Muscle Contraction

Muscle Contraction
The next stop in our body system is the muscular system. The muscles in our body help us move all of the organs in our
body without them we would be a statue.
So first we are going to talk about 3 muscles and where they are located.
Smooth muscle
It is found in the walls of organs such as the Stomach, Oesophagus, Bronchi and in the walls of blood vessels. This muscle
type is heated by involuntary neurogenic impulses and has slow, contractions used in controlling internal organs.
Cardiac muscle
This type of muscle is found in the walls of the heart. It has similarities with skeletal muscles in that it is band and with
smooth muscles in that its contractions are not under control. However this type of muscle is highly specialised. It is ...
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Next we are going to talk about what happens to the muscles if you exercise too much.
Muscle fatigue is the decline in ability of a muscle to generate force. It can be a result of vigorous exercise but abnormal
fatigue may be caused by barriers to or interference with the different stages of muscle contraction. There are two main
causes of muscle fatigue.
Wow only to more topics left. Now it is time to talk about the relationship between the muscles,bones and tendons.
Tendons connect muscle to bone, and Ligaments connect bone to bone. They help each other for mobility, muscles are
connected to bones so you can move it.
Next is the all or none response.
The all or none response means that when the brain send a signal to a muscle it fully contracts. Thereby, a muscle is either
full contracted, or not contracted at all.
Now last but not least are the 10 major muscles.
The most important muscle is the heart. Other big muscle groups are the pectoralis major (in the chest), gluteus maximus
(the butt cheek), quadriceps femoris (front of thigh), biceps femoris (back of thigh ), gastrocnemius (calf muscle), biceps
brachii (part of arm you flex), triceps brachii (back of upper arm), latissimus dorsi (part of back that gives V shape),
trapezius (part of upper mid
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Muscle Contraction Essay
Muscles are tissues that are made of cells that are specialized to generate contractions, in animals that possess skeletons,
these contractions will generate a force that will enable movement to occur. Skeletal muscles are the only muscles that are
under voluntary control of an animal, the other muscle types (cardiac and smooth) are not under conscious control of the
organism(Houghton, 2007). Even though at first sight skeletal muscles might seem to be present for only a locomotory role,
they can also provide structure, support, guard the entry and exit points of a body, maintain temperature, and store
nutrients. Even though muscles perform other roles, they all revolve around a single concept, and that concept is muscular
contraction, which ... Show more content on Helpwriting.net ...
An action potential will be propagated to the axon terminal of the motor neuron, when it arrives, it will trigger an influx of
calcium ions, which will then trigger the exocytosis of acetylcholine to the neuromuscular junction, via the terminal
vesicles. Once the acetylcholine has exited the membrane of the postsynaptic cell(neuron), it will bind to the receptors on
the motor end plates of the muscles, this will trigger the opening of voltage–gated sodium channels, the sodium will
depolarize the membrane of the postsynaptic membrane and then the action potential will be propagated. When the action
potential arrives at the sarcoplasmic reticulum of the muscle, it will trigger a release of calcium; which is a very key factor
in muscular contractions. The contraction cycle starts when calcium ions bind to troponin, this causes tropomyosin to
change its conformation and by doing so it exposes the active sites on the actin. After this cross–bridge formation occurs,
and the thick filament starts to pull on the thin filament. When the tension that is generated from the contraction is released,
a force is generated, and it will enable movement to occur. The contraction cycle will continue to occur if there's ATP, and
an action potential to stimulate the release of calcium(Clark,

Myosin And Muscle Contraction Research Paper
These muscles requires actin filaments and myosin filaments interacting with each other in–order for movement. [1] The
myosin are aligned between the actin and muscle contraction is brought through the sliding of the two filaments. The
myosin head can tightly bind to the place on the actin molecule but generally there are other proteins which prevent the
binding called tropomyosin (form a filament which semi curve around the myosin where the actin would possibly bind) and
troponin (variety of different proteins).[2] Naturally ATP has bounded to the myosin head and when this happens the energy
is slit into ADP and phosphate, however both would still remain attached to myosin. The tropomyosin is coving the binding
place for myosin to attach to ... Show more content on Helpwriting.net ...
This happens very quickly before the pain is apparent.[1] There is no control over this occurrence and also there is no
negative or positive feedback control system. [1]The body is able to still be in a upright position due to signals begin sent
to the muscles in the opposite leg, where the leg stiffen to take the extra weight. This happens when the range of excitatory
impulse up and down the spinal cord to stimulate more motor neurons called irradiation of stimulus and as a result
recruitment. [2,3] As This requires an increase drive to the extensor muscles as there is also a decrease drive to the flexors
muscles. [2] This is also known as the crossed extensor reflex. There are other movements which adjust the body position
to shift the centre of gravity and enable standing on leg, hence, throwing the body in to an unbalanced state, i.e. hopping on
one leg is a method that the body uses when trying to remain balanced while the pained foot is

Skeletal Muscle Contraction Report
To fully understand the mechanisms that cause graded muscle contractions, the effects of fatigue, twitch summation, twitch
recruitment, tetanus and muscle stretch on skeletal muscle were observed. The gastrocnemius muscle of the Rana pipiens
frog was used for each of the 5 experiments performed. When twitch recruitment was observed, one trial was conducted by
stimulating the sciatic nerve and the other, conducted by stimulating the skeletal muscle. The contractile force of the
muscle was increased until reaching its maximum amplitude. This occurred at a preload of 0.37 (N) raw twitch of 0.39 (N).
Optimal length was concluded to be greater than or equal to 5.9 mm, but an exact value was not found due to limitations on
stretching. Summation was studied by decreasing inter–stimulus intervals until two twitches summed together. This
occurred at 100ms, the point where two twitches could no longer be differentiated. One trial was run at different pulse
intervals at 500mV to observe tetanus. Tetanus occurred ... Show more content on Helpwriting.net ...
A motor unit is made up of one motor neuron and all the muscle fibers it has control of or stimulates. Acetylcholine
released from the motor neuron bind to nicotinic acetylcholine receptors on skeletal muscle membranes which result in a
change in permeability throughout the muscle fiber. The change in permeability causes an action potential while rising
cytosolic calcium levels lead to a flow of events ultimately ending in a twitch or muscle contraction. Graded muscle
contractions are completed by two basic mechanisms: alteration of inter–stimulus intervals between successive action
potentials and recruitment processes that control the amount of active motor units (Raikova, 2013). These mechanisms are
used to analyze the processes of twitch recruitment, relationships between length and tension, tetanus, summation and
fatigue in the skeletal

