Lecture 12- Endocrine System I Flashcards
A(n) __________ is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organisms to regulate physiology and/or behavior
Hormone
Hormone
Chemical signaling molecule responsible for regulation. Messenger of endocrine system.
Endocrine Signaling
Hormones are secreted into body fluids, usually blood. The hormones bind to target cells. All cells are exposed, only those with the correct receptor respond.
Receptors
Large proteins or glycoproteins on/in target cells. Recognize and bind to specific hormones. Responsible for specificity of endocrine system. Continually synthesized and degraded.
Hormone up for long period ->
Hormone down for long period->
Receptor down-regulated
Receptor up-regulated
Intercellular communication is classified by:
- The type of secreting cell
- The route taken by signal to target
How does endocrine signaling work?
Endocrine cells secrete hormones into extracellular fluid. These hormones diffuse into the bloodstream and travel to target cells.
Paracrine & Autocrine Signaling
Cells produce and secrete local regulators. Regulators reach target cells by diffusion. Short distance, very quick.
Paracrine: Target cells near secreting cell
Autocrine: Target is self
Where are the target cells located for Paracrine and Autocrine signaling?
Paracrine: Target cells near secreting cell
Autocrine: Target is self
(In both, local regulators produced by cell have a short distance to travel)
What is a key difference between endocrine signaling and paracrine & autocrine signaling?
Endocrine signaling-> endocrine cells secrete HORMONES
Para & Autocrine-> cells secrete LOCAL REGULATORS
Also, short distance for paracrine & autocrine signaling, longer distance for endocrine signaling
Synaptic Signaling
Involves neurons- basic unit of nervous system
Neurons form synapses with target cells -> use neurotransmitters that diffuse across synapses, bind receptors on target cell
Neuroendocrine Signaling
Neurosecretory cells- specialized neurons, secrete neurohormones
These neurohormones diffuse from nerve cell endings into bloodstream.
Signaling by Pheromones
Chemicals released into external environment, target other individuals of same species.
Functions:
- Define territory
- Warn of predators
- Attract mates
Pathway depends on what?
Type of signal and secreting cell
What are local regulators made of? Where are they found?
Paracrine & Autocrine regulators
Made of modified fatty acids
Contain long hydrocarbon chains
Signaling Molecules (examples)
Local regulators (Para & Autocrine)
Gases- NO
Polypeptides- Cytokines, growth factors
Gases as a signaling molecule: Nitric Oxide
Nitric oxide (NO)
When Blood O2 levels rise, blood vessel lining releases NO. NO diffuses to surrounding muscle, activating enzymes + relaxing cells. This leads to vasodilation, which is a dilation of the blood vessels. As a result, more blood flows to tissues, which provides them with the increased oxygen.
3 Major Chemical Classes of Hormones
Polypeptides- tend to be 100s of amino acids (Insulin is 2 polypeptides, joined with disulfide bonds)
Steroids- lipids with 4 rings, all derived from cholesterol
Amines- synthesized from single amino acids
Solubility of 3 chemical classes of hormones
What does solubility affect?
Polypeptides (or peptides)- water-soluble
Steroids- lipid-soluble
Amines- varies
Solubility affects response pathway- different for two types
Water-Soluble Hormones vs. Lipid Soluble Hormones
What can they cross/dissolve in?
Water-Soluble: Can dissolve in blood, cannot cross cell membrane. Involves signal transduction- Signal goes from outside target cell to inside- several signaling molecules involved.
Lipid-Soluble: Cannot dissolve in blood, can cross cell membrane
Pathway: Water Soluble Hormones (Steps)
Hormone is hydrophilic
Secreted via exocytosis
Travels freely in bloodstream
Binds receptor on target
Often G protein-coupled receptor
HORMONE DOES NOT ENTER CELL
G protein activated
G protein binds, activates adenylyl cyclase
Adenynyl cyclase converts ATP to cAMP
cAMP activates protein kinase (enzyme)
Protein kinase acts by adding phosphate to specific protein
-> post-translational control
Inhibit or activate other proteins-> response
How do water-soluble and lipid-soluble hormone pathways differ?
1. Do they enter the cell
2. Can they travel in bloodstream
3. Are they hydrophilic or hydrophobic
4. What do they affect in the target cells + which is faster/slower, longer lasting/shorter
- Water-soluble hormones cannot enter the cell so they must use signal transduction- signal goes from outside target cell to inside- several signaling molecules involved.
Lipid-soluble hormones enter the cell. - Water-soluble hormones can freely travel in the bloodstream.
Lipid-soluble hormones must bind to a transport protein to travel through blood. - Water-soluble hormones are hydrophilic. Lipid-soluble hormones are hydrophobic.
- Water-soluble hormones have effects in cytoplasm of target cells- this is a faster process. Lipid-soluble hormones affect gene expression of target cells- this is slower, but has longer-lasting effects.
Pathway: Lipid Soluble Hormones (Steps)
Hormone is hydrophobic
Diffuses across endocrine cell membrane
Binds transport protein- soluble in blood
Diffuse across cell membrane INTO target cells
Inside target cell- 2 options
Bind receptor in cytoplasm -> hormone-receptor complex enters nucleus
OR
Enter nucleus -> bind receptor inside
Then binds DNA -> change gene expression -> response
Do hormones have single effects or multiple effects? What is an example of this?
Many hormones have more than one type of effect.
Example: Epinephrine
Rapid response by body in emergencies
Triggers glycogen breakdown in liver. Increases blood flow in skeletal muscle, decreases blood flow in smooth muscle. This can be due to different receptors or different intracellular proteins.
How can hormones produce more than 1 type of effect?
Target cells may differ in receptor and response molecule, which causes different results from the same hormone.
Endocrine Tissues and Glands: Do they have ducts? What is the purpose?
Endocrine tissues and glands are ductless- release hormones directly into surrounding fluid. Can be isolated cells, part of organs, or discreet structures.
Function with nervous system to regulate metabolism + maintain homeostasis.
Exocrine Tissues and Glands: Do they have ducts? What are some materials they release?
Exocrine secretion involves ducts. Glands release materials into target area through ducts. Example: sweat, mucus, digestive enzymes.
Purpose of hormones
Chemical signaling molecule responsible for regulation. Messenger of endocrine system.
Are amines water-soluble or lipid-soluble?
Varies
True or False: Exocrine glands have ducts
TRUE
Are steroids water-soluble or lipid-soluble?
Lipid-soluble
What do protein kinases do?
Inhibit or activate proteins (post-translational control)
True or False: Polypeptides are water-soluble
TRUE
What are the three major types of local regulators used for paracrine signaling?
Fatty acids (prostaglandins)/Gases (nitric oxide)/Polypeptides (cytokines)
A(n) _________ is a secreted or excreted chemical factor that triggers a behavioral or physiological response in members of the same species.
Pheromone
True or False: Endocrine glands have ducts
FALSE, EXOCRINE glands have ducts
A rise in the concentration of cAMP activates ________
Protein kinases
___________ cells have large glycoproteins/proteins on their surface and recognize specific hormones.
Receptor
What are the three chemical classes of hormones?
Polypeptides/Steroids/Animes
What is the function of adenylyl cyclase?
Catalyzes the conversion of ATP to cAMP
A(n) _________ is any cell that has a receptor for a hormone.
Target cell
A(n) _________ is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organisms to regulate physiology and/or behavior.
Hormone
