Unit 25. Sensory system.

Ex.1.Read and memorize the word:

Visual – зоровий; significant – значний; to supply – постачати; retina – сітківка; to be completed – бути завершеним; network – мережа; to convert – перетворювати; ray – промінь; pathway – шлях; aqueous humour – водяниста волога; pupil – зіниця; lens – кришталик; vitreous humour - скловидне тіло; retina – сітківка; sound – звук; to be subdivided - підрозділятись; olfactory – нюховий; meatus – отвір; crude – недосконалий; bitter – гіркий; flavor – присмак; taste buds – смакові сосочки; to contribute – вносити; touch – дотик; perception – сприйняття; to ascertain –визначати; peculiar – особливий; feature – риса.

Таsk. Read the text and do the exercises.

The visual sensory system is the most significant sense organ of the man. Almost ninety percent of the information is supplied to the brain through eyes. Visual perception begins with the projection of an image on the retina and is completed in the cerebral cortex. A network of nerves converts the image into electric impulses that are recorded in the brain.

The following succession represents the pathway of light rays through the eye: 1 – conjunctiva; 2 – cornea; 3 – anterior chamber and aqueous humo(u)r; 4 – pupil; 5 – lens; 6 – vitreous chamber and vitreous humo(u)r; 7 – retina (rods and cones); 8 – optic nerve fibers; 9 – optic chiasm; 10 – thalamus; 11 – cerebral cortex.

Hearing may be defined as the reception of sound vibration by ear. This is the main function of the organ. Another function of the ear is that of providing sense of balance (equilibrium).

Auditory sensory system is the second in significance for the normal life of man. Usually the auditory system is subdivided into three parts: the outer ear, the middle ear, and the inner ear.

Smell is one of the five senses. The receptors of the olfactory sensory systems are located in the region of the superior meatuses of the nose.

If one compares the five special senses it can be noticed that taste is a relatively crude sense. Only four basic tastes can be distinguished - sweet, sour, salty, and bitter. Some additional flavours can be determined because of the combination of sense of taste with the sense of smell. Tasting occurs in the mouth where the tongue is covered with a series of small projections called papillae that contains cells (taste buds) sensitive to the chemical nature of flood. We have some ten thousand of them. Receptors for taste carry information on the character and concentration of substances entering the mouth. It was proved that there exists special taste centers on the tongue

Touch and somatosensory perception. When we speak about somatosensory perception we do not only mean the system of skin sensibility but also the sensory system of a skeletomuscular apparatus. They both are capable of responding to touch and perceiving heat, cold, pressure, vibration, and pain. It is only through physical contact and touch with the objects that can be ascertain their peculiar features, such as their size, shape, surface texture and temperature. The skin contains thousands of specialized cells, as well as nerve endings that respond to external stimuli (heat, cold, etc.).

Ex.2. Match the words-combinations:

lubricates and clears -	захищає око
optic nerve -	прозорий шар
lachrymal glands -	зоровий нерв
protect the eye -	зіниця ока
the transparent layer -	зволожує та очищає
the pupil of the eye -	сльозові залози

Ex.3.Match the words-combinations:

detects and analyzes -	середнє вухо
the auditory system -	звукові хвилі
sound waves -	друга за значимістю
conduct sound -	слуховий канал
the middle ear -	досліджує і аналізує
the auditory canal -	проводить звук

Ex.4. Suggest the Ukrainian equivalents:

the main function of this organ; provide sense of balance; sound waves and vibrations; a thin fibrous membrane; deep within the bones of the skull; a sensitive auditory receptor; auditory nerve fibers.

Ex.5. Suggest the English equivalents:

сприйняття звукових коливань; зовнішній слуховий канал; поділяється на три частини; захищає вухо; тонкий шар шкіри; внутрішнє вухо.

Ex.6. Fill in:

1. Hearing is the … of sound vibration by the ear. 2. The ear detects and analyzes noises by conversion of … into electromechanical impulses. 3. Auditory sensory system is the … in significance for the normal life of man. 4. Usually the auditory system is subdivided into three parts.

Ex.7. Answer the questions to the text:

1. What is sight? 2. What are the functions of the ear? 3. How does the tongue detect the chemical nature of food? 4. What do sound waves

and vibrations pass through? 5. How many parts is the visual system subdivided into? 6. What sense is relatively crude? 7. How many tastes can you distinguish? 8. What is capable of responding to touch?

9. What does the skin contain? 10. What responds to external stimuli?