11.2 Movement
Understanding:
- Bones and exoskeletons provide anchorage
for muscles and acts as levers
- Movement of the body requires muscles to
work in antagonistic pairs
- Synovial joints allow certain movements
but not others
- Skeletal muscle fibres are multinucleate
and contain specialised endoplasmic
reticulum
- Muscle fibres contain many myofibrils
- Each myofibril is made up of contractile
sarcomeres
- The contraction of the skeletal muscle is
achieved by the sliding of actin and myosin
filaments
- Calcium ions and the proteins tropomyosin
and troponin control muscle contractions
- ATP hydrolysis and cross-bridge formation
Applications:
- Antagonistic pairs of muscles in an
insect leg
Nature of science:
- Fluorescence was used to study
the cyclic interactions in muscle
contraction
Skills:
- Annotation of a diagram of the
human elbow.
- Drawing labeled diagrams of the
structure of a sarcomere
- Analysis of electron micrographs
to find the state of contraction of
muscle fibres
Bones and exoskeletons
Provide anchorage for muscles and act as levers.
Levers change the size and direction of forces.
In a lever
- Effort force
- Pivot point (fulcrum)
- Resultant force
Different positions of these = different lever classes
Class 1 lever
Nodding head backwards
Fulcrum (pivot) in between the effort force
(muscle) and the resultant force (load)
Class 2 lever
Resultant force (load) is in between effort force
(muscle) and fulcrum (pivot)
Standing on tip toes
Class 3 lever
Bending fore arm
Effort force (muscle) in between fulcrum (pivot)
and load.
Antagonistic muscles
Movement of the body requires muscles to work
in pairs
When one contracts, another relaxes.
Biceps and triceps are antagonistic muscles –
how do they bend and extend your arm?
Annotate the human elbow
Label the following onto your elbow:
- Humerus
- Tricep
Describe the role of
- Bicep
each
- Joint capsule
Add in any drawings
- Synovial fluid
you need to of
muscles
- Radius
- Cartilage
- Ulna
Ludo
Loki
Range of movements at shoulder
Structure of joint determines the movements
Movement
Flexion
Extension
Abduction
Adduction
Outward rotation
Inward rotation
Describe it
Stick man drawing
Flexion and
extension at
shoulder
Outward and inward rotation
Types of joints
Different types of joints allow different
movements
Describe the different types of joints (Hinge,
pivot, ball and socket)
What movements do each of them allow?
Types of joints
Hinge joint – knee/elbow
Flexion and extension
Pivot joint - neck
Rotations
Ball and socket joint – hip/shoulder
All movements!
Structure of muscle fibres
Muscles attached to bone = skeletal muscles
(by tendons)
View using microscope = stripes are visible
Striated muscle
Types of muscles
Type of muscle
Striated
Smooth
Cardiac
What does that
muscle do? Where
is that muscle?
Drawing
Striated muscle
Composed of bundles of muscle cells called muscle fibres
Muscle fibres much longer than typical cells
Many nuclei present
Sarcoplasmic reticulum (modified endoplasmic
reticulum) conveys signal to contract all parts of the
muscle fibre at once
Large numbers of mitochondria to produce ATP for
contractions
Myofibrils
Parallel elongated structures
Alternating light and dark bands
In each light band is a disc shaped structure
called the Z line
Myofibrils
Each myofibril is made up of contractile sarcomeres
Between one Z line and the next is a sarcomere
Sarcomere
Draw and label your own diagram of a sarcomere
- Thick myosin filaments – must have heads
- Thin actin filaments
- Light band (also indicate the range)
- Dark band (also indicate the range)
- Z line
- Sarcomere
Skeletal muscle contractions
Thick myosin
filaments pull the
thin actin filaments
inwards towards the
centre of the
sarcomere
Shortens the
sarcomere and the
overall length of the
muscle fibre
Muscle contractions
Under the microscope – must determine the state of
skeletal muscle contractions
Compare the relaxed and contracted pictures
Control of contractions
Contraction of skeletal
muscle occurs by the
sliding of actin and
myosin filaments
Myosin filaments have
heads that can bind to
special sites on actin
filaments, creating cross
bridges.
Control of contractions
Use energy from ATP and exert a force to move
filaments.
Heads are spread along myosin filaments regularly,
and binding sites are spread along actin filaments –
many cross bridges can form at once.
Control of contractions
Relaxed muscle = tropomyosin protein blocks binding
sites on actin
Motor neuron sends signal to contract muscle fibres
Sarcoplasmic reticulum releases calcium ions
Calcium ions bind to troponin protein which causes
tropomyosin to move – exposing actin binding sites
Myosin can then bind to actin to start contraction
Sliding filaments
ATP hydrolysis and cross bridge formation must occur
for filaments to slide.
Complete the labels on your sheet:
1. Myosin filaments have heads which form crossbridges when they are attached to binding sites on
actin filaments
Sliding filaments
2. ATP binds to the myosin heads and causes them to
break the cross-bridges by detaching from the binding
sites
3. ATP is hydrolysed to ADP and phosphate, causing
the myosin heads to change their angle. The heads
are said to be cocked in their new position as they are
storing potential energy from ATP
Sliding filaments
4. The heads attach to binding sites on actin that are
further from the centre of the sarcomere than the
previous sites
5. The ADP and phosphate are released and the heads
push the actin filament inwards towards the centre of
the sarcomere – this is called the power stroke
Sliding filaments
ATP causes breaking of cross-bridges by attaching to
the myosin heads, causing them to detach from the
actin binding sites
Hydrolysis of ATP to ADP and phosphate provides
energy for the myosin heads to swivel outwards away
from the centre of the sarcomere and attach to a new
binding site.
Sliding filaments
Stages continue until the motor neuron stops sending
signals to the muscle fibres
Calcium ions then pumped back into the sarcoplasmic
reticulum. Actin binding sites are covered again by
tropomyosin.
Muscle relaxes.
Labeling your diagram
Use the powerpoint on my website and the video links too.
Label in each step that occurs during a muscle contraction from start (signal for
contraction) to end (relaxed muscle)
Use the videos:
Action potentials
and muscle
contractions
Break down of
ATP…
Myofilament
contraction
Include the following key words:
- ATP
- ADP + phosphate
- Cross bridges
- Sliding filaments
- Tropomyosin
- Troponin
- Actin
- Actin binding sites
- Contraction
- Calcium ions