<< Chapter < Page Chapter >> Page >

The entire brain contains only about 8.5 tablespoons of CSF, but CSF is constantly produced in the ventricles. This creates a problem when a ventricle is blocked—the CSF builds up and creates swelling and the brain is pushed against the skull. This swelling condition is called hydrocephalus (“water head”) and can cause seizures, cognitive problems, and even death if a shunt is not inserted to remove the fluid and pressure.

Illustration shows the three meninges that protect the brain. The outermost layer, just beneath the skull, is the dura mater. The dura mater is the thickest meninge, and blood vessels run through it. Beneath the dura mater is the arachnoid mater, and beneath this is the pia mater.
The cerebral cortex is covered by three layers of meninges: the dura, arachnoid, and pia maters. (credit: modification of work by Gray’s Anatomy)

Brain

The brain is the part of the central nervous system that is contained in the cranial cavity of the skull. It includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, and cerebellum. There are three different ways that a brain can be sectioned in order to view internal structures: a sagittal section cuts the brain left to right, as shown in [link] b , a coronal section cuts the brain front to back, as shown in [link] a , and a horizontal section cuts the brain top to bottom.

Cerebral cortex

The outermost part of the brain is a thick piece of nervous system tissue called the cerebral cortex, which is folded into hills called gyri (singular: gyrus) and valleys called sulci (singular: sulcus). The cortex is made up of two hemispheres—right and left—which are separated by a large sulcus. A thick fiber bundle called the corpus callosum (Latin: “tough body”) connects the two hemispheres and allows information to be passed from one side to the other. Although there are some brain functions that are localized more to one hemisphere than the other, the functions of the two hemispheres are largely redundant. In fact, sometimes (very rarely) an entire hemisphere is removed to treat severe epilepsy. While patients do suffer some deficits following the surgery, they can have surprisingly few problems, especially when the surgery is performed on children who have very immature nervous systems.

Illustration shows coronal (front) and sagittal (side) sections of a human brain. In the coronal section, the large upper part of the brain, called the cerebral cortex, is divided into left and right hemispheres. A cavity resembling butterfly wings exists between the left and right cortex. The corpus callosum is a band that connects the two hemispheres together, just above this cavity. The surface of the cerebral cortex contains bumpy protrusions called gyri. The cerebral cortex is anchored by the brain stem, which connects with the spinal cord. On either side of the brainstem tucked beneath the cerebral cortex is the cerebellum. The surface of the cerebellum is bumpy, but not as bumpy as the cerebral cortex. The sagittal section reveals that the cerebral cortex makes up the front and top part of the brain, while the brainstem and cerebellum make up the lower back part. The oval thalamus sits in the cavity in the middle of the cerebral cortex. The corpus callosum wraps around the top part thalamus. The basal ganglia wraps around the corpus callosum, starting at the lower front part of the brain and continuing three-quarters of the way around so the back end almost meets the front end. The basal ganglia is separated into segments that are connected along the top and bottom. The amygdala is a spherical structure at the end of the basal ganglia.
These illustrations show the (a) coronal and (b) sagittal sections of the human brain.

Each cortical hemisphere contains regions called lobes that are involved in different functions. Scientists use various techniques to determine what brain areas are involved in different functions: they examine patients who have had injuries or diseases that affect specific areas and see how those areas are related to functional deficits. They also conduct animal studies where they stimulate brain areas and see if there are any behavioral changes. They use a technique called transmagnetic stimulation (TMS) to temporarily deactivate specific parts of the cortex using strong magnets placed outside the head; and they use functional magnetic resonance imaging (fMRI) to look at changes in oxygenated blood flow in particular brain regions that correlate with specific behavioral tasks. These techniques, and others, have given great insight into the functions of different brain regions but have also showed that any given brain area can be involved in more than one behavior or process, and any given behavior or process generally involves neurons in multiple brain areas. That being said, each hemisphere of the mammalian cerebral cortex can be broken down into four functionally and spatially defined lobes: frontal, parietal, temporal, and occipital. [link] illustrates these four lobes of the human cerebral cortex.

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Principles of biology. OpenStax CNX. Aug 09, 2016 Download for free at http://legacy.cnx.org/content/col11569/1.25
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Principles of biology' conversation and receive update notifications?

Ask