Cobine: The Pituitary and Hypothalamus Flashcards
The (blank) is a portion of the brain located just inferior to the thalamus
hypothalamus
The pituitary measures ~1 cm in diameter and is located in the (blank)
sella turcica
How is the hypothalamus connected to the pituitary?
via the pituitary stalk (infundibulum)
The hypothalamus serves many neural functions and plays an important role in connecting the nervous system to the (blank) and regulating (blank)
endocrine system; regulating pituitary function
Six hormones released by the hypothalamus
GRHR, GnRH, SS, TRH, DA, CRH
Two lobes of the pituitary gland
anterior lobe (adenohypophysis) posterior lobe (neurohypophysis)
During embryo development, the two lobes of the pituitary gland originate from different sources. What does the anterior lobe originate from? The posterior lobe?
anterior: an invagination of the pharyngeal apithelium (Rathke’s pouch)
posterior: from a neural tissue outgrowth from the hypothalamus
Secretion by the anterior pituitary is controlled by hormones secreted by neurons within the (blank)
hypothalamus
Secretion from the posterior pituitary is from (blank) which originate in the hypothalamus and terminate in the posterior lobe.
magnocellular neurons
2 major cell types of the anterior pituitary gland
- acidophils
2. basophils
2 major acidophils in the anterior pituitary gland. Which is more abundant, and what do they secrete?
somatotropes (40%) - secrete growth hormone; lactotropes (20%) - secrete prolactin
3 major basophils in the anterior pituitary gland. Which is most abundant, and what do they secrete?
- corticotropes (20%) - secrete adrenocorticotropic hormone (ACTH)
- thyrotropes (5%) - secrete thyroid stimulating hormone (TSH)
- gonadotropes (5%) - secrete FSH and LH
Three hormone types
- peptide and protein
- tyrosine-derived
- steroid
Ex. of peptide/protein hormones
ACTH, ADH, oxytocin
Ex. of tyrosine-derived hormones
thyroid hormones, catecholamine hormones
Ex. of steroid hormones
glucocorticoids, mineralocorticoids, sex hormones
Which type of hormone makes up the majority of hormones?
peptide/protein hormones
Peptide and protein hormones are synthesized as (blank) and require (blank)
preprohormones; post-translational processing
What is the half life of a typical peptide hormone?
4-170 minutes
Steps in protein hormone synthesis
- formation of preprohormone- chain directed to ER lumen by a signal sequence
- enzymes chop off signal sequence to generate prohormone
- prohormones from ER to golgi
- secretory vesicles with enzymes chop the prohormone into active peptides
- contents released into extracellular space
- hormone free in circulation to reach its target
What does post-translational modification of AA do to them? Where does it occur?
alters their function and structure; occurs in the ER, Golgi, and secretory vesicles
Some examples of post-translational modification
cleavage - removal of AA’s, or generating multiple copies of the same hormone
attachment of other biochemical groups (ex: carbohydrates)
changing the chemical nature of the AA
changing the structure (removal of disulfide bridges)
protein folding
3 families of anterior pituitary hormones
- glycoprotein family
- growth hormone/prolactin family
- pro-opiomelanocortin family (POMC)
3 hormones in the glycoprotein family
- Thyroid stimulating hormone (TSH)
- Lutenizing hormone (LH)
- Follice-stimulating hormone (FH)
Glycoproteins have two subunits - what are they? Which is common to all? Which is unique?
alpha and beta; alpha common to all; beta unique
What determines the hormone half life of the glycoprotein family hormones?
greater degree of glycosylation
3 hormones in the glycoprotein family. What is their target and their major action?
- Thyroid stimulating hormone
- Follicle stimulating hormone
- Lutenizing hormone
- thyroid gland - increases synthesis of thyroid hormones
- ovary/testes - increases folliculogenesis and estrogen synthesis in ovaries and sperm maturation in testes
- ovary/testes - increases ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries and increases testosterone in testes
Growth hormone and prolactin are (blank) hormones
polypeptide (190AA’s)
There are three different forms of prolactin; Which is biologically active?
little, big, and bigbig; little
2 hormones in growth hormone/prolactin family. What is their target and their major action?
- growth hormone
- prolactin
- most tissues - growth, IGF-1 production, protein synthesis, decreased glucose utilization, and increased fat utilization
- mammary glands and hypothalamus - increase milk secretion, growth of mammary glands, decreased GnRH
What is unique about growth hormone that sets it apart from other anterior pituitary hormones?
Growth hormone does not function through a target gland - it exerts its effect directly on almost all tissues of the body
Growth hormone causes growth of body organs, skeletal grown and increased metabolism. Discuss each.
- increased size/number of cells in organs
- increased growth of epiphyseal cartilage, conversion of cartilage to new bone, bone thickening, bone remodeling
- increased protein synthesis, fat utilization, and glucose production by liver; decreaed protein breakdown, glucose uptake and utilization
Some growth effects of GH are mediated by (blank)
insulin-like growth factors (IGFs)
Where are IGFs produced? What is their indirect effect? What is the most important IGF?
in liver and at site of action; bone elongation through stimulation of osteoclasts/chondrocytes; somatomedin C
How is GH regulated?
Hypothalamus secreted growth hormone releasing hormone (GHRH) and GHIH or somatostatin to inhibit its release. Also IGFs provide feedback regulation and inhibit GHRH and stimulate GHIH
Growth hormone releasing hormone (GHRH) Ghrelin starvation, protein deficiency decreased blood glucose or fatty acids Exercise/Excitement/Trauma Estrogen & androgens Sleep
Stimulate GH secretion
Somatostatin obesity increased blood glucose or blood fatty acids Aging Somatomedins (IGFs) Growth hormone (-ve feedback)
Inhibit GH secretion
What is panhypopituitarism?
global underactivity of the pituitary gland - under secretion of growth hormone
What are some causes for panhypopituitarism?
pituitary tumors, thrombosis of pituitary vessels, trauma