In biology, a reflex is an involuntary and nearly instantaneous movement in response to a stimulus caused by a simple nervous circuit that involves a nerve impulse passing from a sensory nerve cell to a muscle or gland without reaching the level of consciousness. Scientific use of the term "reflex" refers to a behavior that is mediated via the reflex arc, as an anatomical pathway of a reflex, consisting of afferent (sensory) and efferent(secreto-motor) nerves.
The word “reflex” was introduced into Biology by a 19th- century English neurologist, Marshall Hall. By reflex, Hall meant the automatic response of a muscle or several muscles to a stimulus that excites an afferent nerve.
All reflexes are divided into unconditioned and conditioned ones.
An unconditioned reflex is a normal, instinctive, unlearned reaction to a stimulus that occurs naturally and is not dependent on previous experience. Unconditioned reflexes are also called inborn reflexes.
There are a lot of unconditioned reflexes, such as patellar, plantar, pupillary, lacrimal reflexes and many others, but the simplest ones include swallowing, salivation, sweating, sneezing, yawning, blinking, scratching, sucking (in infants), and others.
Probably the best-known reflex is the pupillary light reflex. If a light is flashed near one eye, the pupils of both eyes contract. Greater intensity light causes the pupil to become smaller, whereas lower intensity light causes the pupil to become larger.
Another reflex involving the eye is known as the lacrimal reflex. When something irritates the eye, the lacrimal reflex causes nerve impulses to stimulate the lacrimal glands. Usually secretion of tears occurs in response to irritation of the cornea or conjunctiva as, for example, when first wearing contact lenses, but it may also be induces by eyestrain, glare, laughing, etc.
Patellar reflex is a reflex produced by sharply tapping the patellar ligament with a small rubber hammer. The normal reaction is contraction of the quadriceps muscle, causing involuntary extension of the lower leg. The absence or decrease of this reflex is a sign of neurodisorders or CNS diseases.
A plantar reflex is a reflex obtained by drawing a pointed object along the outer border of the sole of the foot from the heel to the little toe. The normal flexor response is a bunching and downward movement of the toes. An upward movement of the great toe is called extensor response or Babinski reflex. The presence of the Babinski sign can identify disease of the spinal cord and brain in all persons over the age of 18 months.
A conditioned reflex is an automatic reaction in which the response occurs not to the sensory stimulus that normally causes it but to a separate stimulus, which has been learnt to be associated with. In Pavlov’s classic experiment, dogs learned to associate the sound of a bell with feeding time and would salivate at the bell’s sound whether food was then presented to them or not.
Speaking, reading, writing, walking, running, typewriting, playing different musical instruments, cycling, driving are examples of conditioned reflexes.
Conditioned reflexes are also called acquired reflexes or trained reflexes and behavior reflexes.
Exercise 7. Answer the following questions to the text:
1. What do we call a reflex in biology?
2. In what cases does a reflex occur?
3. What do we call a simple nervous circuit?
4. What does the reflex arc consist of?
5. Who was the first to introduce the term “reflex”?
6. What reflexes may all reflexes be divided into?
7. What reflexes are called unconditioned reflexes?
8. What is the patellar reflex produced by?
9. In what case is the patellar reflex considered to be normal?
10. What is the main function of the pupillary light reflex?
11. What produces the lacrimal reflex?
12. What disease may the plantar reflex or Babinski reflex indicate?
13. What are the examples of conditioned reflexes?
Exercise 8. Match the words from the column A with those from the column B to form word-combinations as they appeared in the text. Translate these collocations into Ukrainian:
Column A Column B
| 1. voluntary 2. feeding 3. classic 4. quadriceps 5. rubber 6. contact 7. lacrimal 8. unconditioned 9. automatic 10. secreto-motor 11. scientific 12. nervous 13. instantaneous | 1. movement 2. circuit 3. use 4. nerves 5. response 6. reflex 7. glands 8. lenses 9. hammer 10. muscle 11. experiment 12. time 13. extension |
Exercise 9.* Match the primitive reflexes in infants with their explanations:
| 1. rooting 2. parachut 3. grasp 4. stepping 5.sucking | a) reflex helps a breastfed infant find the mother's nipple. It occurs when you stroke the baby's cheek. The infant will turn toward the side that was stroked and begin to make sucking motions with the mouth; b) reflex whereby an infant is tested for motor nerve development by suspending him or her in the prone position and then dropping him or her a short distance onto a soft surface; c) reflex occurs if you place a finger on the infant's open palm. The hand will close around the finger; d) reflex occurs when the soles of infants’ feet touch a flat surface and they will attempt to 'walk' by placing one foot in front of the other; e) reflex is linked with the rooting reflex and breastfeeding. It causes the child to instinctively suck anything that touches the roof of their mouth, and simulates the way a child naturally eats. |
Exercise 10. Read and translate using vocabulary more examples about the reflexes. Give examples of conditioned and unconditioned reflexes of your own:
1. Many phobias begin after a person has had a negative experience with the fear object. For example, after witnessing a terrible car accident, a person might develop a fear of driving. This is a conditioned response.
