🔑 Key Definitions
Cell Soma: Cell body containing nucleus and organelles; site of protein synthesis and metabolic processes
Axon Hillock: Region where axon emerges from soma; site where action potential is initiated
Myelin Sheath: Fatty insulation around axons that speeds signal conduction
Nodes of Ranvier: Gaps between myelin segments where action potential is regenerated; enables saltatory conduction
Axon Hillock: Region where axon emerges from soma; site where action potential is initiated
Myelin Sheath: Fatty insulation around axons that speeds signal conduction
Nodes of Ranvier: Gaps between myelin segments where action potential is regenerated; enables saltatory conduction
🧠 Cell Soma Components
- Nucleus: Contains DNA/genetic material; controls cell function and protein production
- Ribosomes: Protein synthesis machinery; found free in cytoplasm and on rough ER
- Endoplasmic Reticulum (ER): Rough ER (with ribosomes) makes proteins; smooth ER synthesizes lipids
- Mitochondria: "Powerhouses" that produce ATP through cellular respiration
- Golgi Apparatus: Packages and modifies proteins for transport
📊 Axon Characteristics
- Axon Hillock: Integration zone; summates EPSPs and IPSPs to determine if action potential fires
- Myelin: Formed by oligodendrocytes (CNS) or Schwann cells (PNS); increases conduction speed
- Nodes of Ranvier: Unmyelinated gaps every 1-2mm; action potential "jumps" between nodes (saltatory conduction)
- Axon Terminal: Contains synaptic vesicles with neurotransmitters
📊 Dendrites & Cell Membrane
- Dendrites: Branching processes that receive input from other neurons; contain receptor sites
- Dendritic Spines: Small protrusions that increase surface area for synaptic contacts
- Phospholipid Bilayer: Cell membrane composed of two layers of lipids with embedded proteins
- Membrane Proteins: Ion channels, receptors, transporters that regulate what crosses membrane
💡 Exam Tips
- Soma = cell body with nucleus and organelles for maintaining cell
- Axon hillock is WHERE the action potential begins (integration point)
- Remember: Nodes of Ranvier = gaps in myelin = where AP regenerates
- Myelin speeds conduction - diseases that destroy myelin (MS) slow neural signals
- Dendrites RECEIVE (input), axons SEND (output)
- Phospholipid bilayer = basic structure of ALL cell membranes