Download Antagonist

Skeletal Muscle Shapes
Muscle Descriptions
• Fusiform muscles
– thick in middle and tapered at
ends
• Parallel muscles have parallel
muscle fibers
• Convergent muscle
– broad at origin and tapering to a
narrower insertion
Muscle Descriptions Cont….
• Pennate muscles
– fascicles insert
obliquely on a tendon
– unipennate, bipennate
or multipennate
• Circular muscles
– ring around body
opening (ex: iris,
mouth)
Interactions of Skeletal Muscles
• Muscles can only pull, they can’t push
• Actions must be “undone” by a different muscle
• Muscles that produce opposite movements usually lie on
opposite sides of a given joint
Muscles Work together to move a joint
• Agonist: “prime mover”, major
responsibility for producing a specific
movement
Antagonist
Agonist
• Antagonist: oppose or reverse a
particular movement
– Usually contract a little to prevent
overshooting the mark or slow the
agonist’s action near the end
– Are being “stretched” or can remain
relaxed when agonist works
• Antagonists for one movement can be
agonists for another
• Synergists help prime movers
– Add a little extra force to the
same movement
– Or reduce undesirable extra
movements (e.g. making a fist
without flexing at wrist)
• Fixators: hold a bone firmly so
agonist has a stable base on which
to move a body part (e.g. fixing
scapula when arm moves)
Muscles work in concert…
the elbow Flexion
• Prime Movers: responsible for
flexing arm)
– Biceps Brachii (lifts radius in
forearm)
– Brachialis (lifts ulna in forearm)
• Synergists: helps stabilizes elbow
joint
– Brachioradialis
• Antagonists: (resists movement of
prime movers)
– Triceps Brachii
• Fixators: (hold shoulder in place)
– Deltoid
– Trapezius
Type of Contractions
• Isometric Contraction
– Muscles are contracting
but there is no
movement
– Muscles trying to allow
for body movement but
can’t – spinning wheels
• Isotonic Contractions
– Movement occurs
when muscles contract
• Bending knee, smiling,
rotating arms
Pushing
on a wall
Lifting weights