Test subject 3, took approximately 67 milliseconds longer to react in comparison to their average reaction time without stimuli, approximately 31% longer than that of the control test. Test subject 3, experienced a 31% increase in reaction time during this test (see figure 1.4), which was by far the greatest increase in reaction time throughout all tests. Test subject 3 had the quickest reaction time across all tests except test 4 but had the largest percentage increase in reaction speeds in both test 2 and test 4 (see table 1 and figures 1, 2, 6, 9, 1.1, 1.2, and 1.4). Test subject 2 had the most consistent reaction times, with only minor percentage increases throughout the subsequent testing, having the smallest percentage change in all tests of 2% (see table 1 and figures 1, 2, 5 and 1.4). Test subject 1 experienced identical average reaction times in both Test 2 (auditory stimuli) and Test 3 (visual stimuli) demonstrating the two stimuli possess a similar effect on reaction time (see table 1 and figures 1, 2, 4, 9, 1.1 and …show more content…
The sensory stimulus (i.e. the colour change) causes these ion channels to open producing a change in the membrane potential of the receptor cell/s resulting in depolarisation.
Once a threshold level of depolarisation is reached, approximately 15mv, the receptor cell stimulates the production of action potentials that are conducted along the membrane of a nerve fibre towards the central nervous system (the brain and spinal cord). An action potential occurs like this:
1. A sensory nerve cell detects a stimulus (e.g. heat, touch, pain, etc.)
2. The cell begins to depolarise, with sodium ion channels in the phospholipid membrane opening at a particular place on the membrane allowing sodium ions (Na+) to enter.
3. If the threshold of excitation is reached (approximately 15millivolts), all sodium ion channels open and the membrane rapidly depolarises. The original membrane polarity decreases to zero, that is, the membrane voltage rises and the inside becomes more positive relative to the outside. This is known as an all-or-none