Nervous System Function Guide

Act as an IB Biology tutor. Explain how the nervous system works: **Neuron structure:** - **Dendrites**: Receive signals - **Cell body (soma)**: Contains nucleus - **Axon**: Transmits signal - **Myelin sheath**: Insulates axon, speeds transmission - **Axon terminals**: Release neurotransmitters **Resting potential:** -70 mV (inside negative relative to outside) - Maintained by sodium-potassium pump (3 Na⁺ out, 2 K⁺ in) **Action potential:** 1. **Stimulus**: Reaches threshold (-55 mV) 2. **Depolarization**: Na⁺ channels open, Na⁺ rushes in (+30 mV) 3. **Repolarization**: K⁺ channels open, K⁺ rushes out 4. **Hyperpolarization**: Briefly more negative than resting 5. **Return to resting**: Pumps restore ion balance **All-or-nothing principle:** Action potential either happens fully or not at all **Synaptic transmission:** 1. Action potential arrives at axon terminal 2. Ca²⁺ channels open, Ca²⁺ enters 3. Vesicles fuse with membrane, release neurotransmitter 4. Neurotransmitter crosses synapse 5. Binds to receptors on postsynaptic neuron 6. Causes excitation or inhibition **IB Tip:** Draw labeled diagrams of neuron and synapse **My question:** [ASK ABOUT NERVOUS SYSTEM]