Chapter 9 Muscles And Muscle Tissue

Front 1

Muscle Tissue

Back 1

Three types
Skeletal
Cardiac
Smooth
Myo, Mys, Sarco- prefixes for muscle

Front 2

Types of Muscle Tissue
Skeletal muscles

Back 2

Organs attached to bones and skin
Elongated CELLS CALLED MUSCLE FIBERS
STIATED (striped)
VOLUNTARY (i.e, conscious control)
Contract rapidly: tire easily: powerful
Require nervous system stimulation

Front 3

Types of Muscle Tissue
Cardiac Muscle

Back 3

Only in heart: bulk of heart walls
STRIATED
Can contact without nervous system stimulation
INVOLUNTARY

Front 4

Types of Muscle Tissue
Smooth muscle

Back 4

In wals of hollow organs, e.g., stomach, urinary bladder, and airway *So sometimes KNOWN AS VISCERAL MUSCLE*
NOT STRIATED
Can contract without nervous system stimulation
INVOLUNTARY

Front 5

SPECIAL CHARACTERISTICS of muscle tissue

Back 5

Excitability(responsiveness): Ability to receive and respond to stimuli
Contractility: ability to shorten forcibly when stimulated
• Extensibility: ability to be stretched
• Elasticity: ability to recoil to resting length

Front 6

Muscle Functions

Back 6

FOUR IMPORTANTT FUNCTIONS
-MOVEMENT OF BONES or fluids (e.g., blood)
-maintaining posture and body position
-Stabilizing joints
-Heat generation (especially skeletal muscle)

Front 7

Skeletal Muscle

Back 7

• Each muscle served by one artery, one nerve, and one or more veins
– Enter/exit near central part and branch through connective tissue sheaths
EVERY SKELETAL MUSCLE FIBER SUPPLIED BY NERVE ENDING THAT CONTROLS ITS ACTIVITY

Front 8

Skeletal Muscle

Back 8

• Connective tissue sheaths of skeletal muscle
– Support cells; reinforce whole muscle
– External to internal
• EPIMYSIUM: dense irregular connective tissue surrounding entire muscle; may blend with fascia
• PERIMYSIUM: fibrous connective tissue surrounding fascicles (groups of muscle fibers)
• ENDOMYSIUM: fine areolar connective tissue surrounding each muscle fiber

Front 9

Skeletal Muscle: Attachments

Back 9

• Attach in at least two places
– Insertion – movable bone
– Origin – immovable (less movable) bone
• Attachments direct or indirect
– DIRECT—epimysium fused to periosteum of bone or perichondrium of cartilage
– iINDIRECT—connective tissue wrappings extend beyond muscle as ropelike TENDON OR SHEETLIKE APONEUROSIS

Front 10

Microscopic Anatomy of a Skeletal Muscle Fiber

Back 10

• Long, cylindrical cell
– 10 to 100 µm in diameter; up to 30 cm long
• Multiple peripheral nuclei
• SARCOLEMMA= plasma membrane
• SARCOPLASM = cytoplasm
– Glycosomes for glycogen storage, MYOGLOBIN for O2 storage
• Modified structures: myofibrils, sarcoplasmic reticulum, and T tubules

Front 11

Myofibrils

Back 11

Contain SARCOMERES- CONTRACTILE UNITS
-sacromeres contain MYOFILAMENTS
Exibit STRIATIONS- perfectly aligned repeating series of DARK A BANDS AND LIGHT I BANDS

Front 12

Striations

Back 12

H ZONE: lighter region in midsection of dark A band where filaments do not overlap
M LINE: line of protein myomesin bisect H zone
Z DISC(LINE):coin-shaped sheet of proteins on midline of light i band that anchors thin filaments and connects myofibrils to one another
THICK FILAMENTS: run entire length of an A band
THIN FILAMENTS: run legth of i band and partway into A band
SARCOMERE: region between two successive Z disc

Front 13

Sarcomere

Back 13

• Smallest contractile unit (FUNCTIONAL UNIT) of muscle fiber
• Align along myofibril like boxcars of train
• Contains A band with ½ I band at each end
• Composed of thick and thin MYOFILAMENTS made of contractile proteins

Front 14

MYOFIBRIL Banding pattern

Back 14

• Orderly arrangement of actin and myosin myofilaments within sarcomere
– Actin myofilaments = thin filaments
• Extend across I band and partway in A band
• Anchored to Z discs
– Myosin myofilaments = thick filaments

Front 15

Ultrastructure of THICK FILAMENT

Back 15

• Composed of protein myosin
• Each composed of 2 heavy and four light polypeptide chains
– MYOSIN TAILS contain 2 interwoven, heavy polypeptide chains
– MYOSIN HEADS contain 2 smaller, light polypeptide chains that act as cross bridges during contraction
_ BINDING SITES FOR ACTIN OF THIN FILAMENTS
_ BINDING SITES FOR ATP
_ ATPASE ENZYMES`

Front 16

Ultrastructure of THIN FILAMENT

Back 16

• Twisted double strand of fibrous protein
F actin
• F actin consists of G (GLOBULAR) ACTIN SUBUNITS
• G actin bears active sites for myosin head attachment during contraction
• ****Tropomyosin and troponin - regulatory proteins bound to actin

Front 17

Structure of Myofibril

Back 17

• Elastic filament
– Composed of proteinTITIN
– Holds thick filaments in place; helps recoil after stretch; resists

Front 18

Sarcoplasmic Reticulum (SR)

Back 18

• Network of smooth endoplasmic reticulum SURROUNDING EACH MYOFIBRIL•
Functions in regulation of intracellular Ca2+ levels
– STORES AND RELEASES Ca2+

Front 19

T Tubules

Back 19

CONTINUATIONS OF SARCOLEMMA
PENETRATE CELL"S INTERIOR at each A band- I band junction
associate with paired terminal cisterns to form TRIADS that encircle each sarcomere

Front 20

Triad Relationships

Back 20

T TUBULES CONDUCT IMPULSES DEEP INTO MUSCLE FIBER;EVERY SARCOMERE
T tubule integral proteins act asVOLTAGE SENSORSs and change shape in response to voltage changes
SR integral proteins are CHANNELS THAT RELEASE Ca2+FROM SR CISTERNSwhen voltage sensors change shape