Topic 11:
Human Health and Physiology
11.2 Muscles and Movement
11.2. 8 Analyze electron micrographs to find the state of contraction of muscle fibers
11.2.1 State the role of bones, ligaments, muscles, tendons and
nerves in human movement
How do muscles move?
• Signals move along a neuron and cause a muscle to contract
• Muscles are connected to the bones by tendons
• The contraction causes the bones to moves
• The bone is moved back to the original position by an “opposing”
muscle
The musculoskeletal system consists of
various organs and tissues which
have different roles
•Bones – provide support and
anchorage (the lever)
•Ligaments – connect bones together
•Tendons – attach bone to muscle
•Nerves – sense stimuli and provide
the impulse to make muscles contract
11.2.2 Label a diagram of the human elbow joint, including
cartilage, synovial fluid, joint capsule, named bones, and
antagonistic muscles
11.2.3 Outline the functions of the structures of the human
elbow joint
A. Humerus (upper arm) bone - Origin for the
biceps tendon
B. Synovial membrane - Encloses the joint
capsule and produces synovial fluid.
C. Synovial fluid - reduces friction and
absorbs pressure
D. Ulna - the lever in the flexion and
extension of the arm.
E. Cartilage (red) - living tissue that reduces the friction at joints.
F. Ligaments (blue) - connect bone to bone and produce stability at the joint.
11.2.2 Label a diagram of the human elbow joint, including
cartilage, synovial fluid, joint capsule, named bones, and
antagonistic muscles
11.2.3 Outline the functions of the structures of the human
elbow joint
Biceps (flexor) muscle provides force
for an arm flexion (bending).
• The scapula and humerus are the
origin for the bicep
• Radius is the insertion for the
bicep
Triceps muscle is the extensor whose
contraction straightens the arm.
• The scapula and humerus are the
origin for the tricep
• The ulna is the insertion
11.2.4 Compare the movement of the hip joint and the knee
joint
11.2.4 Compare the movement of the hip joint and the knee
joint
Similarities:
• Both are synovial joints
• Both involve moving leg
• Both required for walking
Differences:
11.2.5 Describe the structure of striated muscle fibers,
including the myofibrils with light and dark bands,
mitochondria, the sarcoplasmic reticulum, nuclei and the
sarcolemma.
Skeletal muscles (2) consist of bundles of muscle fibers
(3).
At each end of the muscle is the tendon (1)
A muscle fiber is a long, multi-nucleus cell (4 and the
image below)
There are many parallel protein structures inside called
myofibrils.
Myofibrils are wrapped in a membrane called the
sarcolemma and “floating” in cytoplasm (sarcoplasm)
Within the sarcoplasm is the internal membrane called
the sarcoplasmic reticulum
11.2.5 Describe the structure of striated muscle fibers,
including the myofibrils with light and dark bands,
mitochondria, the sarcoplasmic reticulum, nuclei and the
sarcolemma.
The function of the sarcoplasmic reticulum is to
store and release Ca+ ions into the sarcoplasm
to start the muscle contraction
In the cytoplasm are many mitochondria to
provide ATP
Myofibrils contain two types of protein
myofilaments (myosin and actin)
• Myosin proteins are called the thick filaments
• Actin proteins are called thin filaments
The sarcomere is the
structural unit of the muscle
and runs from Z line to Z line
11.2.6 Draw and label a diagram to show the structure of a
sarcomere, including the Z lines, actin filaments, myosin
filaments with heads, and resultant light and dark bands
Under a microscope a sarcomere appears to look like:
light section →dark section→ intermediate section →dark section → light section
The thin filaments (actin) are
attached to the Z line
Hank…HELP!!!
11.2.7 Explain how skeletal muscle contracts including the release of
calcium ions from the sarcoplasmic reticulum, the formation of crossbridges, the sliding of actin and myosin filaments and the use of ATP to
break cross-bridges and break myosin heads
The steps of a muscle contraction
1.First, a myofibril is stimulated by
the arrival of an action potential
from a motor neuron.
This triggers the release of Ca+ ions
from the sarcoplasmic reticulum and
surround the actin molecule
actin
Ca+
11.2.7 Explain how skeletal muscle contracts including the release of
calcium ions from the sarcoplasmic reticulum, the formation of crossbridges, the sliding of actin and myosin filaments and the use of ATP to
break cross-bridges and break myosin heads
2.Ca+ ions react with troponin
which triggers the removal of a
“blocking” molecule,
tropomyosin
3.The binding site is now
exposed
tropomyosin
Exposed binding site
4.Each myosin head (with ADP
and P attached) attach to the
binding site of the actin
molecule forming the crossbridge. The P is removed at this
point
Cross-bridge
myosin head
11.2.7 Explain how skeletal muscle contracts including the release of
calcium ions from the sarcoplasmic reticulum, the formation of crossbridges, the sliding of actin and myosin filaments and the use of ATP to
break cross-bridges and break myosin heads
5. The ADP molecule is released
from the myosin creating the
“power stroke” and the actin
filament is pushed along
6. A fresh molecule of ATP binds
to the myosin head and releases
from the actin filament
(breaking the cross-bridge)
This process is repeated many
times per second to shorten the
muscle by 50%
11.2.8 Analyze electron micrographs to find the state of
contraction of muscle fibers
In a contracted muscle, the distance between Z-bands become shorter
Remember, a sarcomere is defined as Z-Band to Z-Band.