Essay On Muscle Contraction
The Correlation between Eccentric Strength and Agility in Male Field Sport Athletes.
There are three types of muscle contraction, isotonic, isometric and isokinetic. There are two isotonic contractions,
concentric and eccentric. A concentric contraction is a shortening of the muscle fibres, an example of this being a bicep curl
causing a concentric contraction on the biceps brachii causing the elbow to flex. An eccentric contraction is the opposite of
this. During an eccentric contraction as the muscle contracts the muscle fibres lengthen. An eccentric contraction is
important in deceleration where the quadriceps lengthen to slow down the limb. This type of contraction should transfer
into agility as athletes with greater eccentric strength ... Show more content on Helpwriting.net ...
Agility has been described as "a rapid whole body movement with change of velocity or direction in response to a
stimulus". (Sheppard et al, 2006) This description identifies the inclusion of cognitive skills in determining agility. This
definition applies to open skills only. Open skills cannot be pre–planned, however closed skills, such as sprinting or
previously planned changes of direction, can be planned in advance. This is very important in every field sport as the
ability to react quickly and allow the movements to match these reactions enhances performance. Many field sports require
straight line running speed but more often than not fast change of direction is a defining factor of an athlete's performance.
Fast change of direction speed and ability to make the right decision in a game situation makes for an excellent athlete.
Many tests have been designed to test for change of direction speed. The 5–0–5 test is a timed agility test using rapid 180
degree turns and straight line speed. The Illinois test is a timed agility test using straight line speed and many multi
directional changes. The Zig–zag test is a good indication of multiple directional changes. It is a timed test where the
athlete must round cones set out in a figure 8.
Subjects used in this study were 10 male soccer players. The agility test that was chosen to best simulate this sport was the
5–0–5 agility test. This was due to the quick, snappy change

Skeletal Muscle Contractions
The nervous system of the human body is an organized network of nerve cells and fibers that receive, transport, and
respond to stimuli. Skeletal muscle movement involves components of the nervous system. The nervous system is an
organized network of nerve cells and fibers that is subdivided into the central and the peripheral nervous systems. The
central nervous system (CNS) consist of the brain and the spinal cord. This system is considered to be the information
processing center of the body. On the other hand the peripheral system (PNS) is made up of the nerves and ganglia. The
peripheral system is considered to be the communicator between the central nervous system and body parts. This system is
then further subdivided into somatic and autonomic components. The somatic component is associated with skeletal ...
Neurons are responsible for receiving, interpreting, and responding to stimuli. Neurons are classified into three groups:
sensory neurons, interneurons, and motor neurons. Sensory neurons are responsible for detecting stimuli from the body's
internal and external environment.Think of sensory neurons as the input. Interneurons also called association neurons and
are responsible for the distribution of sensory input and the coordination of motor output (Bartholomew and Martini 2007).
Motor neurons carry the information received from the central nervous system and carry the information to organs. These
organs that receive the information are also classified as effectors which are the bodily responses to a stimulant (BBC
2014). Examples of effectors include muscles, glands, and even adipose tissue (Bartholomew and Martini 2007). The target
effector in this case study would be skeletal muscle. The interneurons and the motor neurons are the only two neurons
involved in the transfer of impulses from the central nervous system to the peripheral nervous

Submaximal Contraction
PER– 415
Dr. Kyle Ryan
1.) In the article by Duchateau, Semmler & Enoka, they explained the importance of the behavior of single motor units that
follow training. The Motor Unit is a vital part in both strength training and skill training. The motor unit is comprised of a
motor neuron in the spinal cord, its axon and all of the fibers that innervates. Motor unit's main function is to transform
synaptic input that is received by the motor neuron. On average, 300 muscle fibers are innovated, however, the range can
extend far beyond that median number. Muscle fibers have many varieties that are affected through levels of fatigue, force
and contraction speed. The most important is the size of the motor neuron. The influence of the size creates ... Show more
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However, it is still unclear to researchers the actual affect adaptations have on motor recruitment and coding. Many of the
research in this article explained some of the findings on how strength and skill training help performance through the
usage of motor units. Mostly through learning about submaximal and maximal contractions and the affects that using small
motor neurons and large motor neurons. Small motor neurons use more submaximal contractions whereas, maximal
contraction use large motor neurons. This article explained how surface EMG's are still the most effective way to detect
motor units through different types of contractions. Although through their finding EMG's did not proved to be as effective
in how they pick up motor output. Duchateau and Hainaut in one of their studies talked about how there was a 7% increase
in activation through the motor units produced in hand muscles. Contrast to this, different muscles have different motor
recruitment so it can vary in the effectiveness. Also many of the studies had different amount of time training. Duchateau
and Hainaut did 6 weeks of strength training and Kamen and Knight did 12 weeks. The 10,000 hour rules teaches us that
the more we practice the better gains we receive. So naturally the adaptations used in Kamen and Knight would be different
because they received 6 more weeks of training. The studies did not have

Muscle Contraction Lab Report
First, before this assignment I had no idea of the levels involved in a muscle contraction. We can directly control or
regulate the activity of our skeletal muscles. Striated muscle movement, produced by the interaction of filaments containing
the proteins myosin and actin, is regulated by the proteins tropomyosin and troponin on the actin filaments. When an
electrical signal passes down the motor nerve to a muscle it triggers a depolarization of the muscle membrane
(sarcolemma). In results, triggers the sarcoplasmic reticulum to release calcium ions into the muscle interior where they
bind to troponin, which causes tropomyosin to shift the actin filament to which myosin heads need to bind to produce
contraction. During relaxation calcium is pumped back into the sarcoplasmic reticulum, troponin loses its calcium and
tropomyosin reverts. When this action occurs it blocks mechanism of muscle regulation. ... Show more content on
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Calcium ions exposes the binding sites on the actin filaments. Calcium ions binds to the troponin molecule causing
tropomyosin to expose positions on the actin filament for the attachment of myosin heads. Cross bridges between myosin
heads and actin filaments form. When attachment sites on the actin are exposed, the myosin heads bind to actin to form
cross bridges. ADP and Pi are released, and sliding motion of actin results. The attachment of cross bridges between
myosin and actin causes the release of ADP and Pi. This, in turn, causes a change in shape of the myosin head, which
generates a sliding movement of the actin toward the center of the sacromere. This pulls the two Z discs together,
effectively contracting the muscle fiber to produce a power stroke. ATP causes the cross bridges to unbind. When a new
ATP molecule attaches to the myosin head, the cross bridge between the actin and myosin breaks, returning the myosin
head to its unattached

A Lower Metabolic Cost But With The Higher Forces During...
1. How is there a lower metabolic cost but with the higher forces during eccentric contraction?
During an eccentric contraction, the muscle lengthens under tension due to an opposing force that is greater than the force
being produced by the muscle (Lindstedt et al. 2001). Eccentric contractions require little metabolic energy, however they
are characterized by a high production of force (Semmler 2014). Fick observed that a lengthening muscle contraction could
exert more force than a shortening muscle contraction, while Hill later observed that the body has a lower energy demand
when contracting eccentrically compared to concentrically (Lindstedt et al. 2001). When the force applied is larger than the
force that is created, work is done on the lengthened muscle and mechanical energy is absorbed – this is called "negative
work" (Lindstedt et al. 2001). This absorbed energy can either be dissipated as heat, or it can be temporarily stored as
elastic recoil potential energy for later use (Lindstedt et al. 2001).
2. What is a force–EMG relationship and why is there a tight coupling of these two parameters?
The EMG signal that is observed through the placement of electrodes on the skin is closely coupled with the generation of
muscle force. In normal conditions, the force–EMG relationship is either linear or the increase in EMG at low force levels
is less than proportional (Semmler 2014). However, a different force–EMG relationship was observed following eccentric
exercise,

