muscular

🔹

Muscle Movements, Roles, and Names

🔸 Five Golden Rules of Skeletal Muscle Activity

1. All skeletal muscles cross at least one joint (few exceptions).

2. Bulk of muscle lies proximal to the joint it crosses.

3. Muscles have at least two attachments:
   

   • Origin: fixed or less movable.

   • Insertion: movable.

5. Muscles pull, never push.

6. During contraction, insertion moves toward origin.

🔹

Types of Body Movements

🔸 Basic Movements

• Flexion: Decreases joint angle; e.g., bending elbow or knee.

• Extension: Increases joint angle; e.g., straightening elbow.

• Hyperextension: Extension beyond anatomical position.

🔸 Rotational Movements

• Rotation: Bone rotates around its axis (e.g., head “no” motion).

🔸 Limb Movements

• Abduction: Movement away from midline.

• Adduction: Movement toward the midline.

• Circumduction: Cone-like circular motion; involves flexion, extension, abduction, adduction.

🔹

Special Movements

• Dorsiflexion: Lifting foot toward shin.

• Plantar flexion: Pointing toes down.

• Inversion: Turning foot inward.

• Eversion: Turning foot outward.

• Supination: Palm faces forward; radius and ulna parallel.

• Pronation: Palm faces backward; radius crosses ulna.

• Opposition: Thumb touches fingertips.

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Muscle Roles in Movement

• Prime mover: Main muscle causing movement.

• Antagonist: Muscle opposing prime mover.

• Synergist: Assists prime mover, stabilizes movement.

• Fixator: Specialized synergist that stabilizes the origin of prime mover.

✴ Note: At the knee and ankle, flexion/extension rules reverse due to lower limb rotation in development.

🔹

Muscle Naming Criteria

1. Direction of fibers – rectus (straight), oblique (angled).

2. Size – maximus (largest), minimus (smallest), longus (long).

3. Location – temporalis (temporal bone).

4. Number of origins – biceps (two), triceps (three).

5. Origin and insertion – sternocleidomastoid (sternum, clavicle, mastoid).

6. Shape – deltoid (triangular).

7. Action – flexor, extensor, adductor.

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Fascicle Arrangements in Muscles

• Circular – Surround openings (e.g., orbicularis oris).

• Convergent – Broad origin, converge to tendon (e.g., pectoralis major).

• Parallel – Fibers run parallel (e.g., sartorius).

• Fusiform – Spindle-shaped; wider belly (e.g., biceps brachii).

• Pennate – Short fibers obliquely attach to central tendon:
  

  • Unipennate, bipennate, multipennate types.

🔹

Superficial Muscles Overview

🔸 Anterior View

• Head/Neck: Frontalis, orbicularis oculi, zygomaticus.

• Trunk: Pectoralis major, intercostals.

• Arm/Shoulder: Biceps brachii, deltoid.

• Hip/Thigh/Leg: Sartorius, quadriceps group.

🔸 Posterior View

• Head/Neck/Back: Trapezius, latissimus dorsi.

• Arm/Forearm: Triceps brachii, extensors.

• Leg: Gluteus maximus, hamstrings, gastrocnemius.

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Developmental Aspects of Muscles

1. Motor control matures with nervous system:
   

   • Develops superior to inferior and proximal to distal.

3. Exercise effects:
   

   • No activity ➝ atrophy.

   • Vigorous activity ➝ hypertrophy.

5. Aging:
   

   • Muscle mass decreases, becomes more sinewy.

   • Exercise can slow or reduce these effects.

🔹

Muscle Movements, Roles, and Names

🔸

Five Golden Rules of Skeletal Muscle Activity

1. All skeletal muscles cross at least one joint (few exceptions).

2. Bulk of muscle lies proximal to the joint it crosses.

3. Muscles have at least two attachments:
   

   - Origin: fixed or less movable.

   - Insertion: movable.

4. 5. Muscles pull, never push.

