Download Physio Lab 8 Muscle (1)

Group Number 4
Nick Ha, Andrew Phan
Physiology Lab 8: Muscle
1.1)
1.2)
2.1)
Table 2.1 Increasing Clench Force Data
Assigned
Force
Increment
Peak
SS25L/LA =
#
Kg
SS56L =
kgf/m^2
#1
5.00
Dominant
arm
Nondominant arm
Force
at Peak
Integrated
EMG (mV)
Force at
Peak
Integrated
EMG (mV)
5.021
kg
0.05173
mV-sec
9.820
0.08706
#2
10.00
8.236
0.06365
16.3466
0.13073
#3
20.00
13.152
0.11425
26.8433
0.1881
#4
30.00
24.167
0.20235
#5
35.00
31.693
0.26506
#6
#7
#8
2.2)
2.3)
2.4
3.1)
First a motor neuron sends an action potential which leads to the release of neurotransmitters.
The neurotransmitter then binds to receptors on the muscle cell, creating an action potential
along the muscle cell and the release of calcium, which binds to troponin,causing the actin and
myosin to form cross bridges that attach and pull the filament according to the sliding filament
model granted ATP is present. Once ATP is no longer bound to the myosin, the cross bridges
are no longer present, leading to the stopping of the contraction.
3.2)
The motor neurons are responsible for the EEG signal. This is because the motor neurons
receive neurotransmitters from the central nervous system, and their axon consequently
depolarizes in order to activate the muscle fibers. This depolarization is what causes the spike
in the EEG due to positive ions flowing into the axon.
3.3)
The EMG signal increases due to motor unit recruitment. When there is more strain or force that
the muscle needs to exert, the sensory data from the muscle creates additional feedback that
the more force is needed, and more action potentials are generated to activate more motor units
that would synergistically combine to lead to more force and larger electrical signal as more
motor units undergo depolarization/
3.4)
Subject 1: The percent difference between the dominant arm and the nondominant arm was
5.98%. The dominant arm was significantly stronger than the nondominant.
Subject 2: The percent difference between the dominant arm and the nondominant arm was
1.78%. Although the dominant arm was slightly stronger than the nondominant arm, the
difference was negligible and cannot be used to conclude whether one arm is stronger than the
other.
3.5)
There is a slight positive correlation between the dominant forearm circumference in cm and the
max force in kg. This is shown by an r-squared value of 0.3157. However, the r-squared value is
still fairly low so not many conclusions can be drawn.
3.6)
With two same sized forearm, surprisingly, the nondominant arm produced more force per fiber.
This is because the dominant arm had a ratio of 119.4 kg/mV-sec and the nondominant arm had
a ratio of 142.7 kg/mV-sec
3.7)
The difference of the average time of fatigue between the dominant arm and non dominant arm
is approximately 8.94 seconds. It should also be noted that for the non dominant arm, time to
fatigue was sometimes greater than the time to fatigue for the dominant arm. This could
possibly be due to the non dominant arm exerting a small max force.
3.8) There are no specific trends between time to fatigue and forearm diameter or max force
because the r-squared values from graphs 2 (forearm diameter and time to fatigue) and 3 (Time
to fatigue versus max force) both being too small to draw any proper conclusions.