Muscle Contraction Report
First Muscles perform three types of contractions: concentric, eccentric, and isometric. When executing a strength exercise,
all three of the muscle contractions are involved. As you perform a movement, the main muscles undergo a concentric
contraction while the opposite muscles undergo an eccentric contraction. The adjacent parts of the body that are not in use
are stabilized via the isometric contraction.
The strongest phase is during the eccentric contraction which controlling and stopping movement and prepares the muscles
for an explosive type contraction and counteracts the pull of gravity to guide the movement. When it is strong enough, it
stops the movement.
1) Biceps curl: the primary muscles are Biceps Brachii, Brachialis &Brachioradialis.
During upward phase (lifting/curl the ... Show more content on Helpwriting.net ...
During the Upward phase, the spine flexed to create concentric contraction to rectus abdominous. (Concentric phase of
movement). Holding in this position is an isometric phase of the movement. And in the downward phase spine extended to
create an eccentric contraction which is the –strongest phase– eccentric phase of the movement.
8) Back hyperextension: the primary muscle is erector spinae .during spine extension the primary muscle undergoes
concentric contraction. (Concentric phase of movement). (Upward phase).and to hold the erector spinae in the isometric
phase of the exercise. While downward phase the spine flexed and the primary muscle undergo an eccentric contraction &
that is an eccentric phase of the movement.
9) Leg curl: the primary muscles are Biceps Femoris, Semimembranosus &Semitendinosus. In the upward phase knee
flexed to create a concentric contraction (concentric phase of movement).holding with the knee flexed is an isometric phase
of the movement. And in the downward phase, Knee extended & the primary muscles undergo eccentric contraction which
is eccentric phase & the strongest phase of the

Exercise Physiology : The Eccentric Contraction
The Eccentric Contraction
Exercise Physiology November 26, 2012
Damian Santamaria
Dr. Hildebrand
KNES 3613
Exercise Physiology
Southern Nazarene University
November 26th 2014
One indicator of life that has continually been examined is motion; whether it has been external or internal it is better
understood in the body as muscles. Muscle analysis and locomotion dates back to ancient history. Today there is a more in
depth modern understanding of muscle types, movements and contractions. Both scientists and everyday fitness enthusiasts
debate over knowing how different types of motion and muscle contractions effect muscle function and structure.
Interestingly there are studies that either support or dispute the various types of muscle contractions for building strength
and muscle hypertrophy. Every day we use our muscles and with an in depth look into how they work will lead to
understanding which way to train our muscles for optimal results.
Muscles are not only used during voluntary movements such as lifting weights or running, but also during involuntary
movements, for instance heart contractions or food digestion. These voluntary and involuntary functions of the muscles are
performed by three different muscles smooth muscle, cardiac muscle and skeletal muscle. Interestingly similarities in the
three muscle types are evident, "the anatomical structures of smooth, cardiac and skeletal muscle differ in some respects,
but their control mechanisms and principles of

Effects of Varying Lengths of Rana Pipiens Gastrocnemius on Tetanic Contraction
Joshua Porter, Sofia Tuttle, Yoniko Washington
TA: Ryan Hoffman
Abstract Muscles play an essential role in vertebrate life from maintaining posture and locomotion to controlling the heart.
Better understanding them is essential to better understanding life processes. (2) In this experiment, the effects of muscle
length on the tetanic contraction tension of the gastrocnemius muscle of a rana pipiens were observed. It was hypothesized
that the highest tension would be observed at the equilibrium length as observed in peer–reviewed sources. (3,4,5) The
independent variable was the length of the muscle and the dependent variable was the muscle tension. This experiment was
done on one rana pipiens. The tetanic muscle contraction was observed by stimulating it with a current of 1.5 amps at a
frequency 20 hz at various muscle lengths. The active, passive, and total forces were then plotted against the length of ...
To determine the current at which stimulation was maximal, the stimulator was set to 0 Amps and the muscle was
stimulated. Then the current was increased by 0.1 Amps and the muscle and force chart were observed. This was repeated
until the contraction force stopped increasing, which in this case was at 1.5 Amps. Then the tetanus frequency was
determined. First the current was set to 1.5 Amps. Then, in the VI, the frequency was adjusted to 0 Hz, and the muscle
stimulated. The frequency is set by the 'Pulse' and 'Period' inputs, which signify the number of pulses and the length of each
pulse. So the frequency was increased accordingly and the results of muscle stimulation were observed. The frequency was
tested at 5 Hz (pulse = 5, period = 200), 10 Hz (pulse = 10, period = 100), and 20 Hz (pulse = 20, period = 200). At 20 Hz
tetanus was observed, so that was the frequency value used in

Essay On Pacemaker Contraction
Pacemaker cell activity is very important for heart rate and force of contraction of the heart. There is no constant resting
potential (Figure.2), it's due to a leak of Na+ ions. That leaks causes Na+ ions moves into the cell and depolarises the cells
until a threshold that activate voltage gated Ca+ channels and voltage gated K+ channels. Anova 1, with values of each
section of time after injection of Ringer's solution, shows a p–value of 0.9513. Thus, we are sure at more than 95% that
values aren't significantly differents between the three groups. So Ringer's solution have no effect on heart rate or
amplitude. Ringer it's our normal conditions control, it doesn't affect heart rate or amplitude (=force of heart contraction).
Anova 1, with values at 60s after injection of each products, shows a p–value inferior to 0.0001. Thus, we are sure at more
than 99.9999% that values are significantly differents between the three groups. Tukey tests show that a p–value inferior to
0.01 between M1–M2 and M1–M3 and a p–value inferior to 0.05 between M2–M3. So, ... Show more content on
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Frog or other amphibians have a myogenic heart with only 3 cavities (2 atria and 1 ventricle) because of that there is a mix
of oxygenated and deoxygenated blood in the ventricle prevent by ventricular folding. In mamals the heart have four
cavities so it is bigger than the precedent one. The fourth cavity separates completely oxygenated blood from de–
oxygenated blood. It allows the blood leaving the heart to have more oxygen than in amphibians myogenic heart because
there is no mixing of blood. Tissues, organs, cells will have more oxygen so more energy. That can play a role in the
behaviour of the organisms. Myogenic heart used specialized groups of muscle cells to initiate and regulate heart activity.
In contract, insects have a neurogenic heart. They use external nerves to initiate and regulate heart

The Effect Of Calcium On The Contraction Of The Smooth...
MEDSCI 305 2013 Lab 2 – Role of Calcium in Smooth Muscle Contraction 1.0 Aim The aim of this lab was to identify the
significance of calcium's role on the contraction of the smooth muscle (1 pg. 25). 2.0 Introduction The smooth muscle (SM)
which is found within the wall of blood vessels located in the veins, arteries, arterioles and capillaries. It can also be found
in the stomach, intestines and urinary bladder. It has an important function of modulating the contractility of a vessel; this is
usually controlled by mediators and hormones which are found in the sympathetic nerve terminals (2). These mediators
work by modifying the intracellular calcium stores. The two calcium sources are the intracellular store which is found in
the sarcoplasmic reticulum and the extracellular stores found on the outside of the cell (3 pg. 54). The contraction of the
SM cells occurs following an increase in intracellular calcium; this arises when mediators act on the voltage gated L–type
calcium channels. These channels open either upon response to depolarization of the cells and mediators action on the AT1
adrenoreceptors which work by increasing the amount of inositol triphosphate, allowing calcium to be released or by acting
on ligand gated channels which open in response to release of ATP from the nerves (3 pg 55).Following the release of
calcium from the sarcoplasmic reticulum, myosin light chain kinase (MLCK) is activated by calcium binding to
calmodulin. Myosin

