Exam 5 Review:  Chapter 16:  Pituitary Gland = Hypophysis


pituitary gland = hypophysis
- A small oval endocrine gland attached to the base of the brain by the infundibulum and housed in the sella tursica fossa of the sphenoid bone; it consists of an anterior and a posterior lobe, the secretions of which control many of the other endocrine glands and influence growth, metabolism, and maturation; anterior lobe hormones include growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, prolactin, luteinizing hormone, follicle-stimulating hormone and melanocyte-stimulating hormone and posterior lobe hormones include antidiuretic hormone = vasopressin and oxytocin; this gland is regulated by the hypothalamus of the brain.  nickname - the master gland.

anterior pituitary = adenohypophysis - The anterior/ventral lobe of the pituitary gland/hypophysis, it is located at the base of the brain and connected to the hypothalamus above by the infundibulum; the glandular lobe, which contains a variety of cell types which secrete protein hormones (including growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, prolactin, luteinizing hormone, follicle-stimulating hormone and melanocyte-stimulating hormone) in response to the arrival of hypothalamic releasing and inhibiting hormones/factors; this gland is regulated by the hypothalamus of the brain.

posterior pituitary = neurohypophysis - The posterior/dorsal lobe of the pituitary gland/hypophysis, it is located at the base of the brain and connected to the hypothalamus above by the infundibulum; the neurosecretory lobe, and the infundibulum, which contains glial cells and the axons and axon end bulbs of neurosecretory cells whose cell bodies reside in certain hypothalmic nuclei; when the hypothalamic cells are stimulated, they send action potentials down their axons, which make up the infundibulum of the pituitary gland, to trigger their axon end bulbs to release peptide hormones (including antidiuretic hormone/vasopressin and oxytocin); this gland is regulated by the hypothalamus of the brain.

In the MRI above, the anterior portion of the sella tursica appears black, i.e., it is filled with CSF, indicating that the patient's anterior lobe of the pituitary has atrophied.

somatotrophs - A cell type of the anterior pituitary/adenohypophysis which produces and secretes hGH/somatotropin in response to hypothalamic GHRH and GHIH/somatostatin.

thyrotrophs - A cell type of the anterior pituitary/adenohypophysis which produces and secretes TSH in response to hypothalamic TRH.

gonadotrophs - A cell type of the anterior pituitary/adenohypophysis which produces and secretes FSH and LH in response to hypothalamic GnRH.

lactotrophs - A cell type of the anterior pituitary/adenohypophysis which produces and secretes PRL in response to hypothalamic PRH and PIH.

corticotrophs - A cell type of the anterior pituitary/adenohypophysis which produces and secretes ACTH in response to hypothalamic CRH.

human growth hormone (hGH) = somatotropin - A protein hormone secreted by the anterior lobe of the pituitary gland/adenohypophysis which targets most body tissues, particularly the liver, skeletal muscle, bone and cartilage, and promotes growth of the body, especially by stimulating release of somatomedins from the liver and other tissues, and which stimulates protein catabolism; it is an insulin antagonist contributing to increasing blood glucose levels and fat catabolism.

somatotropic hormones - A general term for a group of diverse hormones and local hormones, including human growth hormone/somatotropin and various immune system regulators which stimulate cell growth in various tissues.

thyroid-stimulating hormone (TSH) - The  adenohypophyseal (anterior pituitary)  protein hormone which stimulates thyroid gland follicular cells to release thyroid hormones, T3 and T4; its secretion is regulated by hypothalamic TRH.  aka - thyrotropin.

follicle-stimulating hormone (FSH) - The adenohypophyseal (anterior pituitary)  protein hormone which: (1) in the female: (in cooperation with LH), regulates the ovarian cycle, stimulates maturation of the ovarian follicle and estrogen production; (2) in the male: stimulates sperm production; FSH secretion is regulated by hypothalamic GnRH.

luteinizing hormone (LH) - The adenohypophyseal (anterior pituitary) protein hormone which: (1) in the female: (in cooperation with FSH), regulates the ovarian cycle, stimulates ovulation and development of the corpus luteum and, thus, estrogen and progesterone production; (2) in the male: stimulates production of androgens, especially testosterone from interstitial cells; in males, it is also known as Interstitial Cell Stimulating Hormone (ICSH); LH secretion is regulated by hypothalamic GnRH.

prolactin (PRL) - The adenohypophyseal (anterior pituitary)  protein hormone which stimulates the mammary glands to produce milk; its secretion is regulated by hypothalamic PRH.

adrenocorticotropic hormone (ACTH) - The adenohypophyseal (anterior pituitary)  protein hormone which stimulates the adrenal gland to release mineralocorticoids and, more importantly, glucocorticoids; its secretion is regulated by hypothalamic CRH.

melanocyte stimulating hormone (MSH) - The adenohypophyseal (anterior pituitary)  protein hormone which stimulates the epidermal melanocytes glands to produce melanin; of limited importance in humans.

dopamine - A catecholamine neurotransmitter and hormone formed in the brain by the decarboxylation of dopa and essential to the normal functioning of the central nervous system; a precusrsor to norepinephrine and epinephrine; a reduction in its concentration within the brain is associated with Parkinson's disease.

