copyright © 2010 pearson education, inc. figure 9.26a arrangement of smooth muscle in the walls of...

Copyright © 2010 Pearson Education, Inc.

Figure 9.26a Arrangement of smooth muscle in the walls of hollow organs.

Small intestine

(a)Pg 306

SkeletalCardiacSmooth

Functions:Support (jts. & organs)MovementHeat Production (75%)


NucleusLight I bandDark A band

Sarcolemma

Mitochondrion

(b) Diagram of part of a muscle fiber showing the myofibrils. Onemyofibril is extended afrom the cut end of the fiber.

Myofibril

Figure 9.2b Microscopic anatomy of a skeletal muscle fiber.

Pg 280

Muscle fiber = Muscle cell

cytoskeleton

LongDensely packed


Figure 4.10a Muscle tissues.

(a) Skeletal muscle

Description: Long, cylindrical,multinucleate cells; obviousstriations.

Function: Voluntary movement;locomotion; manipulation of theenvironment; facial expression;voluntary control.

Location: In skeletal musclesattached to bones oroccasionally to skin.

Photomicrograph: Skeletal muscle (approx. 460x).Notice the obvious banding pattern and thefact that these large cells are multinucleate.

Nuclei

Striations

Part ofmuscle fiber (cell)

Pg 138

-nicotonic receptors-Myoglobin


Figure 4.10b Muscle tissues.

(b) Cardiac muscle

Description: Branching, short striated, generally uninucleate cells that interdigitate atspecialized junctions (intercalated discs).

Function: As it contracts, it propels blood into the circulation; involuntary control.Location: The walls of the heart.

Photomicrograph: Cardiac muscle (500X);notice the striations, branching of cells, andthe intercalated discs.

Intercalateddiscs

Striations

Nucleus

Pg 139

-Muscarinic & Beta receptors-Lots of myoglobin & good blood supply

Lots of mitochondria


(c) Smooth muscle

Description: Spindle-shapedcells with central nuclei; nostriations; cells arranged closely to form sheets.

Function: Propels substancesor objects (foodstuffs, urine,a baby) along internal passage-ways; involuntary control.

Location: Mostly in the wallsof hollow organs.

Photomicrograph: Sheet of smooth muscle (200x).

Smoothmusclecell

Nuclei

Figure 4.10c Muscle tissues.

Pg 139

-Muscarinic & alpha or beta receptors-No myoglobin


307


Figure 9.5 Relationship of the sarcoplasmic reticulum and T tubules to myofibrils of skeletal muscle.

Myofibril

Myofibrils

Sarcotubular Sys.

Tubules ofthe SR

Sarcolemma

Sarcolemma A.P.

Mitochondria

I band I bandA band

H zone Z discZ disc

Part of a skeletalmuscle fiber (cell)

• T tubule• Sarcoplasmic

Reticulum (Ca)

M line

Pg 284

Myofilaments (sarcomeres)


NucleusLight I bandDark A band

Sarcolemma

Mitochondrion

(b) Diagram of part of a muscle fiber showing the myofibrils. Onemyofibril is extended afrom the cut end of the fiber.

Myofibril

Figure 9.2b Microscopic anatomy of a skeletal muscle fiber.

Pg 280


Figure 9.2c Microscopic anatomy of a skeletal muscle fiber.

I band I bandA bandSarcomere

H zoneThin (actin)filament

Thick (myosin)filament

Z disc Z disc

M line

(c) Small part of one myofibril enlarged to show the myofilamentsresponsible for the banding pattern. Each sarcomere extends fromone Z disc to the next.

Pg 280


Figure 9.3 Composition of thick and thin filaments.

Flexible hinge region

Tail

Tropomyosin Troponin ActinMyosin head

ATP-bindingsite

Heads Active sitesfor myosinattachment

Actinsubunits

Actin-binding sites

Thick filamentEach thick filament consists of manymyosin molecules whose heads protrude at opposite ends of the filament.

Thin filamentA thin filament consists of two strandsof actin subunits twisted into a helix plus two types of regulatory proteins(troponin and tropomyosin).

Thin filamentThick filament

In the center of the sarcomere, the thickfilaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap.

Longitudinal section of filamentswithin one sarcomere of a myofibril

Portion of a thick filamentPortion of a thin filament

Myosin molecule Actin subunits

200

Pg 282ATPase


Figure 9.2d Microscopic anatomy of a skeletal muscle fiber.

Z disc Z discM line

Sarcomere

Thin (actin)filament

Thick(myosin)filament

Elastic (titin)filaments

(d) Enlargement of one sarcomere (sectioned lengthwise). Notice the myosin heads on the thick filaments.

pg 280


Figure 9.13 A motor unit consists of a motor neuron and all the muscle fibers it innervates.

