Muscle Physiology 1Dr. Sumera Gul

Associate Professor

Department of Physiology

Learning Objectives:

At the end of the lecture the students should be able to:

• Describe muscle and its types

• Enlist the functions of muscles

• Explain the physiological anatomy of skeletal muscles

• Describe the functions of various components of sarcomere

What is a muscle?

What are the functions of muscle?

Functions of Muscles

• Body movement

• Maintenance of posture

• Respiration

• Production of body heat

• Communication

• Constriction of organs and vessels

• Heart beat

• Protection

• Expressions

• Manipulation of environment

All muscle tissues share basic characteristics

1.Excitability

2.Contractility

3.Elasticity

4.Extensibility

Types of Muscles

1. Skeletal

2. Smooth

3. Cardiac

Muscle Tissue Types

Skeletal

Cardiac

Smooth

Skeletal muscle

Skeletal Muscle

• Long cylindrical cells

• Many nuclei per cell

• Striated

• Voluntary

• Rapid contractions

• Attached to bones

• Occasionally attached to skin

Functions of Skeletal Muscle

• Produce movement

• Maintain posture & body position

• Support Soft Tissues

• Guard entrance / exits

• Maintain body temperature

• Store nutrient reserves

• Makes up approx. 40% of body weight

• Facial expressions

• Protection

Organization of Skeletal Muscle

Muscle fibre:

Skeletal MuscleFunctional Anatomy

Myofibril

• Contains around 1500 myosin

• And 3000 actin filaments

Skeletal MuscleFunctional Anatomy

• The smallest functional unit of skeletal muscle is the sarcomere

Skeletal MuscleFunctional Anatomy

• Sarcomere is composed of various microfilaments and supporting structures

• Titin• largest known elastomeric protein• Connects myosin to z-disc

Skeletal MuscleFunctional Anatomy

• Myosin molecule consists of tail, hinge and heads• Heads contain active sites

for• Actin• ATP

• M-line consists of myomesin and skelemin proteins• stabilize the myosin

filaments• theorized to aid in

transmission of force from sarcomere to cytoskeletal intermediate filaments

Myosin Molecule

• 480,000

• 2 heavy chains: 200,000

• 4 lights chains: 20,000

Myosin Filament

• 200 or more myosin molecules

• Thin filaments are composed of• g-actin molecules in

a helical arrangement• Contain myosin binding

sites

• nebulin• Filament that forms

internal support andattachment for actin

• tropomyosin filaments

• troponin (complex of three molecules)attached to tropomyosin• Has binding sites for Ca2+

Skeletal MuscleFunctional Anatomy

Organization of myofibril

Skeletal MuscleFunctional Anatomy

Skeletal MuscleFunctional Anatomy

• The Z-disc• Anchors the

filaments and interacts with cytoskeletal framework