To start speaking about the biological influences in the human organism, I should analyze the concept of adaptation. Adaptation (from Latin – adaptation – accommodation) means adapting of a living being to different factors of the surrounding world, for example: climatic and temperature factors (acclimatization), height (hypoxia), zero gravity, the influence of different infectious agents (immunity). Adaptation plays an important role in functioning of any organism, making it possible not only to endure the significant and sharp changes of the environment, but to reconstruct rapidly and actively the physiological functions and behavior according to these changes.
Analyzing of the experiments
I have conducted three different experiments, recorded the reactions to analyze the adaptive reactions of the organism. Here is the first one. I rubbed my index finger gently over a piece of very coarse sandpaper for several times and rated its coarseness on a scale from 1 to 7. It was 6. Some time later I rubbed the same finger over the paper and again rated its coarseness. But the perception of the coarseness changed. It became only 4. It means that skin reception, especially tactile reception started its complex work.
The sense of touch (mechanoreceptors) made me feel the coarseness of the paper. The receptors of pressure (force sensors) are Merkel’s disks and Ruffini’s corpuscles, touch receptors (speed sensors) are Meissner’s corpuscles and the receptors of hair follicles. They all, including tactile platens and tactile menisci located in low and profound layers of epidermis, in skin papillae, around hair follicles perceive the irritation, so called impulse. Excitation that appeared in receptors transmits via synapse to the sensitive neuron. The body of the sensitive neuron is usually located outside the central nervous system: in cerebrospinal or vegetative ganglia.
Dendrite leaves such a neuron and leads to the peripheral organs and tissues and axon directs to the spinal cord. But the coarseness of the paper changed because of the tactile adaptation, the change of subjective rating of irrigative intensity in consequence of tactile receptor’s adaptation, fast adaptive multyreceptors.
The second experiment was conducted with hot, cold and lukewarm water in 3 medium-sized bowls. I put, submersed my left hand into hot and right one into cold water for three minutes. Then quickly transfer both hands to the lukewarm bowl. I sensed with my left hand that the water was cold, while my right hand sensed the opposite. In this experiment I observed the work of temperature analyzer (both cold and hot) as the part of somatosensory system. Thermoreceptors especially Crause’s cells and free nervous endings that are located in skin, mucous tissues, cornea and hypothalamus are the peripheral parts of temperature analyzer. The impulse transferred from these receptors via weakly and notmyolized C-filaments to the neurons of spinal and cerebrospinal ganglia and then by their axons to the corresponding sensitive nucleus. I sensed that the water in the same bowl was different because temperature adaptation occurs, i.e. the sensation of temperature during long influence on the receptor with constant temperature.
And at last the third experiment was held for analyzing taste adaptation. I took one cup with fresh water and one cup with sugar water, took a sip of sugar water and swished it around in my mouth for several seconds without swallowing it. Soon it tasted less sweet. After swallowing it, I took a tip from the cup with fresh water. The taste of fresh water was a little bit salty or absolutely tasteless. I sensed it in such a way because the peripheral parts of gustatory or taste analyzer are located in palate, back wall of pharynx, epiglottis and of course taste papillae of tongue. The conductive parts of gustatory analyzer are the taste filaments of facial and glossopharyngeal nerves. Then the impulses go through oblongatal medulla and thalamus to the lower surface of frontal part of cortex (central part). In my experiment I sensed different taste of fresh water, as taste sensitivity increased, a so-called taste contrast appeared after sugar water.
The mechanism of receptor’s adaptation is difficult and complex. As the base of receptor’s activity is formed by generative potential, that irritates the nervous ending and causes the impulses, adaptation of receptors depends on accommodation of nervous endings to constant action of potential.
- Physiology. Sensory system. www.homepages.ius.edu/KEDMONDS/sensory
- Sensory adaptation. www.soma.npa.uiuc.edu/courses/bio303/Ch9
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