Central nervous system

Lesson 6

Aquatic animals

saltwater fish

nitrogenous wastes

excretory organs

dilute urine

the amount of ammonia

4. Read the text and define the meaning of new words.

Translate the text.

As with many aquatic animals, most fish release their nitrogenous wastes as ammonia. Some of the wastes diffuse through the gills into the surrounding water. Others are removed by the kidneys, excretory organs that filter wastes from the blood. Kidneys help fishes control the amount of ammonia in their bodies. Saltwater fish tend to lose water because of osmosis. In saltwater fish, the kidneys concentrate wastes and return as much water as possible back to the body. The reverse happens in freshwater fish, they tend to gain water continuously. The kidneys of freshwater fish are specially adapted to pump out large amounts of dilute urine. Some fish have specially adapted kidneys that change their function, allowing them to move from freshwater to saltwater.

7. Choose the proper prepositions and fill them in:

1. As … many aquatic animals, most fish release their nitrogenous wastes as ammonia, don’t they?

2. Do some of the wastes diffuse … the gills or … the fins?

3. What are the wastes removed …?

4. What helps fishes control the amount … ammonia … their bodies?

5. … saltwater fish, the kidneys concentrate wastes and return as much water as possible back to the body, don’t they?

8. Pair work. Put the questions given above to your group-mate and let him/her answer them.

1. Read the words. Work with the dictionary, translate the words.

marsupial

olfactory lobe

telencephalon

homeostasis

mesencephalon

equivalent

consequently

2. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

marsupial olfactory lobe olfaction nostrils telencephalon diencephalon cerebrum forebrain midbrain hindbrain brain stem optic lobe pineal body circadian cerebellum

сумчатое животное обонятельная доля (головного мозга) обоняние ноздри конечный мозг промежуточный мозг головной мозг передний мозг средний мозг задний мозг стволовая часть мозга зрительная доля пинеальная железа циркадный мозжечок

3. Read the words and put down their Russian equivalents:

mesencephalon _______________________________

metencephalon _______________________________

myelencephalon ______________________________

circadian rhythms _____________________________

detecting light ________________________________

small brains ___________________________________

4. Master the words.

hagfish – миксина

catfish - 1) сом (рыба; также о ряде других рыб)

2) любой головоногий моолюск, в частности, каракатица

mormyr - мормир, слонорыл (Mormyrus);

мормировые, клюворылые (Mormyridae)

5. Put down the English for:

цихлида

минога

дыхание

гомеостаз

осморегуляция

6. Think of eight questions covering the text. Put them to your group-mates.

7. To be translated in written.

(Dorsal view of the brain of the rainbow trout.)

Fish typically have quite small brains relative to body size when compared with other vertebrates, typically one-fifteenth the mass of the brain from a similarly sized bird or mammal. However, some fishes have relatively large brains, most notably mormyrids and sharks, which have brains of about as massive relative to body weight as birds and marsupials.

The brain is divided into several regions. At the front are the olfactory lobes, a pair of structure and process signals from the nostrils via the two olfactory nerves. The olfactory lobes are very large in fishes that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon, the equivalent structure to the cerebrum in higher vertebrates. In fishes the telencephalon is concerned mostly with olfaction. Together these structures form the forebrain.

Connecting the forebrain to the midbrain is the diencephalon (in the adjacent diagram, this structure is below the optic lobes and consequently not visible). The diencephalon performs a number of functions associated with hormones and homeostasis. The pineal body lies just above the diencephalon. This structure performs many different functions including detecting light, maintaining circadian rhythms, and controlling colour changes.

The midbrain or mesencephalon contains the two optic lobes. These are very large in species that hunt by sight, such as rainbow trout and cichlids.

The hindbrain or metencephalon is particularly involved in swimming and balance. The cerebellum is a single-lobed structure that is usually very large, typically the biggest part of the brain. Hagfish and lampreys have relatively small cerebellums, but at the other extreme the cerebellums of mormyrids are massively developed and apparently involved in their electrical sense.

The brain stem or myelencephalon is the most posterior part of the brain. As well as controlling the functions of some of the muscles and body organs, in bony fish at least the brain stem is also concerned with respiration and osmoregulation.

8. Complete the following sentences.

1. The brain is divided ….

2. The olfactory lobes are ….

3. Behind the olfactory lobes is ….

4. The diencephalon is ….

5. The diencephalon performs ….

6. The mesencephalon contains ….

7. The metencephalon is ….

8. The cerebellum is ….

9. The myelencephalon is ….

10. It is concerned with ….

9. Write out words from the text. Arrange them into three columns according to the part of speech.

noun adjective adverb

1. ________________ ___________________ _________________

2. ________________ ___________________ _________________

3. ________________ ___________________ _________________

4. ________________ ___________________ _________________

5. ________________ ___________________ _________________

10. Pair work. Speak about Central nervous system.

Дата добавления: 2014-12-26