1 muscle physiology

MUSCLE PHYSIOLOGY

By :Annisyah (34151266 )

Mai Turgiyanti (3415126630)

Introduction

• Muscle tissue reaches 40% to 50% by weight. Generally composed of contractile cells called muscle fibers. Through contraction, muscle cells produce movement and do the job

Muscular System Functions

• Body movement (Locomotion)• Maintenance of posture• Respiration

– Diaphragm and intercostal contractions• Communication (Verbal and Facial)• Heart beat • Production of body heat (Thermogenesis)

Properties of Muscle

• Excitability: capacity of muscle to respond to a stimulus

• Contractility: ability of a muscle to shorten and generate pulling force

• Extensibility: muscle can be stretched back to its original length

• Elasticity: ability of muscle to recoil to original resting length after stretched

Klasifikasi otot

Otot

Struktural

Fungsional

Involunter

Volunter

Lokasi

Types of Muscle• Skeletal

– Attached to bones– Makes up 40% of body weight– Responsible for locomotion, facial expressions, posture, respiratory

movements, other types of body movement– Voluntary in action; controlled by somatic motor neurons

• Smooth– In the walls of hollow organs, blood vessels, eye, glands, uterus, skin– Some functions: propel urine, mix food in digestive tract, dilating/constricting

pupils, regulating blood flow, – In some locations, autorhythmic– Controlled involuntarily by endocrine and autonomic nervous systems

• Cardiac– Heart: major source of movement of blood– Autorhythmic– Controlled involuntarily by endocrine and autonomic nervous systems

Skeletal Muscle

• Connective Tissue of a Muscle– Epimysium. Dense regular c.t. surrounding entire muscle

• Separates muscle from surrounding tissues and organs• Connected to the deep fascia

– Perimysium. Collagen and elastic fibers surrounding a group of muscle fibers called a fascicle

• Contains b.v and nerves– Endomysium. Loose connective tissue that surrounds individual

muscle fibers• Also contains b.v., nerves, and satellite cells (embryonic stem cells

function in repair of muscle tissue

• Collagen fibers of all 3 layers come together at each end of muscle to form a tendon or aponeurosis.

Muscle Tissue Types

Basic Features of a Skeletal Muscle• Muscle attachments

– Most skeletal muscles run from one bone to another

– One bone will move – other bone remains fixed

• Origin – less movable attach- ment

• Insertion – more movable attach- ment

Skeletal Muscle

• Long cylindrical cells• Many nuclei per cell• Striated• Voluntary• Rapid contractions

Skeletal Muscle Structure• Composed of muscle cells (fibers),

connective tissue, blood vessels, nerves• Fibers are long, cylindrical, and

multinucleated• Tend to be smaller diameter in small

muscles and larger in large muscles. 1 mm- 4 cm in length

• Develop from myoblasts; numbers remain constant

• Striated appearance• Nuclei are peripherally located

Muscle Attachments

Antagonistic Muscles

Sumber energi untuk kontraksi

• 1. kreatin fosfat (CP)• 2. reaksi anaerob • 3.reaksi aerob • 4. oxygen debt

Microanatomy of Skeletal Muscle

Muscle Fiber Anatomy

• Sarcolemma - cell membrane– Surrounds the sarcoplasm (cytoplasm of fiber)

• Contains many of the same organelles seen in other cells• An abundance of the oxygen-binding protein myoglobin

– Punctuated by openings called the transverse tubules (T-tubules)• Narrow tubes that extend into the sarcoplasm at right angles to the

surface• Filled with extracellular fluid

• Myofibrils -cylindrical structures within muscle fiber– Are bundles of protein filaments (=myofilaments)

• Two types of myofilaments1. Actin filaments (thin filaments)2. Myosin filaments (thick filaments)

– At each end of the fiber, myofibrils are anchored to the inner surface of the sarcolemma

– When myofibril shortens, muscle shortens (contracts)

Structure of Actin and Myosin

Myosin (Thick) Myofilament

• Many elongated myosin molecules shaped like golf clubs.

• Single filament contains roughly 300 myosin molecules

• Molecule consists of two heavy myosin molecules wound together to form a rod portion lying parallel to the myosin myofilament and two heads that extend laterally.

