L5-Control Signalling Flashcards
3 Control Mechanisms
- Enzymes
- “Direct communication”
- Chemical Messaging
Gap Junctions are a form of what kind of communication between cells?
Direct intracellular communication
Direct intracellular communication involves _____ _______ between the interacting cells by 3 mechanisms: (list them)
Direct intracellular communication involves PHYSICAL CONTACT between the interacting cells by 3 mechanisms:
- through GAP JUNCTIONS
- through TRANSIENT LINKAGES
- through NANOTUBES
Gap junction as largely used in what kind of muscle?
cardiac/smooth
What are gap junctions? function?
- Gap junctions are minute tunnels that BRIDGE the CYTOPLASM of neighbouring cells in some types of tissues.
- SMALL MOLECULES and IONS are directly exchanged w/o entering ECF
- permit ELECTRICAL SIGNALS to spread from one cell to the next in CARDIAC and SMOOTH muscle.
Gap junctions close in response to:
an increase in intracellular Ca2+ and H+ ion concentrations
Explain transient linkages
some cells (ie. immune system cells) have specialized markers on their outer membranes that allow for direct transient link-ups between cells that have COMPATIBLE MARKERS.
think “space station” when thinking about “transient”
What are nanotubes? function?
- long tubes with internal actin-filament support surrounded by membrane
- allow for transfer of SIGNAL MOLECULES and ORGANELLES
In what types of cells are nanotubes mostly found?
in developing cells (insects and mammals) and in immune cells (mammals)
6 categories of intercellular chemical messengers
- paracrines
- neurotransmitters
- hormones
- neurohormones
- pheromones
- cytokines
INTERcellular messengers are also known as:
ligands
What kind of proteins are receptor proteins usually?
transmembrane glycoproteins
Paracrines: what are they? give an example.
- local chemical messengers whose effect is exerted only on NEIGHBOURING CELLS
- ex: histamine
If the paracrine action of a cell affects the same cell that secreted them, they are called ____
AUTOCRINES
How are paracrines distributed?
by SIMPLE DIFFUSION (hence why it’s short-distance)
Role of histamine
Histamine is a PARACRINE.
During inflammatory response within an invaded or injured tissue, histamine DILATES BLOOD VESSELS in the vicinity to increase blood flow to the tissue.
Neurocrines: what are they? give an example.
- NEUROTRANSMITTERS
- molecules released by neurons as a result of electrical signals
- communicate directly with cells innervated by said neurons
- SHORT-RANGE chemical messengers
- ex: norepinephrine
Endocrines: what are they? give an example.
HORMONES
- LONG-RANGE chemical messengers
- secreted into circulation by ENDOCRINE GLANDS
- ex: testosterone
Neuroendocrine: what are they? give an example.
- NEUROHORMONES
- hormones released by NEUROSECRETORY NEURONS
- LONG-RANGE
ex: oxytocin (associated with positive social behaviour), vasopresin
Pheromones: what are they? give an example.
- chemical signals released into the ENVIRONMENT by glands
- travel through air or water to sensory cells in other animals.
- a type of EXOCRINE secretion
ex: alarm pheromone
Cytokines: what are they?
- can be local or long range
- made in most cells
- involved in development and immunity
Categories of chemical messenger structures (7):
- Eicosanoids
- Gases
- Purines
- Amines
- Peptides and proteins
- Steroids
- Retinoids
Eicosanoids are derivatives of ________
Eicosanoids are derivatives of FATTY ACIDS
Eicosanoids are normally part of which category of intercellular chemical messengers?
paracrines
gases are normally part of which category of intercellular chemical messengers?
paracrines
T/F Gas chemical messenger are organic
FALSE. Inorganic.
NO, CO, H2S
The primary purine messengers are:
adenosine and ATP
Purines are normally part of which category of intercellular chemical messengers?
paracrines and neurotransmitters
Peptides and proteins can be part of which categories of intracellular chemical messengers?
proteins and peptides could be paracrines, cytokines, neurohormones, or hormones
Amines can be part of which categories of intracellular chemical messengers?
paracrines and hormones
amines are ______ and derivatives
Amines are AMINO ACIDS and derivatives
Steroids are derivative of ________
Steroids are derivative of CHOLESTEROL
T/F steroids can directly diffuse through cell membrane
True
Steroids are normally part of which category of intercellular chemical messengers?
mostly hormones, may be pheromones
Retinoids are derivative of ______
Retanoids are derivative of VITAMIN A
Retinoids are _____ involved in _____ and _____
Retinoids are PARACRINES involved in DEVELOPMENT and DIFFERENTIATION
Are responses determined by messengers or receptors?
Messenger connects to receptor, but RESPONSE IS DETERMINED BY RECEPTOR
Why do we have side effects associated with drugs?
Because same messenger can have different effects based on receptor.
T/F: Most messengers enter the cell
FALSE. Most messengers DO NOT enter the cell
2 broad types of signal transduction mechanisms:
- Lipophilic (lipid soluble)
2. Lipophobic (water soluble)
Lipophilic signal transduction
- messenger penetrates or dissolves INTO cell through the plasma membrane
- Binds to receptor INSIDE the cell
Lipophobic signal transduction
-Binds on receptor ON CELL MEMBRANE because it cannot dissolve
3 Things a lipophobic signal transduction can do:
a. open or close specific channels in the membrane to regulate movement of ions into or out of cell
b. activate an enzyme that phosphorylates a protein
c. Transfer signal to a second messsenger
3 types of gated receptor-channels
- Chemically or ligand gated
- Voltage gated
- Mechanically gated
Chemically gated receptor channels general steps
- extracellular messenger binds to receptor
- binding of receptor leads to opening of channel
- ions enter or leave cell
- ion entry brings about desired result
General steps in a receptor-enzyme mechanism
- extracellular messenger binds to receptor
- binding messenger leads to activation of protein kinase enzyme site
- protein kinase activates designated protein
- activated designated protein brings about desired response
Genera steps of a second-messenger (G-protein coupled receptor) mechanism
- extracellular (first) messenger binds to receptor
- Receptor activated G-protein
- G protein activates effector protein
- effector protein produces second messenger
- second messenger activates protein kinase
- protein kinase activates designated protein
- active designated protein brings about desired response
