Wk2 Vid1: Key Terms- hypothalamus + pituitary

The pituitary gland or hypophysis lies in the pocket of the sphenoid bone at the base of the brain just below the hypothalamus

• Hypophysis: another name for pituitary gland
• adenohypophysis: anterior pituitary gland
• neurohypophysis: posterior pituitary

• (or the pituitary stalk) connects the pituitary gland to the hypothalamus.
• The infundibulum contains axons from neurons in the hypothalamus and small vessels.
• [the hollow stalk which connects the hypothalamus and the posterior pituitary gland.]

• the action or process of being turned inside out or folded back on itself to form a cavity or pouch
• eg. The anterior pituitary gland arises embryologically from an invagination of the pharynx called Rathke’s pouch

• The junction of the hypothalamus and infundibulum.
• Capillaries in the median eminence recombine to form the hypothalamo–hypophyseal portal vessels (or portal veins)

• (or portal veins).
• Capillaries in the median eminence recombine to form the hypothalamo–hypophyseal portal vessels.
• These vessels offer a local route for the blood to be delivered directly from the median eminence to clusters of endocrine cells within the anterior pituitary gland

• (SON)
• One of the well-defined clusters of hypothalamic neurons that  produce the posterior pituitary hormones 
• Secrets vasopressin (ADH)

• Many releasing hormones – GnRH, GHRH, CRH, TRH, Dopamine and Somatostatin
• One of the well-defined clusters of hypothalamic neurons that  produce the posterior pituitary hormones 

oxytocin

• Antidiuretic hormone aka vasopressin
• Produced by supraoptic nucleus (SON)
• Acts on smooth muscle cells around blood vessels to cause their contraction
• Vasopressin also acts within the kidneys to decrease water excretion in the urine

Store Vasopressin and Oxytocin in the posterior pituitary.

• Herring bodies or neurosecretory bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations.
• Antidiuretic hormone (ADH) and oxytocin are both stored in Herring bodies, but are not stored simultaneously in the same Herring body

• The collective term for hypothalamic hormones that regulate anterior pituitary gland function.
• They are also commonly called hypothalamic releasing or inhibiting hormones.

• With one exception dopamine, each of the hypophysiotropic hormones is the first in a three hormone sequence
• 1), a hypophysiotropic hormone controls the secretion of 2) an anterior pituitary gland hormone, which controls the secretion of 3) a hormone from some other endocrine gland. This last hormone then acts on its target cells.

• 1. corticotropin-releasing hormone (CRH)
• 2. thyrotropin-releasing hormone (TRH)
• 3. somatostatin (SST)
• 4. growth hormone releasing hormone (GHRH)
• 5. Gonadotropin-releasing hormone (GnRH)
• 6. and dopamine (DA)

• The hypophyseal portal system is a system of blood vessels in the microcirculation at the base of the brain, connecting the hypothalamus with the anterior pituitary.
• Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland.
• Ensures that hypothalamic hormones can reach the endocrine cells of the anterior pituitary with very little delay

Very small amounts of hypothalamic hormones from relatively few hypothalamic neurons to control secretion of anterior pituitary hormones without dilution in the general circulation

• gonadotrophin releasing hormone (from the hypothalamus)
• GnRH stimulates ganadotroph cells of the anterior pituitary
• to produce follicle stimulating hormone FSH and luteinizing hormone (LH)
• which then go on to act on the gonads to control spermatogenesis and follicular genesis.

• GHRH: growth-hormone releasing hormone. Promotes somatotroph cell production of growth hormone
• SST: somatostatin. Inhibits somatotroph cell production of growth hormone
• Growth hormone: acts on the liver and various other tissues to control growth and to a certain degree metabolism.

• TRH: thyroid releasing hormone
• Stimulates thyrothoph cells to produce thyroid stimulating hormone TSH
• Which then goes on to stimulate the thyroid gland to produce the metabolic hormones T3 and T4

• DA: dopamine
• Dopamine inhibits production of prolactin, which acts on the breasts.
• To date, a prolactin stimulating factor has not been identified.

• CRH: corticotropin-realesing factor
• stimulates cortico cells to produce adrenocorticotropic hormone (ACTH).
• ACTH in turn acts on the adrenal gland to regulate the synthesis of various steroids including cortisol

• The situation in which the hormone secreted by the third endocrine gland in a sequence exerts a negative feedback over the anterior pituitary gland and/or hypothalamus
• eg. cortisol

• Some anterior pituitary proteins such as prolactin can themselves act on the hypothalamus to regulate secretion of the hypophysiotropic hormones-
• not as common.