Muscle Contraction Report
Muscle contraction begins when the nervous system generates a signal. A motor neuron conducts an action potential to the
link with the muscle fiber at the neuromuscular junction a neurotransmitter called acetylcholine is released. This chemical
then binds to receptors on the muscle fibers. Acetylcholine receptors are chemically gated ion channels. When
Acetylcholine binds it opens and allows an influx of sodium ions into the muscle fiber. This stimulates the sarcolemma and
generates another action potential that travels through tiny folds knows as transverse tubules the action potential reaches
myofibrils within the muscle fiber, surrounding the myofibrils are membranous sacs called the sarcoplasmic reticulum. The
arrival of the action potential

Muscle Contraction Essay
Q1
Muscle contraction can be understood as the consequence of a process of transmission of action potentials from one neuron
to another. A chemical called acetylcholine is the neurotransmitter released from the presynaptic neuron. As the
postsynaptic cells on the muscle cell membrane receive the acetylcholine, the channels for the cations sodium and
potassium are opened. These cations produce a net depolarization of the cell membrane and this electrical signal travels
along the muscle fibers. Through the movement of calcium ions, the muscle action potential is taken into actual muscle
contraction with the interaction of two types of proteins, actin and myosin. Different steps of activities are involved in
muscle contraction. The ... Show more content on Helpwriting.net ...
This activity is the critical driving force of muscle contraction. The stream of action potentials along the muscle fiber
surface is terminated as Acetylcholine at the neuromuscular junction is broken down by acetyl cholinesterase. The release
of Calcium ions is ceased. The action of the myosin molecule heads is obstructed because of the change in the
configuration of troponin and tropomyosin due to the absence of calcium ions. This will eventually cause the contraction to
be ceased. Together with these physical processes, an external stretching force such as gravity pulls the muscle back to its
normal length.
References
The Mechanism of Muscle Contraction. (n.a), (n.d) Retrieved on 26 June 2011 from http://meat.tamu.edu/muscontract.html
Encyclopedia of Nursing & Allied Health. Bioelectricity: Transmission of nerve impulses to muscle. Retrieved on 26
June 2011 from http://www.enotes.com/nursing–encyclopedia/bioelectricity
Q2
Skeletal Muscle Structure.The cells of skeletal muscles are long fiber–like structures. They contain many nuclei and are
subdivided into smaller structures called myofibrils. Myofibrils are composed of 2 kinds of myofilaments. The thin
filaments are made of 2 strands of the protein actin and one strand of a regulatory protein coiled together. The thick
filaments are staggered arrays of myosin molecules.
* Units of organization of skeletal muscle. The filaments are organized into

Muscle Contraction Research Paper
Emily Branstetter
Duchenne Muscular Dystrophy
Skeletal muscle contractions play a pivotal role in our day–to–day lives. Their main function is to generate force and
provide our bodies with structural integrity. For many of us, muscle contractions seem effortless, but there's actually quite a
bit going on under the surface. Our muscles are composed of sarcomeres, units of skeletal muscle fibers, which are made
up of actin and myosin contractile filaments. These filaments need to bind to each other in order to lengthen and shorten the
sarcomere. However, the binding sites for actin and myosin are blocked by troponin and tropomyosin proteins. In order to
get them off of the binding sites, calcium needs to bind to the troponin, which then lifts ... Show more content on
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Being one of the proteins that initiates the unbinding of actin and myosin, its location allows for easy access to bind to and
change the shape of actin. As dystrophin and actin bind, force is transmitted from within the sarcomere to the extracellular
space and surrounding muscle cells. When dystrophin function is inhibited, it won't bind to actin and the cross bridge cycle
is interrupted; meaning no contractions.
Lastly, because of the flimsy membrane, myo–enzymes and calcium can leak out which has the potential to decrease the
function of the cell. The lack of integrity of the membrane also allows particles to leak into the cell causing a concentration
gradient. This gradient will draw water toward the area to dilute it and with time leads to the bursting of the muscle cell.
Most common symptoms of DMD are muscle weakness and muscle loss progressing from the legs to the arms, and the
condition deteriorates over an extended period of time. This leads to difficulties standing and walking and results in
required use of wheelchairs, often by the age of 12 or so. It is not uncommon for someone with DMD to appear as if they
actually have a large muscle mass, but this is simply due to the buildup of fat content and the fact that muscle fibers are
being replaced by fat

Skeletal Muscle Contraction And Relaxation Is Vital For
Skeletal muscle contraction and relaxation is vital for voluntary body movements to occur. Skeletal muscles contract when
myofibrils composed of actin and myosin slide past each other, which contracts the muscle by altering its length. The
gastrocnemius muscle in Rana pipiens, which is attached to the sciatic nerve, can be stimulated to find threshold and
maximal stimulus voltage. Once threshold is reached, contraction amplitude increases with stimulus voltage until the
maximal voltage is reached, at which point it levels off. Altering the interstimulus interval can induce twitch summation in
the gastrocnemius, leading to one combined contraction with a high amplitude. Increased stimulus frequency can be used to
induce a tetanic ... Show more content on Helpwriting.net ...
Twitches are the resulting contraction from the firing of an AP in muscles. Twitches are much longer than the APs
themselves. Twitch recruitment uses external stimuli to determine the threshold and maximal voltages of nerves and
muscles. Stimuli below the threshold voltage, or the minimum stimulus strength required to elicit an action potential, will
not cause a muscle to twitch. Once threshold potential is determined, increased stimulus voltage will increase the
contraction amplitude of the twitch until the maximal stimulus is reached. The twitch will not significantly increase in
strength for any voltage above maximal. This is because at maximal stimulus voltage all motor units have already been
recruited to contract. The gastrocnemius muscle has a far higher threshold and maximal voltage that the sciatic nerve due to
its size and the number of motor units present in the gastrocnemius. Along with increasing stimulus voltage, contraction
amplitude can also be increased through twitch summation. Twitch summation occurs when a muscle is stimulated twice in
quick succession, so that the second twitch occurs before the first twitch has relaxed. The twitches then combine to form a
stronger muscle contraction. This process is made possible by the temporal relationship between a muscle's AP and the
resulting twitch, which is far longer in duration than the 1 ms AP that causes it. Due to the nature of skeletal muscle
contraction, the length–tension relationship in

Smooth Muscle Contraction And Contraction Of Smooth Muscles
Introduction
Muscles; the way we get around. With smooth muscle gripping bones, creating movement with electric current. Electrical
signals flow from the brain down the spinal cord to open the calcium floodgates. With the flow of calcium, the muscles
contract, and because they're attached to bones, the flow of calcium leads to muscles pulling on the bones, which cause
movement. While the contraction of muscles starts from the brain to get muscles to move from either slightly or greatly,
electricity can be used instead of the brain to create movement.
For the twitch recruitment, I believe that while a muscle will be more likely to flex when it is provided with electricity, the
muscle will not keep flexing at a continuous rate, even if the electricity

