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What is the function of the pituitary gland?
Provides a functional connection between the CNS and periphery
Describe the structure of the pituitary gland?
- Anterior lobe and posterior lobe
- Secretes 9 hormones (which have pluripotent effects)
- About the size of a dime
- Regulates every cell in the body
Which hormones regulare all forms of function within the entire CNS?
- Lipophilic hormones ie. Thyroid H and Steroids
- Free to enter the brain
What is the function of sex steroid hormones?
Act in multiple brain regoins to regulate reproductive and cognitive function in addition to emotion and feelings
Name the three kinds of hormone signaling parameters.
- 1) Autocrine- cell secretes a hormone that binds to receptors on the same cell
- 2) Paracrine - cell secretes a hormone that targets nearby neighboring cells
- 3) Endocrine - Travels over a great distance (in the blood) targeting multiple cell types and organs
What are the four types of hormones?
- 1) Peptides- composed of amino acids arranged as a complex chain or a simple string, ie. oxytocin
- 2) Monoamines - Composed of one amino group connected to an aromatic ring, ie, adrenaline
- 3) Steroids - composed of a core of 4 fused rings and 1 side chainl; activity varies by the functional groups attached to these rings
- 4) Thyroid hormone - derived from 2 amino acid residues; bound to transport proteins in the blood
Which of the four types of hormones are hydrophilic?
Peptides and monoamines
Which of the four types of hormones are lipophilic?
Steroids and Thyroid H
Describe the mode of action for peptides and amines.
Involves a transmembrane (surface) receptor with an internal catalytic unit that will cleave molecules which will then act as secondary messengers
Describe the mode of action for steroids and thyroid H.
The hormones are transported into the cell where they bind to nuclear (soluble) receptors in the cytoplasm. These nuclear receptors then enter the nucleus and exhibit functions as transcription factors. Steroids can also use surface receptors.
Which hormones are released by the anterior pituitary?
ACTH, TSH, FSH-LH, PRL, GH
Which hormones are released by the posterior pituitary?
ADH (AVP), and OT
What is the function of different cell types in the anterior pituitary?
- Each different cell type secretes a unique stimulating hormone ie. corticotropes make ACTH, and gonadotropes make LH/FSH
- Different cell types are regulated by different hypothalamic nuclei
Describe capillary endothelium of the CNS.
- Forms a tight, continuous junction known as the blood-brain-barrier
- Specialized regions can circumvent this barrier
What is the Median Eminence (ME)?
- Area where neurons and portal veins pass through
- Nerves exit here from the hypothalamus
- Either terminate in the posterior pituitary (direct path) or terminate in the ME to regulare anterior pituitary cells (indirect path)
What is the "direct pathway"?
- Involves nerve fibers that pass through the median eminence to terminate within the posterior pituitary.
- Involves AVP/ADH and OT
What is the "indirect pathway"?
- Involves nerve fibers that terminate within the median eminence to release their secretory products into the pituitary portal circulation.
- Within the anterior pituitary, these releasing hormones stimulate different cells to release unique stimulating hormones.
- Always involves 3 steps: release of releasing hormone targeted to pituitary, release of stimulating hormone targeted to endocrine gland, release of hormones by endocrine gland
Name 6 hypothalamic nuclei.
- Medial Preoptic
Describe the function of the supraoptic nuclei.
- Located directly above the optic tract
- Involved in the direct pathway
- Makes only vasopressin and OT- stored within the posterior lobe
Describe the function of the paraventricular nuclei.
- Located on either side of the third ventricle.
- Involved in both the direct and indirect pathways
- Synthesizes multiple peptides
- Contains neurosecretory neurons that terminate within both the posterior pituitary and median eminence- these peptide-synthesizing neurons occupy different regions of the nucleus.