glycogen storage, Fatty Acid increase
    3. Adrenocorticotropic Hormone (ACTH)
      1. Polypeptide synthesized and secreted by Basophil cells in the anterior pituitary
      2. Stimulation (releasing factors) include Corticotropin Releasing Hormone (CRH) and stress
      3. Inhibition by negative feedback loops (Cortisol inhibits CRH and ACTH release)
      4. ACTH stimulates the Adrenal Cortex to release Cortisol (and to a lesser extent Aldosterone and androgens)
    4. Thyroid Stimulating Hormone (TSH)
      1. See Thyroid Physiology
      2. Thyroid Stimulating Hormone (TSH) is a Glycoprotein synthesized in the Basophil cells of the anterior pituitary
      3. Stimulated by Thyroid Releasing Hormone (TRH)
      4. Inhibited by negative feedback from Thyroid Hormones (T4, T3)
      5. Thyroid Stimulating Hormone (TSH) promotes all aspects of Thyroid Hormone production
        1. Increases Iodide uptake and incorporation of Iodine into Thyroglobulin
        2. Increases lysis into active Thyroid Hormones T4 and T3
    5. Follicle Stimulating Hormone (FSH)
      1. FSH is a glyoprotein secreted by Basophil cells in the anterior Pituitary Gland
      2. Stimulation (releasing factors) is by Hypothalamic Gonadotrophic Releasing Hormone (GnRH)
      3. Inhibited via negative feedback loop by Testosterone, Estrogens, Progesterone and inhibin
      4. FSH stimulates ovarian follicle growth (which secretes Estradiol) in women
      5. FSH stimulates spermatogenesis and sperm maturation within Sertoli Cells in men
    6. Luteinizing Hormone (LH)
      1. LH is a Glycoprotein secreted by Basophil cells in the anterior Pituitary Gland
      2. Stimulation is by Hypothalamic Gonadotrophic Releasing Hormone (GnRH)
      3. Inhibited via negative feedback loop by Testosterone, Estrogens, Progesterone and inhibin
      4. LH stimulates ovarian follicles to ovulate and mature into a corpus luteum (produces Estrogen, Progesterone)
      5. LH stimulates Leydig Cells within Testes to produce Testosterone

VI. References

  1. Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 54-60
  2. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 140-1

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