Topic 12: Endocrine System I Flashcards
What does hormone mean?
Greek for “to excite”
What are hormones and what do hormones help do?
chemical signaling molecules responsible for regulation
messenger of endocrine system -> allows cells to communicate with each other
How do hormones work?
secreted in body fluids, usually blood
binds to target cells
all cells are exposed, only those with correct receptor respond
What are receptors and what do they do?
large proteins or glycoproteins on surface of target cells
recognize and bind to specific hormones
responsible for specificity of endocrine system
continually synthesized and degraded
What occurs if hormone levels are too high? What if they are too low?
down-regulation
up-regulation
How does endocrine signaling work?
endocrine cells secrete hormones into extracellular fluid
diffuse into bloodstream -> travel across body
attach to receptors on target cells
Explain short distance signaling
cells produce and secrete LOCAL regulators
reach target cells by diffusion (not through bloodstream)
What are the 5 types of short distance signaling?
paracrine signaling autocrine signaling synaptic signaling neuroendocrine signaling signaling by pheromones
Define paracrine signaling
target cells NEAR secreting cels
Define autocrine signaling
target cells ARE secreting cells
Define synaptic signaling
neurons form synapses with target cells
neurotransmitters are involved
What are neurotransmitters?
signaling molecules are produced by neurons, diffuse across synapse and bind to receptors on target cells
Define neuroendocrine signaling
neurosecretory cells secrete neurohormones which diffuse into bloodstream
What happens in signaling by pheromones?
chemicals released into external environment
target other individuals of same species to:
define territory
warn of predators
attract mates
What are the two classes of local regulators?
modified fatty acids: contain long hydrocarbon chains
gases: diffuses to surrounding muscle, activates enzymes, relaxes cells, vasodilation, more blood to tissue
Which are hydrophilic and hydrophobic? Polypeptides, steriods, amines
hydrophilic - polypeptides and amines
hydrophobic - steroids and amines
What does water-soluble hormones do? What does lipid-soluble hormones do?
water-soluble affects proteins in cytoplasm of target cells - acts faster, but short-term effects
lipid-soluble affects gene expression of target cells - acts slower, but last longer
What does water-soluble hormones involve? Define it
signal transduction: series of changes in cellular proteins that convert extracellular chemical signals into specific intracellular responses
SEQ water-soluble hormone pathway
CANNOT pass through membranes
- hormone secreted via exocytosis
- travels freely in bloodstream
- binds receptor on target cell membrane (often G-protein-coupled receptor)
- G protein binds and activated adenylyl cyclase
- adenylyl cyclase converts ATP to cyclic AMP (cAMP) - 2nd messanger
- cAMP activated protein kinase (enzyme)
- other proteins inhibited or activated -> response
SEQ lipid-soluble hormone pathway
CAN pass through membranes
- diffuses across endocrine cell membrane
- binds transport protein - soluble in blood
- diffuses across cell membrane into target cells
- binds receptor in cytoplasm
- > hormone receptor complex enters nucleus - H-RC binds DNA
- > change in gene expression- > response
Do hormones have only one type of effect?
Many have more than one type of effect
What does epinephrine do?
its a rapid response by body in emergencies
triggers glycogen breakdown in liver
increases blood flow in skeletal muscle
decreases blood flow in smooth muscle
can be due to different receptors or different intracellular proteins
What does the endocrine do? Characteristics of endocrine?
release hormones into surrounding fluid -> bloodstream
ductless
can be isolated cells or part of organs
functions with nervous system to regulate metabolism, maintain homeostasis
What does the exocrine do? Example?
release materials into ducts
carry secreted substances to target area
examples: sweat, mucus, digestive enzymes
