Regulatory Systems Flashcards
Homeostasis
- life process that maintains a balanced/orderly system with changes to enivornment
- constant internal environment that requires energy source
- to regulate, cells must be able to detect change instate, process info and respond
Conformers
- cold blooded, internal state change because of environment
Contact communication
Cells can make physical contact in a way that allows molecules on the surface of one cell to interact with receptors on the other cell. Cells in a tissue specialize and maintain their cooperative behaviours partly through direct contact. Cells in the immune system display antigens from foreign organisms to recruit other immune cells to mount an attack. (one to one, local)
Paracrine communication
Cells may release signal molecules into the interstitial fluid around them. These then diffuse outward and are picked up by receptors on neighbouring cells. Many growth factors that control cell reproduction, immune responses and healing are paracrine signals. Paracrine signaling is local and non-specific. (one to many, local)
Synaptic communication
Cells may release chemical signals only in the vicinity of one or a few neighbouring cells. These substances then diffuse across the narrow gap (synapse) and stimulate only the specific target cell. Neurons, which are long thin cells, use synaptic signaling to carry information from one location in the body to very specific targets in another location. (one to one, remote)
Endocrine communication
Cells in one area of the body may release signal molecules, called hormones, directly into the blood. These molecules are then carried to every cell in the body, where they may be picked up by receptors. (one to many, remote)
‘crine’
secretion (release chemical signal molecule)
The Model:
Stimulus, Receptor, Processor (transduction), Response/Effect, -ve feedback
-ve feedback
can reduce intensity of stimulus/ change in environment
ligands
molecules that produce signal by binding to target protein
Normal results
- physical change, chemical change, secretion
Signal
A molecule released by another cell, or physical change (pressure, light, charge). Small molecules such as fatty acids, amino acids, short polypeptides, steroids and oligio saccharaides are common signals
Receptor
Signal only has meaning if other cell has receptors to bind. Generally a transmembrane protein with active site for signal molecule part outside membrane. The part inside has enzymatic function that is activated when outside part has soemthing bind to active site. Receptor depends on solubility of signal molecule (lipid=diffuse)
Processor
The enzyme part of a receptor protein changes molecule inside cell, starting more changes. Cascade reactions for enzyme. First, new small signals = 2nd messengers which activate more molecules.
Response
After cascade, funcitonal enzymes are activated or inhibited and will carry out new metabolic processes
Effector
Cell may change and alter state of body, contract, synthesize new things or secrete. Can produce signal to other cells, -ve feedback.
g-protein/cAMP transduction (epinephrine)
- Signal molecule binds to receptor protein
- Enzymatic end in cytoplasm is activated by the binding
- Enzyme catalyzes the replacement of GDP by CTP from krebs on G-protein
- Activated g-protein travels and binds to membrane bound enzyme adenylyl cyclase
- Adenylyl cyclase active converts ATP to cAMP
- G-protein catalyzes GTP to GDP, dissociate cyclase
- cAMP binds and activates protein kinase
- Primary protein kinase actives more kinase
- After cascade, enzyme is activated
Transduction Pathway
the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events
Advantages of the transduction pathway
- exponential gro3wth from small signal
- small 2nd messenger diffuse to target enzyme faster than large enzymes could diffuse to receptor for activation
- multiple pathways in different cells can be activated by same signal and receptor
- more control by more steps, regulation
Protein kinase
adds phosphate groups to certain proteins
Hormones
- chemical messages that are relased by endocrine glands, travel in the blood and act on a target organ, allow messages to travel through the body for homeostasis
- lipid and protein hormones
Lipid hormones
Cross cell membranes and bind to receptors in cytoplasm or nucleus. Act as a transcription factor and activate gene expression. Chemically, lipids are steroids because they are libid soluble.
Protein hormone
Bind to receptors embedded in membrane as they are too large or polar to diffue through. Can trigger signal transduction pathways that can cause many respomses. Are hydrophobic, bind on surface ex. Epinephrine
non target cells
lack receptors
