Brain 101: An Overview of the Anatomy and Physiology of the Brain

This week is Brain Awareness Week (BAW). The brain is a fascinating and complex organ. It is responsible for senses, movement and control, emotions and feelings, language and communication, thinking and memory. Research of the brain and understanding the inner workings of the brain will help us to learn about the mechanisms of certain neurological conditions, including hydrocephalus. Increasing our own knowledge of the brain helps us understand our own bodies better and helps us have informed conversations with our doctors, be it as a patient or a caregiver.

To celebrate BAW we present a two-part blog to increase our understanding of the brain and how the brain is impacted by hydrocephalus. We hope you enjoy these blogs and find them both informative and useful.

The Dana Alliance for Brain Initiative launched Brain Awareness Week (BAW) back in 1996. The Hydrocephalus Association proudly partners with the Dana Foundation for this global campaign to increase public awareness about the progress and benefits of brain research. This global coalition of BAW partners includes more than 2000 universities, K-12 schools, hospitals, patient groups, museums, government agencies, services organizations, and professional associations. For more educational resources on the brain go to the Dana Foundation BAW website.

 

Brain 101: An Overview of the Anatomy and Physiology of the Brain

The brain and spinal cord form the central nervous system. These vital structures are surrounded and protected by the bones of the skull and the vertebral column, as shown in the drawing.The bones of the skull are often referred to as the cranium. In infants, the skull is actually composed of separate bones, and an infant’s soft spot (anterior fontanel) is an area where four skull bones nearly come together. The places where the bones meet and grow are called sutures.
A baby’s brain grows rapidly, quadrupling in size by the age of 2. By 3 years old, it is approximately 85% of an adult-sized brain. While the brain is growing, the sutures remain open, giving the brain room to grow. (Odunze, 2011)  Acute changes in head circumference can be an indication of hydrocephalus, as pressure within the brain causes the cranium to expand. The metopic suture closes at around 2 years of age.

The vertebral column, which encases the entire spinal cord, is composed of bones called vertebrae. The spinal cord extends from the brain stem, through a very large opening (the foramen mag­num) in the base of the skull, and down the spine. (About Hydrocephalus, 2011)

Spina Bifida is a neural tube defect (NTD) where the spinal cord is exposed at birth and is often leaking cerebrospinal fluid (CSF). There are two types of Chiari malformation. Both types occur in the bottom of the brain stem where the brain and spinal cord join. The lowest portion of the brain is displaced and is lower than normal pushing down into the spinal column.

At the level of each vertebra in the spine, nerve fibers arise from the spinal cord and emerge through openings between the vertebrae. These are the spinal nerves, which carry messages to and from various regions of our bod­ies. (About Hydrocephalus, 2011)

The brain consists of four main structures: the Cerebrum, the Cerebellum, the Pons, and the Medulla.

The Cerebrum is the upper part of the brain and is arranged in two hemispheres called cerebral hemispheres. The cerebrum is thought to control conscious mental processes. The outer layer of the cerebrum is called gray matter, the inner portion, white matter.

We often hear the terms “gray matter” and “white matter” in radiology reports or when viewing scans with our neurosurgeons. Grade III and IV intraventicular hemorrhages (IVH) as well as periventricular leucomalacia (PVL) can cause damage to the brain tissue, and can lead to hydrocephalus.

 

The cerebral hemispheres are divided into four sections or lobes: the frontal lobe, responsible for thinking, making judgments, planning, decision-making and conscious emotions, the Parietal Lobe, mainly associated with spatial computation, body orientation and attention, the Temporal Lobe, concerned with hearing, language and memory, and the Occipital Lobe, mainly dedicated to visual processing.
The key features of the Dandy Walker syndrome are an enlargement of the fourth ventricle, a partial or complete absence of the area of the brain between the two cerebellar hemispheres and cyst formation near the lowest part of the skull. Approximately 70 to 90 percent of patients have hydrocephalus.

The Cerebellum is the part of the brain located between the brain stem and the back of the cerebrum.  The cerebellum controls muscle coordination and maintains bodily equilibrium.

An increase in cerebrospinal fluid (CSF) in the fourth ventricle can put pressure on the lobe of the cerebellum (hindbrain).  Compression of this lobe can cause gait, balance and postural problems.

The Pons is in front of the cerebellum and coordinates the activities of the cerebrum and the cerebellum by receiving and sending impulses from them to the spinal cord.  

The Medulla is part of the brainstem situated between the pons and the spinal cord and it controls breathing, heartbeat, and vomiting.

There are many other anatomical features of the brain which specialize in various activities.  The Meninges consist of three membranes which cover the brain and spinal cord including the dura mater, the arachnoid membrane and the pia mater. They completely surround the brain and spinal cord.

Hydrocephalus produces pressure on the meninges which in turn can increase pressure on the optic nerve causing vision problems.

Cerebrospinal fluid flows in the space between two of the layers in a space called the subarachnoid space.  CSF is essentially salt water, and it is in constant circulation and serves several important functions. The brain floats in CSF.

Subarachnoid hemorrhage is a bleeding in the subarachnoid space.  Acute hydrocephalus is present in 20 percent of patients with subarachnoid hemorrhage.

In our blog on Saturday we will focus on the two key areas of the brain related to hydrocephalus – the ventricles and the flow of cerebrospinal fluid. To learn more about hydrocephalus, visit these areas of our website:

 

References


Odunze, Millicent, M.D. Craniosynostosis: Why Do Some Children Have Crooked Skulls. About.com Guide, November 2011

About Hydrocephalus: A Book for Families. Hydrocephalus Association, 2011

Carter R. The Human Brain Book. AN ILLUSTRATED GUIDE TO ITS STRUCTURE, FUNCTION, AND DISORDERS. Great Britain: Dorling Kindersley Limited, 2009.

 

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