Texts: the nerves. The nervous system. Pre-reading and reading tasks

1. Study the vocabulary which is intended to aid your comprehension of the text:

contract (v)	[kqn'trxkt]	сокращать(ся)
enclose (v)	[In'klqVz]	окружать
excite (v)	[Ik'saIt]	возбуждать
inhibit (v)	[In'hIbIt]	задерживать
link up (v)	['lINkAp]	связывать
process (v)	['prqVses]	обрабатывать
release (v)	[rI'li:s]	освобождать
arm	[Q:m]	ветвь, отросток
axon	['xksPn]	аксон,нейрит
dendrite	['dendraIt]	дендрит
end-plate	['endpleIt]	концевая пластинка
fiber	['faIbq]	нить, волокно
gap	[gxp]	разрыв
injury	['IndZqrI]	рана, ушиб
junction	['dZANkS(q)n]	место соединения
myelin	['maIqlIn]	миелин
network	['netwE:k]	сеть
passing	['pQ:sIN]	прохождение
sensation	[sen'seIS(q)n]	чувство,ощущение
spinal column	['spaInl 'kPlqm]	позвоночный столб
strand	[strxnd]	нить (ДНК, белка)
synapse	['saInxps]	синапс
digestive	[d(a)I'dZestIv]	пищеварительный

2. Make sure you can supply an adequate translation for each of the following word combinations:

throughout one’s body	smooth muscles
to speed up the conduction	reflex action
sensory nerves	somatic system
motor neurons	peripheral system
muscle fiber	parasympathetic system
voluntary control	cardiac muscles

3. Read and translate the text.

The nerves

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 our body by the spinal cord, a thick cable that runs down the spinal column in our back.

Nerves are made up of thin 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 the axon. Some axons are enclosed in a fatty layer called myelin, which helps to speed up the conduction, or passing, of nerve messages along the axon. Nerve cells in our spinal cord cannot be replaced, so spinal injury can be serious.

Nerves carrying sensations, such as pain, are known as sensory nerves. When a wasp stings your leg the sensory impulse travels up the leg and into the spinal cord. It is then transmitted to neurons in the grey matter of the cord, which link up with motor neurons. The impulse travels back down the leg in the motor nerve and the leg muscle tightens, making the leg jerk. The reflex action does not involve the brain.

Nerve impulses link up neurons by jumping across a gap called a synapse. When an impulse reaches the end of an axon, chemicals are released that allow it to pass across the synapse and on to the next neuron.

The axon of a motor neuron meets the muscle at a special junction called the motor end-plate. When the nerve impulse is received at the motor end-plate a substance called acetylcholine is released, which sticks to the outside of the muscle fiber, causing gates in the muscle fiber to open and let in sodium. This activity makes our muscle contract and movement occurs.

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 involuntarily. 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.