Skeletal Skeletal – striated, multinucleate, voluntary, 10-100 m Smooth Smooth - found in walls...

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SkeletalSkeletal – striated, multinucleate, voluntary, 10-100 m

SmoothSmooth - found in walls of hollow visceral organs; ex. stomach, bladder, respiratory passages; visceral, nonstriated, involuntary; discuss peristalsis

CardiacCardiac – in heart only, striated, involuntary, intercalcated disks

Muscle function:• produce movement• maintain posture• stabilize joints• generate heat• move substances within the body

Functional Characteristics:• Excitability- respond to a stimulus• Contractility- ability to shorten

forcibly when adequately stimulated • Extensibility- the ability to be

stretched• Elasticity- the ability of a muscle

fiber to resume its resting length after being stretched

Skeletal Muscle Skeletal Muscle TissueTissue

Smooth Muscle Smooth Muscle TissueTissue

Cardiac Muscle Cardiac Muscle TissueTissue

Skeletal MuscleSkeletal MuscleConnective tissue sheaths of skeletal muscle:Connective tissue sheaths of skeletal muscle:

• Epimysium: dense regular connective tissue Epimysium: dense regular connective tissue surrounding entire muscle surrounding entire muscle

• Perimysium: fibrous connective tissue Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)surrounding fascicles (groups of muscle fibers)

• Endomysium: fine areolar connective tissue Endomysium: fine areolar connective tissue surrounding each muscle fibersurrounding each muscle fiber

Figure 9.1

Perimysium

Endomysium(between individualmuscle fibers)

Muscle fiber

Fascicle(wrapped by perimysium)

Epimysium

Tendon

Epimysium

Muscle fiberin middle ofa fascicle

Blood vessel

Perimysium

Endomysium

Fascicle(a)

bundle of muscle fibers

muscle fiber(cell)

myofibril

sarcomere

Muscle Muscle AnatomyAnatomy

Muscle Fiber

Myofibril

SarcomereSarcomere

Z lines

SarcomeSarcomerere A band

SarcomeSarcomerere I bands

SarcomeSarcomerere H zone

Actin and Myosin FilamentsActin and Myosin Filaments

myosinactin

Myosin (Thick) FilamentMyosin (Thick) Filament

Actin (Thin) FilamentActin (Thin) Filament

Sliding Filament HypothesisSliding Filament Hypothesis

Z ZHAI I

Actin (Thin) FilamentActin (Thin) FilamentNo Calcium IonNo Calcium Ion

tropomyosin

troponin

Actin (Thin) FilamentActin (Thin) Filament

Calcium Ion PresentCalcium Ion Present

tropomyosin

myosin binding sites

Actin & Myosin InteractionActin & Myosin Interaction

Biology 100Biology 100Human BiologyHuman Biology

Motor UnitMotor Unit

spinal cord

motor neurons

muscle bundle

muscle fibers

neuromuscular junctions

Neuromuscular Neuromuscular junctionsjunctions

branching axon branching axon to motor unitto motor unit

muscle fibersmuscle fibers

Axon(motor neuron)

sarcolemma

myofibrils

sarcomere

sarcoplasmSarcoplasmic Reticulum

Neuromuscular junction

T tubules

sarcoplasmic reticulum

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

Stimulation of Skeletal Muscle

Figure 9.9

Open Na+

Channel

Closed Na+

Channel

Closed K+

Channel

Open K+

Channel

Action potential++++++

Axon terminal

Synapticcleft

Sarcoplasm of muscle fiber

2 Generation and propagation ofthe action potential (AP)

3 Repolarization

1 Local depolarization: generation of the end plate potential on the sarcolemma

Wave ofde

Figure 9.9, step 1

Open Na+

ChannelClosed K+

Channel

Na+ K+Action potential

++++++

Axon terminal

Synapticcleft

Wave ofde

Figure 9.9, step 2

Open Na+

ChannelClosed K+

Channel

Na+ K+Action potential

++++++

Axon terminal

Synapticcleft

Generation and propagation of the action potential (AP)

