Cranial nerves

The cranial nerves consist of 12 pairs of nerves originating directly from the brain and brainstem. They supply both motor and sensory information from the brain to other parts of the body, primarily supplying the region of the head and neck.

The nervous system is divided into the central nervous system, so the brain and the spinal cord, and the peripheral nervous system, which is further divided into the somatic and the autonomic nervous systems. Broadly speaking, the nervous system is split into an afferent and an efferent division. The afferent division brings sensory information - like vision, smell, touch, and proprioception - from the outside world into the brain. On the other hand, the efferent division brings motor information from the brain to the periphery, ultimately resulting in contraction of skeletal muscles to trigger movement through the somatic nervous system, as well as the contraction of the smooth muscles to trigger activity of the glands and organs through the autonomic nervous system.

Now, neurons are the main cells of the nervous system. And they’re composed of a cell body, which contains all of the cell’s organelles, and when there’s a group of neuron cell bodies found in the central nervous system, the whole thing is called a nucleus, while a group of neuron cell bodies that are located outside of the central nervous system is called a ganglion. Neurons also have nerve fibers that extend out from the neuron cell body - these are either dendrites that receive signals from other neurons, or axons that send signals along to other neurons. Where two neurons come together is called a synapse, and that’s where one end of an axon releases neurotransmitters, further relaying the signal to the dendrites or directly to the cell body of the next neuron in the series.