cell communication

Question 1

where does cellular communication occur?

Answer 1

• between cells
• within cells

Question 2

what are different types of cellular communication between cells?

Answer 2

• electrical
• chemical

Question 3

how does electrical communication between cells occur?

Answer 3

by direct contact via gap junctions

Question 4

what is the function of gap junctions?

Answer 4

allow the flow of current from cell to cell (rapid transmission in both directions)

Question 5

what is a syncytium?

Answer 5

linked cells acting as one unit

Question 6

what is an example of a syncytium?

Answer 6

cardiac and some smooth muscle

Question 7

how does chemical communication occur between two cells?

Answer 7

a synapse

Question 8

how does chemical communication occur between one cell and several other cells?

Answer 8

paracrine transmission

Question 9

how does cellular communication between many cells to many cells occur?

Answer 9

endocrine transmission

Question 10

describe chemical synapse transmission

Answer 10

• Cell to cell using a chemical transmitter
• Effect depends on transmitter and the receptor it acts on
• One way transmission

Question 11

where are synapses common?

Answer 11

the nervous system

Question 12

describe the sequence of events that occur at a chemical synapse

Answer 12

• 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

Question 13

what cells often use paracrine communication?

Answer 13

defence cells (inflammation)

Question 14

what is the name for cell communication where a chemical acts on itself (the cell which releases the chemical)?

Answer 14

autocrine

Question 15

describe endocrine transmission

Answer 15

• the chemical can be sent to all parts of the body via the blood stream

Question 16

what cells can hormones act on?

Answer 16

cells with the correct membrane receptor protein (target cells)

Question 17

what is the name for communication by nerves?

Answer 17

neural

Question 18

describe neural communication

Answer 18

• specific/localised actions
• quick impulse transmission
• suitable for rapid response

Question 19

what are examples of neural communication?

Answer 19

• voluntary muscle contraction control
• sensory systems
• salivary gland response
• control of blood pressure

Question 20

describe hormone communication

Answer 20

• many different cells in different parts of the body are affected
• co-ordinated, body-wide actions
• slow to act, but the effect persists

Question 21

what are examples of hormone communication?

Answer 21

• gasto-intestinal gland responses
• metabolism and growth control
• menstrual cycle regulation

Question 22

what is the ‘first messenger’ within the cell?

Answer 22

the chemical transmitter which acts on the receptor protein

Question 23

what can vary about first messengers?

Answer 23

some can pass through the target cell membrane and act on internal receptors but some cannot

Question 24

what are ‘second messengers”?

Answer 24

the various intracellular signalling molecules and pathways

Question 25

what are steriods?

Answer 25

lipids than can pass through the cell membrane and act on internal cell receptors

Question 26

where is DNA found?

Answer 26

the nucleus

Question 27

what initiates protein synthesis?

Answer 27

the steroid-receptor complex acting on DNA

Question 28

can peptide pass through the cell membrane?

Answer 28

no

Question 29

how do peptide transmitters work?

Answer 29

• 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

Question 30

how does calcium act as a 2nd messenger?

Answer 30

• 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