6 The Brain
Learning Objectives:
By the end of this lab, students will:
- Explain the directional terms associated with the orientation of the brain in the cranial cavity.
- Describe the layers of tissue that cover the brain and explain their function.
- Describe the structures of the cerebral hemispheres, including the lobs of the brain and their components, using the whole-brain and midsagittally sectioned specimens.
- Explain the various functions associated with identified regions of the brain.
- Describe the Circle of Willis.
Terms to Know
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Directional Terms
Cerebrum
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Meninges
Ventricles
Other Structures
Blood Supply to the Brain
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Introduction
In this lab, you will learn about the brain. The brain is a mass of neurons and glial cells controlling everything from our ability to breathe, speak, and move our limbs, to our personalities, emotions, and higher-level thinking.
It is important to address two additional directional terms that are used with respect to the brain. A change in the long axis of the nervous system occurs between the cerebrum and the brainstem. The long axis of the cerebrum is relatively horizontal, while the long axis of the brainstem and spinal cord is relatively vertical.
As a result, some of the directional terms may have slightly different meanings depending on the structure to which they refer. Rostral is a term referring to the most frontal portion of the brain (rostrum = nose), while caudal describes structures closer to the tip of the spinal cord (caudal = tail). When used in the context of the cerebrum, rostral refers to structures closer to the nose (as before), but caudal now refers to structures toward the back of the head (posterior). The terms ventral and dorsal can be used interchangeably with anterior and posterior with respect to the plan of the brainstem and spinal cord. However, in the plane of the cerebrum, these terms are interchangeable with inferior and superior.
The University of British Columbia has excellent resources that you may find helpful in studying the brain. These resources at neuroanatomy.ca. The site contains videos, interactive modules, 3D models, cross-sectional images, radiology, and other tools.
Lab Activities
Activity 1: The Meninges
Three connective tissue membranes cover the brain: dura mater, arachnoid mater, and pia mater. The brain has a consistency like somewhat firm jelly during life. The meninges function to protect this soft structure by anchoring it to the skull and preventing excessive movement within the skull.
The dura mater is the thick outer layer of meninges. The dura mater follows the contours of the skull’s inner surface and does not dive into the sulci of the brain. In a few places, it folds and dives into spaces between parts of the brain. These are called the dural reflections. You can explore the dural reflections using the images below.
The arachnoid mater is the middle layer of the meninges, and it is a delicate, transparent membrane that can be seen coveri