Nervous system anatomy and physiology

The nervous system is involved in nearly everything we do - from how we see, to how we walk and talk.

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 can be split into an afferent and an efferent division.

The afferent division brings sensory information from the outside into the central nervous system, and includes visual receptors, auditory receptors, chemoreceptors, and somatosensory or touch receptors.

On the other hand, the efferent division brings motor information from the central nervous system to the periphery, ultimately resulting in contraction of skeletal muscles to trigger movement through the somatic nervous system, as well as contraction of the smooth muscles to trigger activity of the internal organs through the autonomic nervous system.

The nervous system is made up of two main types of cells: neurons and glial cells.

Neurons are the main cells of the nervous system. They’re composed of a cell body, which contains all the cell’s organelles, and when there’s a group of neuron cell bodies that are next to each other 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 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.