Muscles and Movement
Crash Course video: https://www.youtube.com/watch?v=jqy0i1KXUO4
IB Assessment Statement
• State the roles of bones, ligaments, muscles, tendons and
nerves in human movement.
Muscles & Movement Intro
• A mammalian skeleton has more than 200 bones
• Some are fused; others are connected at joints by
ligaments that allow freedom of movement
Human Movement
• Human movement is produced by the skeletal
acting as simple lever machines
Parts of the Muscle System
IB Learning Objective
• Label a diagram of the human elbow joint,
including cartilage, synovial fluid, joint
capsule, named bones and antagonistic
muscles (biceps and triceps).
IB Learning Objective
Outline the functions of the structures in the
human elbow joint named in cartilage, synovial
fluid, joint capsule, named bones and
antagonistic muscles (biceps and triceps).
Muscles move skeletal parts by contracting
• The action of a muscle is always to contract
• Skeletal muscles are attached in antagonistic
pairs, with each member of the pair working
against each other
LE 49-27
Human
Grasshopper
Extensor
muscle
relaxes
Biceps
contracts
Biceps
relaxes
Triceps
contracts
Flexor
muscle
contracts
Forearm
flexes
Triceps
relaxes
Tibia
flexes
Extensor
muscle
contracts
Forearm
extends
Tibia
extends
Flexor
muscle
relaxes
Joint structure and antagonistic muscle pairs
(example: Elbow Joint)
A. Humerus (upper arm)
bone.
B. Synovial membrane
that encloses the joint
capsule and produces
synovial fluid.
C. Synovial fluid (reduces
friction and absorbs
pressure).
Joint structure and antagonistic muscle pairs
(example: Elbow Joint)
D. Ulna (radius) the levers
in the flexion and
extension of the arm.
E. Cartilage (red) living
tissue that reduces the
friction at joints.
F. Ligaments that connect
bone to bone and produce
stability at the joint.
Antagonistic Pairs
(example: Elbow Joint)
• To produce movement
at a joint m
• uscles work in pairs.
• Muscles can only
actively contract and
shorten.
• They cannot actively
lengthen.
Antagonistic Pairs
(example: Elbow Joint)
• 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.
Elbow joint structure & function
1. Humerus forms the
shoulder joint also the
origin for each of the two
biceps tendons
2. Biceps (flexor) muscle
provides force for an arm
flexion (bending). As the
main muscle it is known as
the agonist.
3. Biceps insertion on the
radius of the forearm
Elbow joint structure & function
• 4. Elbow joint which is
the pivot for arm
movement
• 5. Ulna bone one of
two levers of the
forearm
Elbow joint Structure & Function
• 6. Triceps muscle is the
extensor whose
contraction straightens
the arm.
• 7. Elbow joint which is
also the pivot
(fulcrum)for this
movement.
Animations on Muscles
• http://www.freezeray.com/flashFiles/antagoni
sticPair.htm
IB Learning Objective
• Compare the movements of the hip joint and
the knee joint.
Movement at the hip and knee joint:
Knee
• The knee joint is an
example of a hinge
joint.
• The pivot is the knee
joint.
• The lever is the tibia
and fibula of the lower
leg.
Movement at the hip and knee joint:
Knee
• A knee extension is
powered by the
quadriceps muscles.
• A knee flexion (bending)
is powered by the
hamstring muscles.
• Movement is one plane
only.
Movement at the hip and knee joint:
HIP
• Rotation is in all planes
and axis of movement.
• The lever is the femur
and the fulcrum is the
hip joint.
• The effort is provided
by the muscles of
quadriceps, hamstring
and gluteus.
Comparison of Hip and Knee Joint
Pivot Bones at Lever
Joint
Flexion/
effort
Hip
Femur
Quadriceps Hamstrings
Many
Tibia
Hamstring
one
Pelvis/
Femur
Knee Tibia/
Femur
Extension/
effort
Quadriceps
Planes of
movement
Joint Animation
• http://www.midsouthorthopedics.com/educat
ion.htm
• http://www.freezeray.com/flashFiles/hipJoint.
htm
• http://choroknamu.com/tt/site/db/board/om
_gungol/upload/1_10000/1692/is_en_pt_kne
e.swf
IB Learning Objective
Describe the structure of striated muscle fibres,
including
– the myofibrils with light and dark bands,
– mitochondria,
– the sarcoplasmic reticulum,
– nuclei
– and the sarcolemma.
Muscles
• Tendons – Bones and muscles are connected
via non-elastic structures called tendons.
•
•
1. Tendon connecting muscle to bone. These are non-elastic structures which transmit the
contractile force to the bond.
2. The muscle is surrounded by a membrane which forms the tendons at its ends.
Muscle Fibres
• A skeletal muscle consists of a bundle of
muscle fibres.
