There are two types of muscle contractions: isotonic and isometric. Isotonic contractions maintain constant tension as the muscle changes length, and include concentric contractions where muscles shorten against resistance, and eccentric contractions where muscles elongate while generating force. Isometric contractions generate force without changing muscle length. Muscle contraction occurs via the sliding filament theory, where the actin filament slides into the myosin filament in the A band region, causing sarcomeres to shorten and Z lines to move closer together. This occurs through a cross-bridge cycling process using ATP energy.

1. TYPES OF MUSCLE CONTRACTION
AND MECHANISM OF
CONTRACTION
DR. JASJYOT KAUR SABHARWAL (PT)
J

2. TWO TYPES OF CONTRACTIONS
• Isotonic Contraction
• Isometric contraction

3. ISOTONIC
CONTRACTION
• Isotonic contractions
maintain constant tension
in the muscle as the
muscle changes length.

4. TWO TYPE OF ISOTONIC CONTRACTION
Concentric Contraction
Isometric Contraction

5. CONCENTRIC
CONTRACTION
• A concentric contraction is a
type of muscle contraction in
which the muscles shorten
while generating force,
overcoming resistance.
• For example, when lifting a
heavy weight, a concentric
contraction of the biceps
would cause the arm to bend
at the elbow.

6. ECCENTRIC
CONTRACTION
• An eccentric contraction
results in the elongation of
a muscle while the muscle
is still generating force.
• Eccentric contractions can
be both voluntary and
involuntary.

7. ISOMETRIC CONTRACTION
• Isometric contractions generate force without
changing the length of the muscle
• Isometric contractions are frequently used to
maintain posture.
• Common in the muscles of the hand and
forearm responsible for grip.

8. SLIDING
FILAMENT
THEORY
Muscle contraction occurs by sliding filament
mechanism whereby the sarcomere shorten ( the
Z-line come close together) by the action of actin
filament sliding over the myosin filament.
The force behind the muscle contraction is the
ratchet movement of myosin head towards centre
of sarcomere.
Electron microscopy shows that muscle is
composed of 2 contractile proteins:
•Thin filament actin attached to Z line
•Thick filament myosin, found in A band

9. • When muscle contracts the actin filament slides
into A band, overlapping with myosin.
• When muscle contracts:
1. Z line moves close together.
2. I band becomes shorter.
3. A band stays at the same length.

10. • The process of a muscle contraction can be divided:
1. A nerve impulse arrives at the neuromuscular junction, which causes a release
of a chemical called Acetylcholine (Ach) into the synaptic cleft. The presence of
Acetylcholine causes Calcium (Ca+) to be released from the sarcoplasmic
reticulum.
2. In the presence of high concentrations of Ca+, the Ca+ binds to Troponin
changing its shape. This moves Tropomyosin from the active site of the Actin to
expose uncovered sites. Therefore, Myosin filaments can now attach to the
Actin forming a cross-bridge.

11. 3. The cross bridge binds to the active sites. Energy from ATP is used to break the
bond straighten the cross bridge and form new bond with another active site.
4. This process of muscular contraction can last for as long as there is enough ATP
and Ca+ stores. Once the impulse stops the Ca+ is pumped back to the
Sarcoplasmic Reticulum and the Actin returns to its resting position causing the
muscle to lengthen and relax.

12. THANKYOU