Chapter 12Chapter 12

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Dee Unglaub Silverthorn, Ph.D.

H ^UMAN P ^HYSIOLOGY H ^UMAN P ^HYSIOLOGY

PowerPoint^® Lecture Slide Presentation by

Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University

AN INTEGRATED APPROACH

T H I R D E D I T I O N

Chapter 12 Chapter 12

Muscles

(2)

About this Chapter About this Chapter

• Muscle types

• What muscles do

• How muscles contract

• Contraction to locomotion

• Roles of smooth muscles

(3)

Muscles Muscles

• Contract!

• Generate motion

• Generate force

• Generate heat

• Support

(4)

Muscular System Functions Muscular System Functions

• Body movement (Locomotion)

• Maintenance of posture

• Respiration

• Diaphragm and intercostal contractions

• Communication (Verbal and Facial)

• Constriction of organs and vessels

• Peristalsis of intestinal tract

• Vasoconstriction of b.v. and other structures (pupils)

• Heart beat

• Production of body heat (Thermogenesis)

(5)

Properties of Muscle 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

(6)

Muscle Types Muscle Types

• Cardiac – heart

• Smooth – internal organs

• Skeletal – "voluntary"

• Attach to bone

• Move appendages

• Support body

• Antagonistic pairs

• Flexors

• Extensors

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Types of Muscle 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

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S12-8

Categories of skeletal muscle actions Categories of skeletal muscle actions

• Categories Actions

• Extensor Increases the angle at a joint

• Flexor Decreases the angle at a joint

• Abductor Moves limb away from midline of body

• Adductor Moves limb toward midline of body

• Levator Moves insertion upward

• Depressor Moves insertion downward

• Rotator Rotates a bone along its axis

• Sphincter Constricts an opening

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Connective Tissue Sheaths Connective Tissue Sheaths

• 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.

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Muscle Types Muscle Types

Figure 12-1: Three types of muscles

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Muscle Tissue Types

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• About 40% body mass

• Muscle fibers – cells

• Fascicle – bundle

• Motor unit

• Muscle

• sheath

• Attach to tendons (which attach to bone) Skeletal Muscle Anatomy

Skeletal Muscle Anatomy

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Nerve and Blood Vessel Supply Nerve and Blood Vessel Supply

• Motor neurons

• stimulate muscle fibers to contract

• Neuron axons branch so that each muscle fiber (muscle cell) is innervated

• Form a neuromuscular junction (= myoneural junction)

• Capillary beds surround muscle fibers

• Muscles require large amounts of energy

• Extensive vascular network delivers necessary

oxygen and nutrients and carries away metabolic

waste produced by muscle fibers

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Skeletal Muscle Anatomy Skeletal Muscle Anatomy

Figure 12-3a-1: ANATOMY SUMMARY: Skeletal Muscle

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Skeletal Muscle Anatomy Skeletal Muscle Anatomy

Figure 12-3a-2: ANATOMY SUMMARY: Skeletal Muscle

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• Multiple nuclei

• Sarcolemma

• T-tubules

• Sarcoplasmic reticulum

• Sarcoplasm

• Mitochondria

• Glycogen & ions

• Myofibrils

Muscle Fiber Structure

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Muscle Fiber Structure Muscle Fiber Structure

Figure 12-3b: ANATOMY SUMMARY: Skeletal Muscle

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Muscle Fiber Structure Muscle Fiber Structure

Figure 12-4: T-tubules and the sarcoplasmic reticulum

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• Actin – "thin fibers"

• Tropomysin

• Troponin

• Myosin – "thick fibers"

• Titin – elastic anchor

• Nebulin – non-elastic

Myofibrils: Site of Contraction

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Myofibrils: Site of Contraction Myofibrils: Site of Contraction

Figure 12-3c-f: ANATOMY SUMMARY: Skeletal Muscle

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• Z disks

• I band

• A band

• H Zone

• M line

• Titin

• Nebulin

Sarcomere: Organization of Fibers Sarcomere: Organization of Fibers

Figure 12-5: The two- and three-dimensional organization of a sarcomere

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Sarcomere: Organization of Fibers Sarcomere: Organization of Fibers

Figure 12-6: Titin and nebulin

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Skeletal Muscle Contraction: Mechanism Skeletal Muscle Contraction: Mechanism

Figure 12-11a: Excitation-contraction coupling

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Skeletal Muscle Contraction: Mechanism Skeletal Muscle Contraction: Mechanism

Figure 12-11b: Excitation-contraction coupling

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One Postulated Cause of Muscle Fatigue One Postulated Cause of Muscle Fatigue

• Stress responses in skeletal muscle during E-C coupling. Stress-induced RyR1 dysfunction can result in SR Ca

²⁺

leak, which potentially activates numerous Ca

²⁺

-dependent cellular damage

mechanisms. AC, adenylate cyclase.

