Exam One - 1.7 Communication and Cell SIgnaling Flashcards
Physiological signals
Electrical signals
Chemical signals
Extracellular vesicles
Local cell to cell communication
gap junctions - create cytoplasmic bridges
contact-dependent signals - chemicals diffuse through ECF to act on nearby cells (*paracrine or *autocrine)
Extracellular vesicles
Long distance cell to cell communication
chemical (cytokines, myokines, exerkines, and hormones)
electrical signals
gap junction
form direct cytoplasmic junctions between adjacent cells
contact-dependent signals
require interaction between membrane molecules on two cells
autocrine signaling
act on same cell that secreted them
paracrine signaling
are secreted by one cell and diffuse to adjacent cells
Ctyokines
- both local and long distance signals
- peptides, synthesized and secreted by all nucleated cells in response to a stimuli
- *growth factors (important family)
- in development and differentiation, they usually function as autocrine or paracrine signals
- in stress and inflammation, some may act on relatively distant targets
- differ from hormones because they cannot be stored for later
Extracellular vesicle types
Exosomes
microvesicles
- may contain proteins, peptides, RNA
- can merge with other cells (targets)
When does a cell respond to a chemical signal???
A cell responds to a particular chemical signal only if the target has a receptor
Describe the basic signal pathway
- Signal molecule (ligand)
binds to… - Membrane receptor protein
which activates… - Intra-cellular signal molecules
which alters… - Target proteins
which creates… - The Response
Receptor locations can be…
Inside the cell or outside the cell
Where are lipophilic signal molecule receptors?
Inside the cell!
- signal molecules diffuse through the cell membrane and usually bind to cytosolic receptors or nuclear receptors
Where are lipophobic signal molecules?
On the cell membrane!
- signal molecules bind to receptors on the cell membrane!
Membrane receptor categories
- Channel: ligand opens or closes channel
- G protein-coupled: opens an ion channel or alters enzyme activity
- Catalytic: receptor enzyme (activates intracellular enzyme) or integrin receptor (alters enzymes or cytoskeleton).
Signal transduction
transducer converts a signal from one form to another
- extracellular signal is first messenger (activates protein kinases and amplifier enzymes)
- intracellular signal is the second messenger (alter gating of ion channels, increase intracellular CA, change enxyme activity)
know difference between cascades of activation steps and signal amplification
What type of membrane receptor does signal transduction often use?
G protein coupled receptors (GPCR)
Many lipophobic hormones use GPCR-cAMP pathways
GCPR also use lipid-derived second messengers
Integrin receptors
membrane-spanning proteins
outside the cell, integrins bind to extracellular matrix proteins or to ligands
inside the cell, integrins attach to the cytoskeleton via anchor proteins
Ca+ as an intracellular messenger
often used for signal amplification
is not left to hang around in cytoplasm after an AP
Soluble Gases
short acting paracrines or autocrines
Nitric oxide (NO)
diffuse into smooth muscle and causes vasodilation
synthesized by nitric oxide synthase (NOS)
Other gas signal molecules:
carbon monoxide (CO)
hydrogen disulfide (H2S)
Are carbs, lipids, or proteins important for paracrine signaling?
-lipids
ex. Leukotrienes have an important roles in asthma and anaphylaxis
modulation of signal pathways
specificity
saturation
competition
agonist/antagonist
up-regulation versus down-regulation
cells must be able to terminate signal pathways
many diseases and drugs target the proteins in signal transduction
target response depends on target receptor. Explain epinephrine and blood vessel example
Epi binds to alpha adrenergic receptor and the blood vessel constricts (intestinal blood vessel)
Epi binds to beta adrenergic receptor and the blood vessel dilates (skeletal muscle)
How does cholera toxin affect signal pathways?
antagonist to enzyme activity of G proteins, cell keeps making cAMP
ions secrete into lumen of intestine, causing massive diarrhea
Homeostatic reflex pathways (4)
1 - nervous regulation of internal environment
2 - tonic control
3 - antagonistic control
4 - one chemical signal can have different effects in different tissues
Tonic control
like a radio volume dial. not just on or off, but somewhere in the middle
Antagonistic control
ex. sympathetic nerves increase HR but parasympathetic nerves decrease HR
What does target response depend on?
Target response depends on target receptor!
What do long distance pathways maintain?
Homeostasis
What are the steps in a reflex pathway?
1 - stimulus
2 - sensor
3 - input signal
4 - integrating signal
5 - output signal
6 - target
7 - response
control systems vary in?
speed and specificity
specificity - neural is more specific than endocrine
What are the 3 different kinds of signals in a control system?
neural - electrical and chemical
endocrine - only chemical (hormones)
neuroendocrine - electrical and chemical (neurohormone)
speed - neural is faster than endocrine
duration of action - neural is shorter than endocrine
How fast is nerve conduction velocity?
if mylenated motor neurons can be 268 mph
how fast is nerve conduction velocity for pain?
3mph
how fast is blood flow velocity?
- depends on HR
- about 3-4 mph
