43
Muscle and Muscle Tissue Chapter 9 & 10

Muscle and Muscle Tissue

Embed Size (px)

DESCRIPTION

Muscle and Muscle Tissue. Chapter 9 & 10. Muscle Tissue. 3 Types Smooth – smooth muscle Skeletal – skeletal muscle Cardiac – cardiac muscle. Differ in: Structure Function Location Means of activation. Functions of Muscle. Skeletal responsible for locomotion - PowerPoint PPT Presentation

Citation preview

Page 1: Muscle and Muscle Tissue

Muscle and Muscle Tissue Chapter 9 & 10

Page 2: Muscle and Muscle Tissue

Muscle Tissue•3 Types

•Smooth – smooth muscle •Skeletal – skeletal muscle •Cardiac – cardiac muscle

•Differ in: •Structure•Function•Location•Means of activation

Page 3: Muscle and Muscle Tissue

Functions of Muscle • Skeletal

• responsible for locomotion• Posture, stabilize joints, generate heat

• Cardiac• responsible for movement of blood

• Smooth muscle • helps maintain blood pressure, and

squeeze or propel substances through organs

Page 4: Muscle and Muscle Tissue

Functional Characteristics of Muscle Tissue • Excitability (irritability) – the ability to

receive and respond to stimuli

• Contractility – ability to shorten forcibly

• Extensibility – ability to stretch or extend

• Elasticity – ability to recoil and resume original resting length

Page 5: Muscle and Muscle Tissue

Muscle Tissue Similarities•Muscle Terminology

•Sarcolemma – muscle plasma membrane •Sarcoplasm – cytoplasm of a muscle cell•Prefixes:

•Myo•Mys all mean muscle•Sarco

•Skeletal and smooth muscle are elongated and are called muscle fibers

•Muscle will contract based on 2 types of microfilaments

•Actin•Myosin

Page 6: Muscle and Muscle Tissue

Skeletal Muscle Tissue• Muscle that attaches to and covers

bone • Creates motion• Has obvious striations (stripes)• Is voluntary

• most of the time

• Contracts rapidly but tires easily• Extremely adaptable and can exert

forces ranging from a fraction of an ounce to over 70 lbs.

Page 7: Muscle and Muscle Tissue

Skeletal Muscle

• Each muscle is an organ • Consisting of

• Blood vessels • Nerve fibers• Connective tissues

• Endomysium – fine sheath of connective tissue composed of reticular fibers surround each muscle fiber

• Perimysium – fibrous connective tissue that surrounds a group of muscle fibers called fascicles

• Epimysium – an overcoat of dense regular tissue that surrounds the entire muscle

Page 8: Muscle and Muscle Tissue

Skeletal Muscle

Page 9: Muscle and Muscle Tissue

Skeletal Muscle•Nerve & Blood Supply

•Each muscle has •One nerve •One artery •One or more veins

•Each muscle fiber has •One nerve controlling contraction

•Muscles need•Oxygen and nutrients•Waste elimination

•Attachments•Most muscles are attached to bones in 2 places

•Attach either •Directly – epimysium of the muscle is fused to the bone •Indirectly – connective tissue wrappings extend beyond the muscle as a tendon

Page 10: Muscle and Muscle Tissue

Microscopic Anatomy

• Muscle Fibers: • Each fiber is long, cylindrical with multiple

nuclei just beneath sarcolemma• Each fiber has unique oxygen-binding

proteins called myoglobin

Page 11: Muscle and Muscle Tissue

Myofibrils•Muscle fibers are made up of densely packed myofibrils

•Rod like contractile elements

•Myofibrils are what gives muscle its striated appearance

•Because it makes perfect Dark A Bands and Light I Bands

Page 12: Muscle and Muscle Tissue

Sarcomere•Myofibrils are composed of the sarcomeres

•Smallest contractile unit of the muscle•Composed of myofilaments

•Thick – myosin (entire A band)•Thin – actin (across I band and partway into A band) Z disc – connects myofibrils to one another

