Transcript Section 11.2 Muscles and Movement

Chapter 25 in Book
Mrs. Ragsdale
IB Biology
The Physics of Movement
 Human movement can easily be compared to a lever
using physics terminology
 A lever minimizes the amount of effort or work that
goes into moving objects.
http://www.cool-science-projects.com/simple-machine-science-project.html
Physics of Movement
 Lever = Bone
 Work Done (Effort) = Muscle
 Fulcrum = Joint
 Heavy Rock = Body weight (or
an object you are lifting)
http://science.howstuffworks.com/life/human-biology/muscle.htm
Muscle and Movement
Equipment
 Bones provide the rigid framework for muscles to
attach to. They also provide leverage for our muscles
to move our body or other objects.
 Ligaments are what connect bone to bone. They
reinforce our joints by restricting movement,
preventing dislocation.
 Tendons connect muscle to bone.
 Nerve impulses are what drive muscle movement.
They use a communication network that sends out
messages and signals muscle movement allowing
coordinated movement.
11.2.2 Label a diagram of the human elbow joint including cartilage,
synovial fluid, joint capsule, named bones and named antagonistic
muscles (biceps and triceps).
A. Radius and Ulna
B. Synovial Membrane
C. Synovial Fluid
D. Humerus
E. Cartilage (red)
F. Ligaments
11.2.3. Outline the functions of the structures of the
human elbow joint named in 11.2.2.
 cartilage: covers bones, prevents friction
 synovial fluid: lubricates joint to reduce friction
 joint capsule: seals the joint to hold in synovial fluid,
prevent dislocation
 humerus: upper arm bone: attachment of biceps & triceps
 ulna & radius: forearm bones: attachment of biceps (radius)
and triceps(ulna)
 Triceps - extends joint
 Biceps - flexes the joint

http://medicalpict
uresinfo.com/wpcontent/uploads/2
011/08/ElbowJoint-31.gif
Antagonistic Pairs
 To produce movement at a
joint muscles work in pairs.
 Muscles can only actively
contract and shorten. They
cannot actively lengthen.
 One muscles bends the limb
at the joint (flexor) which in
the elbow is the biceps.
 One muscles straightens the
limb at the joint (extensor)
which in the elbow is the
triceps.
Exercise:
 Bend your arm in a flexion.
 Point your elbow upwards vertically.
 Raise your hand vertically above your head.
 This is a true concentric contraction of the triceps
 Pick up a heavy object in concentric biceps flexion.
 Now lower and straighten your arm.
 You should feel your biceps contracted but triceps
relaxed.
 That an eccentric contraction of the biceps.
This shows how complex movement can be!
Movement at the Hip Joint
 Ball and socket joint – allows
movement in 3 planes
 Protraction / Retraction – forwards
and backwards
 Abduction / Adduction – sideways
 Rotation - circular
 The lever is the femur and the
fulcrum is the hip joint
 The effort is provided by the
muscles of quadriceps, hamstring
and gluteus.
Movement at the Knee
 Hinge joint – movement in
one plane only
 Pivot is the knee joint
 Lever is the tibia and fibula of
the leg
 Knee extension – powered by
quadriceps
 Knee flexion – powered by
hamstring
Comparison of the Hip and
Knee Joint
Basic Muscle Functions
1.
Skeletal movement
2.
Posture and body position
3.
Support of soft tissues
4.
Guarding of entrances & exits
5.
Maintenance of body temperature
Skeletal Muscle Structure
 Muscles are essentially
tubular cells (or fibres)
 Muscles cells are known
as myocytes
 Cells are multinucleated
 Striated Muscle –
meaning there are both
light and dark bands
 Basic unit of skeletal
muscle tissue is the
sarcomere
Structure of the Muscle Cell
 Sarcolemma – the plasma
membrane of a muscle cell
 Contains tons of little holes called
T Tubules that act like a sieve
 Sarcoplasm – (cytoplasm)
 Sarcoplasmic Reticulum – a special
form of smooth E.R. that controls
the storage and release of calcium
ions (Ca2+)
 Majority of cell volume comes from
long filaments called myofibrils
Structure of Striated Muscle
 Muscle fibres are
multinucleated (more than
one nucleus)
 Whole muscle is made up of
myofibrils that are bound
together
 Myofibrils are proteins that
run parallel to one another
 Contain combinations of
two proteins


Actin
Myosin
Actin and Myosin
 Actin and myosin
proteins overlap. This
causes the distinct
banding pattern
(something seen in
electron microscopes).
 Actin is considered the
thin filament in a
myofibril
 Myosin is considered
the thick filament in a
myofibril
A = Actin only
C = myosin attachment region
which adds stability
B = Myosin only D = Actin and myosin overlap
The Structure of a Sarcomere
 The “sarcomere” is the functional





unit of a muscle
Thousands of sarcomeres contract
together
 1 sarcomere = Z line to Z line
Z lines are so-named because they
zig-zag
Actin filaments are attached to the
Z lines
Z lines may have hundreds of actin
myofilaments attached to them
Myosin filaments are attached to
each other at the M line
11.2.6 Draw and label a diagram to show the structure of a
sarcomere, including Z lines, actin filaments, myosin filaments
with heads, and the resultant light and dark bands
 The H zone is the area
only occupied by the
thick filaments (myosin)
 The I bands (light) are
the regions occupied by
only thin filaments
(actin)
 The A bands (dark) are
the regions occupied by
both filaments (overlap)
 The Z lines represent the
extremities of a single
sarcomere
Muscle Contraction
 Sarcoplasmic reticulum hordes Ca2+ ions by creating a
concentration gradient
 When the nerve impulse moves to the muscle via an action
potential from a motor neuron, it triggers the release of the Ca2+
ions
 The Ca2+ ions expose myosin heads by binding to blocking
molecules (troponin and tropmyosin) which causes a structural
change
 Once their binding sites are removed, a cross bridge can form
between the actin binding sites and myosin heads
Muscles Relaxing
 ATP is what causes the breaking of the cross-bridges
 ATP attaches to the myosin heads, distracting them away from actin
causing them to detach from the binding sites
 The hydrolysis of ATP into ADP provides the energy for myosin heads
to swivel away from the centre of the sarcomere
 A new cross-bridge is formed where myosin heads attach to the actin at
an adjacent binding site
 Stored energy in the myosin head from the ATP causes the head to
swivel inwards towards the centre of the sarcomere causing the
movement of actin a short distance
Electron Micrographs
 Muscle fibres can be fully relaxed, slightly contracted,
moderately contracted and fully contracted
 You can tell when a muscle is contracted because the
sarcomere is shorter, however the A band is not