Exam 5 Review:  Chapter 16:  Hypothalamus

 

hypothalamus - That portion of the central nervous system found surrounding the lower portion of the third ventricle which receives and integrates many types of sensory information about the internal environment and directs actions to control internal homeostasis by both initiating commands carried by autonomic neurons and by regulating some of the endocrine activity of the pituitary gland.

infundibulum - the short, delicate stalk which connects the pituitary gland to the base of the brain and the hypothalamus and through which run the blood vessels of the hypothalamic/hypophyseal portal system.

hypothalamic releasing hormones = hypothalamic releasing factors* - Neurosecretory substances, usually peptides, which are synthesized by hypothalamic neurons which are monitoring aspects of internal homeostasis, the substances are released into the hypophyseal portal circulation to travel to the anterior pituitary where they stimulate specific adenohypophyseal cells to synthesize and secrete particular trophic hormones.  [*Note:  These substances are more likely to be called "factors" if their exact molecular structure has not been identified.]

hypothalamic inhibiting hormones = hypothalamic inhibitory factors* - Neurosecretory substances, usually peptides, which are synthesized by hypothalamic neurons which are monitoring aspects of internal homeostasis, the substances are released into the hypophyseal portal circulation to travel to the anterior pituitary where they inhibit specific adenohypophyseal cells from synthesizing or secreting particular trophic hormones.  [*Note:  These substances are more likely to be called "factors" if their exact molecular structure has not been identified.]

tropins = tropic hormones - Hormones which control other endocrine glands, i.e., have other endocrine glands as their target organs; most are produced in the pituitary gland.

GHRH = growth-hormone-releasing-hormone - A peptide hormone, related to the glucagon family, produced by the hypothalamus which stimulates the anterior pituitary gland to produce and begin secreting human growth hormone.

GHIH = growth-hormone-inhibiting-hormone = somatostatin - A pair of peptide hormones produced chiefly by the hypothalamus, but also in by other cells in other locations such as the delta cells of the pancreatic islets and certain gastrointestinal cells, which inhibits the secretion of various other hormones, such as human growth hormone (hGH) = somatotropin, glucagon, insulin, thyroid stimulating hormone (TSH) = thyrotropin, and gastrin; it also serves as a neurotransmitter in the CNS.

TRH = thyroid-releasing hormone - A peptide hormone produced by the hypothalamus which stimulates the anterior pituitary gland to produce and begin secreting thyroid stimulating hormone (TSH) = thyrotropin.

GnRH = gonadotropin-releasing hormone - A peptide hormone produced by the hypothalamus which stimulates the anterior pituitary gland to produce and begin secreting luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

PRH = prolactin-releasing-hormone - A yet-to-be-identified hormone presumably produced by the hypothalamus which stimulates the anterior pituitary gland to produce and begin secreting prolactin (PRL).

PIH = prolactin-inhibiting-hormone - An amine hormone, dopamine, produced by the hypothalamus which inhibits the anterior pituitary gland from secreting prolactin (PRL).

CRH = corticotropin-releasing hormone - A peptide hormone produced by the hypothalamus that stimulates the anterior pituitary gland to release adrenocorticotropic hormone (ACTH).

hypophyseal portal veins - The system of small veins which collect venous blood from the capillary beds in the region of the hypothalamus and transport that blood along the outside of the infundibulum to the capillary beds of the pituitary gland; this circulatory path permits the hypothalamus to deliver its hypothalamic releasing hormones/factors and its hypothalamic inhibitory hormones/factors efficiently to their target cells in the anterior lobe of the pituitary, the adenohypophysis, without having the signal molecules being diluted by being first routed to the heart.

hypothalamic portal system - The system of blood vessels which includes the capillaries of the hypothalamus, the small veins which route the venous blood from the hypothalamus to the pituitary gland and the capillary beds of the pituitary gland; this circulatory path permits the hypothalamus to deliver its hypothalamic releasing hormones/factors and its hypothalamic inhibitory hormones/factors efficiently to their target cells in the anterior lobe of the pituitary, the adenohypophysis, without having the signal molecules being diluted by being first routed to the heart.

