Histo Lecture 19
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How does the Hypothalamus control endocrine function?
- Receives sensory input from various organ systems
- Directs pituitary gland secretion of various "releasing hormones"
- Pituitary gland stimulates hormone secretion from the major endocrine organs of the body
What hormones is the pancreas associated with?
What hormones are the Parathyroid glands associated with?
What hormones are the adrenal glands associated with?
What hormones is the Thyroid gland associated with?
Tri-iodothyronine-T3, Thyroxine - T4, calcitonin
What hormones are the gonads associated with?
- Estrogen, progesterone
How does the basic endrocine signaling system work?
- Regulated secretion of hormones
- Diffusion of hormones through the systemic circulation
- Diffusion of hormones out of the vasculature, to the target cell
- Binding to specific hormone receptor on cell
Most endocrine system utilize what feedback?
Negative feedback loop
What is physiologic response-driven feedback?
Hormone production is inhibited by change in physiologic parameter
What are some examples of a physiologic response-driven feedback?
- Blood glucose
- Blood Ca2+
- Blood osmolarity
- Blood Na+, K+, H+
How does endocrine axis-driven feedback work?
- Hypothalamus secretes releasing hormones
- Releasing hormones stimulates secretion of tropic hormones (from pituitary glands)
- Tropic hormones stimulate release of hormones from peripheral endocrine glands
Neural input provides stimulus for secretion of:
Daily rhythm of hormone release occurs due to input from the:
What does the Pineal gland do?
Secretes melatonin in cyclical fashion to inform the system of the light-dark cycle
Systemic and psychological stress also stimulates what?
What are the three types of hormones released?
- Proteins & polypeptides
- Tyrosine derivatives - amines
What three things does the hormone type determine?
- Mode of transport
- Binding to target cell
- Action on target cells
Protein/peptide and amine hormones are produced and stored where?
in intracellular vesicles
Steroid/thyroid hormones are produced from what?
Steroid/thyroid hormones circulate how?
Bound to plasma protein
What do protein-bound hormones allow for?
- Provides a reservoir of circulating hormones
- Increases the half-life of hormones
- Controls movement of hormones into target cells
Binding of cell membrane receptors (proteins, peptides, catecholamines) activates what?
Intracellular 2nd messenger system that stimulates target cells
Binding to intracellular receptors (steroid hormones) activates what?
Binds to DNA and stimulate/repress transcription
Binding to nuclear receptors (thyrod hormones) affects what?
Directly affects gene transcription to promote metabolic activity of cells
Thyrotropin releasing hormone (TRH) stimulates what?
Release of TSH
Gonadotropin releasing hormone (GnRH) stimulates what?
release of FSH/LH
Corticotropin-releasing hormone (CRH) stimulates what?
release of ACTH
Growth hormone-releasing hormone (GHRH) stimulates what?
Release of GH
Where is Oxytocin released from?
- paraventricular nucleus of hte hypothalamus
- -Stimulates breast duct contraction (milk ejection)
Where is ADH released from?
supra-optic nucleus of the hypothalamus
What are some facts about the anterior pituitary (adenohypophysis)?
- Contains a collection of tropic hormone-releasing cells
- Each hormine is secreted by only one type of cell
What are some facts about hte posterior pituitary (neurohpophysis)?
- Distal continuation of the hypothalamus; modified neurons
- Nuclei of the hypothalamus secrete hormone and sore them in axon terminals of the posterior pituitary
- Hormones are released upon appropriate stimulation
Name the 6 pituitary hormones
- ACTH - adrenocorticotropic hormone
- TSH - thyrod-stimulating hormone
- FSH - follicle-stimulating hormone
- LH - Leutenizing hormone
- GH - growth hormone
- PRL - prolactin
What do somatotropes do?
What do cotricotropes do?
Release ACTH to stimulate release of adrenal hormones
What do thyrotrops do?
Release TSH to stimulate release of thyroid hormones (T3/T4)
What do gonadotrops do?
Release FSH and LH to stimulate sex steroid release from gonads
What do lactotropes do?
Release PRL to stimulate milk production
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