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Energy for Contraction: ATP & Phosphocreatine Energy for Contraction: ATP & Phosphocreatine

• Aerobic Respiration

• Oxygen

• Glucose

• Fatty acids

• 30-32 ATPs

• Anaerobic Respiration

• Fast but

• 2 ATP/glucose

• Phosphocreatine ATPs

(28)

Energy for Contraction: ATP & Phosphocreatine Energy for Contraction: ATP & Phosphocreatine

Figure 12-13: Phosphocreatine

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• Central

• "Feeling"

• Lactic acid

• Peripheral

• Glycogen depletion

• Ca

²⁺

interference

• High P

i

levels

• ECF high K

⁺

• ACh depletion

Muscle Fatigue: Causes not well known Muscle Fatigue: Causes not well known

Figure 12-14: Locations and possible causes of muscle fatigue

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• Rate

• 2-3 times faster

• SR uptake of Ca

²⁺

• ATP splitting

• Anaerobic/Fatigue easily

• Power lifting

• Fast/delicate

• Sprint

Fiber Contraction Speed: Fast Twitch

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Fiber Contraction Speed: Fast Twitch Fiber Contraction Speed: Fast Twitch

Figure 12-15: Fast-twitch glycolytic and slow-twitch muscle fibers

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• Oxidative Fast Twitch

• Intermediate speed

• Anaerobic & aerobic

• Slow Twitch: Aerobic, less fatigue

• More mitochondria

• More capillaries

• Myoglobin

• Endurance activities

• Postural muscles

Fiber Contraction Speed: Oxidative Fast & Slow

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Coordinating the Fibers: Force of Contraction Coordinating the Fibers: Force of Contraction

Figure 12-16: Length-tension relationships in contracting skeletal muscle

• Excitation and Twitch

• Length–Tension: more crossbridges: more

tension

(34)

Coordinating the Fibers: Summation to Tetanus Coordinating the Fibers: Summation to Tetanus

Figure 12-17: Summation of contractions

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Smooth Muscle Smooth Muscle

• Fusiform cells

• One nucleus per cell

• Nonstriated

• Involuntary

• Slow, wave-like

contractions

(36)

Smooth Muscle Smooth Muscle

• Cells are not striated

• Fibers smaller than those in skeletal muscle

• Spindle-shaped; single, central nucleus

• More actin than myosin

• No sarcomeres

• Not arranged as symmetrically as in skeletal muscle, thus NO striations.

• Caveolae: indentations in sarcolemma;

• May act like T tubules

• Dense bodies instead of Z disks

• Have noncontractile intermediate filaments

(37)

Smooth Muscle Smooth Muscle

• Grouped into sheets in walls of hollow organs

• Longitudinal layer – muscle fibers run parallel to organ’s long axis

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

• Both layers participate in peristalsis

(38)

Smooth Muscle Smooth Muscle

• Is innervated by autonomic nervous system (ANS)

• Visceral or unitary smooth muscle

• Only a few muscle fibers innervated in each group

• Impulse spreads through gap junctions

• Whole sheet contracts as a unit

• Often autorhythmic

• Multiunit:

• Cells or groups of cells act as independent units

• Arrector pili of skin and iris of eye

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Smooth Muscle Cell

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Smooth Muscle Contraction: Mechanism

(41)

Smooth Muscle Relaxation: Mechanism

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Contractile fibers are arranged in oblique bundles rather than in parallel sarcomeres

Contractile fibers are arranged in oblique bundles

rather than in parallel sarcomeres

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(45)

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Myosin of Smooth Muscle Myosin of Smooth Muscle

• Different isoform than that found in skeletal muscle

• Smooth muscle myosin ATPase

activity is much slower, contraction is longer

• Myosin light chain in the myosin head

regulates contraction and relaxation

(47)

Smooth Muscle Smooth Muscle

• Relatively little sarcoplasmic reticulum

• Lacks T-tubules

• Chemically linked to the cell membrane, rather than mechanically linked

• Ca

⁺²

Chapter 12Chapter 12

H UMAN P HYSIOLOGY H UMAN P HYSIOLOGY

Chapter 12 Chapter 12

Muscles

About this Chapter About this Chapter

• Muscle types

• What muscles do

• How muscles contract

• Contraction to locomotion

• Roles of smooth muscles

Muscles Muscles

• Contract!

• Generate motion

• Generate force

• Generate heat

• Support

Muscular System Functions Muscular System Functions

• Body movement (Locomotion)

• Maintenance of posture

• Respiration

• Diaphragm and intercostal contractions

• Communication (Verbal and Facial)

• Constriction of organs and vessels

• Peristalsis of intestinal tract

• Vasoconstriction of b.v. and other structures (pupils)

• Heart beat

• Production of body heat (Thermogenesis)

Properties of Muscle 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

Muscle Types Muscle Types

• Cardiac – heart

• Smooth – internal organs

• Skeletal – "voluntary"

• Attach to bone

• Move appendages

• Support body

• Antagonistic pairs

• Flexors

• Extensors

Types of Muscle Types of Muscle

Categories of skeletal muscle actions Categories of skeletal muscle actions

• Categories Actions

• Extensor Increases the angle at a joint

• Flexor Decreases the angle at a joint

• Abductor Moves limb away from midline of body

• Adductor Moves limb toward midline of body

• Levator Moves insertion upward

• Depressor Moves insertion downward

• Rotator Rotates a bone along its axis

• Sphincter Constricts an opening

Connective Tissue Sheaths Connective Tissue Sheaths

• Connective Tissue of a Muscle

• Epimysium. Dense regular c.t. surrounding entire muscle

• Perimysium. Collagen and elastic fibers

surrounding a group of muscle fibers called a fascicle

• Endomysium. Loose connective tissue that surrounds individual muscle fibers

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

aponeurosis.

Muscle Types Muscle Types

Muscle Tissue Types

Muscle Tissue Types

• About 40% body mass

• Muscle fibers – cells

• Fascicle – bundle

• Motor unit

• Muscle

• sheath

• Attach to tendons (which attach to bone) Skeletal Muscle Anatomy

Skeletal Muscle Anatomy

Nerve and Blood Vessel Supply Nerve and Blood Vessel Supply

• Motor neurons

• Capillary beds surround muscle fibers

• Muscles require large amounts of energy

• Extensive vascular network delivers necessary

oxygen and nutrients and carries away metabolic

waste produced by muscle fibers

H ^UMAN P ^HYSIOLOGY H ^UMAN P ^HYSIOLOGY