Myosin Skeletal Muscle Contraction
Myosin is a conventional term used to reference a group of molecular motors that translocate actin filaments or translocate
vesicles on fixed actin filaments in living organisms[1]. The human genome also contains 24 unconventional Myosins
divided into 11 distinct classes including some nonmuscle Myosins[2]. This poster will cover in particular Myosin II which
is responsible for skeletal muscle contraction[1]
Myosin II has a molecular weight of 520 kDa contains two heavy chains, each roughly 2000 amino acids in length[3]. Each
of these heavy chains are comprised of an N–terminal head domain and C–terminal tails that together take on a coiled–coil
morphology holding the two heavy chains together[4]. Apart from the 2 heads and heavy chains Myosin ... Show more
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Myosin can hydrolyze a single ATP in 30 seconds which is slow when compared to the 5–10 ATP hydrolyzed every second
when combined with Actin[7]. One Myosin head binds to one Actin filament to hydrolyze ATP, this occurs due to the
polarity of the Actin molecule[7][Img2]. After completion of the hydrolyzation process and release of the products the
usually weak bond between Myosin and Actin is strengthened due to the release of Phosphate[6]. This change is referred to
as the "Power Stroke"' as it pulls the Actin filament down the line, ADP is released and the Myosin head detaches once a
new ATP is secured so the process can repeat[1][Img2].
Rigor Mortis is a stiffening of the body caused in part by the lack of aerobic respiration[8]. In death the body releases
Calcium ions which interact with Actin and Myosin to contract muscles throughout the body[8]. Due to the cessation of
respiration the body is unable to efficiently produce ATP[9]. This causes a shortage that denies Myosin and Actin the ability
to disconnect, Calcium ions are unable to be pumped back out of the muscle cell so the muscles remain tense and the body

Ring Contraction Of A Ring
RING CONTRACTION
All the carbons of a ring are equivalent (a ring has no ends like an open–chain compound does),1 ring compounds can be
classified as either monocyclic or polycyclic compounds.
As the word "contraction" means shrinking, ring contraction can be defined as the process of shrinking larger ring
compounds which are less strained into a more strained smaller ring structures. Instead of making small strained ring by
chemical reaction which is very strenuous to do, ring contraction is a process of easing the stress of forming smaller
strained ring on their own.
A ring contraction reaction is a type of organic reaction in which usually a hydrocarbon ring is reduced in size.2 Ring
contraction reactions are an important method to increase molecular complexity in a single step, because, in many cases,
the reorganization of the bonds occurs with a high level of selectivity, affording products not easily accessible by other
synthetic approaches.2. and 3.
The smallest ring compound possible is cyclopropane, this is so because we need at least three carbon atoms to form a ring
structure. Cyclopropane is the most strained ring compound due to the fact that its carbon atoms are sp3 hybridized, sp3
carbon have an angle of 1090, but the carbon atoms in cyclopropane are strained in an angle of 600. Scheme 1: Mechanism
of a typical ring contraction
METHODS FOR RING CONTRACTION
Ring contraction occurs through rearrangement of carbon atoms to form a smaller ring structure. Two

Expansion and Contraction of Matter
SMJK AVE MARIA CONVENT
SCIENCE
B6D7E1 – The Principles of expansion and contraction of matter
Name: Lim Li Fern (14)
Class: 1P11
Identification Card No.: 990412–11–5206
Subject teacher: Puan Norlida
Heat does to matter is changes it state. There is something more subtle though that can cause big problems. Look at this
devise. When you heat both this ball and the ring the ring expands like a long bar of metal. The ball expands less so when
they are heated the ball fits through the ring. You may want to look for these and try this demo as many of you probably
have these.
Another neat tool to show the expansion of metals is this bimetal bar. It is made with one metal on one side and another
metal on the other side. One metal expands ... Show more content on Helpwriting.net ...
What Happened: The water level was slightly below full. As the water cooled, it contracted causing the water level to drop.
However, there may also be another effect here as well. If you used water with a lot of bubbles, those bubbles also took up
a part of the volume inside the bottles. As the bubbles eventually floated to the top, they would have decreased the volume
slightly. Can you think of some way to insure that what you are seeing is not a result of the bubbles?
A Major Exception to the Rule
The general rule that has already been stated is that matter expands when heated and contracts when cooled, but there are a
few exceptions. The most important exception is water when it freezes.
Procedure: Fill the bottle to the top with water and replace the cap. Wrap the bottle in several layers of newspaper and place
the bottle and paper in the bag. Put the bag in the freezer and leave it there until the water freezes.
Remove the bag and paper and examine the bottle. What do you see?
What Happened: The bottle was shattered or very swollen. When water is cooled, whether as a gas (water vapor), a liquid,
or a solid, it will contract. The one major exception to this is when water reaches the freezing point and changes from liquid
water to ice. At that point, the water expands, rather than contracts. This expansion caused the bottle to break.
The reason water behaves this way has to do with the shape of it's

Excitation Contraction Merger
Excitation–contraction coupling (ECC) is the connection between the electrical action potential and the mechanical muscle
contraction. Physiologically, it is a mechanism whereby an electrical signal detected by the dihydropyridine receptor is
converted into an increase in calcium via activation of ryanodine receptors (RyRs). Per the article, mutations in RYR1, the
gene encoding, are the underlying cause of various congenital myopathies including central core disease, multiminicore
disease (MmD), which is a disorder that primarily affects muscles used for movement, as well as some forms of
centronuclear myopathy (CNM), a condition characterized by muscle weakness, and congenital fibre–type disproportion.
Patients with recessive, but not dominant,

Two Types Of Contraction
Types of contractions
Isometric: During isometric contractions, muscles stay in a static position and this helps muscular endurance as you will be
working on the muscles endurance on how long it will be able to last whilst static. For example when you stop halfway
through a press–up or if you are doing a plank, these are good examples as you have to stay in an isolated position. Also
another example of this would be dorsal raises in a static position, when you hold your head up and your legs up when you
are laid on your front. This type of muscle work is easy to undertake but it can cause sharp increases in blood pressure as
the blood flow is increased and it is also rapidly leads to fatigue.
Concentric:
This occurs when a muscle shortens against ... Show more content on Helpwriting.net ...
Most of these contractions you will need specialised equipment to measure the rate of the consistency of the work out. A
practical example of isokinetic contractions would be bench pressing at a low weight but a high repetition, this would be
isokinetic as you would need to do it at a constant speed so therefore you would need it at a suitable weight to do these
contractions correctly. If you had it at a high weight you would get worn out and start struggling at the end of the set of
repetitions. An everyday example of isokinetic example would be doing your teeth as you would be doing it at the same
pace and contractions and shortenings would take