List and Describe:

 

6.  the hypothalamic hormones and describe their effects.

 
Hypothalamic Hormone Hypothalamic Hormone  Effect(s) at the Anterior Pituitary = Adenohypophysis
GHRH = growth-hormone-releasing-hormone stimulates the production and secretion of human growth hormone (hGH)
GHIH = growth-hormone-inhibiting-hormone = somatostatin inhibits the secretion of  human growth hormone (hGH) = somatotropin and thyroid stimulating hormone (TSH) = thyrotropin  [Note: elsewhere in the body, other than in the anterior pituitary, GHIH also inhibits the secretion of various other hormones, such as glucagon, insulin, and gastrin; GHIH also serves as a neurotransmitter in the CNS]
TRH = thyroid-releasing hormone  stimulates the production and secretion of thyroid stimulating hormone (TSH) = thyrotropin
GnRH = gonadotropin-releasing hormone stimulates the production and secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
PRH = prolactin-releasing-hormone (yet-to-be-identified)  presumably stimulates the production and secretion of prolactin (PRL).
PIH = prolactin-inhibiting-hormone = dopamine inhibits the secretion of prolactin (PRL).
CRH = corticotropin-releasing hormone stimulates the release of adrenocorticotropic hormone (ACTH)

 

9.  the hypothalamic releasing hormones.

 
Hypothalamic Releasing Hormone Hypothalamic Hormone  Effect(s) at the Anterior Pituitary = Adenohypophysis
GHRH = growth-hormone-releasing-hormone stimulates the production and secretion of human growth hormone (hGH)
TRH = thyroid-releasing hormone  stimulates the production and secretion of thyroid stimulating hormone (TSH) = thyrotropin
GnRH = gonadotropin-releasing hormone stimulates the production and secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
PRH = prolactin-releasing-hormone (yet-to-be-identified)  presumably stimulates the production and secretion of prolactin (PRL).
CRH = corticotropin-releasing hormone stimulates the release of adrenocorticotropic hormone (ACTH)

 

10. the hypothalamic inhibiting hormones.

 
Hypothalamic Inhibiting Hormone Hypothalamic Hormone  Effect(s) at the Anterior Pituitary = Adenohypophysis
GHIH = growth-hormone-inhibiting-hormone = somatostatin inhibits the secretion of  human growth hormone (hGH) = somatotropin and thyroid stimulating hormone (TSH) = thyrotropin  [Note: elsewhere in the body, other than in the anterior pituitary, GHIH also inhibits the secretion of various other hormones, such as glucagon, insulin, and gastrin; GHIH also serves as a neurotransmitter in the CNS]
PIH = prolactin-inhibiting-hormone = dopamine inhibits the secretion of prolactin (PRL).

Sketch and label:


1.  the hypothalamus and pituitary glands.

 
The figure immediately below and on the right would make a good model for your sketch.  It shows the pituitary gland seated in the sella tursica of the sphenoid bone, and attached to the base of the brain by the infundibulum.
The figure below is to remind you of the many hypothalamic nuclei which monitor aspects of internal environment and which secrete hypothalamic releasing or inhibiting hormones to regulate the pituitary gland = hypophysis.  This figure like the one above, is oriented with anterior to your left. The figure below is an actual photomicrograph of the pituitary gland.  Ironically, the words "pituitary gland" in the figure are situated over tissue of the hypothalamus.  The terms "pars tuberalis" and "pars distalis" identify the regions we refer to as the anterior pituitary = adenohypophysis while the term "pars nervosa" identifies the region we refer to as the posterior pituitary = neurohypophysis.  This figure like the one below, is oriented with anterior to your right.
The figure below is to remind you of the hypophyseal portal circulation which delivers hypothalamic releasing and inhibiting hormones to the anterior pituitary = adenohypophysis and it also reminds you that the posterior pituitary = neurohypophysis is a direct outgrowth of the brain and contains white matter, axons with axon end bulbs which store oxytocin and antidiuretic hormone (ADH) = vasopressin.