Parts of the Human Brain

The main players: Two cerebral hemispheres account for 85% of the brain’s weight. The billions of neurons in the two hemispheres are connected by thick bundles of nerve cell fibers called the corpus callosum. The left hemisphere appears to focus on details (such as recognizing a particular face in a crowd). The right hemisphere focuses on broad background (such as understanding the relative position of objects in a space). The cerebral hemispheres have an outer layer called the cerebral cortex. This is where the brain processes sensory information received from the outside world, controls voluntary movement, and regulates cognitive functions, such as thinking, learning, speaking, remembering, and making decisions. The hemispheres have four lobes, each of which has different roles:

· The frontal lobe controls executive function activities like thinking, organizing, planning, and problem solving, as well as memory, attention, and movement.

· The parietal lobe, which sits behind the frontal lobe, deals with the perception and integration of stimuli from the senses.

· The occipital lobe, which is at the back of the brain, is concerned with vision.

· The temporal lobe, which runs along the side of the brain un­der the frontal and parietal lobes, deals with the senses of smell, taste, and sound, and the formation and storage of memories.

The cerebellum sits above the brain stem and beneath the occipital lobe. It takes up a little more than 10% of the brain. This part of the brain plays roles in balance and coordination. The cerebellum has two hemispheres, which receive information from the eyes, ears, and muscles

and joints about the body’s movements and position. Once the cerebellum processes that information, it sends instructions to the body through the rest of the brain and spinal cord. The cerebellum’s work allows us to move smoothly, maintain our balance, and turn around without even thinking about it. It also is involved with motor learning and remembering how to do things like drive a car or write your name.

The brain stem sits at the base of the brain. It connects the spinal cord with the rest of the brain. The brain stem controls the functions that happen automatically to keep us alive—our heart rate, blood pressure, and breathing. It also relays information between the brain and the spinal cord, which then sends out messages to the muscles, skin, and other organs. Sleep and dreaming are also controlled by the brain stem.

Other crucial parts of the brain: Several other essential parts of the brain lie deep inside the cerebral hemispheres in a network of structures called the limbic system. The limbic system links the brain stem with the higher reasoning elements of the cerebral cortex. It plays a key role in developing and carrying out instinctive behaviors and emotions and also is important in perceiving smells and linking them with memory, emotion, and instinctive behaviors. The limbic system includes the following:

· The amygdala, an almond-shaped structure involved in process­ing and remembering strong emotions such as fear. It is located in the temporal lobe just in front of the hippocampus.

· The hippocampus, which is buried in the temporal lobe, is impor­tant for learning and short-term memory. This part of the brain is thought to be the site where short-term memories are convert­ed into long-term memories for storage in other brain areas.

· The thalamus, located at the top of the brain stem, receives sen­sory and limbic information, processes it, and then sends it to the cerebral cortex.

· The hypothalamus, a structure under the thalamus, monitors activities such as body temperature and food intake. It issues in­structions to correct any imbalances. The hypothalamus also controls the body's internal clock.

The human brain is made up of billions of neurons. Each has a cell body, an axon, and many dendrites. The cell body contains a nucleus, which controls much of the cell’s activities. The cell body also contains other structures, called organelles that perform specific tasks.

The axon, which is much narrower than the width of a human hair, extends out from the cell body. Axons transmit messages from neuron to neuron. Sometimes, signal transmissions—like those from head to toe—have to travel over very long distances. Axons are covered with an insulating layer called myelin (also called white matter because of its whitish color). Myelin, which is made by a particular kind of glial cell, increases the speed of nerve signal transmissions through the brain. Dendrites also branch out from the cell body. They receive messages from the axons of other neurons. Each neuron is connected to thousands of other nerve cells through its axon and dendrites. Groups of neurons in the brain have special jobs. For example, some are involved with thinking, learning, and memory. Others are responsible for receiving information from the sensory organs (such as the eyes and ears) or the skin. Still others communicate with muscles, stimulating them into action. Several processes all have to work smoothly together for neurons, and the whole organism, to survive and stay healthy. These processes are communication, metabolism, and repair.

Nerve cells are formed during fetal life and for a short time after birth. Unlike most cells, which have a fairly short lifespan, neurons in the brain live a long time. These cells can live for up to 100 years or longer. To stay healthy, living neurons must constantly maintain and repair themselves. In an adult, when neurons die because of disease or injury, they are not usually replaced. Research, however, shows that in a few brain regions, new neurons can be generated, even in the old brain.

 

1. Answer the questions:

1) What value does a living-being brain have?

2) What parts of the brain are critical for humans?

3) What is the main function of the brain?

4) What parts of the brain are critical for other vertebrates?

5) What is each part of the brain responsible for?

6) Could a living-being survive without a brain?

 

2. Say if these statements are true or false:

1) The brain is the center of the nervous system.

2) The brain manages many body functions.

3) The human brain is made up of billions of neurons.

4) Nerve cells are formed during natal period.

5) The thalamus, located deep in the back of the brain stem, receives sen­sory and limbic information, processes it, and then sends it to the cerebral cortex.

6) Axons are covered with an insulating layer called myelin.

7) Each hemisphere is further divided into lobes.

8) The human brain is very large compared to most animals.

9) The cerebellum takes up a little more than 15% of the brain.

10) Everything about ourselves and the environment is experienced through the brain.

3. Which word in the list is odd?

1) brain, head, skull, nervous system;

2) sensory apparatus, vision, hearing, balance, taste, and smell;

3) neurons, dendrites, axons, head;

4) spinal cord, cerebral cortex, sensory apparatus;

 

4. Give synonyms from the text to the following words:

- the organ inside the head which controls body, allows to think and feel;

- the bones of the head;

- one half of the brain, divided between left and right;

- the smallest part of a living structure that can operate as an independent unit;

- the outer layer of the brain.

- an almond-shaped structure involved in process­ing and remembering strong emotions such as fear;

- sits at the base of the brain and connects the spinal cord with the rest of the brain.

5. Make up the plan of the text. Here are the topics\ paragraphs in the wrong order. Make it correct:

- the structure of the brain

- general information about the brain

- functions of the brain

- important areas of the brain