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Sensory information used to control actions is processed in neural pathways separate from the afferent pathways that contribute to conscious perception.

The actions of the sympathetic and parasympathetic system are often antagonistic, but always divergent.

The auditory system enables hearing by capturing sound waves, amplifying vibrations, and converting them into neural signals processed by the brain. The inner ear also supports balance and spatial orientation through the vestibular system.

Histamine is produced from the amino acid histidine by histidine decarboxylase and degraded by methyltransferase and monoamine oxidase. In the brain, histamine is primarily found in neurons of the hypothalamus that project widely throughout the brain.

The nervous system is divided into two main components: the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which includes all nervous system structures located outside of the CNS.

The brain receives oxygenated blood primarily through the internal carotid arteries and the vertebral arteries.