produce movement maintain posture stabilize joints generate heat move substances within the body...

• produce movement• maintain posture• stabilize joints• generate heat• move substances

within the body

Muscle Function

• 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

Functional Characteristics

Skeletal Muscle

• Striated• Multinucleate• Voluntary

Cardiac Muscle

• Striated• Uninucleate• Involuntary• Branching• Intercalated discs

Smooth Muscle

• Unstriated• Uninucleate• Involuntary• Hollow walled

organs and blood vessels

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

Bone

Perimysium

Endomysium(between individualmuscle fibers)

Muscle fiber

Fascicle(wrapped by perimysium)

Epimysium

Tendon

Epimysium

Muscle fiberin middle ofa fascicle

Blood vessel

PerimysiumEndomysium

Fascicle(a)

(b)

Gross Anatomy Skeletal Muscle

Muscle AnatomyMuscle Anatomy

myofibril

sarcomere

muscle fiber (cell)

Muscle CellMuscle CellSarcoplasmic

reticulum

SarcomereSarcomere

Myofibril

Myosin (Thick) FilamentMyosin (Thick) Filament

Actin (Thin) FilamentActin (Thin) Filament

Cross BridgesCross Bridges

Sliding Filament Hypothesis

No Calcium Ion

Calcium Ion Present

tropomyosin

troponin

myosin binding sites

actin

Actin & Myosin InteractionActin & Myosin Interaction

Biology 100Biology 100Human BiologyHuman Biology

Motor 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.youtube.com/watch?v=kvMFdNw35L0http://www.youtube.com/watch?v=Ct8AbZn_A8A

http://www.youtube.com/watch?v=kvMFdNw35L0

Stimulation of Skeletal Muscle

Figure 9.9

Na+

Na+

Open Na+

Channel

Closed Na+

Channel

Closed K+

Channel

Open K+

Channel

Action potential++++++

++++++

Axon terminal

Synapticcleft

ACh

ACh

Sarcoplasm of muscle fiber

K+

2 Generation and propagation ofthe action potential (AP)

3 Repolarization

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

K+

K+Na+

K+Na+

Wave of dep

olar

izat

io n

Figure 9.9, step 1

Na+

Na+

Open Na+

ChannelClosed K+

Channel

K+

Na+ K+Action potential

+++++++++++

+

Axon terminal

Synapticcleft

ACh

ACh


K+


1Wave of

depo

lariz

atio

n

Figure 9.9, step 2

Na+

Na+

Open Na+

ChannelClosed K+

Channel

K+

Na+ K+Action potential

+++++++++++

+

Axon terminal

Synapticcleft

ACh

ACh


K+

Generation and propagation of the action potential (AP)


2

1Wave of

depo

lariz

atio

n

Figure 9.9, step 3

Na+

Closed Na+

ChannelOpen K+

Channel

K+

Repolarization3

Figure 9.9

Na+

Na+

Open Na+

ChannelClosed K+

Channel

Action potential++++++

++++++

Axon terminal

Synapticcleft

ACh

ACh


K+

2 Generation and propagation ofthe action potential (AP)

3 Repolarization


K+

K+Na+

K+Na+

Wave of dep

olar

izat

io n

Closed Na+

ChannelOpen K+

Channel

Figure 9.10

Na+ channelsclose, K+ channelsopen

K+ channelsclose

Repolarizationdue to K+ exit

Threshold

Na+

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

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

O2

3. aerobic respirationGlucose pyruvate acetyl CoA KrebsCO2

+ H2O + ATP

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

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

Muscle FibersMuscle Fibers

Muscle Fiber Types

• Fast glycolitic• Slow oxidative• Fast oxidative-glycolytic

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

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

Fast glycolitic:

Slow oxidative: • red muscle• aerobic• high myoglobin• low glycogen stores• lots mitochondria• slow• long distance

Fast glycolitic-oxidative: • red pink• aerobic• fast• high myoglobin• intermediate amt. of

mitochondria• intermediate glycogen• intermediate fatigue resistance

Red vs White Muscle• long distance blue fin tuna- mostly

red meat• quick bursts- yellow tail- more white

meat

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

Disuse- atrophyMuscles must be physically active if they are to remain healthyCastCast- muscle strength can decrease at a rate of 5%/ day; can use e- stimulusAvoid muscle injuries:Avoid muscle injuries:

• warm up muscles- walk fast 5 minutes

• then stretch- avoids pulls and tares

Effects of Exercise

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

• strain- muscle pull• spasm- tics

Muscle Injuries

• hernia- protrusion of organ through body cavity wall may be due to heavy wts.

Inquiry1. 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?

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