Unit 19. The nervous system. The brain.

WARM-UP: Spend a minute writing down all of the different constituent and types of our nervous system. Share your ideas with the group.

VOCABULARY: Learn the following words and word combinations.

Brain spinal cord spinal column neuron dendrite axon myelin to conduct sensation voluntary involuntary glands to inhibit skull to be responsible for skills cerebral hemispheres cerebrum frontal lobes cerebellum to excite

Guess the meaning of the following words.

Nervous system; sensory nerves; somatic nervous system; central nervous system; cardiac muscles; smooth muscles; right-handed people; vision; hearing; speech; movement; digestive system; heart; logical thinking.

Practice the following for pronunciation.

spinal cord [ˈspaɪ.nl kɔːd]

spinal column [ˈspaɪ.nl ˈkɒl.əm]

neuron [ˈnjʊə.rɒn]

dendrite [ˈden·drɑɪt]

axon [ˈæk·sɑn]

myelin [ˈmaɪə.lɪn]

sensation [senˈseɪ.ʃn]

sensory nerve [ˈsent .sər.i nɜːv]

voluntary [ˈvɒl.ən.tri]

inhibit [ɪnˈhɪb.ɪt]

skull [skʌl]

excite [ɪkˈsaɪt]

cerebral hemisphere [ˈser.ɪ.brəl ˈhem.ɪ.sfɪə]

cerebrum [sɪˈriː.brəm]

frontal lobes [ˈfrʌn.tl ləʊb]

cerebellum [ˌser.əˈbel.əm]

READING: Read the text and do the tasks that follow.

Our nervous system is a busy network of nerves. It includes the nerves in our brain and the nerves that stretch throughout our bodies. Our brain is connected to the rest of the body by the spinal cord, a thick cable that runs down the spinal column in our back.

Nerves are made up of thing strands called neurons. There are millions of these throughout the nervous system and each consists of a cell body, which has short branches called dendrites. The long arm of the neuron is called axon. Some axons are enclosed in a fatty layer called myelin, which helps to speed up the conduction of nerve messages along the axon. Nerve cells in our spinal cord can’t be replaced. Nerves carrying sensations, such as pain, are known as sensory nerves.

The brain and spinal cord compose the central nervous system. The somatic nervous system conducts nervous impulses that have already been processed, away from the central nervous system to the skeletal muscle tissue. The somatic nervous system is under voluntary control. All the parts of the nervous system, excluding the brain and spinal cord are collectively known as the peripheral nervous system.

The autonomic nervous system consists of the nerves that carry nervous impulses from the central system to the heart (cardiac muscles), to the muscles in the digestive system (smooth muscles), and to the glands. All of these muscles and glands contract and function involuntary. The autonomic nervous system is subdivided into two parts, the sympathetic and parasympathetic systems. These function in opposition to one another; the first inhibits organs, while the latter usually excites organs.

The brain looks like a mass of grey jelly and is very soft. It is protected in the hard, bony case known as the skull. The human brain is quite large but is wrinkled, which makes it compact.

The brain is the body’s control center. It is involved with what we do and what we think, as well as what we feel and remember. The left-hand side of our brain controls the right side of the body, and the right-hand side of our brain controls the left side of the body. Most people are right-handed, because the left side of the brain is generally used more than the right side. It has been found that each side of our brain is responsible for different skills. The right side holds our artistic talent and imagination, and the left side is more responsible for practical abilities and logical thinking.

The largest part of the brain consists of two sections. Together they are known as the cerebral hemispheres or cerebrum. The cerebrum is highly organized. It is arranged in areas that relate to different parts of the body and to different needs. Vision is interpreted at the back of the cerebrum; hearing and speech at the side. The areas for sensation and movement are in the middle. The area at the front of the cerebrum, the frontal lobes, controls our behavior. Below and to the back of the cerebrum lies the cerebellum. It contains nerve cells that are mainly concerned with the balance.