Lesson Video: The Brain Biology

In this video, we will learn how to identify regions of the brain, describe their functions, and explain how to investigate brain function.


Video Transcript

In this video, we will identify several different areas of the brain and discuss their functions. Then we’ll explain how different methods can be used to investigate brain function and damage. So let’s put our brains to work and get started.

Many people consider the brain to be the most important organ of the human body. This is because the brain functions within the nervous system to regulate and coordinate the functions of the other organ systems. The brain is also where we process and integrate the information that we’re constantly gathering from the world around us. The brain and spinal cord make up the central nervous system. The function of the spinal cord is to relay information to and from the brain. The spinal cord is also responsible for controlling simple reflexes or involuntary reactions that occur without input from the brain.

The nerves that carry information between the central nervous system and the rest of the body are collectively known as the peripheral nervous system. The tissue of the brain is soft, delicate, and easily damaged. The brain is protected by the skull and specialized layers of fluids and connective tissue that protect and cushion the brain from impact. The brain consumes about 20% of our body’s oxygen and about 60% of our body’s glucose. So the brain is covered by a dense web of blood vessels that bring it the glucose and oxygen that it needs.

Within the brain, there are two different types of tissue referred to as grey matter and white matter. The outer layer of the brain is composed of gray matter, which has neurons that are specially designed to process and integrate information. The inner part of the brain is made of white matter. White matter has neurons designed to transmit signals quickly, so white matter allows communication between the different areas of gray matter. Now that we’ve got an overview of the brain and the role it plays in the nervous system, let’s take a look at those different parts.

The brain is made of a symmetrical left and right hemisphere. So this larger diagram is showing us an external side view of the right hemisphere. The cerebrum is the largest part of the brain. And the outer layer of gray matter is called the cerebral cortex. Cortex is a word that’s Latin for bark, as in what you find on a tree. And like bark, the cerebral cortex is the outer layer and characterized by deep wrinkles. Well, the cerebral cortex is made of gray matter. And we know that gray matter is responsible for processing and integrating information. But what does that actually mean?

Let’s look at our sense of vision as an example. Cells in our eyes are able to detect patterns of light, dark, and color using light. The optic nerve transmits this information to a specific region in the cerebral cortex, where the brain decodes these patterns into things like blue square, human face, or fast-moving object. The brain is able to take the information, transmit it from our sensory nerves, and translate it into useful information, which is what we mean by processing. Then we may store this information for later, have an emotional response, or take action. And that’s what we mean by integration.

The cerebral cortex controls many of our mental functions, including attention, memory, awareness, thought, perception, emotions, language, vision, hearing, decision-making, and movement. The second most prominent feature of the brain is the cerebellum. Cerebellum is a word that means little brain and that also describes its appearance. The cerebellum is located at the back of the brain and is also covered with small wrinkles. The cerebellum is primarily responsible for motor control. And this includes things like coordination, precision, timing, fine movements, balance, posture, and motor learning.

It’s important to remember that the cerebellum doesn’t initiate movement but instead controls and fine-tunes our motor activities, which means that damage to this part of your brain wouldn’t keep your body from moving but would make your movements less coordinated and more difficult.

The last feature we’re able to see from this external view is the brain stem. The brain stem connects the brain to the spinal cord, which conveys information between the brain and the rest of the body. And within the brain stem is a structure called the medulla oblongata. Besides connecting the brain to the spinal cord, the medulla oblongata plays the essential role of coordinating and regulating cardiac and respiratory function. Damage to this part of the brain could quickly become life threatening because it could interrupt these critical life processes. Now that we’re familiar with the external view, let’s take a look at the brain from the inside.

Here we have a diagram of a cross section of the brain. This shows us the view of the left hemisphere from the inside. The structures that we’ve already identified have been labeled. This pea-sized structure, situated deep within the brain, may be familiar if you’ve studied the endocrine system. It’s the pituitary gland. The pituitary gland is known as the master gland because it produces and releases hormones that affect lots of life processes. But how does the pituitary gland know what hormones to release and when?

That question is largely answered by the specialized region just above the pituitary gland known as the hypothalamus. Its central location means that it connects and interacts with many different regions of the brain. The hypothalamus is often thought of as a bridge between the endocrine system and the nervous system because it’s able to detect changes in the body and trigger responses by the pituitary gland. The hypothalamus has several functions that can be summarized as maintaining homeostasis within the body.

Recall that homeostasis is the maintenance of a constant normal internal environment. The hypothalamus controls things like body temperature, fluid balance, appetite, and sleep cycles. Next, let’s learn about how scientists study the brain.

In order to understand the brain, scientists and physicians generally used three main methods. We can study the effects of stimulating the brain, we can study the changes brought about by injury to the brain, and we can look at images of the brain produced by brain scanning devices.

In brain stimulation experiments, devices like electrodes or strong magnets are used to activate different parts of the brain. And then the effects on the person are observed or tested. Stimulating a certain part of the brain may affect a person’s hearing, while stimulating another part may make it difficult for them to make decisions.

Another method involves looking at the effects of traumatic injuries, strokes, and even brain tumors to learn about the different roles of the different parts of the brain. Depending on the area affected by damage or disease, the effects shown in the patient will be different. In a famous 19th century case, an iron bar shot through the skull of a railroad worker named Phineas Gage tearing a hole through a particular region of the cerebral cortex. He miraculously survived but with significant changes to his personality.

Since doctors knew what part of the brain was damaged and could observe the changes that resulted, they were able to gain valuable insights into the function of that part of the brain, specifically that it has to do with personality. This information also works in reverse. Once we know the functions of different parts of the brain, we can localize an injury by observing its effects. For example, if a patient with a brain tumor is having issues with coordinated movement and balance, doctors then know that the tumor is likely located within the patient’s cerebellum. The relationship between injury to a particular part of the brain and an observable change in function has historically been one of the most useful methods for studying the brain and diagnosing brain disorders.

Modern technology has given rise to several sophisticated methods to scanning and taking images of the inside of the body. The three main types of brain scans used are MRI scans, CT scans, and PET scans. MRI stands for magnetic resonance imaging. MRI uses strong magnetic fields and generates two-dimensional images like slices of the brain. An MRI scan is able to measure the structure and function of brain tissue because MRI scans can produce images in real time, showing changes that occur within the brain. And they do this without exposing the patient to any ionizing radiation.

However, MRIs take a relatively long time. And patients must lie still within the device while they’re being scanned, which may be difficult for patients like children. Also, because of the strong magnets, these scans cannot be used on patients that have any metal implants.

CT stands for computed tomography. CT scans use X-rays to construct two-dimensional images like slices of the inside of the body. CT scans are much faster than MRIs. And metal implants are not a concern. But CT scans only show structure and not function, since X-rays takes still pictures like a camera. And CT scans produce less detailed images when used on soft tissues like the brain.

PET stands for positron emission tomography. A PET scan uses a radioactive chemical marker which is injected into the body and detected by the scanner. Since more active cells will absorb more of the radioactive marker, these scans are able to produce highly detailed 3D images at the cellular level. PET scan Images are highly detailed and show both structure and function. So they’ll often be able to detect disease or damage before an MRI or CT scan would be able to. But PET scans are relatively expensive, so they’re used less often.

Let’s wrap up our lesson by taking a moment to review what we’ve learned. In this video, we learned to identify the structure and function of several different parts of the brain, including the cerebrum, the cerebral cortex, the cerebellum, the medulla oblongata, the hypothalamus, and the pituitary gland. Then we learned several methods scientists use to investigate and diagnose the brain, including imaging methods such as MRI, CT scans, and PET scans.

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