The nervous system and the peripheral nervous system

The Investigation of
the Response time of the Dominant and Non-Dominant Hand

Introduction:

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The nervous
system is made up of the central nervous system and the peripheral nervous
system which work together to enable the body to respond to environmental stimuli,
this response is done by motor control. Specialised receptors transform the
stimuli to which they are specific to into electrical nerve impulses.
Specialised cells known as nerve cells or neurons form the central nervous
system, these cells come together to form nerve fibres. Neurons respond to and
interpret the stimuli received and react appropriately, such reactions are
carried out by effectors, as discussed by (Technologies, 1999-2018). Response to a stimulus is produced by effectors. When
neurons are stimulated by stimuli, the information is transmitted by “a series of electrical impulses passing
along the length of the neuron.” (Chemistry, 2004) Electric impulses only travel in one
direction in a neuron.

There are
three types of neurons, all neurons stimulate cells, and transmit electrical
impulses. Motor neurons retrieve information from other neurons, and cause reactions
to occur, as discussed by (Academy, 2018). A neuron contains a nucleus, and cytoplasm; this
cytoplasm produces Dendron’s. Dendron’s branch off into finer structures known
as Dendrite’s which are stimulated by the electrical impulses from other
neurons. The axon is formed by the extension of cytoplasm, it transmits
impulses away from the cell. Nerves consist of many axons from many neurons. Axons
end in synaptic knobs which stimulate nerves. Some axons are surrounded by
myelin sheath, “Glial cells produce
myelin, which is a fatty substance that protects the nerves.” (SparkNotes, 2017) Schwann cells
line and wrap around axons, which speed up the transmission of pulses and act
as an insulator. A neuron lined with Schwann cells is known as being myelinated.

Neurons have
a membrane potential established across the cell membrane, meaning there is an
unequal distribution of ions between the outside of the cell membrane and the
electrical field inside. The most abundant ions in extracellular fluid are
sodium (Na+) and chloride (Cl-). Potassium (K+) is the main positive ion within
the cell, neutralized by organic anions. The extracellular fluid and cytoplasm
are electrically neutral, being a potential difference in comparison to the
negative interior. The interior is negative when the neuron is not conducting a
signal, known as the resting potential, as discussed by (Rajakumar & Kiernan, 2013) The cell is
polarised as it has an unequal distribution of ions on either side. The
permeability of the cell transfers Na+ and Cl- by pumps which carry out active
transport, ensuring that at any given time there are more Na+ ions outside, and
more K+ ions inside, as discussed by (Biologist, 2018) When a nerve
cell membrane is stimulated, the action potential occurs rapidly causing the
sodium pumps to open, allowing more Na+ ions inside the cell meaning the inside
becomes more positive than the outside. This is known as depolarisation as
charge distribution has changed. Potassium pumps then proceed to open, allowing
the ions to flow out meaning the charge returns to its original state, a
process known as repolarisation.

 “A reflex is the simplest, quickest form of
activity in the nervous system. It is an automatic, involuntary, unthinking
response to a stimulus.” (Teacher, n.d.) Examples include, moving your finger away from a
flame, breathing and blinking. To catch a falling object includes a degree of
reflex action, as your brain is reacting to the visual stimuli.

 

Aim of the Investigation

My aim is to
investigate the speed of the reflexes of both a person’s dominant and
non-dominant hand in response to the external stimuli of a ruler being dropped.
I will test reaction time by timing how long it takes to catch a ruler in each
hand.

A similar
investigation was carried out by (Dana Badau, 2014) in which the
goal was to record the difference of simple reaction time between the left and
right hand to the visual stimuli with regards to the dominant hand of each
student that took part. This was done so using the ruler test with both hands,
consisting of the ruler being caught twice with each hand and an average then
calculated as the result. The overall results shown that there were significant
differences between both hands, especially when cerebral dominance was
accounted for.