5. During contraction, insertion moves toward origin.

🔹

Types of Body Movements

🔸

Basic Movements

- Flexion: Decreases joint angle; e.g., bending elbow or knee.

- Extension: Increases joint angle; e.g., straightening elbow.

- Hyperextension: Extension beyond anatomical position.

🔸

Rotational Movements

- Rotation: Bone rotates around its axis (e.g., head “no” motion).

🔸

Limb Movements

- Abduction: Movement away from midline.

- Adduction: Movement toward the midline.

- Circumduction: Cone-like circular motion; involves flexion, extension, abduction, adduction.

🔹

Special Movements

- Dorsiflexion: Lifting foot toward shin.

- Plantar flexion: Pointing toes down.

- Inversion: Turning foot inward.

- Eversion: Turning foot outward.

- Supination: Palm faces forward; radius and ulna parallel.

- Pronation: Palm faces backward; radius crosses ulna.

- Opposition: Thumb touches fingertips.

🔹

Muscle Roles in Movement

- Prime mover: Main muscle causing movement.

- Antagonist: Muscle opposing prime mover.

- Synergist: Assists prime mover, stabilizes movement.

- Fixator: Specialized synergist that stabilizes the origin of prime mover.

✴

Note: At the knee and ankle, flexion/extension rules reverse due to lower limb rotation in development.

🔹

Muscle Naming Criteria

1. Direction of fibers – rectus (straight), oblique (angled).

2. Size – maximus (largest), minimus (smallest), longus (long).

3. Location – temporalis (temporal bone).

4. Number of origins – biceps (two), triceps (three).

5. Origin and insertion – sternocleidomastoid (sternum, clavicle, mastoid).

6. Shape – deltoid (triangular).

7. Action – flexor, extensor, adductor.

🔹

Fascicle Arrangements in Muscles

- Circular – Surround openings (e.g., orbicularis oris).

- Convergent – Broad origin, converge to tendon (e.g., pectoralis major).

- Parallel – Fibers run parallel (e.g., sartorius).

- Fusiform – Spindle-shaped; wider belly (e.g., biceps brachii).

- Pennate – Short fibers obliquely attach to central tendon:

- Unipennate, bipennate, multipennate types.

- 🔹

Superficial Muscles Overview

🔸

Anterior View

- Head/Neck: Frontalis, orbicularis oculi, zygomaticus.

- Trunk: Pectoralis major, intercostals.

- Arm/Shoulder: Biceps brachii, deltoid.

- Hip/Thigh/Leg: Sartorius, quadriceps group.

🔸

Posterior View

- Head/Neck/Back: Trapezius, latissimus dorsi.

- Arm/Forearm: Triceps brachii, extensors.

- Leg: Gluteus maximus, hamstrings, gastrocnemius.

🔹

Developmental Aspects of Muscles

1. Motor control matures with nervous system:
   

   - Develops superior to inferior and proximal to distal.

2. 3. Exercise effects:
   

   - No activity ➝ atrophy.

   - Vigorous activity ➝ hypertrophy.

3. 5. Aging:
   

   - Muscle mass decreases, becomes more sinewy.

   - Exercise can slow or reduce these effects.

4. Muscle Attachments: Origin vs. Insertion

• Origin:

• Attached to an immovable or less movable bone.

• Usually proximal (closer to the body’s center).

• Insertion:

• Attached to a movable bone.

• Usually distal (further from the body’s center).

• During contraction, the insertion moves toward the origin.

💡 Example: In a bicep curl, the biceps brachii’s origin is on the scapula, and the insertion is on the radius. As it contracts, the forearm (radius) moves toward the upper arm (scapula).
Muscle Attachments: Origin vs. Insertion

• Origin:

• Attached to an immovable or less movable bone.

• Usually proximal (closer to the body’s center).

• Insertion:

• Attached to a movable bone.

• Usually distal (further from the body’s center).

• During contraction, the insertion moves toward the origin.