Muscle Contraction Lab
This lab was conducted to test the muscle reaction to three different solutions and observe the muscle contraction in the
presence of each solution. We predicted that ATP solution in distilled water might cause muscle contraction since ATP
alone binds to myosin to break the cross–bridge and enable the myosin to rebind to actin at the next muscle contraction.
("ATP and Muscle Contraction." Boundless Biology) All three groups were given a 2cm length of psoas muscle, which was
placed on a microscope slide with a small drop of glycerol. First, we measured each fiber, and then added 2 drops of one of
the solutions, Solution A; .25% & ATP in distilled water, Solution B; .25% ATP solution in water, .05M KCI, .001 M
MgC12 in distilled water, and Solution C; .05 M KC1, .001 M MgC12 in distilled water. We waited 30 seconds after
adding the solution and we measured the fiber again to see if there was any muscle concentration after adding the solution.
Our hypothesis was not supported, because the fiber size did not change.
Purpose:
The purpose of this lab was to learn if any of the three solutions used for the experiment would cause the fiber to have a
muscle contraction and if there wasn't any muscle contraction, understand why the solution didn't cause a muscle
contraction.
Introduction:
Muscle contractions are a reduction in size of muscle ... Show more content on Helpwriting.net ...
(Table 1) ATP alone causes myosin to break the cross–bridge and allow the myosin to reattach to the actin causing a muscle
contraction, since the solution we used had ATP; I believed that that was enough to cause the fiber contraction. I thought
that we had done our experiment in correctly because there was no muscle contraction. I believed that it was due to the
amount of solution we added to the fiber. We re did the experiment and added four drops of the solution but there was no
muscle contraction as

Muscle Contraction Experiment
The introduction of this lab report discussed and elaborated how muscle contraction is an intricate and precise step–by–step
process in the body. The concepts outlined at the introduction intertwine with the experiments performed in this lab. The
experiments aimed to showcase the physiological cause and effect of skeletal muscle responses towards various situations.
For instance, the first experiment demonstrated spatial summation through the form of muscle recruitment. The cause of
this reaction was due to the increased voltage input on the sciatic nerve. Furthermore, the second case study exhibited
temporal summation, where constant stimulus exposure led to a fusion of twitches called a tetanic contraction. As for the
third experiment, the ... Show more content on Helpwriting.net ...
The previous trial involved multiple sources of motor units contracting together to generate a strong tension. This time,
fusion of contraction came from the frequency of stimulus input. In this case, the stimulus magnitude remained the same
throughout the trial, while the frequency of parts per second increased in succession per 30 seconds. Going back to Figure
2, the graph revealed a sigmoidal trend, or an "s" shaped graph. The correlation existed between an increase in twitch
tension and frequency of stimulus on the sciatic nerve. The physiology behind this paralleled relationship was due to the
fusion of small muscle twitches with no relaxation period. This resulted in a sustained, and maximal contraction better
known as a fused tetanus. It can be said that the frequency of action potential determines the level of tension increase, until
the maximum tension is obtained (Widmaier et al, 2015,

The theory of the sliding filament explains how the muscles contract to produce power. , actin and myosin filaments in
sarcomeres of muscle fibers bind to the formation of cross–bridges and slide past each other, creating compression. This
theory explains how these cross–bridges are formed and the subsequent contraction of muscle.
For contraction to occur it is necessary to stimulate the muscle in the form of an impulse (action potential) from the motor
neuron. one motor neuron does not stimulate the entire muscle, but only a few muscle fibers in the muscles. The individual
motor neuron plus the muscle fibers that it stimulates is called the motor. The end plate of the motor (also known as the
neuromuscular junction) is a mix of axons of motor ... Show more content on Helpwriting.net ...
Myosin head attaches to actin. myosin head pivots pulling the actin filament toward the center, The cross bridge detaches
when a new ATP binds with the myosin.
6) The result would cause shortening of a sarcomere, this how a muscle contracts. (3)
Muscle contraction requires ATP, ATP is required to separate myosin from actin and re–cycle. Several cycle cycles in many
myosin heads lead to a reduction in sarcomere. The decomposition of ATP releases energy that allows the myosin to pull
the threads of actin inward and thus contract the muscles. This occurs along the entire length of each myofibril in the
muscle cell.(2)
Muscle contractions are controlled by the action of calcium, thin actin filaments are associated with regulatory protein
called troponin and tropomyosin. When the muscle is relaxed tropomyosin blocks cross bridge binding sites on actin. When
calcium ions level is high enough and Atp is present," Ca++ attaches to a protein called tropomyosin that covers the
attachment site on the actin myofilaments. This causes the tropomyosin to uncover the attachment site which permits the
myosin head to bind to the attachment site and begin the cycle described above. As long as the Ca++ concentration remains
high cycling, or contraction, continues"

In a healthy person, muscle contraction and movement is cause by a series of events coming from the brain, going to the
neuromuscular junction (the place between the nerve ending and the muscle fiber), into the synapse, and into sodium ion
channels. The way muscle movement is supposed to work is with a starting action potential from the brain. Once the signal
reaches the neuromuscular junction, it causes voltage gated calcium ion channels to open up and calcium comes flooding
in. Inside the neuromuscular junction, there are vesicles that contain a neurotransmitter called acetylcholine. When calcium
is flooded into the cell, it causes these vesicles filled with acetylcholine to merge with the border of the synaptic cleft,
filling the inside

Smooth Muscle Contraction
Smooth muscle cells of the ileum spontaneously contract due to the presence of pacemaker cells, called Cajal cells
(Widmaier et al., 2014d). However, these smooth muscle they are also innervated by autonomic nerves, which can be
stimulated to change contraction rates by stimulating. Figure 1, shows the effect of nerve stimulation of 17volts on isolated
ileum tissue. Stimulating sympathetic (sympathetic nerves was stimulated for this particular tissue), causes release of
noradrenaline, which inhabits contraction of smooth muscle cells. Furthermore, according to table 1, there is a –58.83%
change in contraction amplitude. It can be extrapolated that fewer smooth muscles are contracting. At lower voltages, a
weaker response was observed, as voltage is increased a stronger response was observed. Increasing the voltage, means
more neurons are being recruited (Widmaier et al., 2014b). In this particular experiment, stimulation of nerves around the
mesenteric artery caused an inhibitory response, therefore at higher voltages, more smooth muscles are being inhibited.
The frequency was set to 20Hz. Interstitial cells of Cajal, are responsible for spontaneous contraction of smooth muscle
cells in the gastrointestinal tract (Widmaier et al., 2014d). Once ... Show more content on Helpwriting.net ...
To confirm this finding Phentolamine, which block adrenergic receptors, was added to the organ bath. After 10 minutes,
once the Phentolamine was in equilibrium with the solution, the nerve was stimulated again. Comparing figure 1 and 5, it
can be concluded, that the nerves being stimulated could not cause change in contraction of the muscle in the presence of
Phentolamine. Thus, the nerve being stimulated must be releasing noradrenaline. Noradrenaline, released by sympathetic
nerve causes decrease in motility, by inhibiting muscle contraction (Widmaier et al.,

The Isometric Phases Of The Isometric Phase Of Muscle...
The isometric phase of muscle contraction occurs when the length of the muscle body is constant, with no visible
shortening, as the tension increases (Kroeker, 2017). Isometric tension is the first phase of the SEC model of contraction, in
which the cross–bridges formed by actin and myosin filaments shorten, but add tension only to SEC (Kroeker, 2017). The
isotonic phase of muscle contraction occurs when the tension remains constant, but the muscle body begins to shorten
(Kroeker, 2017). In regard to SEC, the isotonic shortening phase occurs when the actin/myosin cross–bridges cause visible
shortening after tension when PEC=SEC=Load, as for the muscle to visibly shorten as a unit the tension in SEC must be
equal to the load (Kroeker, 2017). The muscle must shorten as an outcome of the elastic elements already being stretched
(Kroeker, 2017). The latent period represents the force generated by the sarcomeres of each filament that is transmitted
through the connective tissues and tendons prior to movement, but will cause movement (Kroeker, 2017). Therefore, the
latent period is the time between the stimulus and contraction, as it occurs during the isometric tension phase during the
time between stimulus application and isotonic shortening (Kroeker, 2017). When a load is higher, the latent period will be
longer as more tension is needed for the muscle to generate a force large enough to move the weight (Kroeker, 2017). A
longer latent period allows for muscle tension to