Page 13: Muscle and Muscle Tissue
Page 14: Muscle and Muscle Tissue

Sarcoplasmic Reticulum (SR) and T Tubules

•SR – an elaborate, smooth ER that mostly runs longitudinally and surrounds each myofibril•Functions in regulation of calcium levels

•T Tubules – elongated tubes that penetrate the cell’s interior at the A – I band junction

•Conduct impulses to the deepest parts of the muscle •Part of the SR

Page 15: Muscle and Muscle Tissue

Skeletal Muscle Contraction•Sliding Filament Model of contraction:

•Thin Filaments slide past Thick filaments (filaments overlap more than before)•Causes the muscle to shorten

Page 16: Muscle and Muscle Tissue

Contraction• In order to contract a skeletal muscle

must:• Be stimulated by a nerve ending – motor

neurons • The size of the muscle relates to the size of the

motor neuron

• Receive an electrical impulse along sarcolemma and T tubules

• Have a rise in Ca2+ levels (final trigger for muscle contraction)

Page 17: Muscle and Muscle Tissue

Stages of Muscle Contraction• Cross Bridge formation – myosin

cross bridge attaches to actin filament

• Working (power) stroke – myosin pulls actin filament toward M line

• Myosin releases actin filament • ATP attaches to myosin and the cross

bridge is broken• “Cocking” of the myosin – energy for

hydrolysis of ATP cocks myosin into high-energy position

Page 18: Muscle and Muscle Tissue
Page 19: Muscle and Muscle Tissue

Types of Contractions•Isometric contraction

•Increasing muscle tension

•Muscle doesn’t shorten during contraction

•Isotonic Contraction•Decreasing muscle length

•Muscle shortens during contraction

Page 20: Muscle and Muscle Tissue

Muscle Tone

• Constant, slightly contracted state of all muscles, which does not produce active movement

• Keeps muscles firm, healthy, and ready to respond to stimuli

Page 21: Muscle and Muscle Tissue

Muscle Metabolism: Anaerobic Glycolysis

• When muscle contractile activity reaches 70% of the maximum• Bulging of the muscle compresses blood

vessels• Oxygen delivery is impaired• Pyruvic acid is converted to lactic acid

• Causes muscle soreness

Page 22: Muscle and Muscle Tissue

Muscle Fatigue

• The muscle is in a state of physiological inability to contract • Occurs when:

• ATP production fails to keep pace with ATP demand

• Lactic acid accumulates in the muscle

Page 23: Muscle and Muscle Tissue

Heat Production

• Only 40% of the energy released in muscle activity is actually used in the work

• The remaining 60% is given off as heat

Page 24: Muscle and Muscle Tissue

Cardiac Muscle

• Found only in the heart• Striated • Involuntary• Contracts at a steady rate due to the

heart’s pacemaker• Changes beat based upon body’s needs

• Running – speeds up • Sleeping – slows down

Page 25: Muscle and Muscle Tissue

Smooth Muscle

• Found in the walls of hollow organs • Stomach, urinary bladder, vessels

• Forces food and other substances through internal body channels • Responsible for peristalsis

• Not striated • Involuntary

Page 26: Muscle and Muscle Tissue

Smooth Muscles• Made up of small spindle –shaped fibers

• Lacks the coarse connective tissue sheath of skeletal muscle • But has endomysium

• Organized into 2 layers • Longitudinal – muscle fibers run parallel to the long axis

of the organ• Circular – fibers run around the circumference of the

organ

• Has same contractile mechanism as skeletal

Page 27: Muscle and Muscle Tissue
Page 28: Muscle and Muscle Tissue

Peristalsis• Peristalsis – alternating contraction and

relaxation of smooth muscles that mix and squeeze substances through the hollow organs

• Caused by:• Longitudinal layer of smooth muscle contracts

• When the longitudinal layer contracts the organ elongates

Page 29: Muscle and Muscle Tissue

Microscopic Smooth Muscle

• SR is less developed

• T tubules are absent

• Plasma membrane has pouch like infoldings called caveoli

• No visible striations (no sarcomere)