💡 Example: In a bicep curl, the biceps brachii’s origin is on the scapula, and the insertion is on the radius. As it contracts, the forearm (radius) moves toward the upper arm (scapula).

Detailed Types of Movement (Illustrative Examples) Movement Type
Description
Example
Flexion
Decrease joint angle
Curling arm
Extension
Increase joint angle
Straightening leg
Hyperextension
Extension beyond normal
Looking upward
Rotation
Bone turns on axis
Shaking head “no”
Abduction
Away from midline
Raising arms sideways
Adduction
Toward midline
Lowering arms back
Circumduction
Circular movement (combo of 4)
Shoulder windmill motion

🔹

Muscle Movements, Roles, and Names

🔸

Five Golden Rules of Skeletal Muscle Activity

1. All skeletal muscles cross at least one joint (few exceptions).

2. Bulk of muscle lies proximal to the joint it crosses.

3. Muscles have at least two attachments:
   

   - Origin: fixed or less movable.

   - Insertion: movable.

4. 5. Muscles pull, never push.

5. During contraction, insertion moves toward origin.

🔹

Types of Body Movements

🔸

Basic Movements

- Flexion: Decreases joint angle; e.g., bending elbow or knee.

- Extension: Increases joint angle; e.g., straightening elbow.

- Hyperextension: Extension beyond anatomical position.

🔸

Rotational Movements

- Rotation: Bone rotates around its axis (e.g., head “no” motion).

🔸

Limb Movements

- Abduction: Movement away from midline.

- Adduction: Movement toward the midline.

- Circumduction: Cone-like circular motion; involves flexion, extension, abduction, adduction.

🔹

Special Movements

- Dorsiflexion: Lifting foot toward shin.

- Plantar flexion: Pointing toes down.

- Inversion: Turning foot inward.

- Eversion: Turning foot outward.

- Supination: Palm faces forward; radius and ulna parallel.

- Pronation: Palm faces backward; radius crosses ulna.

- Opposition: Thumb touches fingertips.

🔹

Muscle Roles in Movement

- Prime mover: Main muscle causing movement.

- Antagonist: Muscle opposing prime mover.

- Synergist: Assists prime mover, stabilizes movement.

- Fixator: Specialized synergist that stabilizes the origin of prime mover.

✴

Note: At the knee and ankle, flexion/extension rules reverse due to lower limb rotation in development.

🔹

Muscle Naming Criteria

1. Direction of fibers – rectus (straight), oblique (angled).

2. Size – maximus (largest), minimus (smallest), longus (long).

3. Location – temporalis (temporal bone).

4. Number of origins – biceps (two), triceps (three).

5. Origin and insertion – sternocleidomastoid (sternum, clavicle, mastoid).

6. Shape – deltoid (triangular).

7. Action – flexor, extensor, adductor.

🔹

Fascicle Arrangements in Muscles

- Circular – Surround openings (e.g., orbicularis oris).

- Convergent – Broad origin, converge to tendon (e.g., pectoralis major).

- Parallel – Fibers run parallel (e.g., sartorius).

- Fusiform – Spindle-shaped; wider belly (e.g., biceps brachii).

- Pennate – Short fibers obliquely attach to central tendon:

- Unipennate, bipennate, multipennate types.

- 🔹

Superficial Muscles Overview

🔸

Anterior View

- Head/Neck: Frontalis, orbicularis oculi, zygomaticus.

- Trunk: Pectoralis major, intercostals.

- Arm/Shoulder: Biceps brachii, deltoid.

- Hip/Thigh/Leg: Sartorius, quadriceps group.

🔸

Posterior View

- Head/Neck/Back: Trapezius, latissimus dorsi.

- Arm/Forearm: Triceps brachii, extensors.

- Leg: Gluteus maximus, hamstrings, gastrocnemius.

🔹

Developmental Aspects of Muscles

1. Motor control matures with nervous system:
   

   - Develops superior to inferior and proximal to distal.