2. The sound of a can opener or bag being opened can trigger excitement in pet. If your pet is accustomed to being fed after hearing the sound of a can or bag being opened, he or she might become very excited whenever they hear that sound. This behavior is a conditioned response.
3. Many children receive regular immunizations, and a child may cry as a result of these injections. In some instances, a child might come to associate a doctor's white jacket with this painful experience. Eventually, the child might begin to cry whenever they see anyone wearing a white jacket. This crying behavior is a conditioned response.
4. Sally and Jeff are in love. They spend an entire summer together and often pick strawberries from his uncle's farm and feed them to each other. Every time he's with Sally, Jeff feels happy and content. But at the end of the summer, they have to go back to college on opposite sides of the country. After that, every time he sees strawberries, he feels happy and content. In this example, Jeff's feeling of joy and contentment when he's with Sally, are his unconditioned response; it is automatic and natural. Contrast this with Jeff's happy feeling when he sees strawberries; this feeling is caused because he's learned to associate strawberries with Sally and is a conditioned response.
Exercise 11. Translate the following word combinations into English:
Простий нервовий ланцюг; мимовільна дія; у відповідь на подразник; ступінь свідомості; поведінка; наукове застосування; через рефлекторну дугу; анатомічний шлях; відцентрований та доцентрований нерв; збуджувати; проиродна діяльність; необумовлений рефлекс; пателярний; чотириголовий м'яз; пупіломоторний рефлекс; інтенсивність світла; слізний; плантарний; групування пальців ніг; показник хвороби; стимулюючий секрецію нерв; миттєвий рух; неврологічні порушення; анатомічний шлях нервів; слинотеча
Exercise 12. Insert the prepositions where it is necessary:
1. Russian physiologist Ivan Pavlov first discovered classical conditioning when he ran an experiment....which he rang a bell every time he fed a group of dogs.
2. When a sensory nerve ending is stimulated a nerve impulse travels along a sensory (afferent) neuron... the spinal cord.
3. The dogs had learned to associate the bell... food, and their reaction... the bell was a conditioned response.
4. A patellar reflex (the knee-jerk) is a test to the connection between the sensory nerves to stretch receptors … the muscle, the spinal cord, and the motor neurons.
5. Disease or damage may result … absence of the reflex.
6. A papillary (light) reflex is the reflex change...the size of light entering … the eye.
7. In dim light the pupils open due … stimulation of the sympathetic nervous system.
8. The motor neuron carries the impulse... a muscle which contracts and moves the body.
Exercise 13. Put questions to the underlined words:
1. Now the term “reflex” is widely being used by many scientists to describe an action that is an inborn central nervous system activity.
2. English neurologist Marshall Hall introduced the term “reflex” into Biology in the 19th century.
3. To test the patellar reflex, the examiner taps the ligament below the patella with a small rubber hammer.
4. By reflex, Hall meant the automatic response of a muscle or several muscles to a stimulus that excites an afferent nerve.
5. Russian physiologist Pavlov found that a hungry dog trained to associate the sound of a bell with food.
6. Pavlov divided all reflexes into unconditioned and conditioned reflexes.
7. Generally, decreased reflexes indicate a peripheral problem.
8. Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes.
Exercise 14.Translate into Ukrainian paying attention to Grammar:
1. The scientist noticed that the dogs began to salivate whenever they heard the bell, even in instances where there was no food present.
2. The pediatrician stated that in future the problems with the peripheral system would occur due to the child’s decreased reflexes.
3. The lecture explained that the most serious problems with the spinal cord and brain would be able to avoid due to Babinski reflex.
