Chapter 6: Cell Communication

Question 1

Describe the extracellular environment.

Answer 1

• The extracellular environment includes everything located outside the cells
• Cells receive nourishment from and release wastes into the extracellular environment
• Cells communicate with each other by secreting chemical signal molecules into ECF

Question 2

What are the two types of physiological signals used in cell to cell communication.

Answer 2

• There are 2 basic types of physiological signals
  Electrical signals
  Changes in membrane potential of cell
  Chemical signals
  Secreted by cells into ECF
• Only target cells have receptors to signal molecule

Question 3

What are the four ways cells communicate?

Answer 3

• Gap junctions
• Contact-dependent signals
• Autocrine & paracrine signals
• Long distance communication using electrical and chemical signals

Question 4

Explain gap junctions.

Answer 4

Gap junctions form direct cytoplasmicconnections between adjacent cells.

Question 5

Explain Contact-dependent signals.

Answer 5

Contact-dependent signals require interaction between membrane molecules on two cells.

Question 6

What are the autocrine and paracrine signals?

Answer 6

• Autocrine act on cell that secreted them.
• Paracrine signals are secreted by one cell and diffuse to adjacent cells.

Question 7

How do long distance signals work?

Answer 7

• Endocrine cells secrete hormones into blood. Only target cells with receptors for the hormone respond to the signal

• Nervous system uses electrical and chemical signals to communicate.
• Neurotransmitter chemicals secreted by neurons diffuse across a small gap (synapse) to target cell.

• Neurohormones are chemicals released by neurons into blood to act at distant targets.

Question 8

List and describe the signal pathways.

Answer 8

If a target cell has a receptor for a signal molecule, binding of this messenger molecule initiates a response.

1. 1st messenger binds
2. Binding activates receptor
3. Receptor activates intracellular 2nd messenger
4. Last molecule in pathway initiates protein response

Question 9

What are the 4 types of membrane receptors?

Answer 9

1. Receptor-channel: ligand binding opens or closes the channel
2. Receptor-enzyme: ligand binding to a receptor-enzyme activates an intracellular enzyme
3. G protein-coupled receptor: ligand binding to a G-protein coupled receptor an ion channel or alters enzyme activity
4. Integrin receptor: ligand binding to integrin receptors alters the cytoskeleton

Question 10

What is Tyrosine Kinase?

Answer 10