While
researching possible outcomes of this investigation, it was discussed by (Reaction TIme Ruler, n.d.) that it can be expected that the dominant hand
will be faster as it is used more regularly, meaning neurons carry along
messages along a well-worn pathway. Such repetitiveness results in improved
motor skills.

 

Hypothesis:

I expect
that the response time of the participants dominant hand to the visual stimulus
of a dropped ruler will be faster in comparison to the nondominant hand, due to
the daily repetitive and more frequent usage of the dominant hand which equates
to improved motor skills and greater dexterity than that of the nondominant.  Therefore, the distance that the ruler drops should
be smaller when caught by the dominant hand.

 

Apparatus:

·       30cm ruler

·       Table

·       Chair

·       Pencil

·       Paper to record data

 

Method:

1.     I will get my participant(s) to sit
down in a chair and place their dominant arm flat across the table top, with
their wrist aligned with the edge of the table. Their hand will not be in
direct contact with the table top.

2.     I will be stood in front of the
participant, holding the ruler between my thumb and forefinger. The ruler’s
zero mark (0cm) will be level with the table top.

3.     I will get the participant to enclose
their thumb and forefinger around either side of the zero mark, ensuring that
they are approximately 2cm apart with the ruler in the centre.

4.     I will say “Ready” and will drop it
within 5 seconds of saying so. The participant is to catch the ruler with their
forefinger and thumb once I’ve said this.

5.     I will record the distance the ruler
dropped (in centimetres) in a table by reading where the participant has caught
the ruler.

6.     I will repeat the above steps twice
again to receive more measurements.

7.     I will get the participant to switch
to their non-dominant and repeat steps 1-6.

8.     Once all my readings are completed
for both hands, I will calculate the mean dropping distance of each hand by
adding up the three results and dividing them the number of trials (3).

9.     I will gather the results of all the participants
and find the average for the dominant and non-dominant hands overall.

 

Independent Variable:

Hand
Dominance is the only way in which to vary this variable, is by switching the
hands to catch the ruler after three turns with each. From the dominant hand to
the nondominant hand.

Dependent Variable:

This is the
time of reflex response to catch the ruler. To collect this data, I will be
measuring and recording the distance the ruler has dropped when it has been
caught. I will be measuring in centimetres from a fixed height. Each hand will
catch the ruler three times so as to increase the reliability of my results. I
will be calculating the mean response time by dividing the sums of all three
results by the number of trials carried out.

Control Variables:

·       Caffeine Intake: It is important to ensure that this stimulant is not ingested between
the switching of the dominant and nondominant hand, or between trials carried
out. Caffeine will affect the results of reaction times, especially over time
as it takes effect.

·       Warning of Stimulus: I will warn the participant by saying “Ready”, and will proceed to drop
the ruler within a five second limit.

·       Distance of Participants Thumb and Forefinger from Ruler: It is important to try to ensure
that the Thumb and Forefinger are approximately 2cm apart with the ruler in the
centre. This is slightly difficult to regulate as one’s fingers tend to shake
in anticipation of a falling object. If the fingers get closer to the ruler
while shaking, it causes a smaller distance, meaning the ruler will be caught
quicker and subsequently lowering the reaction time. And vice versa if the
fingers move outwards.

·       Distance from Which the Ruler is dropped: The distance needs to be the same
with each test, to ensure this happens the participants will rest their arm
flat on the table top so their hand level will not change. I will hold the
ruler so that the zero mark (0cm) is at level with the hand.

 

Ethical Assessment:

·       I will not carry out the
investigation until I have the consent of the participants to partake.

·       I will explain the investigation to
the participants, so they can partake in it with full knowledge of the
situation.

·       I will ensure all results will be
confidential and anonymous in my recordings of data.

·       Participants may withdraw from the
experiment at any stage.

·       All participants shall be treated
equally and fairly.

 

Risk Assessment:

·       Trip & Collison: I will ensure
there is nothing on the floor, for example, a schoolbag to collide with. I will
advise participants to store bags and belongings safely to remove this hazard.