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Muscles and Movement
Muscles and Movement
Skeletal muscle is a type of muscle which we use to move. Tendons attach
muscle to bones, whereas ligaments attach bones to other bones. Skeletal
muscle contracts and relaxes in order to move bones at a joint. Muscles work
in antagonistic pairs because they can only pull.
Skeletal muscles are made up of large bundles of long cells, which are called
muscle fibres. The cell membrane of the muscle fibre cells is called the
sarcolemma. Bits of the sarcolemma fold inwards across the fibre and stick
into the sacromere. These folds are called transverse tubules (T); they help the
spread of electrical impulses through a Sarcoplasm, this allows it to reach all
the parts of a muscle fibre. There is a network of internal membranes which
are called the sarcoplasmic recticulum. This stores and releases calcium ions
into the Sarcoplasm, this is needed for the muscles to contract. Muscle fibres
have a lot of mitochondria in them this is to provide the ATP for the muscle
contractions. Muscle fibre are multinucleate (contains many nuclei).
The muscle fibres are long, cylindrical
organelles called myofibrils. They're
made up of proteins and are highly
specialised for contraction. Each
myofibrils contain thick myosin filaments
and thin actin filaments; they move past
each other to make the muscles contract.
The thick Myofilaments are made up of
myosin and the think myofilaments are
made up of actin. If a myofibril is look at
under an electron microscope, then a
pattern of light and dark bands will be
Dark bands contain the thick myosin
filaments and some overlapping thin
Actin filaments. These are called A
bands.Light bands contain think actin filaments only. These are called I bands
A myofibril is made up of many short units called sarcomeres, the ends of
each sacromere is marked with a Z line. In the middle of each sacromere is a
M line, which is the middle of the myosin filament. Around the M line is the H
zone which is where myosin is only found.
The sliding filament theory explain muscle contraction. Myosin and actin
filaments slide over one another to make the sarcomeres contract. The
simultaneous contractions of lots of sarcomeres means the myofibrils and

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Sarcomeres return to their original length as the
muscle relaxes
Muscle Contractions
Myosin filaments have globular heads with binding sites on them, they are
hinged so they can move back and forth. Each myosin head has a binding site
for actin and a binding site of ATP. Actin filament have a binding site for
myosin heads, this is called actin-myosin binding sites. Two other proteins are
involved, tropomyosin and troponin; these proteins are attached to each other
and they help myofilaments move past each other.…read more

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Starting off with glucose (6C), this is split into 2x pyruvate (3C). This pyruvate
is taken into the mitochondria and enters the krebs cycle.
Glycose (6C) used 2 ATP to change into pyruvate (2X3C). This reaction is called
glycolysis. During the glycolysis 2 oxidised
NAD is used and changed to reduced NAD,
and Four ATP is produced, creating a two
extra ATP.
If there is no O2 then it occurs in the
cytoplasm, and incomplete oxidation occurs,
and lactic acid is produced.…read more

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The energy lost from the
electrons is used to help pump the protons into the intermembrane space
from the mitochondrial matrix. This creates a higher concentration of protons
in the intermembrane space, forming a electrochemical gradient. The
protons move back down the concentration gradient, via ATP synthase, this
movement drive the synthesis of ADP + Pi to ATP. The movement of protons
across the membrane creating ATP is called Chemiosmosis. In the end the
Protons, Electrons and O2 combine to create water.…read more

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The process starts in the sinoatrialo node (SAN), which is in the wall of
the right atrium.
2. The SNA is like the pacemaker of the heart, it sets the rhythm. This is
done by sending out regular waves of electrical activity into the atrial
walls (a wave of depolarisation)
3. This causes the right and lift atria to contract at the same time.
4. A band of non-conducting collagen tissue prevents the electrical activity
from passing directly from the atria to the ventricles.
5.…read more

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P wave Depolarisation of the atria, leading to atria contraction
PR interval Time taken for the impulse to be conducted from the SAN
across the atria to the ventricles through the ANS
QRS complex The wave of depolarisation resulting in contraction of the
T wave Repolarisation of the ventricles during the hearts relaxation
Heart rate is controlled by the cardiovascular control centre, which is located
in the medulla of the brain.…read more

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As the lungs inflate, stretch receptors in the lungs are stimulated. The
stretch receptors send a nerve impulse back to the medulla. These
impulses inhibit the action of the inspiratory centre.
4. The expiratory centre then sends nerve impulses to the diaphragm and
intercostals muscles to relax. This causes the lungs to deflate, expelling
air. As the lungs deflate, the stretch receptors become inactive. The
inspiratory centre is no longer inhibited and the cycle starts again.…read more

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Carbon dioxide dissolves in blood plasma making carbonic acid
2. Carbonic acid dissociated into hydrogen ions and hydroengcarbonates
ions which lowers the blood PH
3. Chemoreceptors sensitive to hydrogen ions are located in the
ventilation centre of the mendulla oblongata.
4. Impulses are sent to other parts of the ventilation centre
5. Impulses are sent from the ventilation centre to stimulate the muscles
involved in breathing.
Investigation ventilation
Tidal Volume The volume of air inhaled and exhaled in a natural
breath.…read more

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Exercise causes an increase in breathing rate and tidal volume. A spirometer
can be used to measure the change in breathing rate and tidal volume at rest,
during exercise and after exercise.
Homeostasis is the maintenance of a constant internal environment. Your
external environment and what you're doing will affect the internal
environment; the blood and tissue fluids that surround your cells. Homeostasis
involves control system that keep your internal environment roughly constant
to deliver a dynamic equilibrium.…read more

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The effector responds to restore the body temperature back to
normal. The control of body temperature is called thermoregulation.
Hormones switch genes on to help regulate temperature. In a cell there are
proteins called transcription factors that control the transcription of genes.
Transcription factors bind to DNA sites near the start of genes and increase or
decrease the rate of transcription. Factors that increase the rate are called
activators and those that decrease called repressors.…read more


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