7.10 Antagonistic Arrangement of Skeletal Muscles

Bones are attached to the bones through connective tissue called ligament. When a muscle contracts one end normally remains stationary and the other end is drawn towards it. The end which remains stationary is called origin and that which moves is called insertion. For the movement of the bone in two directions, muscles work in pairs. Such arrangement of muscles is called antagonistic arrangement.

Definition

Antagonistic Arrangement: When flexors contract, the extensors relax and vice versa. Such arrangement of muscles is called antagonistic arrangement.

Origin: The end which remains stationary is called origin.

Insertion: The end which moves is called insertion.

Belly: Belly is the thick part between origin and insertion which contracts.

Main Idea

• Bones are attached to the bones through connective tissue called ligament.
• When a muscle contracts, one end normally remains stationary.
• The other end is drawn towards it.
• The end which remains stationary is called origin.
• The end which moves is called insertion.
• Both are points of attachment to bones.
• Every muscle has its own origin and insertion.
• Belly is the thick part between origin and insertion which contracts.
• Normally the bones of insertion is pulled upon when muscle contracts and drawn towards origin.
• One bone moving on the other at the joints.
• Flexor muscle, when contracts, it bends the bone at joint.
• Extensor muscle, when contracts, it straightens the bone at joints.
• For the movement of the bone in two directions muscles work in pairs.
• When flexors contract, the extensors relax and vice versa.
• Such arrangement of muscles is called antagonistic arrangement.

Core Concept

• Ligament = connective tissue attaching bone to bone
• Origin = stationary end of muscle attachment
• Insertion = moving end of muscle attachment
• Belly = thick part between origin and insertion
• Flexor muscle = bends the bone at joint
• Extensor muscle = straightens the bone at joint
• Antagonistic arrangement = muscles work in pairs
• When flexors contract = extensors relax
• When extensors contract = flexors relax

Detailed Explanation

Antagonistic Arrangement of Skeletal Muscles

• Bones are attached to the bones through connective tissue called ligament.
• When a muscle contracts one end normally remains stationary and the other end is drawn towards it.
• The end which remains stationary is called origin and that which moves is called insertion.
• Both are the points of attachment to bones.
• Every muscle has its own origin and insertion.
• Belly is the thick part between origin and insertion which contracts.
• Normally the bones of insertion is pulled upon when muscle contracts and drawn towards origin, one bone moving on the other at the joints.
• Flexor muscle, when contracts, it bends the bone at joint.
• Extensor muscle, when contracts it straightens the bone at joints.
• For the movement of the bone in two directions muscles work in pairs.
• When flexors contract, the extensors relax and vice versa.
• Such arrangement of muscles is called antagonistic arrangement.

Summary Table of Antagonistic Arrangement

Example of Antagonistic Arrangement

Intermediate Level

Antagonistic Arrangement of Skeletal Muscles

Example of Antagonistic Arrangement

Movement at Knee Joint

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Bones are attached to bones by ligaments.
• 2. Origin is the stationary end.
• 3. Insertion is the moving end.
• 4. Belly is the thick part between origin and insertion.
• 5. Every muscle has its own origin and insertion.
• 6. Flexor muscle bends the bone at joint.
• 7. Extensor muscle straightens the bone at joint.
• 8. Muscles work in pairs for movement in two directions.
• 9. When flexors contract, extensors relax.
• 10. When extensors contract, flexors relax.
• 11. This arrangement is called antagonistic arrangement.
• 12. Biceps flexes the arm.
• 13. Triceps extends the arm.
• 14. Quadriceps femoris extends the leg at knee.
• 15. Hamstring muscles flex the leg at knee.
• 16. Antagonistic arrangement allows movement in two directions.
• 17. It allows bending and straightening of limbs.
• 18. It is essential for all movement.
• 19. Muscle imbalance can cause problems.
• 20. Proper function requires balanced antagonistic muscles.

Remember

• - Ligament = connective tissue attaching bone to bone
• - Origin = stationary end of muscle attachment
• - Insertion = moving end of muscle attachment
• - Belly = thick part between origin and insertion
• - Flexor muscle = bends the bone at joint
• - Extensor muscle = straightens the bone at joint
• - Antagonistic arrangement = muscles work in pairs
• - When flexors contract = extensors relax
• - When extensors contract = flexors relax
• - **Biceps** = flexes the arm
• - **Triceps** = extends the arm

Common Mistakes

• 1. Confusing origin and insertion — Origin = stationary; insertion = moving.
• 2. Mixing up flexor and extensor — Flexor = bends; extensor = straightens.
• 3. Forgetting the role of ligaments — Connect bone to bone.
• 4. Thinking muscles work alone — Muscles work in antagonistic pairs.
• 5. Mixing up the examples — Biceps = flexor; triceps = extensor.
• 6. Forgetting the role of the belly — Thick part that contracts.
• 7. Believing both muscles contract at the same time — One contracts while the other relaxes.
• 8. Mixing up the movements — Flexion = bending; extension = straightening.
• 9. Forgetting the role of antagonistic arrangement — Allows movement in two directions.
• 10. Mixing up the knee joint muscles — Quadriceps = extensor; hamstrings = flexor.

Quick Revision

Bones are attached to the bones through connective tissue called ligament. When a muscle contracts one end normally remains stationary and the other end is drawn towards it. The end which remains stationary is called origin and that which moves is called insertion. Both are the points of attachment to bones. Every muscle has its own origin and insertion. Belly is the thick part between origin and insertion which contracts. Normally the bones of insertion is pulled upon when muscle contracts and drawn towards origin, one bone moving on the other at the joints. Flexor muscle, when contracts, it bends the bone at joint. Extensor muscle, when contracts it straightens the bone at joints. For the movement of the bone in two directions muscles work in pairs. When flexors contract, the extensors relax and vice versa. Such arrangement of muscles is called antagonistic arrangement.

60-Second Revision

• Ligament = connective tissue attaching bone to bone
• Origin = stationary end of muscle attachment
• Insertion = moving end of muscle attachment
• Belly = thick part between origin and insertion
• Flexor muscle = bends the bone at joint
• Extensor muscle = straightens the bone at joint
• Antagonistic arrangement = muscles work in pairs
• When flexors contract = extensors relax
• When extensors contract = flexors relax
• Biceps = flexes the arm
• Triceps = extends the arm
• Warning: Muscles work in antagonistic pairs; one contracts while the other relaxes

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• 7. Support and Movement

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• 7.11 MUSCLE DISORDERS

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