Transcript muscles slideshow

Muscles
Muscles work by
contracting.
Muscles pull.
A pair is needed to
move a bone two
ways.
An antagonistic pair.
A muscle is made up of
bundles of muscle cells.
Muscle cells are made of
bundles of myofibrils. These
are groups of protein fibres.
Muscle cells also
have many
mitochondria,
transverse
tubules and an
extended set of
sacs called the
sarcoplasmic
reticulum. What
are they likely to
be for?
Myofibrils are made of protein
fibres. They appear banded
under the microscope.
The banding relates to how two
protein fibres overlap. They
form units called sarcomeres.
The thin fibres
are made of
actin.
The thick fibres
are made of
myosin.
Contraction happens
when the myosin and the
actin interact by forming
cross links.
First there has to be an
impulse from a motor neurone.
Describe what happens here.
An impulse arrives at the neuromuscular junction.
Acetyl choline is secreted.
The muscle membrane
depolarises.
What then happens to the acetyl
choline?
The actin has
sites for the
myosin to link
to it.
But, the sites
are covered by
proteins called
troponin and
tropomyosin.
The calcium
binds to the
complex.
It moves part
of it out of
the way.
The myosin can
then bind.
This triggers it
to change its
position.
It shifts to the
side.
The myosin slides over the
actin.
The muscle gets shorter as
the proteins overlap more.
Sarcomeres shorten during
contraction.
The calcium is pumped out of
the cytoplasm.
The protein complex on the
actin goes back to its normal
position.
The myosin cannot bind.
The muscle contraction stops,
this is relaxation.
Put these in the correct order and
then learn the sequence.
Depolarisation
Impulse
Sliding
Calcium
Troponin
Vesicles
Vesicles
Depolarisation
Interaction
Calcium
Calcium
Troponin
Impulse
Interaction
Calcium
Sliding
The Twitch
H-zone
Z-line
I-band
A-band
Z-line
Rest
Since I made such a pigs ear of teaching this
Contracted
yesterday, which bands will change in size when
the
muscle contracts?
Thin filament
Thick filament
H-zone
Z-line
I-band
A-band
Z-line
Rest
Contracted
Thin filament
Thick filament
The ATP is
hydrolysed,
returning the
head to its
original
position.
ATP binds with
the myosin
head and this
releases it from
the actin.
Myosin heads
bind to the actin
forming cross
links.
The heads
change position
pulling the actin
over the myosin.
ADP is released.
Fatigue
The ATP…
Pumps sodium and potassium across
membrane after the action potential.
Pumps Calcium back into the sarcoplasmic
reticulum.
Knocks the myosin heads off actin binding
sites and primes the head for the next
movement.
Is used in the manufacture of acetyl choline
in the neuromuscular junction.
The ATP
hydrolyses,
releasing energy.
The Myosin heads’
position reset
ready for the next
power stroke.
Calcium allows the
myosin heads to
attach to actin
binding sites.
The myosin heads
change position,
sliding the actin
over the myosin –
the power stroke.
ADP is released.
ATP attaches to
the myosin heads
and they detach
from the actin
binding sites.