Page 30: Muscle and Muscle Tissue

Microscopic•Thin and Thick filaments are present

•Ratio of thick to thin filaments is much lower than skeletal•Arranged diagonally – causing smooth muscle to contract in a corkscrew manner

Page 31: Muscle and Muscle Tissue

Smooth Muscle

• Some unique features of smooth muscle • Smooth muscle is very tone

• Slow, prolonged contractile activity

• Low energy requirements

• Response to stretch

Page 32: Muscle and Muscle Tissue

Response to Stretch• Smooth muscle exhibits a phenomenon called

stress-relaxation response in which

• Smooth muscle responds to stretch briefly and then adapts to new length

• The new length, however, retains its ability to contract

• This enables organs such as the stomach and bladder to temporarily store contents

Page 33: Muscle and Muscle Tissue

Hyperplasia• Hyperplasia – is the ability of smooth

muscle to divide and increase in number

• Exhibited in women• At puberty, the estrogen stimulates the

synthesis of more smooth muscle, causing the uterus to grow to adult size

• At pregnancy, estrogen stimulates uterine growth to accommodate the increasing size of the growing fetus

Page 34: Muscle and Muscle Tissue

Types of Smooth Muscle

• Single Unit

• Multiunit

Page 35: Muscle and Muscle Tissue

Single Unit

• Commonly called visceral muscle

• Contracts rhythmically as a unit

• Arranged in opposing sheets and exhibit stress-relaxation response

Page 36: Muscle and Muscle Tissue

Multiunit

• Structurally independent muscle fibers • Have a rich nerve supply• Responds to neural stimuli• Found:

• Large airways to lungs• In large arteries• In arrector pilli muscle and attached to hair

follicles• Internal eye muscles

Page 37: Muscle and Muscle Tissue

Muscular Dystrophy

• Muscular Dystrophy – • Group of inherited muscle destroying

diseases where the muscles enlarge due to fat and connective tissue deposits, but muscle fibers atrophy and degenerate

Page 38: Muscle and Muscle Tissue

Muscular Dystrophy

• Most common type: Duchenne Muscular Dystrophy (DMD) • Inherited, sex-linked trait, carried by women

and exhibited in men (1/3500)• Diagnosed between age 2-10• Victims become clumsy and fall • Progress from extremities upward • Usually die in 20s due to respiratory failures• No cure, but myoblast therapy is promising

Page 39: Muscle and Muscle Tissue

Developmental Aspects of Muscle

• Muscle tissue develops from embryonic mesoderm called myoblast

• Agrin – growth factor • Skeletal Muscle – multinucleated due to

the fusing of myoblasts• Smooth and Cardiac – myoblasts do not

fuse but do develop gap junctions

Page 40: Muscle and Muscle Tissue

Regeneration

• Cardiac and Skeletal muscles become amitotic but retain ability to lengthen and thicken

• Satellite cells – cells that float around fixing damaged skeletal fibers • Limited regenerative ability

• Cardiac cells lack satellite cells • Smooth muscle has good regenerative

abilities

Page 41: Muscle and Muscle Tissue

After Birth

• Muscular development reflects neuromuscular coordination

• Development occurs head-to-toe and proximal-to-distal

• Athletics and training can improve neuromuscular control

Page 42: Muscle and Muscle Tissue

Male vs. Female• Men

•Biological factors make men stronger than women

•Skeletal muscle makes up 42% of body mass

•Men have testosterone, sex hormone due to difference in men and women

• Women• Skeletal muscle make up 36% of body mass

•Body strength per unit muscle mass is about the same in males as females

Page 43: Muscle and Muscle Tissue

Aging

• With age, connective tissue increase and muscle fibers decrease

• Muscles become stringier • By age 80, 50% of muscle mass is lost

(sarcopenia)• Regular exercise reverses sarcopenia• Aging of cardiovascular system affects

every organ in the body