Lesson 2

Cell Signaling Overview

• Definition: Intracellular response to extracellular signals, enabling cellular communication.
• Signal Transduction: Conversion of signals into chemical changes, a fundamental property of living cells.

Forms of Information Arrival

• Purely Physical: Includes light, sound, heat, pressure, electricity.
• Chemical: Involves neurotransmitters, hormones, eicosanoids, drugs, toxins.
• Cellular: Gap junctions facilitate communication.
• Extracellular Matrix Molecules: Such as collagen, integrins, laminin.

Methods of Intercellular Communication

• Main Types:
  1. Endocrine: Signaling molecules (hormones) travel through circulation to distant targets.
  2. Paracrine: Signaling molecules act locally on neighboring cells.
  3. Autocrine: Cells respond to signaling molecules they produce themselves.

Endocrine Cell Signaling

• Hormones secreted by endocrine cells, affecting distant cells.
• Neuroendocrine Signaling: Neural sources of hormones affecting other systems (e.g., epinephrine from adrenal medulla).

Paracrine Cell Signaling

• Molecules released by one cell and acting on adjacent cells (e.g., neurotransmitters).

Autocrine Cell Signaling

• Cells respond to their own secreted signaling molecules (e.g., norepinephrine acting on the same cell).

Additional Terminology

• Autocoids: Local hormones; can act in autocrine and paracrine ways.
• Paracrine Hormones: Local signals produced and metabolized locally; distinct from systemic endocrine hormones.