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Mark Louie D. LopezDepartment of BiologyCollege of SciencePolytechnic University of the Philippines

MUSCLE PHYSIOLOGY

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MOVEMENT

How do animals move?

How do they overcome friction and

gravity in their various environments?

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CILIATES AND FLAGELLATES

Unicellular organisms w/o skeletal-muscular

systems

Protozoans (unicellular heterotrophic protists) and

primitive algae

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CILIATES AND FLAGELLATES

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CILIATES AND FLAGELLATES

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PSEUDOPODIAUsed by amoeba to move

Cell extensions (no microtubules)

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CHEMOTAXIS

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PHOTOTAXIS

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HYDROSTATIC SKELETON

Fluid held under pressure in a closed body

compartment

Helps protect other body parts (cushion from

shocks)

Gives body shape

Gives support for muscle action

Cnidarians (hydra) and annelids (earthworms)

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HYDROSTATIC SKELETON

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EXOSKELETONHard external skeleton covering all the muscles

and organs of some invertebrates

Made of chitin in Arthropods

Calcium carbonate in mollusks

Muscles attach to inside of exoskeleton

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ENDOSKELETONHard or leathery support tissue situated among the

soft tissues of animals

Sponges (Porifera)

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ENDOSKELETONSite of muscle attachment

Protection and overall support

Contains both cartilage and bone

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MUSCLES FOR MOVEMENT

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HOW MUSCLES WORK?

HOW MUSCLES

CONTRACT AND RELAX

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OUTLINE

• A. Review of Neuromuscular Junction

• B. Classification of muscles

• C. Functional anatomy of Skeletal Muscles

– Connective Tissue coverings

– Skeletal Muscle fibers

– Myofilaments

• D. Molecular mechanism of muscle contraction

– Excitation-Contraction Coupling

– Cross-Bridge Cycle

– Sliding Filament Theory

– Sources of ATP

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OUTLINE

• A. Review of Neuromuscular Junction

• B. Classification of muscles

• C. Functional anatomy of Skeletal Muscles

– Connective Tissue coverings

– Skeletal Muscle fibers

– Myofilaments

• D. Molecular mechanism of muscle contraction

– Excitation-Contraction Coupling

– Cross-Bridge Cycle

– Sliding Filament Theory

– Sources of ATP

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OUTLINE

• A. Review of Neuromuscular Junction

• B. Classification of muscles

• C. Functional anatomy of Skeletal Muscles

– Connective Tissue coverings

– Skeletal Muscle fibers

– Myofilaments

• D. Molecular mechanism of muscle contraction

– Excitation-Contraction Coupling

– Cross-Bridge Cycle

– Sliding Filament Theory

– Sources of ATP

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OUTLINE

• A. Review of Neuromuscular Junction

• B. Classification of muscles

• C. Functional anatomy of Skeletal Muscles

– Connective Tissue coverings

– Skeletal Muscle fibers

– Myofilaments

• D. Molecular mechanism of muscle contraction

– Excitation-Contraction Coupling

– Cross-Bridge Cycle

– Sliding Filament Theory

– Sources of ATP

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STRUCTURAL ORGANIZATION OF SKELETAL MUSCLES

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STRUCTURAL ORGANIZATION OF SKELETAL MUSCLES

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MICROSTRUCTURE OF SKELETAL MUSCLES

ANIMAL PHYSIOLOGY

MUSCLE

BUNDLE OF MUSCLE FIBER

MUSCLE FIBER

MYOFIBRILS

SARCOMERE

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MICROSTRUCTURE OF SKELETAL MUSCLES

ANIMAL PHYSIOLOGY

The sarcolemma, also called the myolemma, is the cell membrane of a

skeletal, cardiac, or smooth muscle cell. It consists of a true cell

membrane, called the plasma membrane, and an outer coat made up of

a thin layer of polysaccharide material that contains numerous

thin collagen fibrils.

A T-tubule (or transverse tubule) is a deep invagination of

the sarcolemma. These invaginations allow depolarization of the

membrane to quickly penetrate to the interior of the cell

The sarcoplasmic reticulum (SR) is smooth ER found in muscle.

