Biological Influences of Psychology, Research Paper Example

Abstract

Three experiments were conducted all involving sensory adaptation. The first involved transferring sensation from hot to cold water, then dipping both hands into lukewarm water; the second focused on tasting sugar-laced water succeeded by fresh water, whilst the third involved rubbing a coarse sandpaper, repeating that motion, and again rating sensation. An explanation of sensory adaptation follows, and the evolutionary benefits of sensory adaptation, together with a comprehensive discussion on the somatosensory field of touch.

Biological Influences

Response to touch and subsequent adaptation to experience is an essential part of human functioning and of his or here adaptation to her existence.  This essay employs three experiments to investigate sensory adaptation. An explanation of sensory adaptation follows, and the evolutionary benefits of sensory adaptation, before concluding with a comprehensive discussion on the somatosensory field of touch.

My response to the experiments: The first experiment with the three bowls of water gave me, I thought, some sort of tingling in my right hand that lasted for a few moments before fading. The second experiment, the one with the sweet water, caused even the fresh water to briefly taste sweet, whilst the last experiment, that involving touch of the sandpaper (that I rated an 8 the first  time) made me feel the sandpaper less (I accorded it a 3) the second time that I touched it.

The detection of this touch and its response started with the “mechanoreceptors”, which is the name given to most of the sensory receptors in the skin (Rosenzwieg, Breedlove, & Leiman, 2002).  They monitor contact with the skin, as well as with other elements of the internal physiological system, such as pressure in the heart and blood vessels, stretching of the digestive organ and urinary tract, and force against the teeth.   Each receptor has an axon, which has mechanosensitive ion channels, whilst gating depends on stretching or changes in tension of the surrounding membrane.  Mechanoreceptors vary in the way they respond to stimuli, in the frequency of times they respond to these stimuli, and in their degree of sensitivity to the stimuli.  They also vary in the persistence of their response to certain stimuli. Feeling that stimuli, the receptor changes it into energy  (the process called “sensory transduction”), which then initiates movement of nerve impulses in a nerve fiber leading away from the receptor and involving changes of membrane potential; this is called “generator potentials”.  These action potentials are similar to, and, indeed, are sometimes referred to, as coding. The sensory information is encoded into all-or-none action potentials dependent on the frequency of the impulses, the rhythm in which these impulses occur, the quality and intensity of these impulses, and so forth.  Multiple nerve cells, for instance, working in sync intensify the depth and range of the stimulus effect.

What is so interesting in regards the sensory results of both the tasting and the touching experiments was that I could discriminate among variables of taste, and a variety of skin sensations. How could this occur? What kind of coding underlies these qualitative differences? Biology calls it “labeled lines” where each type of receptor (each of which has different sensitivities and ranges to stimuli) has a distinct pathway linking its surface to the brain (Bear,  Connors, & Paradiso, 2001), so that different qualities of stimulation and taste (as in this case) can be communicated to distinct places in the brain. Each of these receptors uses action potentials that vary according to their strength and frequency.

I was also able to feel the stimulus location only because of the position of the distinct excited receptors. In other words, a receptor on my finger transferred information about the sandpaper; it informed me about its position, so each receptor activates pathways that convey unique positional information.

Sensory adaptation, as for instance experienced in this series of experiments, emerges when receptors show progressive loss of response when stimulation is maintained.  In connection with adaptation, there are two kinds of receptors: (1) Tonic receptors which show a slow or nonexistent decline in the frequency of nerve impulses, i.e. they show relatively little adaptation and  (ii) Phasic receptors which show a rapid decrease in the frequency of nerve impulses (Rosenzwieg, Breedlove, & Leiman, 2002).

Adaptation connotes that the rate of firing is initially rapid and strong when the stimulus first reaches the receptive field, but then the receptive field adapts, slowing its activation (or firing) to a steady rate. In evolutionary terms, this is adaptive for human existence, for continuance and maintenance of sensation to stimuli would be unendurable and disturbing to humane existence. Reaction to pain is an extreme case in point.  It is only with adaptation to pain that we can continue our daily activity. Sensory adaptation, too, prevents the nervous system from becoming overwhelmed by stimuli that is supposed to be of little impact to us. For instance, we are saved by the constant neural barrage of an itching on the back by several suppression mechanisms, including adaptation.

This collection of sensory information enters the central nervous system through the spinal cord, then the brainstem, before reaching the thalamus. In the brainstem, the fibers from each side of the body cross over to the opposite side of the brain. The thalamus shares the incoming information with the cerebral cortex, which, in turn, directs the thalamus to suppress certain information (Weiten, 2007).

Another observation from our experiment attests to the fact that the use of one sensory system influences perception derived from another. For instance, I had to both taste the water and touch the cup with my lips. Many sensory areas in the brain show a mixture of inputs from different modalities.

In conclusion, receptors, leading from peripheral nervous system to central nervous system, through a complex procedure of firing and transmission of messages, make us aware of our stimuli. The process of adaptation shortly, thereafter, occurs which desensitizes us to effects of particular stimuli.  The whole is very conducive to our existence.

References

Rosenzwieg, M.R., Breedlove, S.R. & Leiman, A.L.(2002) Biological Psychology.  Mass: Sinauer Assoc.

Bear, M. F, Connors, B. W., & Paradiso, M. A.  (2001).  Neuroscience: Exploring the brain. USA: Lippincott Williams & Wilkins

Weiten, W.  (2007). Psychology: Themes & variations. USA: Thomson/ Wadsworth