The Effect Of A 15 Concentration Of Creatine Phosphate On...
The Effects of a 15 mM Concentration of Creatine Phosphate on the Percent Contraction of Glycerinated Rabbit Psoas
Muscle Fibers
Group 4
Saria Sultan
Meghan Shmunes
Prachee Patel
General Biology III Laboratory. 81296.02
Fall 2013
____________________________________________________________________________________________________
Abstract: The purpose of this study was to compare contractility of individual preparations glycerinated rabbit psoas
muscle exposed to two different solutions known to cause muscle contraction. A standard contracting solution without 15
mM of creatine phosphate and a second contracting solution with 15 mM of creatine phosphate were compared to one
another. Creatine phosphate has been found as ... Show more content on Helpwriting.net ...
____________________________________________________________________________________________________
Introduction:
Creatine phosphate has been heavily experimented upon to show that it is an important effector towards muscle activity.
When creatine phosphate is present in a solution containing muscle fibers without the presence of ATP, it serves as the
energy supplier due to the fact that it absorbs bound adenine nucleotide, which is firmly linked to the contractile elements
on muscle fibers (Bozler, 1953). Even in low concentrations this nucleotide can be considered an energy transfer
mechanism, for it takes full advantage of the creatine phosphates energy supply, thus acting as a substrate for the enzymatic
activity of the contractile elements of a muscle group. Consumption of this nucleotide leads to an increase in the strength of
contraction. Creatine phosphate also speeds up rate of relaxation of muscles, for it induces the relaxing effect of ATP
(Bozler, 1953). Thus, this research suggests that creatine phosphate is directly linked to instigate muscle contractibility.
Creatine phosphate has also been reported to be a primary determinant in controlling the actomyosin cross bridge cycling
kinetics of cardiac muscles (Ogut and Brozovich, 2014). Creatine phosphate has been directly linked to being responsible
for the rephosphorylation of ADP,

Right Atrial Contractions
On the right side the flow of blood enters the heart through the inferior and superior vena cava that throws out the poor
oxygen blood to the right atrium. On the left side of the heart the pulmonary veins takes action that dumps the rich oxygen
blood that is coming from the lungs to the left atrium. This has both sides of the heart working together. When it comes to
the atrial contraction, the right side makes the blood flow to the right atrium to the right ventricle to the tricuspid valve.
Once the ventricles fill up completely, that is when the tricuspid valves shut closed. This is to prevent the blood from going
backwards to the atria, making the ventricles squeeze together. The left side of the atrial contraction makes the blood flow
from

Muscle Contraction Lab
Observation of a Muscle Fiber Concentration with ATP and Salts
By: Joez Suarez INTRODUCTION:
Muscle contractions can be studied based on its length and tension. If the muscle tension changes but the muscle length
remains the same, it would be described as isometric. However, a muscle contraction is isotonic if the muscle tension
remains the same, but the muscle length changes. It is not necessarily for muscle contraction to mean "muscle shortening,"
because muscle tension can be produced without changes in muscle length such as holding a heavy book or a dumbbell at
the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle
fibers to their low tension–generating state.
OBJECTIVE:
To become familiar with the skeletal ... Show more content on Helpwriting.net ...
Once at the supply table, muscle fibers were placed in the petri dish, with a small amount of glycerol over the muscle
fibers. With clean fine glass needles, the muscle segment was teased to separate its fibers. Three single muscle fibers were
obtained and measured their initial lengths using a millimeter ruler. Later they were transferred onto three different clean
microscope slides with a glass needle, each fiber was flooded with several drops of the solutions, containing ATP, K+, and
Mg^2. After 30 seconds, the fibers were remeasured to compare the ending lengths.
RESULT:
To find the contraction percentage of the muscle fiber when mixed with the different solutions. The initial length (mm) was
subtracted by the ending length (mm) which equated to the net change in

Most accepted model of muscle contraction
The explanation for how muscles contract to produce force
Structures that are involved: Myofibril, Sarcomere, Actin, Myosin, Tropomyosin, and Troponin
Myofibril: cylindrical organelle running the length of the muscle fiber, containing Actin and Myosin filaments
Sarcomere: functional unit of the Myofibril, divided to I, A and H bands
Actin: thin contractile protein filament, containing active or binding sites
Myosin: thick contractile protein filament,
Tropomyosin: actin–binding protein which regulates muscle contraction
Troponin: complex of three proteins, attached to tropomyosin
Myosin head attaches to Actin Myofilament:
Formation of a new cross bridge leads to the release of Pi
The Myosin head enters it's high–energy configuration and binds to the Actin Myofilament. ... Show more content on
Helpwriting.net ...
Before this the ADP and Pi are still bound to the Myosin head
After binding to the Actin Filament the Pi detaches from the Myosin head
Pi release triggers the "Power Stroke"
Change in Myosin head moves the Actin and Myosin filaments relative to each other
"Power Stroke" = "Working Stroke"
The Myosin undergoes another conformational change c
Myosin head pivots and moves the thin filament closer to the M line (center structure of the H zone) proteins as the thick
filament slides past
The Z lines/Z disc ('z' like formation) of the sarcomere move closer together, the entire contractile unit shortens
ATP binds to the Myosin
The cross bridge between the two fibers breaks as the Myosin head dissociates from the Actin Myofilament
Myosin heads act as a molecular motor, attaches to Actin molecules to create a cross bridge between the Sarcomere
Then ATP binds to the Myosin head, separating it from the Actin

PowerPhys:Activity 2 Twitch Contractions and Summation Essay
LABORATORY REPORT
Activity 2: Twitch Contractions and Summation
PREDICTIONS
Effect of Muscle Fiber Length on Contraction
1. As muscle fiber length increases: contraction force increases, becoming maximum at an optimal length, then decreasing
at longer lengths.
Effect of Stimulation Frequency on Contraction
2. As the frequency of stimulation increases, the force of contraction: increases.
MATERIALS AND METHODS
Measurement of Threshold Stimulus
1. Dependent Variable: contraction force.
2. Independent Variable: stimulation voltage
3. Controlled Variables: temperature, frequency of stimulation and muscle fiber length.
Effect of Muscle Length on Contraction
1. Dependent Variable: contraction force.
2. Independent Variable: ... Show more content on Helpwriting.net ...
60 Hz.
10. What was the maximum force generated in this experiment? 0.277 gf
11. How does increasing stimulation frequency affect force production? The tension produced during a sustained
contraction is greater than that produced by a single twitch.
The more stimuli per second, the greater the force generated by the muscle due to a sustained contraction. Muscle tension
depends on the frequency of stimulation of motor units and the number of motor units stimulated. By increasing the
frequency of muscle stimulation, a sustained force generation is being produced.
DISCUSSION
1. Explain why muscle contraction does not occur below threshold stimulus. It does not occur below the threshold stimulus
because it needs a minimal voltage that can induce an action potential. The stimulus causes depolarization in either the
nerve or muscle. If depolarization doesn't reach the threshold, then the nerve or the muscle will not generate that necessary
action potential to cause a muscle contraction. A subthreshold stimulus does not cause an action potential because it does
not bring the membrane potential to threshold.
2. The maximum stimulation voltage used was 500 mV. If the stimulation voltage was increased to 600mV volts, would the
force of contraction decrease, stay the same, or increase? Explain your choice. The force of contraction will decrease. Once
the stimulation voltage rises above threshold, force generation

