figure 6.4b muscle cells

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Figure 6.4b Muscle cells.


Figure 6.1a Movement of bones.


Figure 6.1b Movement of bones.


Figure 6.3 Muscle structure.


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

Bone

Endomysium(between individualmuscle fibers)

Muscle fiber

Fascicle(wrapped by perimysium)

Epimysium

Tendon

Blood vessel


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.


Figure 6.5 Structure of a myofibril.


Figure 9.2e Microscopic anatomy of a skeletal muscle fiber.

I bandthin

filamentsonly

Actinfilament

Myosinfilament

H zonethick

filamentsonly

M linethick filaments

linked byaccessoryproteins

Outer edgeof A band

thick and thinfilaments overlap

(e) Cross-sectional view of a sarcomere cut through in different locations.


Figure 6.5d Structure of a myofibril.


Figure 6.8 Role of calcium in contraction.


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


Figure 9.4 Transmission electron micrograph of part of a sarcomere clearly showing the myosin heads forming cross bridges that generate the contractile force.

Thin filament (actin) Thick filament (myosin)Myosin heads


Figure 6.9a Motor units.


Figure 9.8 Events at the Neuromuscular Junction (1 of 4)

Nucleus

Action potential(AP)

Myelinated axonof motor neuron

Axon terminal ofneuromuscular junction

Sarcolemmaof the musclefiber


Figure 6.9b Motor units.


Acetylcholine, a neurotransmitter, diffuses across the synaptic cleft and binds to receptors in the sarcolemma.


Ca2+

Axon terminalof motor neuron

Synaptic vesiclecontaining ACh

Synaptic cleft

Fusingsynaptic vesicles

ACh

Sarcoplasm of muscle fiber

Ca2+



Postsynaptic mem-brane ion channel opens; ions pass.

Na+ K+

5 ACh binding opens ion channels that allowsimultaneous passage of Na+ into the muscle fiber and K+ out of the muscle fiber.

• Resting Potential of muscle cells – – Potassium higher inside– Sodium higher outside– A voltage difference of about 90 mvolts

• Action Potential – – A wave of depolarization that propogates from

the point of stimulation over the entire membrane, followed by a wave of repolarization.


Figure 9.9 Summary of events in the generation and propagation of an action potential in a skeletal muscle fiber.

Na+ K+

Axon terminal

Synapticcleft

ACh–

ACh

1 Local depolarization:

Na+

Na+

Open Na+

ChannelClosed K+

Channel

K+

K+

K+

2 Generation and propagation ofthe action potential (AP)

3 Repolarization

Sarcoplasm of muscle fiber

Na+


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

Myofibrils

Sarcolemma

Mitochondria

Terminal cisternae of SR

T tubuleTriad


Figure 9.11 Excitation-Contraction Coupling (3 of 4)

Calciumions arereleased.

Steps inE-C Coupling:

Terminalcisterna of SR

Voltage-sensitivetubule protein

T tubule

Ca2+

releasechannel

Ca2+

Sarcolemma

Action potential ispropagated along thesarcolemma and downthe T tubules.

1

2

figure 6.4b muscle cells

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