HHP-L22

What is cell signaling?

process by which cells communicate with each other

What happens during cell signaling?

receptors throughout the body detect changes and respond to maintain homeostasis

What is cell signaling utilized for?

to monitor and communicate conditions that are regulated through feedback loops

• negative or positive feedback

Negative feedback

communication system tells something to stop—bringing it back to its original state Ex. lowering body temperature back to normal

• more common

Positive feedback

communication system amplifying stimulus, moving system away from original state

What receives the message and where can they be located?

receptors, and they can be inside or outside of the cell

How can cells respond to changes in the environment?

• they can respond to chemical stimuli that increases other proteins in their membrane

• Ex. insulin signals the cell to position glucose transport channels into its membrane

Types of Cell-Cell communication

• direct communication: signals pass through intracellular receptor from cytosol of one cell to an adjacent cell

• contact dependent: uses membrane bound signaling molecules which bind to receptors on adjacent cells

• contact independent: messenger molecules are released to communicate

Contact independent signaling

autocrine, paracrine, neurotransmitter, endocrine

Autocrine

an autocrine messenger stimulates the cell that originally secreted the signal

• Ex. WBCs stimulate their own replication

Paracrine

• para=adjacent

• chemical messengers that act on cells in the local environment

• Ex. histamine during allergic reactions; protective response against viruses

Neurotransmitter

chemical messengers secreted by neurons to adjacent cells

Endocrine

chemical messengers released by glands that utilize the blood to travel to target cells

3 steps of cell signaling

1. signal reception

2. signal transduction

3. cell response

Extracellular membrane receptors

Receptors on the cell membrane bind signaling molecule

• Ex. GPCR, RTKs

Ligand

signaling molecule

Secondary messengers

when receptors produce their own signal

Intracellular receptors