Introduction: Skeletal muscle contraction happens when Ca2+ floods into the muscle cell binding with troponin allowing
actin and myosin to bind. The actin and myosin cross bridges bind and contract using ATP as energy. Muscle fatigue is
defined as the inability to maintain a desired power output. Muscle contraction can be affected by peripheral fatigue which
refers to fatigue mediated by factors outside of the central nervous system, specifically within the muscle fibers, or central
fatigue which involves the central nervous system and occurs predominantly due to afferent reflexes that inhibit output
from the motor cortex. Peripheral fatigue can be caused by decreased levels of any of the molecules/metabolites involved
in muscle contraction. Central fatigue can be caused by ... Show more content on Helpwriting.net ...
Methods: This week experiment had two main parts. To start the experiment 1, one of the students volunteered to be the
subject of this experiment and two other students helped to set up the experiment. We used the PowerLab software and grip
force transducer for this experiment, which records the force production (percentage of max) by hand muscles. First, we
calibrated the grip force transducer by having the subject squeeze the grip force transducer as hard as possible with one
hand for 2–5 seconds and then relax. This gave us a period of stable baseline followed by a period of maximal force
production. We started to record and asked the volunteer to produce 20% of her maximal grip strength and hold this grip
consistently for 60 seconds by looking at the force meter. After 60 seconds, volunteer relaxed her muscles. Allowed the
subject to recover for approximately 60 seconds. Repeated this process for contractions of 40%, 60%, 80%, and 100% of
maximal grip strength. Allowed our volunteer to relax when she could not hold the force constant at the desired

Personal Narrative On A Contraction
That night was excruciating! Hell that whole Saturday going into the night was terrible. Hubby was keeping count of each
contraction and they were a lot closer now. Again, I kept waking up through every contraction. I was in agonizing pain,
crying and babe was right next to me trying to be supportive. I knew he was stressed and exhausted. I kept getting up to
squat and walk around, being on my feet made it a little bearable. I craved sleep, I was so tired and wanted nothing more
than to lie down. At 2am l called my doctor and told her what was going on but again they told me to stay hydrated and
keep count. I hung up frustrated and helpless. It was now 4am and I couldn't take it anymore. I could not stop crying and
my fiance felt so helpless, we both did. We headed to the hospital. ... Show more content on Helpwriting.net ...
Hubby wanted to drop me off at the front of the hospital while he parked the car. I didn't want to be alone and the thought
of him being away from me made me anxious. He was the one getting me through this and I didn't want anyone else
helping me, so I went with him to park the car. I was in so much pain, we had to stop every few steps so I could let the
contraction pass. They were coming in huge overwhelming waves. I couldn't talk or stand through them. We got into the
ward and they offered me a wheelchair, I didn't want to use one but my legs almost gave out so I gave in. When I finally
got on it, it was so awkward! I was sitting in this stupid wheel chair, having an extremely painful contraction. It felt like it
was the slowest wheelchair ever

Muscles contract through an action potential moving along a motor neuron toward the skeletal muscle and they connect to
a neuromuscular junction  acetylcholine vesicles being released  binding on the sarcolemma  causes Na+ influx in the
muscle fiber generating an action potential within the muscle fiber  action potential moves through the T–tubules
Calcium channels open calcium is released into the cytoplasm  actin–myosin binding sites and cross–bridges are
activated by calcium ions between the actin/ myosin heads  ATP is hydrolyzed to flex myosin head  this flexion makes
the actin filaments move close to the middle of the sarcomere  The length of the sarcomere becomes shorter 
contraction. I would like to define a few terms discussed within this ... Show more content on Helpwriting.net ...
A twitch is a contraction caused by one action potential. HYPOTHESIS!!!!!!!!!!!!!!!! In experiment 2, we measured
muscular twitch in the thumb by using a finger pulse transducer and attaching a stimulus electrode to send shock through
the ulnar nerve in the wrist. In experiment 3, we observed summation and tetanus by opening a new chart window, and
placing the bar stimulus on the left wrist to send impulses to. In experiment 4, we measured the electrical activity of the
median nerve stimulation by using the Bio Amp and the bar stimulus to stimulate the median nerve in the wrist and elbow.
In experiment 5, we measures the nerve conduction velocity by opening a new window and placing extra pressure on the
nerve in the elbow and increasing the amplitude to 15–20 mA. In experiment 2 the lowest stimulus that had a response was
7.5 mA with a response of 0.013 v/s, and the highest was 17.5 mA with a response of .147 v/s. In experiment 3 we found
two responses up until the frequency of 10 Hz, we measured summation (.05s, .171 mV) and tetanus (.05s, .353 mV) at 20
Hz. In experiment 5 we measured latency and distances between the wrist and

Skeletal Muscle Contraction
Neuromuscular junctions play a key role in skeletal muscle contractions, and they consist of axon terminals, synaptic clefts,
and junctional folds. The contraction begins with the arrival of a nerve impulse at an axon terminal which causes
acetylcholine (ACh) to be released into the synaptic cleft. ACh then diffuses across the synaptic cleft and binds with
receptors on the sarcolemma of skeletal muscles. This binding creates electrical events that allow an action potential
through muscle fiber which causes a muscle contraction. However, normal communication between a muscle and nerve can
be interrupted due to the neurological disorder, myasthenia gravis. In Latin and Greek, Myasthenia gravis means "grave
muscle weakness," (fact sheet). As stated ... Show more content on Helpwriting.net ...
A study was conducted from January 2005 to January 2010 in order to determine if the presence of myasthenia gravis
affected the prognosis of patients that underwent an extended thymectomy. The study consisted of 104 patients (61 men, 43
women, and 38 of these patients had myasthenia gravis with the average age being about 55 years old) with thymoma.
According to Zhefeng et. al., myasthenia gravis complicates a significant amount of thymomas, and the primary treatment
method for thymomas are extended thymectomies (2016). 11 patients faced a reappearance of a thymoma or suffered to
respiratory failure due to myasthenia gravis during this five–year study period. The survival rate for patients with
myasthenia gravis was 76%, and 89.1% in patients without myasthenia gravis. In conclusion, patients with thymomas and
myasthenia gravis had a poorer prognosis than patients with thymomas without myasthenia gravis (Zhefeng et al.). Another
study was conducted from 1999 to 2014 to describe the outcomes of patients with myasthenia gravis that had gone through
a thymectomy. The patients in this study were 12 children (under 18 years of age) that had a thymectomy at Phoenix
Children's Hospital. The time for the patients' hospital stay ranged from one to five days, and after a month these children
did not contract an illness or faced death. This

Muscle Contraction

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