oxytocin (OT) - A neurohypophyseal (posterior pituitary) peptide hormone which stimulates the contraction of smooth muscle of the uterus during labor and delivery and facilitates ejection of milk from the breast during nursing.  For a summary of some of the behavioral actions of oxytocin, visit The Two Faces of Oxytocin.

lactation - The production and secretion of milk by the mammary glands under the complex control of the nervous system and the endocrine system (estrogens, progesterone, prolactin, oxytocin).

neuroendocrine reflex - A group of complex visceral reflexes involved in the maintenance of internal homeostasis; visceral sensory information is routed to the nervous system where motor commands are then generated and sent to endocrine organs and the release of the hormones triggers a response in the target tissues which restores internal equilibrium; e.g., pathways which involve the hypothalamus, the pituitary gland, and target organs and the pathway which involves the sympathetic division of the ANS, the adrenal medulla, and target organs.

milk ejection reflex - The neuroendocrine reflex in which an infant suckling at the nipple is the sensory stimulus routed to the hypothalamus causing oxytocin release from the posterior pituitary/neurohypophysis which in turn causes lacteal duct smooth muscle contraction and ejection of milk from the breast.

antidiuretic hormone (ADH) = vasopressin - the neurohypophyseal (posterior pituitary) peptide hormone which stimulates contraction of smooth muscle in blood vessel walls and stimulates the kidney tubules to reabsorb water; both target responses tend to increase blood pressure.

osmoreceptors - Receptors in the CNS, particularly in the hypothalamus, which respond to changes in the osmotic pressure of the blood.


Compare and Contrast:

 

3.  anterior pituitary hormones to posterior pituitary hormones.

 
Anterior Pituitary Hormones Posterior Pituitary Hormones
1.  their release is under neuro-endocrine control by hypothalamic releasing and inhibiting hormones generated in specific hypothalamic nuclei

2.  some individual hormones (there are seven) are released by a different type of cell, while some cell types produce more than one kind of adenohypophyseal hormone

3.  the seven hormones are of the protein classification

4. some of the seven hormones, TSH, FSH, LH, and ACTH, are trophic hormones, i.e., they target other endocrine glands to secrete hormones

5.  three of the seven hormones, FSH, LH, and PRL, regulate reproductive functions

6.  none of the seven hormones regulates renal functions

7.  none of the seven hormones have a specific antagonistic hormone

8.  one of the seven hormones, PRL, has no particular function in males

1.  their release is under nervous system control by nerve impulses generated in specific hypothalamic nuclei

2.  each individual hormone (there are two) is released by a different type of cell

3.  the two hormones are of the peptide classification

4. none of the hormones are trophic hormones

5. one of the two hormones, OT, regulates reproductive functions

6. one of the two hormones, ADH = vasopressin, regulates renal functions

 

7.  neither of the two hormones has a specific antagonistic hormone

8.  one of the two hormones, OT, has no particular function in males

 

List and Describe:

 

7.  the pituitary hormones and describe their effects.

 
Anterior Pituitary
human growth hormone (hGH)
thyroid-stimulating hormone (TSH)
follicle-stimulating hormone (FSH)

luteinizing hormone (LH)

prolactin (PRL)
adrenocorticotropic hormone (ACTH)
melanocyte stimulating hormone (MSH)
(hGH) growth, protein synthesis in most body cells
(TSH) stimulate T3 & T4 release from the thyroid gland
(FSH) stimulate follicular growth and estrogen production from the follicles in the ovary; stimulate spermatogenesis in the testes
(LH) stimulate ovulation and progesterone production  in the ovary; stimulate androgen production in the testes
(PRL) stimulate mammary gland growth and milk production
(ACTH) stimulate adrenal cortical hormone production, especially glucocorticoids
(MSH) little action in humans
Posterior Pituitary

oxytocin (OT)

 

 

antidiuretic hormone (ADH) = vasopressin

 

smooth muscle contractions in the uterus for labor & delivery

smooth muscle contractions in the mammary ducts for milk letdown

conserve water from the urine increasing blood pressure

vasoconstriction increasing blood pressure

 

8.  the five secretory cell types in the pituitary.

somatotrophs - thyrotrophs - gonadotrophs - lactotrophs - corticotrophs

11. the tropic/trophic hormones.

thyroid-stimulating hormone (TSH)
follicle-stimulating hormone (FSH)

luteinizing hormone (LH)
adrenocorticotropic hormone (ACTH)
(TSH) stimulate T3 & T4 release from the thyroid gland
(FSH) stimulate follicular growth and estrogen production from the follicles in the ovary; stimulate spermatogenesis in the testes
(LH) stimulate ovulation and progesterone production  in the ovary; stimulate androgen production in the testes
(ACTH) stimulate adrenal cortical hormone production, especially glucocorticoids

Sketch and Label:

 

6. a negative feedback pathway for the regulation of:

 

       a.  Growth Hormone

 

 

       c.  ADH = vasopressin

 
The figure below reminds you of the anatomical relationships.  ADH = vasopressin will target the kidney and the smooth muscle in blood vessels walls.  the figure to the right illustrates the negative feedback control pathways.