Chemical Messengers (Topic 6) Flashcards
What two organ systems are primarily used for communication pathways? (2)
the nervous and endocrine systems
What are the characteristics of the nervous system? (2)
fast signaling
- response is often short-lived
What are the characteristics of the endocrine system? (2)
slower signaling
- response is often long-acting
Compare the nervous and endocrine systems: (2)
- share the basic elements found in all homeostatic systems (sensors, integrating center, effectors).
- Both act as transducers
What is a transducer? (2)
converts some form of stimulus into an electrochemical message
How are chemical messengers characterized? (3)
characterized by:
- what type of cell makes them
- how they get to their target
Neurotransmitters (3)
- produced by neurons
- does not enter the blood stream; they travel by diffusion to a neighboring cell
Hormones (3)
- produced by endocrine cells
- enters blood stream
- travels to distant places in the body
Neurohormone (3)
- made by a neuron
- enters the blood stream
Paracrine substance (3)
- produced by local cells
- does not enter the blood stream; they travel by diffusion to a neighboring cell
Autocrine substance (3)`
- produced by local cells
- targets itself
T/F a substance can serve as more than one type of messenger? (3)
True
ex: norepinephrine
- depends on whether or not it s dropped in the bloodstream
What does an agonist do? (4)
binds to a receptor and initiates a physiological response
What does an antagonist do? (4)
binds to a receptor but does NOT produce a physiological response (INHIBITS SIGNAL)
Does it make sense that lipid-soluble messengers have receptors in the cell? Why or why not? (5) ?
Yes, it can cross the membrane so receptors are in the cell
What do receptors bind to? (5)
recognized sequences in the DNA
What happens when a receptor binds to a recognized sequence in the DNA? (5)
alters gene expression
What are some characteristics of lipid-soluble messengers? (5)
- they are intracellular
- bind to recognized sequences in DNA
- they are slower, more sustained responses compared to membrane receptors
- one receptor can regular many genes
What is an example of lipid-soluble messengers? (5)
Steroid hormones
Where are water-soluble messengers found? (6)
In the membrane
What are the four types of water-soluble messenger receptors? (6)
- ligand-gated ion channel
- receptor tyrosine kinase
- coupled to janus kinase
- coupled to G-protein
What is the most common water-soluble messenger receptor? (6)
coupled to G-protein
What happens in G-protein receptors? (6)
GDP leaves and GTP comes in
Steps of adenylyl cyclase and cyclic AMP (9)
Water-soluble (first) messenger binds to receptor -> gene expression is altered -> GDP leaves and GTP binds -> alpha subunit is now active and slides along the membrane to activate another protein -> ATP converts to cAMP -> second messenger binds to cAMP dependent protein kinase to make it active -> active kinases phosphorylates other proteins and those activate other pathways that lead to -> cellular response
G-protein + cAMP allows for what? (10)
for 100x amplification
“amplification cascade” is crucial for what? (10)
crucial for fast complex responses
Example of signal amplification (10)
binding of 1 molecule of epinephrine can cause the liver to release 108 glucose