Wave ofde

Figure 9.9, step 3

Closed Na+

ChannelOpen K+

Channel

Repolarization3

Figure 9.9

Open Na+

ChannelClosed K+

Channel

Action potential++++++

Axon terminal

Synapticcleft

2 Generation and propagation ofthe action potential (AP)

3 Repolarization

Wave ofde

Closed Na+

ChannelOpen K+

Channel

Figure 9.10

Na+ channelsclose, K+ channelsopen

K+ channelsclose

Repolarizationdue to K+ exit

Threshold

channelsopen

Depolarizationdue to Na+ entry

Relaxation of Skeletal Muscle

Muscle TwitchMuscle Twitch

Contraction Contraction ResponseResponse

single twitches

wave summation tetanus

action potentials in motor neuron

Isotonic and Isometric ContractionsIsotonic and Isometric Contractions

Isotonic contraction • Contraction with a change in length• The muscle shortens and movement occurs.

Isometric contraction • Contraction without any change in length• The muscle does not shorten and there is no

movement produced even though the muscle contracts.

Isotonic and Isometric ContractionsIsotonic and Isometric Contractions

Isotonic

Isometric

Slow-Twitch Versus Slow-Twitch Versus Fast-TwitchFast-Twitch

Muscle FibersMuscle Fibers

ATP is Generated by:1. creatine phosphate

ADP + creatine phosphatecreatine + ATP

2. lactic acid fermentationFrom stored glycogen via anaerobic glycolysis; glucosepyruvic acid (no O2) lactic acid

3. aerobic respirationKrebsCO2 + H2O + ATP

Energy for muscle contraction:Energy for muscle contraction:ATP is the only energy source ATP(ATPase + H2O) ADP + Pi

Muscle Fiber Types

• Fast glycolitic• Slow oxidative• Fast oxidative-glycolytic

Ratio- red:white (all 3 types in body)

Fast glycolitic:

• white muscle fibers• low myoglobin• anaerobic glycolysis• few mitochondria• fast twitch fibers• high glycogen stores• short bursts• fatigues easily

Slow oxidative:

• red muscle• aerobic• high myoglobin• low glycogen stores• lots mitochondria• slow• tonic• long distance

Fast oxidative-glycolitic:

• red pink• Aerobic & anaerobic• fast• high myoglobin• intermediate amt. of mitochondria• intermediate glycogen• intermediate fatigue resistance

Tuna- long distance swimmer

Snapper- short bursts

Sprinter- anaerobic respiration

Long distance Runner- aerobic respiration

Smooth Muscle FibersSmooth Muscle Fibers

• Mainly aerobic• Arranged in

opposing sheets

Smooth Muscle FibersSmooth Muscle Fibers

peristalsis

Cardiac TissueCardiac Tissue

• More mitochondria• Longer refractory period• Mainly aerobic respiration• Can use multiple fuel molecules

Effects of ExerciseEffects of ExerciseHypertrophy- excessive enlargement of muscle tissue

Atrophy- disuse

Muscles must be physically active if they are to remain healthy

CastCast- muscle strength can decrease at a rate of 5%/ day; can use e- stimulus

Avoid muscle injuries:Avoid muscle injuries:

-warm up muscles- walk fast 5 minutes

-then stretch- avoids pulls and tares

SteroidsSteroidsAnabolic steroids • similar to testosterone • large doses required for good

effect • Side effects:

• overall - kidney and heart damage, aggressiveness

• females - sterility, facial hair, breast & uterine atrophy

• males - baldness, atrophy of testis

• cramp- sustained spasm or tetanic contraction; may be due to low blood sugar levels, electrolyte depletion, dehydration

how to care for cramp: RICE• strain- muscle pull• spasm- tics• hernia- protrusion of organ through body cavity

wall may be due to heavy wts.

Muscle DisordersMuscle Disorders

Inquiry

1. What is stored in SER?2. Which protein blocks the heads of myosin?3. When a neuron synapses with a muscle it is called---.4. The neuron going to a muscle is called ____.5. A muscle that shortens or lengthens is called ____.6. Which ion floods into the sarcolemma after stimulation by a

neuron?7. Which neurotransmitter binds to the sarcolemma?8. Which type of muscles undergo aerobic respiration?9. Which type of fuel is stored in muscle tissues?10.Which pigment is stored in muscles that has a high affinity

for oxygen?11.Which muscle tissue has intercalated discs?12.What is depolarization?

Skeletal Skeletal – striated, multinucleate, voluntary, 10-100 m Smooth Smooth - found in walls...

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