muscle tissue. summary general general types of muscle tissue types of muscle tissue functional...

41
Muscle Tissue Muscle Tissue

Upload: imogene-bruce

Post on 17-Dec-2015

247 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Muscle TissueMuscle Tissue

Page 2: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

SummarySummary

• GeneralGeneral• Types of muscle tissueTypes of muscle tissue• Functional characteristicsFunctional characteristics• FunctionsFunctions• Structural organization of skeletal Structural organization of skeletal

musclemuscle• Gross and microscopic anatomyGross and microscopic anatomy• Contraction sequenceContraction sequence• Muscle metabolismMuscle metabolism

Page 3: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

GeneralGeneral

• Skeletal muscle represents about 40% of our Skeletal muscle represents about 40% of our body mass, including smooth and cardiac body mass, including smooth and cardiac muscle the figure may be as high as 50%muscle the figure may be as high as 50%

• Muscles transform chemical energy into Muscles transform chemical energy into mechanical energy, i.e. exert a force.mechanical energy, i.e. exert a force.

• Muscles pull they do not push.Muscles pull they do not push.• Skeletal and smooth muscle cells are called Skeletal and smooth muscle cells are called

fibers.fibers.• Myo-, mys- and sarco- refer to musclesMyo-, mys- and sarco- refer to muscles

Page 4: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Muscle TypesMuscle Types

• SkeletalSkeletal• SmoothSmooth• CardiacCardiac

Page 5: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Functional CharacteristicsFunctional Characteristics

• ExcitabilityExcitability (irritability) – receive and respond (irritability) – receive and respond to stimuli. to stimuli. – Stimuli = neurotransmitters, extracellular pHStimuli = neurotransmitters, extracellular pH– Response = generation of an electrical impulse (AP)Response = generation of an electrical impulse (AP)

• ContractilityContractility = ability to shorten, requires = ability to shorten, requires energyenergy

• ExtensibilityExtensibility = ability to stretch, does not = ability to stretch, does not require energyrequire energy

• ElasticityElasticity = ability to recoil, i.e. return to = ability to recoil, i.e. return to resting lengthresting length

Page 6: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Functions of Muscle TissueFunctions of Muscle Tissue

• Produces movementProduces movement– LocomotionLocomotion– PropulsionPropulsion– ManipulationManipulation

• Maintains postureMaintains posture• Stabilizes jointsStabilizes joints• Generates heat – primarily skeletal Generates heat – primarily skeletal

m.m.

Page 7: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Structural Organization of Structural Organization of Skeletal MuscleSkeletal Muscle

• Muscle (Organ) Muscle (Organ) • Fascicles Fascicles • Fiber (Cell) Fiber (Cell) • MyofibrilsMyofibrils• MyofilamentsMyofilaments

– ActinActin– MyosinMyosin

Page 8: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Skeletal Muscle Gross Skeletal Muscle Gross AnatomyAnatomy

• Tissues:Tissues:– Blood vessels Blood vessels – Nerves – branches to each fiberNerves – branches to each fiber– Connective Tissue Connective Tissue

• EndomysiumEndomysium –wraps each fiber –wraps each fiber• PerimysiumPerimysium –wraps fibers into fascicles –wraps fibers into fascicles• EpimysiumEpimysium –wraps fascicles into a muscle –wraps fascicles into a muscle• All are continuous with each other and the All are continuous with each other and the

tendons.tendons.

Page 9: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Skeletal Muscle Microscopic Anatomy

Page 10: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Skeletal Muscle Microscopic Skeletal Muscle Microscopic AnatomyAnatomy

• Myofibrils – hundreds to thousands Myofibrils – hundreds to thousands per cell contain the contractile per cell contain the contractile proteins = proteins = myofilamentsmyofilaments – Actin – thin filamentsActin – thin filaments– Myosin – thick filamentsMyosin – thick filaments

Page 11: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Contraction – Sliding Filament Contraction – Sliding Filament ModelModel

• Sliding filament theorySliding filament theory– Hugh Huxley 1950’sHugh Huxley 1950’s– Contraction (shortening) - the thin Contraction (shortening) - the thin

filaments slide past the thick filaments filaments slide past the thick filaments and overlap increases. and overlap increases.

– Relaxation (lengthening) - thin filaments Relaxation (lengthening) - thin filaments return to their original position.return to their original position.

– Occurs simultaneously in sarcomeres Occurs simultaneously in sarcomeres throughout the fiber = muscle shortening.throughout the fiber = muscle shortening.

