16 Anatomical Terminology
Understanding anatomical terminology is essential for studying neuroscience, as precise language enables clear communication about brain structures and their relationships. This chapter introduces the directional terms, anatomical planes, and organizational principles used to navigate the complex three-dimensional structure of the nervous system.
Directional Terms
Directional terms are used to locate one structure, usually in relation to another structure. Some terms, like dorsal or ventral, are relative to the axis of the central nervous system, so the direction these terms define changes if used for brain regions versus other body regions. Other terms, like superior or inferior, keep their meaning across the entire body.
- Anterior: In front of; toward the face
- Posterior: Behind; toward the back
- Superior: Above; toward the head
- Inferior: Below; toward the feet
- Medial: Toward the middle
- Lateral: Toward the edge
- Dorsal: Toward the top of the brain or the back of the spinal cord
- Ventral: Toward the bottom of the brain or the front of the spinal cord
- Rostral: Toward the front of the brain or the top of the spinal cord
- Caudal: Toward the back of the brain or the bottom of the spinal cord
In four-legged animals, the imaginary line running through the center of the CNS is straight, so dorsal and ventral point in the same direction throughout the brain and spinal cord. In humans, upright posture puts a roughly 90° bend in the neuraxis at the midbrain. This is why dorsal points toward the top of the skull in the brain but toward the back in the spinal cord, and why rostral means “toward the front” in the brain but “toward the head” in the spinal cord.
Anatomical Planes
There are planes or axes that can be used to examine the nervous system. The frontal or coronal plane is a vertical plane in a medial to lateral direction, dividing objects into front and back pieces. The sagittal plane is also a vertical plane but in a rostral-caudal direction, meaning it divides objects into right and left regions. Finally, the horizontal plane divides objects into top and bottom regions.
Nervous System Divisions
The nervous system is divided into two primary components. The central nervous system (CNS) is comprised of the brain and the spinal cord. The peripheral nervous system (PNS) is comprised of the cranial and spinal nerves. When information flow is described in the nervous system, it can either be afferent communication, meaning it is moving from the periphery to the brain, or efferent communication, meaning it is moving from the brain to the periphery.
Tissue in the central nervous system can be further divided into either white matter or gray matter. White matter regions are comprised of axons. It appears white due to the myelin sheath on the axons. Gray matter regions are comprised of cell bodies and dendrites. Gray matter is the location of most synapses.
Conclusion
Mastering anatomical terminology provides the foundation for understanding brain structure and function. These directional terms, planes, and organizational principles create a standardized language that enables precise communication about neural anatomy and serves as the basis for exploring more complex brain systems.
Key Takeaways
- Directional terms (anterior/posterior, superior/inferior, medial/lateral) describe location relative to another structure; dorsal/ventral and rostral/caudal shift direction depending on whether they’re applied to the brain or the spinal cord.
- The frontal, sagittal, and horizontal planes divide the nervous system along three different axes to expose internal structures.
- The CNS (brain and spinal cord) and PNS (cranial and spinal nerves) are the two major divisions of the nervous system; afferent signals travel toward the brain, efferent signals travel away from it.
- White matter is made of myelinated axons; gray matter is made of cell bodies, dendrites, and synapses.
Important Terminology
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Communication that carries information from the periphery toward the brain.
In front of, or toward the face. A directional term that applies consistently throughout the body.
Toward the back of the brain or the bottom of the spinal cord. Caudal points in different directions in the brain versus the spinal cord because of the bend in the axis of the CNS at the midbrain.
The brain and spinal cord.
Toward the top of the brain or the back of the spinal cord. Dorsal points in different directions in the brain versus the spinal cord because of the bend in the axis of the CNS at the midbrain.
Communication that carries information from the brain toward the periphery.
A vertical plane running in a medial-to-lateral direction that divides an object into front and back pieces. Also called the coronal plane.
Central nervous system tissue composed primarily of cell bodies and dendrites. Gray matter is the location of most synapses.
A plane that divides an object into top and bottom regions.
Below, or toward the feet. A directional term that applies consistently throughout the body.
Toward the edge, away from the midline.
Toward the middle, or midline.
The cranial and spinal nerves.
Behind, or toward the back. A directional term that applies consistently throughout the body.
Toward the front of the brain or the top of the spinal cord. Rostral points in different directions in the brain versus the spinal cord because of the bend in the axis of the CNS at the midbrain.
A vertical plane running in a rostral-caudal direction that divides an object into right and left regions.
Above, or toward the head. A directional term that applies consistently throughout the body.
Toward the bottom of the brain or the front of the spinal cord. Ventral points in different directions in the brain versus the spinal cord because of the bend in the axis of the CNS at the midbrain.
Central nervous system tissue composed primarily of axons. White matter appears white because of the myelin sheath surrounding the axons.
