Chapter 18 — Neural Control and Coordination

Chapter 18 of the Class 11 Biology NCERT textbook, "Neural Control and Coordination", covers this topic. It explains how the neural system coordinates body functions through neurons, nerve impulses, and synapses, and how the brain controls voluntary movements and vital organs through three divisions: forebrain, midbrain, and hindbrain.

• Neural system for homeostasis — The chapter frames the neural system—divided into central and peripheral parts—as the body's fast coordinator, using neurons to detect, receive, and transmit stimuli that keep internal conditions stable.
• How impulses travel — It explains nerve impulses as action potentials driven by ion movements—sodium influx depolarizing and potassium efflux restoring the membrane—and how myelin and nodes of Ranvier speed conduction along axons.
• The brain's divisions and synapses — The chapter shows how signals cross synapses via neurotransmitters and how the forebrain, midbrain, and hindbrain divide labour over sensory processing, emotion, and vital functions like respiration and heart rate.

1. 01The neural system maintains homeostasis through coordination of organ systems via neurons that detect, receive, and transmit stimuli.
2. 02Neurons have three parts: cell body (with Nissl's granules), dendrites (transmit impulses toward cell body), and axon (transmit impulses away from cell body).
3. 03Nerve impulses are generated by ion channel permeability changes — Na⁺ influx depolarizes the membrane, while K⁺ efflux restores resting potential.
4. 04Synapses are junctions between neurons; chemical synapses use neurotransmitters released from synaptic vesicles to transmit impulses across the synaptic cleft.
5. 05The brain divides into forebrain (controls sensory/motor functions, temperature, eating, emotions), midbrain, and hindbrain (controls respiration, heart rate, balance).
6. 06Myelinated axons conduct impulses faster than unmyelinated axons due to myelin sheath insulation and nodes of Ranvier.