The Nervous System: Brain and Nerves

The nervous system is divided into the central nervous system (CNS — brain and spinal cord) and the peripheral nervous system (PNS — cranial and spinal nerves).

The brain consists of the cerebrum (higher functions), cerebellum (coordination), and brainstem (vital functions). The cerebral cortex is divided into four lobes: frontal (planning, motor), parietal (sensation), temporal (hearing, memory), and occipital (vision).

The spinal cord extends from the medulla oblongata to approximately L1-L2 vertebral level. It transmits sensory and motor signals and mediates spinal reflexes. 31 pairs of spinal nerves exit through intervertebral foramina.

Neurons communicate through electrical impulses (action potentials) and chemical neurotransmitters at synapses. The autonomic nervous system (sympathetic and parasympathetic divisions) controls involuntary functions.