• Myosin heads1. Can bind to active sites on the actin

molecules to form cross-bridges. (Actin binding site)

2. Attached to the rod portion by a hinge region that can bend and straighten during contraction.

3. Have ATPase activity: activity that breaks down adenosine triphosphate (ATP), releasing energy. Part of the energy is used to bend the hinge region of the myosin molecule during contraction

Actin (Thin) Myofilaments

• Thin Filament: composed of 3 major proteins1. F (fibrous) actin2. Tropomyosin3. Troponin

• Two strands of fibrous (F) actin form a double helix extending the length of the myofilament; attached at either end at sarcomere.– Composed of G actin monomers

each of which has a myosin-binding site (see yellow dot)

– Actin site can bind myosin during muscle contraction.

• Tropomyosin: an elongated protein winds along the groove of the F actin double helix.

• Troponin is composed of three subunits: – Tn-A : binds to actin– Tn-T :binds to tropomyosin,– Tn-C :binds to calcium ions.

Smooth Muscle

– Spool shape– One nucleus– Tropomyosin– No troponin– Dense bodies analogous to Z line– Slow myosin ATPase– Myosin has light chains– Little sarcoplasmic reticulum– Three type of filament

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Smooth Muscle Cell

Figure 12.33

Type of Smooth Muscle

1. Plain Muscle Multi Unit- Consists of many units that function independently of each other- Neurogenic Characteristically, the autonomic nervous system involuntary- There is a large blood vessels, airways in the lung smooth, eye muscles to adjust the lens, the iris to change the size of the pupil, and the base of hair follicles which the contractions cause goosebumps standing.

2. Muscle Plain Single Unit / Visceral- Muscle cells form a functional syncytium- The walls are hollow organs- Is miogenik- There are two types of spontaneous depolarization.

Pontaneous Depolarization Type

1. Potential TriggersMembrane potential is gradually depolarized themselves as passive ion flux shifts that accompany changes in the permeability of the channel automatically

2. Potential Slow WaveHyperpolarization and depolarization gradual changes due to changes in the cyclic alternating speed automatic active transport of sodium ions penetrate the membraneAn outbreak if the action potential depolarization brings the membrane to threshold

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Spontaneous Depolarizations

Figure 12.36

Cardiac Muscle

• Only in the heart and miogenik• The combination of skeletal muscle and

smooth muscle• Miofilamen form a pattern of regular

tape, so mottled• Thin filament troponin and tropomyosin

have• have many mitochondria and

myoglobin• T-tubules and sarcoplasmic reticulum

sufficiently developed

Skeletal Cardiac Smooth

Appearance

Control voluntary unvoluntary Unvoluntary

Neural input somatic ANS ANS

Hormone 0 Epi Epi/others

Ca++ prot Troponin Troponin Calmodulin

Gap junctions No Yes Yes

Pacemaker No Yes No

Cross-bridge Formation

Mechanism of Muscle Contraction

Contraction

Muscle Contraction• Nerve impulse reaches myoneural junction• Acetylcholine is released from motor neuron• Ach binds with receptors in the muscle

membrane to allow sodium to enter• Sodium influx will generate an action potential

in the sarcolemma

Muscle Contraction• Action potential travels down T tubule• Sarcoplamic reticulum releases calcium• Calcium binds with troponin to move the

troponin, tropomyosin complex• Binding sites in the actin filament are

exposed

Muscle Contraction• Myosin head attach to binding sites and create

a power stroke• ATP detaches myosin heads and energizes

them for another contaction• When action potentials cease the muscle stop

contracting

Contraction Speed

Smooth Muscle Contraction

Isometric/Isotonic Contractions

• Isometric: muscle contraction without movement no muscle shortening

• Isotonic: muscle contraction with movement muscle shortens

Energy Sources• ATP provides immediate energy for muscle contractions from 3

sources– Creatine phosphate

• During resting conditions stores energy to synthesize ATP– Anaerobic respiration

• Occurs in absence of oxygen and results in breakdown of glucose to yield ATP and lactic acid

– Aerobic respiration• Requires oxygen and breaks down glucose to produce

ATP, carbon dioxide and water• More efficient than anaerobic

Color differences Muscles

• The presence of pigment or color on muscle protein called myoglobin that can bind oxygen, and iron-containing red lead to muscleRed and white color differences occur due to differences in the amount of myoglobin and oxygen levels are needed.The more myoglobin binds oxygen, the more red muscle.