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27 terms

Endocrine System

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Endocrine System
System in charge of regulating mood, growth, and development, tissue function, metabolism, and sexual function and reproductive processes
Hormones
Transfer information and instructions from one set of cells to another. Each type is designed to affect only certain cells
Gland
Group of cells that produce and secrete, or give off, chemicals
Endocrine Glands
Release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body
Direct Communication
Specialized case where cellular activities are coordinated by the exchange of ions and molecules between adjacent cells across gap junctions. Occurs between two cells of the same type
Paracrine Communication
The use of chemical messengers to transfer information from cell to cell within a single tissue
Target Cells
Specific cells that possess the receptors needed to bind and "read" the hormonal message when it arrives
Synaptic Communication
Across synaptic clefts through neurotransmitters
Endocrine Communication
Through the circulatory system--The activity of hormones in coordinating cellular activities in tissues and distant protions of the body
Three groups of hormones
Amino acid derivates, peptide hormones, lipid derivatives
Prohormones
Inactive molecules tjat are converted to active hormones either beofre or after they are secreted (peptide hormones in general are)
Eicosanoids
Small molecules witha five-carbon ring at one end. Important paracrine factors that coordinate cellular activities and affect enzymatic factors that coordinate celluar activities and affect enzymatic processes (such as blood clotting) in extracellular fluids
Leukotrienes
Eicosanoids released by activated white blood cells, or leukocytes
Prostaglandins
A second group of eicosanoids, are produced in most tissues of the body. Involved primarily in coordinating local cellular activities
Prostaglandins are sometimes convered to:
Thromboxanes and prostacyclins which also have strong paracrine effects
Steroid hormones
Lipids structurally similar to cholesterol. Released by male and female reproductive organs
First messenger
Does something that leads to the appearance of a second messenger in the cytoplasm
Second messenger
May act as an enzyme activator, inhibitor, or cofactor, but the net results is a change in the rates of various metabolic reactions
Down-regulation
A process in which the presence of a hormone triggers a decrease in the numebr of hormone receptors. When levels of a particular hormone are high, cells become less sensitive to it
Up-regulation
A process in which the absence of a hormone triggers an increase in the number of hormone receptors. When levels of a particular hormone are low, cells become more sensitive to it
G protein
An enzyme complex coupled to a membrane receptor. The link between the first and second messenger usually involves this.
Endocrine Reflexes
Functional counterparts of neural reflexes
Humoral stimuli
Changes in the composition of the extracellular fluid
Hormonal stimuli
The arrival or removal of a specific hormone
Neural stimuli
The arrival of neurotransmitters at neuroglandular junctions
Three things that can trigger endocrine reflexes:
Humoral stimuli, hormonal stimuli, and neural stimuli
Regulatory Hormones
Special hormones that control endocrine cells in the pituitary gland