Page 12: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Brain Brain Spinal Cord Spinal Cord Motor Neuron Motor Neuron MuscleMuscle

Motor = movement

Neuron = nerve cell

Page 13: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Motor Neuron Motor Neuron Muscle Fiber Muscle Fiber

Motor neuron releases neurotransmitter called acetylcholine (ACh).

ACh causes muscle fiber to produce an electrical signal.Electrical signal causes actin &

myosin to move, and this causes muscle to move.

Page 14: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

A Myofibril at RestA Myofibril at Rest

Page 15: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Recall: Section through a Recall: Section through a MuscleMuscle

Page 16: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

A Myofibril at RestA Myofibril at Rest“At rest” = fiber has not received message to move

Page 17: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

A Myofibril at RestA Myofibril at Rest“At rest” = fiber has not received message to move

Actin (thin) attaches to Z-line.

Myosin (thick) does not attach to actin or the Z-line.

Myosin heads are bent back (cocked).

Page 18: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Contraction in the MyofibrilContraction in the Myofibril

1.1. Signal from ACh to contractSignal from ACh to contract

2.2. Myosin attaches to actinMyosin attaches to actin

3.3. Pushes actin toward center of Pushes actin toward center of sarcomere.sarcomere.

4.4. Sarcomere gets shorter.Sarcomere gets shorter.

Page 19: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

ContractionContraction Let’s compare length of sarcomeres:Let’s compare length of sarcomeres:

Relaxed:Relaxed:

Contracted:Contracted:

Page 20: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Contraction in the MyofibrilContraction in the Myofibril If each sarcomere gets shorter, then If each sarcomere gets shorter, then

the myofibril as a whole gets the myofibril as a whole gets shorter.shorter.

Myofibrils shorten Myofibrils shorten fibers shorten fibers shorten Fibers shorten Fibers shorten Muscle contracts Muscle contracts

Page 21: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Contraction in the MyofibrilContraction in the Myofibril After contraction, muscle relaxes (back After contraction, muscle relaxes (back

to original length).to original length).– Myosin heads pick up ATP & break it apart.Myosin heads pick up ATP & break it apart.– This cocks the head, detaching it from actin.This cocks the head, detaching it from actin.

Now ready to contract again.Now ready to contract again.

Head is Cocked

ATP

Page 22: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

ContractionContraction

Page 23: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions
Page 24: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Types of muscular contractionTypes of muscular contraction•IsometricIsometric

– Muscular contraction where the Muscular contraction where the tension developed occurs with no tension developed occurs with no change in lengthchange in length

– Otherwise known as static Otherwise known as static contraction or position.contraction or position.

– Improves muscular strength at Improves muscular strength at fixed joint anglefixed joint angle

– Does not develop aerobic fitnessDoes not develop aerobic fitness– Can be done anywhereCan be done anywhere– Examples; rugby scrum, tug of Examples; rugby scrum, tug of

war.war.

Page 25: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Types of muscle Types of muscle contractioncontraction

IsotonicIsotonic

Muscles contact at speed controlled by Muscles contact at speed controlled by the performer the performer

Motor unit recruitment is at the speed Motor unit recruitment is at the speed required for the specific sports activity.required for the specific sports activity.

Develops aerobic and anaerobic fitnessDevelops aerobic and anaerobic fitness

Most physical activities are isotonicMost physical activities are isotonic

Can occur in two ways: Can occur in two ways: concentricconcentric and and eccentriceccentric..

Page 26: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

ContractionContraction

•Concentric contractionConcentric contraction– Muscle shortens under tensionMuscle shortens under tension– Insertion moves towards originInsertion moves towards origin– Occurs in agonist muscleOccurs in agonist muscle– e.g. Chin-ups – use of bicep brachii e.g. Chin-ups – use of bicep brachii

in upward phasein upward phase

Page 27: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

ContractionContraction

Eccentric contractionEccentric contraction

Muscle lengthens under tensionMuscle lengthens under tension

Insertion moves away from originInsertion moves away from origin

Occurs in antagonist muscleOccurs in antagonist muscle

Only occurs if the antagonist is acting as a Only occurs if the antagonist is acting as a brake to help control the joint movementbrake to help control the joint movement

E.g. Chin-ups – use of biceps in downward E.g. Chin-ups – use of biceps in downward phase.phase.

Page 28: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Two major factors determine Two major factors determine thethe

capabilities of a particular capabilities of a particular skeletal muscle:skeletal muscle:

1) 1) Types of muscle fibers within the Types of muscle fibers within the muscle.muscle.