Spinal cord

Motor neuroncell body

Muscle

Branching axonto motor unit

Nerve

Motorunit 1

Motorunit 2

Musclefibers

Motor neuronaxon

Axon terminals atneuromuscular junctions

Axons of motor neurons extend from the spinal cord to the muscle.There each axon divides into a number of axon terminals that formneuromuscular junctions with muscle fibers scattered throughoutthe muscle.

Branching axonterminals formneuromuscularjunctions, one permuscle fiber (photo-micrograph 330x).

(b)

(a)

Pg 294

4 100 fibers All or nothing

Polio


Figure 9.1a Connective tissue sheaths of skeletal muscle: epimysium, perimysium, and endomysium.

Bone

Perimysium

Endomysium(between individualmuscle fibers)

Muscle fiber

Fascicle(wrapped by perimysium)

Epimysium

TendonDense Reg. Blood vessel

Fascicle

Pg 279

Tendon vs. Aponeurosis


Figure 10.6 Lateral view of muscles of the scalp, face, and neck.

Corrugatorsupercilii Orbicularis oculiLevator labiisuperiorisZygomaticusminor and majorBuccinatorRisoriusOrbicularis orisMentalisDepressorlabii inferiorisDepressor anguli orisPlatysma

Galeaaponeurotica

Frontal belly

Occipitalbelly

Temporalis

MasseterSternocleidomastoidTrapezius

Splenius capitis

Epicranius

Pg 331


Figure 10.14c Muscles crossing the shoulder and elbow joint, causing movements of the arm and forearm, respectively.

Long headBicepsbrachii Short head

O = origin I = insertion

(c)Pg 352

Extrinsic vs. Intrinsic

Prime moverSynergistAntagonist


Figure 9.8 Events at the Neuromuscular Junction

Nucleus

Actionpotential (AP)

Myelinated axonof motor neuron

Axon terminal ofneuromuscular junction

Sarcolemma ofthe muscle fiber

Ca2+ Ca2+

Axon terminalof motor neuron

Synaptic vesiclecontaining AChMitochondrionSynapticcleft

Junctionalfolds ofsarcolemma

Fusing synaptic vesicles

ACh

Sarcoplasm ofmuscle fiber

Postsynaptic membraneion channel opens;ions pass.

Na+ K+

Ach–

Na+

K+

Degraded ACh

Acetyl-cholinesterase

Postsynaptic membraneion channel closed;ions cannot pass.

1 Action potential arrives ataxon terminal of motor neuron.

2 Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal.

3 Ca2+ entry causes some synaptic vesicles to release their contents (acetylcholine)by exocytosis.

4 Acetylcholine, aneurotransmitter, diffuses across the synaptic cleft and binds to receptors in the sarcolemma.

5 ACh binding opens ionchannels that allow simultaneous passage of Na+ into the musclefiber and K+ out of the muscle fiber.

6 ACh effects are terminated by its enzymatic breakdown in the synaptic cleft by acetylcholinesterase.

Motor End Plate-1/cell-Middle of cell-Location of receptors

Pg 287


Figure 9.11 Excitation-Contraction Coupling (1 of 4)

Axon terminalof motor neuron

Muscle fiberTriad

One sarcomere

Synaptic cleft

Setting the stage

Sarcolemma

Action potentialis generated

Terminal cisterna of SR ACh

Ca2+

Pg 290


Figure 9.11 Excitation-Contraction Coupling (2 of 4)

Steps in E-C Coupling:

TroponinTropomyosinblocking active sites

Myosin

Actin

Active sites exposed andready for myosin binding

Ca2+

Terminal cisternaof SR

Voltage-sensitivetubule protein

T tubule

Ca2+

releasechannel

Myosincrossbridge

Ca2+

Sarcolemma

Action potential is propagatedalong the sarcolemma and downthe T tubules.

Calcium ions are released.

Calcium binds to troponin andremoves the blocking action oftropomyosin.

Contraction begins

The aftermath

1

2

4

3

Pg 291

ECC Clip


Figure 9.12 Cross Bridge Cycle

Actin

Cross bridge formation.

Cocking of myosin head. The power (working)stroke.

Cross bridgedetachment.

Ca2+

1

2

3

4

Myosinhead

Thickfilament

Thin filament

ADP

Myosin

P i

ADP

P iATPhydrolysis

ADP

P i

ATP

ATP

Pg 292

charged

Rigor mortisCramps

CBC clip


Figure 9.6 Sliding filament model of contraction.

I

Fully relaxed sarcomere of a muscle fiber

Fully contracted sarcomere of a muscle fiber

IA

Z ZH

I IA

Z Z

1

2

Pg 285


Figure 9.18a Isotonic (concentric) and isometric contractions (1 of 2).

(a) Concentric isotonic contraction

On stimulation, muscle develops enough tension (force) to liftthe load (weight). Once the resistance is overcome, the muscleshortens, and the tension remains constant for the rest of thecontraction.

