Any neural element outside the brain or spinal cord; such as the nerve cells and processes, cranial nerves, and spinal nerves.

Can be further ssubdivided into:

• Somatic NS (SNS) - voluntary skeletal muscle
• Autonomic NS (ANS) - automatic motor and sensory impulses
• Sympathetic - "emotional" responses, upregulates system (fight/flight/fright)
• Parasympathetic - downregulates systems (rest/recovery/relaxation)

• Dura Mater - The outermost layer of the brain made up of fibrous connective tissue. It has two layers: the superficial layer attached to the periosteum of the skull, and a deeper layer that externally covers the brain and continues as the spinal dura matter. Separates the two lobes via the Falx cerebri.

Subdural Space

• Arachnoid mater - Middle layer.Does not dip into the sulci. 

Subarachnoid Space

• Pia Mater - The innermost layer. Clings tightly to the brain and follows all the convolutions.

• Gyrus/Gyri - ridges
• Sulcus/Sulci - shallow grooves (what gives the brain that squiggly look)
• Fissures - deep grooves that visibly divide regions of the brain