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NROSCI/BIOSC 1070 MSNBIO/NROSCI 2070 September 8, 2014. Control 2. Functions of Hormones. Hormones act on their target cells in one of three basic ways: Control the rate of enzymatic reactions Control transport of molecules across cell membranes Control gene expression and synthesis. - PowerPoint PPT Presentation
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NROSCI/BIOSC 1070 MSNBIO 2070
September 14, 2015
Control 2
Functions of Hormones
Hormones act on their target cells in one of three basic ways:
1.Control the rate of enzymatic reactions
2.Control transport of molecules across cell membranes
3.Control gene expression and synthesis
Types of Hormones
PeptidesAmino AcidsSteroids
Divisions of Pituitary
Anterior pituitary (also called adenohypophysis)True glandular tissue
Posterior pituitary(also called neurohypophysis)Extension of brain
Hypothalamic-Hypophyseal Portal System
Tropic Hormones — Control the Release of Other
Hormones
Anterior Pituitary Hormones are Tropic
Hormones
End Products Regulate Tropic
Hormone Secretion
Short Loop FeedbackLong Loop FeedbackUltra Short Loop Feedback
Anterior Pituitary Hormones
No Known TropicRole
Proopiomelanocortin(POMC)
POMC is cleaved within a vesicle to form ACTH, β-Endorphin, γLPH, and
16K fragment
Hypophysiotropic Hormones: Control Anterior Pituitary
Secretions
Others likely exist, but have not been discovered because of their low
concentrations in blood
What happens if feedback mechanisms are dysfunctional?
Tumors can produce large amounts of hormones without feedback regulationAutoimmune diseases can damage receptors on hormone-secreting cells, so they no longer respond to tropic hormonesIntracellular signal transduction pathways can become aberrantly altered, thereby affecting how hormone-producing cells respond to tropic hormones.
Posterior Pituitary Hormones
Arginine Vasopressin Named as such because the first vasopressin discovered was
from pig; this hormone has a lysine instead of arginine as residue 8
Produces vasoconstriction when present in high concentrations (hence the name)
Affects water reabsorption in kidney at lower concentrations, hence the secondary name: antidiuretic hormone
Oxytocin Triggers uterine contractions during birthing Triggers milk release from mammary glands during suckling May have roles in cardiovascular control and renal function (men
and women who are not of child-bearing age also synthesize oxytocin)
Posterior Pituitary Hormones
Posterior pituitary hormones are synthesized by neurons in the paraventricular and supraoptic nuclei of the hypothalamus
These hormones are released like neurotransmitters when the neurons fire
The release of the hormones is dependent on the number of neurons that fire and the rate and duration of their firing
Examples of Some Hormones
Hormone
Where Produce
dEffect Stimu-
lationInhi-bition
LH Anterior Pituitary
Stimulates Leydig cells of
testis to synthesize &
release testosterone;
stimulates estrogen &
progesterone secretion by
corpus luteum; stimulates ovulation
GnRH from Hypo-
thalamus
Testos-terone,
estrogen, proges-terone, Inhibin
Testos-terone
Leydig Cells of Testis
(mainly)
Production & maintenance
of male sexual characteristics
LH from anterior pituitary
None
Erythro-poietin
Tubular epithelial cells of Kidney
Stimulation of red blood cell production by bone marrow
Hypoxia of tubular
epithelial cells
None
Aldos-terone
Adrenal cortex
Promotes reabsorption of
Na+ and excretion of K+
by tubular epithelial cells
of kidney
Increased K+ in plasma,
Angiotensin II
Increased Na+ in plasma
Gastrin G cells of stomach
Stimulates acid secretion by stomach
Peptides and amino
acids in stomach; enteric nervous system
Somato-statin
and low pH in
stomachInsulin
Islets of Langer-
hans
Enhances glucose
transport by many tissues;
increases glucose
metabolism and storage
High plasma glucose levels,
hormone GIP,
parasym-pathetic activity
Sympa-thetic
activity
Epin-ephrine
Adrenal medulla
Many effects mediated by binding to β-
receptors
Sympathetic nervous system
influences on Adrenal
medulla
None