• A muscle fibre consists of long multinucleate
cells.
Muscle bundle which
contains a number of muscle
cells
The plasma membrane of a
muscle cell is called the
sarcolemma and the
membrane reticulum is called
.
the sarcoplasmic reticulum
Ultrastructure of a skeletal muscle
• Skeletal muscles
consist of many
muscle fibres cells.
• Muscle fibre consist
of many parallel
myofibril within a
plasma membrane
called a
sarcolemma
Ultrastructure of a skeletal muscle
• The cytoplasm of
the cell contains
many
mitochondria.
Ultrastructure of a skeletal muscle
• The cell membrane
(sarcolemma) folds
inside the cell
forming a
transverse tubular
endoplasmic
reticulum called the
sarcoplasmic
reticulum
Electron Micrograph of a muscle fibre
cell.
Muscle Fibre Cell
• There are many parallel
protein structures inside
called myofibrils.
• Myofibrils are
combinations of two
filaments of protein
called actin and myosin.
IB LEARNING OBJECTIVE
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.
Actin & Myosin
– Actin in muscles cells consist of two strands thin
filaments and one strand of regulatory protein
called tropomyosin.
Actin & Myosin
– Myosin are staggered arrays of thick filaments
– Myosin molecules have bulbous heads with
protrude from the filament. These bulbous head
will bond to binding sites on the actin filament
Actin & Myosin
• The filaments of actin
and myosin overlap to
give a distinct banding
pattern when seen
with an electron
microscope.
Banding pattern of actin & myosin filaments on a electron
micrographs
Banding Pattern of muscle fibre cells
• Skeletal muscle are called striated muscle because of
this banding pattern
• Banding is cause by regular arrangement of actin
and myosin that create a pattern of light and dark
bands
• Each unit is a sarcomere (cell membrane), bordered
by Z lines
Banding Pattern of Muscle Cells
IB LEARNING OBJECTIVE
• Explain how skeletal muscle contracts,
including the release of calcium ions from the
sarcoplasmic reticulum, the formation of
cross-bridges, the sliding of actin and myosin
filaments, and the use of ATP to break crossbridges and re-set myosin heads.
Mechanism of muscle contraction
• 1. An action
potential arrives at
the end of a motor
neuron, at the
neuromuscular
junction.
• 2. This causes the
release of the
neurotransmitter
acetylcholine.
Mechanism of muscle contraction
• 3 This initiates an
action potential in
the muscle cell
membrane.
• 4. This action
potential is carried
quickly throughout
the large muscle cell
by invaginations in
the cell membrane
called T-tubules.
Mechanism of muscle contraction
• 5. The action
potential causes
the sarcoplasmic
reticulum (large
membrane vesicles)
to release its store
of calcium into the
myofibrils.
• For a muscle fiber to contract, myosin-binding
sites on the actin fibre must be uncovered
• This occurs when calcium ions (Ca2+) bind to a
set of regulatory proteins, the troponin
complex – making the binding sites exposed
Actin Filament
Contracted vs. Relaxed Muscle
• This exposed myosin-binding sites bond with the
bulbous heads (cross bridge) of myosin filament.
• Cross bridges include an ATPase enzyme which can
oxidise ATP and release energy.
• The cross bridge swings out from the myosin (thick
filament) and attaches to the actin (thin filament).
• The cross bridge (bulbous head) changes shape and
rotates through 45°, causing the filaments to slide.
The energy from ATP is used for this “power stroke”
step.
• A new ATP molecule binds to myosin and the cross
bridge detaches from the Actin (thin filament).
• The cross bridge changes back to its original shape,
while detached (so as not to push the filaments back
again).
• It is now ready to start a new cycle, but further along
the thin filament.
Electron micrographs of muscle fibre
contraction.
Electron micrographs of muscle fibre contraction.
If electron micrographs of a relaxed and contracted myofibril are
compared it can be seen that:
•These show that each sarcomere gets shorter (Z-Z) when the
muscle contracts, so the whole muscle gets shorter.
•But the dark band, which represents the thick filament, does not
change in length.
•This shows that the filaments don’t contract themselves, but
instead they slide past each other.
Muscle Contraction Animations
• http://brookscole.cengage.com/chemistry_d/templates/student_resource
s/shared_resources/animations/muscles/muscles.html
• http://media.pearsoncmg.com/bc/bc_campbell_biology_6/cipl/ins/49/HT
ML/source/71.html
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter10/animation__action_
potentials_and_muscle_contraction.html
• http://www.lab.anhb.uwa.edu.au/mb140/corepages/muscle/muscle.htm#
CONTRACT
• http://www.sumanasinc.com/webcontent/animations/content/muscle.ht
ml
Muscle Contraction tutorial
• https://www.youtube.com/watch?v=zopoN2i7
ALQ