4. The neurologist supposed that the absence of patellar reflex in his patient was the major cause of his neurodisorders.
5. On ophthalmoscopic examination the ophthalmologist reported the students that it was the pupillary light reflex that regulated the intensity of light entering the eye.
6. The expert informed the parents that their child would not be able to wear contact lenses because of serious eyestrain.
7. They were reported that the patient had lost his consciousness suddenly.
8. Sir Michael Foster recorded in his textbook of Physiology in 1877 that striking the tendon below the patella gave rise to a sudden extension of the leg, known as the knee-jerk.
Exercise 15. Open the brackets using the verb in the appropriate form. Translate them into your native language:
1.The physician said that sanatorium treatment (to be) helpful for the neurological patients.
2.The patient stated that four hours before admission he (to lose) suddenly consciousness.
3.The students were informed that in medicine, reflexes often (to use) to assess the health of the nervous system.
4.The doctor was told that the conjunctiva (to infect).
5.The patient said he never (to experience) such acute pain on swallowing before.
6.He believed that the new method of treatment (to use) more extensively next year.
7.The neurologist declared that the negative extensor response (to indicate) the disease in the brain.
8. The patient was informed that his pathologic reflexes (to underlie) some internal diseases.
Exercise 16. Arrange the following sentences in a correct order to describe the following term “рефлекси”:
1. All reflexes are divided into unconditioned and conditioned ones.
2. A conditioned reflex is an automatic reaction in which the response occurs to a separate stimulus, which has been learnt to be associated with.
3. In biology, a reflex is an involuntary and nearly instantaneous movement in response to a stimulus caused by a simple nervous circuit that involves a nerve impulse passing from a sensory nerve cell to a muscle or gland without reaching the level of consciousness.
4. Marshall Hall, a 19th- century English neurologist, was the first to introduce the term “reflex”.
5. An unconditioned reflex is a normal, instinctive, unlearned reaction to a stimulus that occurs naturally and is not dependent on previous experience.
6. A simple nervous circuit is composed of a nerve impulse passing from a sensory nerve cell to a muscle or gland without reaching the level of consciousness.
Exercise 17.Translate the sentences into English, paying attention to Grammar:
1. Нам розповіли, що слово «рефлекс» було введено англійським неврологом Маршалом Холлом.
2. Вчений стверджував, що умовні рефлекси формуються внаслідок взаємодії кори великого мозку і підкіркових центрів.
3. І. П. Павлов з'ясував, що утворення умовних рефлексів базується на встановленні тимчасових зв'язків у корі великого мозку між нервовими центрами безумовного рефлексу й умовного подразника.
4. Лікар сповістив, що у дитини відсутній рефлекс Бабінського.
5. Пацієнта проінформували, що в майбутньому, відсутність пателярного рефлексу зможе стати причиною серйозних неврологічних станів.
6. Завдяки експерименту, Павлов довів, що у голодного пса кожен раз буде віділятися слюна на звук дзвіночка, навіть тоді, коли не буде їжі.
7. Було доведено, що подразники потраплять в головний мозок експериментальної тварини через спинний мозок дуже швидко, приблизно зі швидкістю 100 м. за секунду.
8. Лектор зробив висновок, що звуки, світло, кольори, запахи, смакові речовини, дотик, тиск, тепло, холод, положення тіла в просторі – усі ці подразники при поєднанні з безумовним подразником стають сигналами, що викликають безумовний рефлекс.
Завдання для самостійної роботи студентів (СРС)
| I. Перекладіть словосполучення: мимовільні і миттєві рухи простий нервовий ланцюг рефлекторна дуга у відповідь на подзразник безумовний рефлекс зіничний та слізний рефлекси надколінний та підошовний рефлекси чутливий показник хвороби доцентровані та відцентровані нерви вроджена діяльность центральної нервової системи II. Дайте відповідь на питання: In what cases does a reflex occur? What do we call a simple nervous circuit? What is the reflex arc composed of? Who was the first to introduce the term ”reflex”? What is the difference between conditioned and unconditioned reflexes? III. Розкрийте поняття: Рефлекси |
| I.P. Pavlov and his Investigations |
Exercise 1. Topical vocabulary:
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| Sensory, sympathetic, autonomic, receptor, reflex, neurons, cranial, central, grey matter, ganglion. | | | Exercise 2. Form antonyms of the following words using either prefix non- or mis-. |