Sarcoplasmic reticulum stores and pumps calcium ions. The

sarcoplasmic reticulum contains large stores of calcium, which it

sequesters and then releases when the muscle cell is stimulated. It

plays a major role in excitation-contraction coupling

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MICROSTRUCTURE OF SKELETAL MUSCLES

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MICROSTRUCTURE OF SKELETAL MUSCLES

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MICROSTRUCTURE OF SKELETAL MUSCLES

ANIMAL PHYSIOLOGY

A myofibril is a basic rod-like unit of a muscle. Myofibrils are composed

of long proteins such as actin, myosin, and other proteins that hold them

together. These proteins are organized into thin filaments and thick

filaments, which repeat along the length of the myofibril in sections called

sarcomeres.

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MICROSTRUCTURE OF SKELETAL MUSCLES

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SARCOMERE

ANIMAL PHYSIOLOGY

Sarcomere is the basic unit of a muscle. Myofibrils are composed of

repeating sections of sarcomeres, which appear under the microscope

as dark and light bands. Sarcomeres are composed of long, fibrous

proteins that slide past each other when the muscles contract and relax.

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MICROSTRUCTURE OF SKELETAL MUSCLES

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PARTS OF SARCOMERE

ANIMAL PHYSIOLOGY

• I band - Light band; thin

filaments composed primarily of

actin)

• Z line - in between I bands

• A band - at the dark end,

overlapping or interdigitation of

thin and thick filaments

composed primarily of myosin)

• H zone - region of the A band,

thick filaments only

• M line - center of the

sarcomere

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MICROSTRUCTURE OF SKELETAL MUSCLES

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SARCOMERE

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THICK FILAMENT (MYOSIN)

ANIMAL PHYSIOLOGY

• Myosin - primary composition

• bipolar arrangement; Heads face the lateral

portion or point outwards (2 golf clubs).

• S1 region (myosin globular head)

• S2 region (neck)

• tail region

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MYOSIN MOLECULE

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MYOSIN MOLECULE

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MYOSIN MOLECULE

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MYOSIN MOLECULE

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THIN FILAMENT

ANIMAL PHYSIOLOGY

• Actin – primary composition

• (F-actin) Fibrous/Filamentous-actin -

aggregation of globular actin or G-actin into

two stranded helical filament.

• Tropomyosin - dimers of this protein extend over the

entire actin filament covering the binding site at rest

(absence of Ca++).

• Troponin - (3 subunits) are present on each

tropomyosin dimer.

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THIN FILAMENT

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THIN FILAMENT

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THIN FILAMENT

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ADDITIONAL PROTEINS

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ACTIN AND MYOSIN

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HOW STRIATED MUSCLE WORK

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HOW STRIATED MUSCLE WORK?

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ANIMAL PHYSIOLOGY

HOW WILL AN ACTION POTENTIAL PRODUCE MUSCLE

CONTRACTION

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ANIMAL PHYSIOLOGY

HOW WILL AN ACTION POTENTIAL PRODUCE MUSCLE

CONTRACTION

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ANIMAL PHYSIOLOGY

EXCITATION CONTRACTION COUPLING: MOLECULAR

BASIS FOR MUCLE CONTRACTION

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MUSCLE ACTION POTENTIAL

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ACTIN AND MYOSIN CROSS BRIDGE CYCLE

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IMPORTANCE OF ATP

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IMPORTANCE OF ATP

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IMPORTANCE OF ATP

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SIZE PRINCIPLE

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FACTORS AFFECTING MUSCLE TENSION

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MUSCLE FATIGUE

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MECHANISM OF MUSCLE FATIGUE

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MUSCLE CRAMPS

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MUSCLE CRAMPS

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SPRAIN VS STRAIN

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RIGOR MORTIS

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4th review

ANIMAL PHYSIOLOGY

Prepare a powerpoint presentation of the review

Josephson, R. E. 1993. Contraction dynamics

and power output of skeletal muscle. Annu. Rev.

Phsyiol. 55: 527-546.

Limit your presentation to 10 slides

Must be presentable within 15 minutes given time

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CHEERS

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