3 kg

3 kg

Musclecontracts(isotoniccontraction)

Tendon

Tendon

Pg 297

Muscle shortensSame tension


Figure 9.18b Isotonic (concentric) and isometric contractions (1 of 2).

(b) Isometric contraction

Muscle is attached to a weight that exceeds the muscle’s peaktension-developing capabilities. When stimulated, the tensionincreases to the muscle’s peak tension-developing capability,but the muscle does not shorten.

6 kg 6 kg

Musclecontracts(isometriccontraction)

Pg 297

No ShorteningIncreasing TensionMaintains Posture


Figure 9.19 Pathways for regenerating ATP during muscle activity.

Coupled reaction of creatinephosphate (CP) and ADP

Energy source: CP Energy source: glucose Energy source: glucose; pyruvic acid;free fatty acids from adipose tissue;amino acids from protein catabolism

Glycolysis and lactic acid formation

(a) Direct phosphorylation (b) Anaerobic pathway (c) Aerobic pathway

Aerobic cellular respiration

Oxygen use: NoneProducts: 1 ATP per CP, creatineDuration of energy provision:15 seconds

Oxygen use: NoneProducts: 2 ATP per glucose, lactic acidDuration of energy provision:60 seconds, or slightly more

Oxygen use: RequiredProducts: 32 ATP per glucose, CO2, H2ODuration of energy provision: Hours

Creatinekinase

ADPCP

Creatine

Glucose (fromglycogen breakdown ordelivered from blood)

Glucose (fromglycogen breakdown ordelivered from blood)

Glycolysisin cytosol

Pyruvic acid

Releasedto blood

net gain

2

32Lactic acid

O2

O2

O2

O2

H2OCO2

Pyruvic acidFattyacids

Aminoacids

Aerobic respirationin mitochondriaAerobic respirationin mitochondria

ATP

ATP

ATP

net gain perglucose

Pg 299

60-70%

Rapid ATP Production


Figure 9.20 Comparison of energy sources used during short-duration exercise and prolonged-duration exercise.

Short-duration exercise Prolonged-durationexercise

ATP stored inmuscles isused first.

ATP is formedfrom creatinePhosphateand ADP.

Glycogen stored in muscles is brokendown to glucose, which is oxidized togenerate ATP.

ATP is generated bybreakdown of severalnutrient energy fuels byaerobic pathway. Thispathway uses oxygenreleased from myoglobinor delivered in the bloodby hemoglobin. When itends, the oxygen deficit ispaid back.

Pg 300

Lactic Acid Byproduct

70% max muscle activity

Twitch

The contraction of a muscle in response to a brief, single stimulus.

Example: Blinking

Consists of 3 distinct phases


Figure 9.14a The muscle twitch.

Latentperiod

Singlestimulus

Period ofcontraction

Period ofrelaxation

(a) Myogram showing the three phases of an isometric twitch

Pg 295

Refractory period

Increasing # of motor units

No recruitment

Twitches fusing

Piggy-backing twitchesPartial relaxation


Figure 9.15c Muscle response to changes in stimulation frequency.

Stimuli

High stimulation frequencyfused (complete) tetanus

(c) At higher stimulus frequencies, there is no relaxation at all between stimuli. This is fused (complete) tetanus.

ONLY Skeletal Muscle

-Stimulate at peak of twitch-No relaxation-Normal

RotationMuscle Tone

Pg 295


Sarcomeresgreatly

shortened

Sarcomeres atresting length

Sarcomeres excessivelystretched

170%

Optimal sarcomereoperating length(80%–120% ofresting length)

100%75%

Figure 9.22 Length-tension relationships of sarcomeres in skeletal muscles.

Pg 302

Congestive heart failure

Smooth Muscle-Accommodation-Bladder, Uterus

Temperature

Too cool-Decreases enzyme functioning

Too warm-Decreases enzyme functioning-May even denature enzymes and muscle proteins (107-108 degrees F)-Heat rigor

Fatigue

1. Build up of waste products

2. Decreased energy stores

3. Increased temperature

4. Synaptic fatigue

Exercise and Training

Aerobic• Continuous, prolonged• Cellular respiration• Increases mitochondrion• Usage of fat as fuel• Improves endurance• Improves muscle tone

• (red)

AnaerobicBursts of activityCellular respiration &

anaerobic glycolysisIncreases size of muscles

(hypertrophy)Increases strength

(white)

Muscle fiber types

Red Fibers (Slow Oxidative)

• Increased Mitochondrion• Lots of myoglobin• Highly vascular• Slow to fatigue• Use for endurance activities• Slow contraction time

• Efficiency vs. Endurance

White Fibers (Fast Glycolytic)

• Less mitochondrion• Decreased myoglobin• High levels of ATPase• Use for anaerobic activity• Increase in size• Fast contraction time

? Fast Oxidative Glycolytic

copyright © 2010 pearson education, inc. figure 9.26a arrangement of smooth muscle in the walls of...

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