Endocrine system and hormones Flashcards
The Endocrine System
coordinates and integrates cellular activity throughout the body to maintain homeostasis
Functions of the Endocrine System
homeostasis
control of the storage and utilization of energy
regulation of growth, development, reproduction
regulates the body’s response to environmental stimuli
Endocrine Glands
Ductless glands that secrete hormones into blood stream (directly release into blood stream)
Target organs
The organ that contains cells with receptors that have hormone specific receptors
Hormones
Messengers transported through the blood
“chemical messengers released by one cell and exert a biological action on a target cell)
chemical substances produced by the body and exerts a regulatory effect on the activity of cell/tissue/organ
Hormone Signaling
endocrine, paracrine, autocrine and intracrine
Endocrine Signaling
- target tissue is distant
- hormone travels through blood stream to reach target tissue
Paracrine Signaling
Target tissue is more local
Examples of Paracrine Signaling
nitric oxide, bradykinin, neurotransmitters, cytokines (small proteins, interleukins, TNF, IF, growth factors, TGF), prostaglandins
Nitric Oxide
paracrine signaling
in blood vessel walls and released into immediate area, promotes vasodilation
Bradykinin
paracrine signaling
Promote BV vasodilation, often with injury
Neurotransmitters
paracrine signaling
Epi and NE
Cktokines
paracrine signaling
small proteins, immunoregulating and growth function (interleukins, TNF, IF, growth factors, TGF
Prostaglandins
paracrine signaling
fatty acid messengers, multiple functions
Autocrine
target cell is same cell
hormone released by a cell and then acts on the same cell that released it
Intracrine
hormone produced in cell, acts within its self
Regulation of hormone secretions
Negative Feedback–> most common, hormone actions directly or indirectly inhibit further release of that hormone
Positive feedback–> less common, hormone actions stimulate further release of that hormone
ex: lutinizing hormone
2 classifications of hormones
derivative content classification, solubility classification
Derivative Content Classifications
-Amino acids derivatives: catecholamines, thyroid hormones
Peptide/protein derivatives: Glycoproteins…many of the “releasing hormones”are formed of peptides
Steroid derivatives: estrogens, testosterone, etc…
Fatty acid derivatives- eicosanoids, Prostaglandins
Solubility Classification: Lipid Soluble
Steroid Hormones and thyroid hormones (cholesterol is precursor for all steroid hormones)
circulate in plasma via binding to plasma proteins (longer half life)
Hormone/protein carrier will disassociate at target tissues
Solubility Classification: Water Soluble
most hormones are water soluble
GH, TSH, PTH
circulates freely in plasma, easily borken down
short half life
Hormone receptors
located on or in cell membrne. Not a fixed quanity, continuous receptor turn over
Up Regulation
low concentration of hormone=increase # of receptors on target tissue
=increased sensitivity to hormone
Down Regulation
high concnetration of hormone=decreased # of receptor in target tissue
=decreased sensitivity to hormone
Signal trasnduction
extracellular signlas (hormones) are communicated into a cell
primary messenger, secondary messenger
Primary Messenger
hormone enters cell and mediates cell fxn
fat soluble (lipophilic) hormones, easily diffuse across cell membrane to communicate to receptors within
Secondary Messenger
link between primary messenger (hormone) and inside cell, communicates to interior structures of cell to produce desired physiological action
Water soluble–> require secondary mechanism, cant diffuse across the membrane. Primary messenger communicates w/secondary messenger mechanism to reach internal structures of cell (using cAMP)
