Lecture 7 week 4? Flashcards
What are the two types of intercellular communication?
Direct and indirect communication
What does direct communication include?
i. Gap junctions
ii. Membrane (tunnelling) nanotubes
iii. Mechanosignals
What does indirect communication include?
i. Chemical messengers
What are connexons? (direct)
The subunits that form a gap junction
How big are connexons?
Pore size is very small
What do connexons do? give an example.
Permits passage of sugars amino acids and ions between cells
ex. metabolic and electric exchange
Where are connexons found?
Found in virtually all cells except mature skeletal muscle
What are intercalated disks? (direct)
Type of gap junction in cardiac muscle
What do intercalated disks do?
Allows propagation of action potentials for rhythmic contractions
How big are intercalated disks?
Smaller than connexons
How can intercalated disks be acutely regulated?
Can be acutely regulated (activated or deactivated) by phosphorylation or dephosphorylation
Where are membrane nanotubes formed from?
Formed from the plasma membrane
How big are membrane nanotubes ?
Longer than gap junctions and have a larger pore diameter
What do membrane nanotubes do?
- Transfer of nucleic acids & even
small organelles between cells - Might be a way to transfer
cellular components from
stressed to healthy cells
What does mechanosignal transduction do?
- Conversion of mechanical stimuli into a cellular response
- Direct physical stress to cells eliciting a chemical or metabolic response
What are some examples of mechanosignal transduction
E.g. 1) Conversion of a soundwave into an electrical signal (hearing)
E.g. 2) Pulsatile & shearing stresses from blood flow on arterial endothelial cells
* Can induce formation of new blood vessels
* If excessive, mediates vascular inflammation & progression of atherosclerosis
E.g. 3) Mechanical stress to muscle fibers from weightlifting resulting in increased protein synthesis
E.g. 4) Remodeling of bone & cartilage through physical stresses (such as weight lifting)
E.g. 5) Conversion of pressure on skin into a neural (electrical) impulse
What are the 4 chemical messengers? (indirect)
- Paracrine signalling
- Neurotransmitters
- Hormones
- Neuroendocrine signalling
(autocrine when possible, considered more direct)
Where does paracrine signalling act?
Acts on a nearby cell
What does paracrine signalling do?
Clotting factors, growth factors e.g. estrogen
(promotes ovary maturation)
What can secreted hormone from paracrine signalling act in?
Can act in both a paracrine and endocrine manner.
Explain about neurotransmitters.
- Synapse is a short distance
- Neurotransmitter signal must be tightly controlled
- Not too many molecules released
- Need an auto shutoff (reuptake or
degradation)
What two things can hormones be?
Either water or lipid soluble
What must hormones end up doing?
Must cross membranes
Where are hormones intended to go?
Intended to go to target specificity (receptor
