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Chapter 10 Muscle Tissue

Muscle tissue

functions Movement

Posture

Joint stabilization

Heat generation

(11.5a)

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Muscle tissue properties

Contractile

Excitable

Extensible

Elastic

(11.5a)

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Muscle tissue types

Skeletal

Striated,voluntary

Cardiac

Heart,

striated,involuntary

Smooth

Nonstriated,

involuntary Table 10.2

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Muscle tissue terminology

Fiberskeletal, cardiac & smooth muscle

cell Myofilaments

Actinthin filaments

Myosin

thick filaments Sarcolemmaplasma membrane

Sarcoplasmcytoplasm

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Skeletal muscle CT

Epimysiumsurrounds entiremuscle/organ

Perimysiumsurrounds muscle

fascicle Endomysium

surrounds individualmuscle fiber (10.1a)

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Skeletal muscle fiber

Cylindrical

10-100 m diameter Varied lengthup to entire muscle

Formed by cell fusion

Multinucleated Peripheral nucleus

Striated

LM Demonstration

Table 10.2

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Myofibrils

Bundles ofmyofilaments

Z discs

A band

actin &myosin overlap

I bandactin only

H zonemyosin only

SarcomereZ to Z

Striationsalignmentof myofilaments &

myofibrils (10.4)

Muscle fiber

myofibril

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Sliding filament theory

Muscle contracts by actin and myosin sliding

past each other Myosin forms cross-bridges that attach to actin

Cross bridges all swing in same direction and

pull actin along Increased overlap of

filaments results in

contraction of muscle(10.6)

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Sliding filament

theory

Actin and myosin do

not shorten A band does not

change

I band shortens

Sarcomere shortens

(10.7)

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The NMJ Neuromuscular

Junction (pp. 401-402)

Axon terminal

Mitochondria

Synaptic vesicles

ACh

Synaptic cleft

Motor end plate

AChR

AP to muscle fiber (14.5ab)

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T tubules

Invaginations ofsarcolemma

Runs betweenmyofibrils

Conducts electrical

impulses fromsarcolemma

Excites SR to release

Ca++

(10.8)

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Sarcoplasmic reticulum

SR surrounds each

myofibril

Stores Ca++

Release Ca++ for

contraction

Ca++ uptake for

relaxation

(10.8)

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Muscle contraction

AP to axon terminal

ACh released

AChR activated Muscle excited

Excitation travels down t-tubule

SR releases Ca++

Ca++ activates sliding filament process

Muscle contracts

http://www.blackwellpublishing.com/matthews/myosin.html

(14.5b)

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Motor Unit

Definition: a motor neuron andall the muscle fibers itinnervates.

When a motor neuron fires, allmuscle fibers in the motor unitcontract.

All or none principle

A motor unit may containhundreds to four muscle fibers(average ~ 150)

Each muscle fibers receivesone NMJ (14.6)

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Summary: skeletal muscle fibers

muscle

fascicle

fiber

myofibril

Myofilaments :actin & myosinTable 10.1

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Cardiac muscle

Only in heart

Sliding filament theory

Striated

No NMJ

18.4

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Cardiac muscle cells

15 m wide X 100 m long

Branched

Intercalated discs

Desmosomes

adhesion

Gap junctions

transmit electrical impulses

Forms two networksatrial

and ventricular

(10.10a)

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Cardiac muscle cells

Central 1-2 nuclei

Mitochondrianumerous

Less SR

Fewer T tubules

Myofibrils

Sarcomeres

A band I band

Z disc

H zone

Striated

(10.10cd)

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Smooth muscle

Six major locations

Blood vessels

Respiratory system Digestive system

Urinary system

Reproductive system

Eye (lens and iris)

Siding filament theory applies

Actin & myosin

No myofibrilsno striations

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Smooth muscle fibers

Spindle shaped

2-10 m diameter

20-200 m long

Nonstriated

Central nucleus

Arranged in sheets

Usually in layersaround a tube

Peristalsis - waves ofcontraction to propel

contents along tube(10.12b)

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Smooth muscle properties

Slower to contract vs. skeletal muscle

Slower to relax vs. skeletal muscle

Can maintain contraction longer

Resistant to fatigue

Unconscious control ANSautonomic nervous system

Stretch

Hormones

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Smooth muscle organization

Single unit innervation

Smooth muscle fibers connected by gap junctions

Network receives single innervation

Coordinated contraction

Multiunit innervation

Each fiber innervated

Locations

Iris of eye

Arrector pili muscle of skin