2) 2) Physical conditioning or training.Physical conditioning or training.

Page 29: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Two contrasting types ofTwo contrasting types ofskeletal muscles fibers in skeletal muscles fibers in

thethehuman body:human body:

1)fast fiber 1)fast fiber

2)slow fiber2)slow fiber

Page 30: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Fast fiberFast fiber

large in diameter & use massive large in diameter & use massive amounts of ATP.amounts of ATP.

contract in 0.01 sec or less following contract in 0.01 sec or less following stimulation.stimulation.

Page 31: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Slow fibersSlow fibers

half the diameter of fast fibershalf the diameter of fast fibers take three times as long to contracttake three times as long to contract continue to contract for extended continue to contract for extended

periods.periods.

Page 32: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Muscle MetabolismMuscle Metabolism

• Stored ATP – 4-6 seconds but is regenerated by Stored ATP – 4-6 seconds but is regenerated by 3 mechanisms:3 mechanisms:– Direct phosphorylationDirect phosphorylation of ADP from creatine of ADP from creatine

phosphate (CP) with the help of creatine kinase. phosphate (CP) with the help of creatine kinase. SUPER FAST gives another 6-10 seconds of activity.SUPER FAST gives another 6-10 seconds of activity.

– Anaerobic glycolysisAnaerobic glycolysis – glucose is broken down into 2 – glucose is broken down into 2 pyruvate molecules and 2 ATP molecules. Fast but pyruvate molecules and 2 ATP molecules. Fast but short term – supports another 30-40 seconds of short term – supports another 30-40 seconds of activity. Problem - lactic acid build-upactivity. Problem - lactic acid build-up

Page 33: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Muscle MetabolismMuscle Metabolism

• EnergyEnergy– Aerobic glycolysisAerobic glycolysis (respiration) or Kreb’s (respiration) or Kreb’s

CycleCycle• Glucose + O2 yields CO2 + HGlucose + O2 yields CO2 + H22 O + 30 ATP’s O + 30 ATP’s

• Pyruvate, amino acids, and fatty acids can Pyruvate, amino acids, and fatty acids can also enter this cycle. Slow process, more also enter this cycle. Slow process, more useful for endurance exercise.useful for endurance exercise.

Page 34: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Muscle FatigueMuscle Fatigue

Page 35: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

FatigueFatigue

• Physiological inability of a muscle to contract – Physiological inability of a muscle to contract – not enough ATP; different from psychological not enough ATP; different from psychological fatigue. ATP production lags behind use – fatigue. ATP production lags behind use – contractures (no ATP to release cross bridges.contractures (no ATP to release cross bridges.

• Accumulation of lactic acid decreases pH and Accumulation of lactic acid decreases pH and inhibits ATP production.inhibits ATP production.

• Restoration of ionic balance of Na and K Restoration of ionic balance of Na and K requires ATP also – impaired with intense requires ATP also – impaired with intense exercise.exercise.

Page 36: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

FatigueFatigue

Oxygen debtOxygen debt = amount of oxygen = amount of oxygen needed to restore muscle anaerobic needed to restore muscle anaerobic fuel stores.fuel stores.

Page 37: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

What is oxygen debt?What is oxygen debt?

Oxygen debt- is the temporary Oxygen debt- is the temporary lack of oxygen availability.lack of oxygen availability.

Page 38: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

What causes it?What causes it? It is caused by heavy exertion and It is caused by heavy exertion and

the respiratory and circulatory the respiratory and circulatory systems not delivering enough systems not delivering enough oxygen to meet the demands of oxygen to meet the demands of energy productionenergy production

Page 39: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

Oxygen debt leads to the build up ofOxygen debt leads to the build up ofwhat in the muscles?what in the muscles?

Lactic acid Lactic acid is the metabolic waste that builds up is the metabolic waste that builds up

in the muscle fiber after prolonged in the muscle fiber after prolonged exercise.exercise.

Page 40: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions

HeatHeat

• 60% of the energy released by 60% of the energy released by muscle contraction is in the form of muscle contraction is in the form of heat – 40% is in the form of work. heat – 40% is in the form of work. Shivering is muscle contraction used Shivering is muscle contraction used to warm a cold body.to warm a cold body.

• When you exercise strenuously your When you exercise strenuously your body heats up. How is the heat body heats up. How is the heat dissipated?????dissipated?????

Page 41: Muscle Tissue. Summary General General Types of muscle tissue Types of muscle tissue Functional characteristics Functional characteristics Functions Functions