Flashcards in Intro Deck (34):
The endocrine system Coordinates hormone signaling pathways that regulate: ?
2. Growth & development
3. Water & electrolyte balance
What other system does the endocrine system work closely with?
Compare the endocrine and nervous systems
1. Endocrine System
A. Secretes hormones that travel through bloodstream
B. Action relatively slow
C. Effects are prolonged
D. More general effetcs
2. Nervous System
A. Electrochemical impulses via neurons
B. Rapid response
C. Effects are brief and specific
What does the heart secrete?
ANP & BNP
Important in sodium and water balance
What does the kidney secrete?
Hormone essential for production of red blood cells
1. Chemical substances that regulate activity of certain cells
2. Hormones react with specific receptors
3. Organs, tissues, or cells lacking the specific receptor do not respond to its stimulating effects
How are hormones secreted? What are the characteristics of each method?
1. Continuous release
2. Steroid hormones
1. Peak & ebb relative to:
-Response to meals
-Hormone releasing factors
What is the action of a hormone?
1. Once secreted by endocrine organs, hormones travel to their target tissue
A. Bind to specific receptors
B. Initiate chain of events
-Physiologic effects of hormone
Which type of glands have ducts?
Which type of glands do not have ducts?
How are hormones transported?
1. Circulate bound to carrier proteins or free
A. Free = active hormone
B. Bound = reservoir to prolong half life
What are circulating levels of hormones regulated by?
1. Rate of secretion
2. Nature of secretion
3. Hormone degradation and/or uptake
4. Receptor binding
5. Receptor availability
6. Affinity of hormones for plasma carriers
What is the action and source of thyroid hormone?
2. Controls basal metabolism
What is the action and source of cortisol?
1. Adrenal cortex
2. Energy metabolism; basis for sex hormones
What is the action and source of mineralcorticoids?
1. Adrenal cortex
2. Regulates plasma volume via effects on serum electrolytes
What is the action and source of vasopressin?
1. Post pit
2. Regulates plasma osmolality via effects on water excretion
What is the action and source of PTH?
1. Parathyroid glands
2. Regulates Ca & PO4
What is the action and source of insulin?
2. Regulates glucose concentration
What are the classes of hormones?
3. Biogenic amines
What are the characteristics of peptide hormones?
1. Formed from chains of amino acids
2. Longer chains are called protein hormones
3. Example: growth hormone
What are the characteristics of steroid hormones?
1. Type of lipid derived from cholesterol
2. Example: aldosterone, testosterone
What are the characteristics of biogenic amines?
1. Small molecules produced by altering the structure of tyrosine
2. Example: thyroid hormone
Where are cell surface hormone receptors located?
What are the classes of hormones that bind to cell surface receptors?
Proteins and Amines
What is the moa of protein and amine hormone/receptor binding?
1. Hormone binds to receptor (first messenger); stimulates chemical response via a second messenger
2. Second messengers alter activity of enzymes within the cell
3. Receptor binding increases adenylate cycalse activity -> ATP converted to cyclic AMP -> stimulates changes in cell processes (activate enzymes, alter cell membrane permeability, stimulates protein synthesis, stimulates secretion)
Where are intracellular hormone receptors located?
Located in cytoplasm or nucleus
What are the classes of hormones that bind to intercellular receptors?
Steroid and thyroid hormones
What is the moa of steroid and thyroid hormone/receptor binding?
1. Alters transcriptional activity of genes
2. Causes synthesis of proteins in target cells via translation
define negative feedback regulation
1. Responsiveness of target cells to hormonal action -> Feeds back to control secretion
2. Inhibition of initial hormone release mechanism
define positive feedback regulation
Continued stimulation of the original hormone release mechanism
ex. Prolactin and oxytocin
What is the function of the hypothalamus?
1. Secretes regulatory hormones that control endocrine cells in anterior pituitary gland
2. Synthesizes & releases hormones from posterior pituitary gland. Hormones affect adrenal, thyroid, and gonadal glands
What can hormone deficiency result from? What are some examples?
1. Results from destruction of glandular structure
A. Hashimoto’s thyroiditis
B. Diabetes mellitus Type I
What can hormone resistance result from? What is an example?
1. Adequate levels of hormone synthesized and released
2. Target tissues are resistant to hormone’s effects
A. Diabetes Mellitus Type II