Class 12 Biology Chapter 15 Human Nervous System Notes | Punjab Board PDF

Class 12 Biology Chapter 15 Human Nervous System presents a comprehensive study of neural regulation and communication in the human body. Nervous coordination relies on specialized cells called neurons, supported by neuroglia. Students explore neuron structure (cell body, dendrites, and axon), the three functional types of neurons (sensory, motor, and inter-neurons), and the monosynaptic and polysynaptic reflex arcs, such as the knee-jerk reflex.

The biophysical mechanisms of nerve impulses are analyzed in detail – moving from the resting membrane potential (-70mV maintained by the Na+/K+ pump) to the generation and propagation of the active membrane potential (action potential). The chapter further covers synaptic transmission across chemical synapses via excitatory and inhibitory neurotransmitters, the structural organization of the Central Nervous System (CNS) (cerebrum, diencephalon, limbic system, cerebellum, brainstem, ventricles, and spinal cord), and the Peripheral Nervous System (PNS) with its somatic and autonomic (sympathetic and parasympathetic) divisions.

Additional sections detail sensory receptors (taste, smell, touch, and pain), the impact of addictive drugs (caffeine, nicotine, heroin, cannabis, alcohol) on neural pathways, classifications of nervous system disorders (vascular, infectious, structural, functional, degenerative), and modern diagnostic tools like EEG, CT, and MRI. For HSSC Part 2 students across Lahore Board, Rawalpindi Board, Gujranwala Board, and other Punjab boards, Chapter 15 is vital for exam success. These notes conform to the PCTB / PECTAA 2026-2027 syllabus, offering complete solved exercises, MCQs, short questions, and long questions.