cell communication Flashcards
where does cellular communication occur?
- between cells
- within cells
what are different types of cellular communication between cells?
- electrical
- chemical
how does electrical communication between cells occur?
by direct contact via gap junctions
what is the function of gap junctions?
allow the flow of current from cell to cell (rapid transmission in both directions)
what is a syncytium?
linked cells acting as one unit
what is an example of a syncytium?
cardiac and some smooth muscle
how does chemical communication occur between two cells?
a synapse
how does chemical communication occur between one cell and several other cells?
paracrine transmission
how does cellular communication between many cells to many cells occur?
endocrine transmission
describe chemical synapse transmission
- Cell to cell using a chemical transmitter
- Effect depends on transmitter and the receptor it acts on
- One way transmission
where are synapses common?
the nervous system
describe the sequence of events that occur at a chemical synapse
- Impulse arrives at terminal of presynaptic cell
- Transmitter released from storage vesicles
- Transmitter diffuses in synaptic cleft
- Transmitter binds to receptor on postsynaptic cell
- Alters postsynaptic cell:
- ‘excitatory’ e.g. impulse generated; muscle contracts; gland secretes
- ‘inhibitory’: cell is switched off
what cells often use paracrine communication?
defence cells (inflammation)
what is the name for cell communication where a chemical acts on itself (the cell which releases the chemical)?
autocrine
describe endocrine transmission
- the chemical can be sent to all parts of the body via the blood stream
what cells can hormones act on?
cells with the correct membrane receptor protein (target cells)
what is the name for communication by nerves?
neural
describe neural communication
- specific/localised actions
- quick impulse transmission
- suitable for rapid response
what are examples of neural communication?
- voluntary muscle contraction control
- sensory systems
- salivary gland response
- control of blood pressure
describe hormone communication
- many different cells in different parts of the body are affected
- co-ordinated, body-wide actions
- slow to act, but the effect persists
what are examples of hormone communication?
- gasto-intestinal gland responses
- metabolism and growth control
- menstrual cycle regulation
what is the ‘first messenger’ within the cell?
the chemical transmitter which acts on the receptor protein
what can vary about first messengers?
some can pass through the target cell membrane and act on internal receptors but some cannot
what are ‘second messengers”?
the various intracellular signalling molecules and pathways
what are steriods?
lipids than can pass through the cell membrane and act on internal cell receptors
where is DNA found?
the nucleus
what initiates protein synthesis?
the steroid-receptor complex acting on DNA
can peptide pass through the cell membrane?
no
how do peptide transmitters work?
- The transmitter binds to a membrane receptor
- G-protein is activated by GTP (guanosine triphosphate)
- ATP (in cytosol) is converted to cyclic AMP by the enzyme adenyl cyclase
- cAMP activates an enzyme, called protein kinase
- This, in turn activates a specific enzyme which catalyses a chemical reaction
- Resulting in formation of molecule, e.g. protein
how does calcium act as a 2nd messenger?
- Transmitter binds to a membrane receptor
- This activates a G-protein, which activates an enzyme: phospholipase C
- This in turn causes opening of Ca2+ channels; Ca2+ enters by diffusion
- Ca2+ binds to a protein in the cytosol; here, it is calmodulin
- Ca2+-calmodulin complex acts as a 2nd messenger,
then which regulates an enzyme which regulates a chemical reaction - In some cells, the Ca 2+ is released from stores within the cell, but the basic principle is much the same