2. 3. Exercise effects:
   

   - No activity ➝ atrophy.

   - Vigorous activity ➝ hypertrophy.

3. 5. Aging:
   

   - Muscle mass decreases, becomes more sinewy.

   - Exercise can slow or reduce these effects.

4. Muscle Attachments: Origin vs. Insertion

• Origin:

• Attached to an immovable or less movable bone.

• Usually proximal (closer to the body’s center).

• Insertion:

• Attached to a movable bone.

• Usually distal (further from the body’s center).

• During contraction, the insertion moves toward the origin.

💡 Example: In a bicep curl, the biceps brachii’s origin is on the scapula, and the insertion is on the radius. As it contracts, the forearm (radius) moves toward the upper arm (scapula).
Muscle Attachments: Origin vs. Insertion

• Origin:

• Attached to an immovable or less movable bone.

• Usually proximal (closer to the body’s center).

• Insertion:

• Attached to a movable bone.

• Usually distal (further from the body’s center).

• During contraction, the insertion moves toward the origin.

💡 Example: In a bicep curl, the biceps brachii’s origin is on the scapula, and the insertion is on the radius. As it contracts, the forearm (radius) moves toward the upper arm (scapula).

Detailed Types of Movement (Illustrative Examples) Movement Type
Description
Example
Flexion
Decrease joint angle
Curling arm
Extension
Increase joint angle
Straightening leg
Hyperextension
Extension beyond normal
Looking upward
Rotation
Bone turns on axis
Shaking head “no”
Abduction
Away from midline
Raising arms sideways
Adduction
Toward midline
Lowering arms back
Circumduction
Circular movement (combo of 4)
Shoulder windmill motion
Special Movements – Lower Limb & Forearm Movement
Description
Example
Dorsiflexion
Foot upward toward shin
Standing on heels
Plantar flexion
Foot downward (pointing toes)
Tiptoe
Inversion
Sole inward (medial)
Twisting ankle inward
Eversion
Sole outward (lateral)
Twisting ankle outward
Supination
Palm faces anterior (radius & ulna parallel)
Holding soup bowl
Pronation
Palm faces posterior (radius crosses ulna)
Typing
Opposition
Thumb touches fingers
Grasping a pen

Muscle Roles Explained (With Examples) Role
Definition
Example
Prime Mover (Agonist)
Main muscle responsible for movement
Biceps brachii (elbow flexion)
Antagonist
Opposes/reverses movement
Triceps brachii (extends elbow)
Synergist
Helps prime mover by reducing unnecessary movement
Brachialis (assists biceps)
Fixator
Stabilizes the origin of a prime mover
Postural muscles (hold scapula in place)
Antagonistic pairs allow smooth coordination. When one contracts, the other relaxes.

Muscle Naming Conventions – In Practice Naming Factor
Examples
Fiber Direction
Rectus abdominis (straight)
Size
Gluteus maximus (largest), teres minor (small)
Location
Tibialis anterior (front of tibia)

of Origins

Biceps brachii (two heads)
Origin/Insertion
Sternocleidomastoid (sternum → mastoid)
Shape
Deltoid (delta = triangle)
Action
Flexor carpi ulnaris, Extensor digitorum

🎯 Structure = Function: Arrangement influences range of motion and power.

⸻

🔹 Developmental Aspects of Muscles

📈 Motor Control Development
• Achieved in:
• Superior → inferior direction (e.g., neck before legs)
• Proximal → distal (shoulder before fingers)

💪 Muscle Use & Health
• Use it or lose it:
• No use ➝ atrophy
• Intense use ➝ hypertrophy
• Regular exercise maintains mass and strength

👵 Aging & Muscles
• Muscle mass naturally declines
• Muscle becomes sinewy (stringy)
• Resistance training helps reduce loss. Fascicle Arrangement & Function Type
Description
Example
Circular
Surround openings
Orbicularis oris (mouth)
Convergent