19 terms

Cellular Communication

What are the rules for physiological regulation?
1. Target cell must have a specific receptor protein for the signal chemical.

2. The combination of signal and receptor protein must cause a change in the target cell.

3. A mechanism must be in place to turn off the action of the signal chemical.
What are the 5 steps to signal pathways and what acts in those steps in cells? In the endocrine system?
1. Signal Molecule
2.Membrane Receptor Protein
3.Intracellular Signal Molecules
4. Target Proteins
What are the physiological systems in place for telecrine signaling in the body?
Endocrine & Nervous System(Hormones)
What is used as signals in physiological regulation? What steps are required for signal transduction?
1)Direct Communication
-Gap Junctions
-Cellular Contact/Recognition

2)Indirect Communication
-Chemical & Electrical Signals

3) Messengers

Steps Required:
-Ligand, Receptor, Response
What are the three properties of hormone/receptor interaction? Be able to recognize them from examples.
-Specificity (hormones bind only to cells with receptors)
-High affinity (high bond strength between hormone and receptor)
-Low capacity (limited number of receptors per cell)
How does calcium act as a ligand?
1)Remember minute amounts
- Stored in ER

2)Small changes in [Ca++] are
large signal to cell

3) Actions
- Binds to calmodulin: alters
NZ activity and/or
transporter activity
- Binds to regulatory proteins:
contraction of muscle,
triggers exocytosis of
secretory vesicles
- Binds directly to gated ion
- Initiates embryonic
Know how lipophilic and hydrophilic ligands are carried in the blood.
Lipophilic-In blood plasma by carrier proteins.
All diffuse through the PM and interact with a cytoplasmic receptor which moves them to the nucleus

Hydrophilic-Signal transduction
What is a homodimer? A heterodimer? Know the domains of the receptor in the nucleus, know the response and know which hormone/neurotransmitter binds with which receptor. Know which thyroid hormone acts as a reserve and why.
-Homodimer- 2 steroid receptors
-Heterodimer-a protein composed of two polypeptide chains differing in composition in the order, number, or kind of their amino acid residues.

-Three domains
1) Ligand binding
2)DNA binding
3)Transcription regulation

1)Steroid diffuses
through PM and binds
with nuclear receptor

2) Receptor-ligand
complex dimerizes
and binds to DNA

3. DNA is transcribed

4. mRNA exits nucleus
and protein is
translated: steroid
hormone response

-T4 higher affinity
Be able to describe the response generated by ligand-gated receptor channels, receptor enzymes, G-protein coupled receptors (all types), and the integrin receptor. Know specifically which types of hormones/neurotransmitters interact with them, what (if any) 2nd messengers are involved, and what responses are generated. Be able to discern which type is involved from an example.
What is meant by the term "signal amplification" and how do lipophilic and hydrophilic ligands use it? What is an amplifier enzyme?
- One signal molecule results in multiple mRNA
- mRNA molecules result in protein formation

What is meant by the terms physiological dose and pharmacological dose?
-Physiological dose is small
-Pharmacological dose is orders of higher magnitude
What is an enzyme cascade, what does it accomplish, and which type of signal molecule uses it?
-Signal sets of
metabolic enzyme
-Final step is enzymatic
conversion of
substrate to product
-Intracellular Signals
Summarize the basic transduction pathway and the actions of 2nd messengers (slides 50 and 51 of .pdf).
Which ligand/receptor complex gives the fastest response?
ligand-gated ion channels
What is the importance of phosphodiesterase?
• "Off switch"
• Hydrolysis of cAMP into inactive fragments
• What is the consequence to the action of
these hormones?

Unlike steroid hormones, hormones which use adenylate cyclase must
continuously generate new cAMP molecules

Response of the target cell depends on the secretion rate of the hormone
What effects do competition and specificity (affinity and Kd) have on transduction? Saturation? Up- and down-regulation? Agonists and antagonists? What effect does half-life of ligands have on transduction?
What is a neural reflex? An endocrine reflex? A neuroendocrine reflex? What pathways and feedback are involved? Be sure to know the steps of the reflex feedback loops.
Chart on phone
What is meant by the terms tonic and antagonistic control?
Tonic: Always on, vary intensity

Antagonistic: Different signals, to control set point
Know the mediators in neural and endocrine reflex pathways, including how variations in speed, specificity, signal type, duration of action, and coding are achieved.