LECTURE 5. The senses
1. The senses of sight, hearing, smell, taste, skin sensitivity)
Vision. Bookmark eye occurs on the 3rd week of fetal development. To the birth of the development of the eye and of the visual analyzer is not completed.
For the newborn characterized by moderate photophobia, his eyes almost permanently closed, pupils contracted, the lacrimal glands do not function.
With 3 weeks, the child steadily binocular fixes his eyes on still subjects and a short time watching live.
In 6 months the child sees the bright yellow and red colors, steadily coordinates eye movements.
To 9 month installed capacity stereoscopic perception of space, there is a sense of the depth and remoteness of the location of objects.
To the year the child can perceive geometric shapes. After 3 years, all children have a developed color vision. In 4 years achieved a maximum visual acuity, a child is ready to start reading.
Hearing. The ear of the newborn morphologically sufficiently developed.
Newborn hears, and his reaction to the sound is expressed in General motor reactions, scream, change the frequency and rhythm of heartbeat or respiration, ECG and EEG.
In subsequent improved the sensitivity of auditory perception and the ability to differentiate sounds, the volume, frequency and timbre.
The sense of smell. The peripheral part of the olfactory analyzer developed in the period from 2 to 7 months of fetal development.
Receptor cells are located in the mucosa of the nasal septum and the upper nasal the sink.
Neural mechanisms of differentiation of olfactory sensations begin enough to function in the period between 2 and 4 months of life, when well seen different reactions of the child to pleasant or unpleasant odors. Differentiation of complex smells improved up to primary school age.
Taste. The taste of the bulb formed in the last months of fetal development.
Taste buds of the newborn is more extensive than that of an adult, in particular, they capture almost the entire tongue, lips, hard palate and buccal surface of the oral cavity.
The taste threshold of the newborn is higher than in adults.
Develops gradually and in the early school years ends to develop the ability to distinguish not only the main taste, but also the gradation of concentrations and correlations between components of different taste.
The sensitivity of the skin. Receptors in pain sensitivity appear at the end of the 3rd month of fetal development and newborn immediately detect sensitivity to pain, but the pain threshold is much higher than in older children and adults.
Tactile sensitivity of the skin occurs very early (already at 5-6 weeks of fetal development), and at first it is localized exclusively in the perioral region, and then spreads rapidly, and by 11-12 weeks the entire surface of the skin of the fruit becomes reflexogenic zone.
Tactile sensitivity of the fetus and newborn is far ahead in terms of its appearance all the other senses.
Thermoreceptive presented at the newborn in morphologically and functionally complete form.
Receptors cooling almost 10 times more than the heat.
Your child’s sensitivity to cooling is significantly higher than to overheat.
2. Methods of investigation and semiotics of disorders
Visual function in the newborn can be checked by bringing to the light source. If the child is awake, he will crinkle his eyes and will seek to turn the face to the light. In bright and sudden light of the child’s closed eyelids and tilts back head (the reflex of Paper). If the baby is sleeping, approaching the light source will enhance the eyelids. Starting from the 2nd month of the sighted child is watching a bright toy, floating near face. In older children the function of the visual analyzer (visual acuity, the amount of visual fields and color perception) is investigated using a set of special tables.
The function of the auditory analyzer in the newborn check in response to a loud voice, cotton or noise rattles. Hearing the child closes the eyelids and tries to turn his head towards the sound. Sometimes the reaction is generalized restlessness: newborn stretches hands, opens his mouth makes sucking movements, his expression changes to a grimace of weeping. Starting at 7-8 weeks the child turns head toward sound stimulus (toys, rattles). If the child does not hear, he does not react to the sound of toys. Auditory function in older children explore the perception of whispered, loud speech and sound of the tuning fork. The perception of certain frequencies of the sound spectrum is investigated using audiometry.
Research methodology of smell. If the nose of a newborn bring odorous substance, not irritating the mucous membrane, such as Valerian drops, while maintaining the sense of smell child will react to facial expressions of displeasure, cry or chehalem, sometimes General restlessness.
The older child can alternately bring to a nose equally painted solutions – odorous and odorless, asking him if it smells or not?
The taste is investigated when applied to the tongue sweet, bitter, sour and salty solutions. The older child should be called taste of the applied solution. Newborn on the sugar solution will react sucking and smacking, bitter, salty and sour protrusion of the lips, salivation, facial wrinkling, sometimes the restlessness, crying, coughing, vomiting.
The research technique of skin sensitivity. The preservation of the haptic, or tactile, sensitivity is tested by touching the skin of the child with a piece of cotton or a brush. The most sensitive areas are the tips of your fingers, the red border of the lips, genitals. When researching this kind of sensitivity older child is asked to close his eyes and count the number of touches the word “Yes”. About tactile sensitivity of the newborn is judged by the occurrence of the unconditioned reflex: touching the eyelashes and eyelids baby close your eyes, touching or to the lips and tongue will cause sucking movements, if skin irritation cheeks the child turn the head toward the stimulus, stroking the soles will cause dorsiflexion of the toes, before touching or hand – grasp reflex. The child II half life stop tickling, neck, armpits will cause the response emotional response (crying, laughing).
Temperature sensitivity is determined by applying to the skin of test tubes with cold and warm water. Newborn to temperature stimulus responds restlessness and crying. The older child says “warm” or “cold.”
Pain sensitivity. The child is asked to close his eyes and cause him a few needle sticks, alternating with the touch of a blunt end of the needle. While maintaining sensitivity to pain, the child distinguishes irritation, replying “acute” or “stupid”. A small child reacts to the injections anxiety and cry.