Signals are constantly sent and recieved to maintain homeostasis

• Organism → Communication → Cell → Communication → Organism

• communication

  • first and second messengers

  • hormones

  • growth factors

  • cytokines

  • neurotransmitters

  • action potenial

• cell responses

  • secretion

  • contraction

  • metabolic

Communication modes

• probably not all of the modes we have

• endocrine

  • hormones

  • takes longer

  • travels in bloodstream

• paracrine

  • different types of cells, but next to each other (diffusion)

  • controls development and differentiation

  • growth factors, cytokines, vasoactive agents, neurotransmitters

• autocrine

  • same type of cells next to each other

  • basically paracrine, but with the same type of cell

• juxtacrine

  • next to each other, giving handshakes

  • integral membrane proteins

  • B and T cels

  • adhesion molecules, membrane-bound cytokines, extracellular matrix

• synaptic

  • specialized paracrine

  • neurotransmitters

Signal Pleiotropy

• one signal has many meanings

• different cell types and different receptors/proteins do different things with the same signal

Early and Late Responses

• Early (fast): just have to modify a protein (seconds)

• Late (slow): requires transcription/translation (min-hour)

Vocab Review

• Ligand: binds to a receptor

• Agonist: binds to and activates receptor

• Antagonist: binds to and inhibits receptor

• Receptor: binds ligand and transduces signal

• transduction/transduce: to change the form of

• Second messanger: ligand produced (cAMP) or relased (Ca2+) into cytosol that carries the signal around the cell

• Inverse agonist: binds to receptor and inhibits its intrinsic activity (keeps it inactive)