Neuromuscular junction Fig. 11-12 Somatic motor neuron Muscle fiber The neuromuscular junction Motor end plate Terminal bouton Mitochondria Synaptic vesicle (ACh) Presynaptic membrane Synaptic cleft Postsynaptic membrane Schwann cell sheath Axon terminal Nicotinic ACh receptors
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Neuromuscular junction Fig. 11-12 Somatic motor neuron Muscle fiber The neuromuscular junction Motor end plate Terminal bouton Mitochondria Synaptic vesicle.
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Neuromuscular junction
Fig. 11-12
Somatic motor neuron
Musclefiber
Theneuromuscularjunction
Motor end plateTerminalbouton
Mitochondria
Synaptic vesicle (ACh)
Presynapticmembrane
Synaptic cleft
Postsynapticmembrane
Schwann cell sheath
Axon terminal
Nicotinic AChreceptors
Neuromuscular junction
Fig. 11-13
Skeletal muscle
fiber
AChE
Voltage-gatedCa2+ channel
Action potential
ACh
Ca2+Ca2+
Acetyl + choline
Nicotinicreceptor
Motor endplate
Somatic motor neuron
Axon terminal
K+
Na+
Na+
K+
AChClosed channel Open channel
T-tubules and SR
Fig. 12-4
Sarcolemma
Thin filament
Thick filament
T-tubule brings actionpotentials into interiorof muscle fiber.
Sarcoplasmic reticulumstores Ca2+
Excitation-contraction coupling
Axon terminal ofsomatic motor neuron
Myosin head
Myosin thick filament
M line
Motor end plate
Sarcoplasmicreticulum
ACh
DHP
RyR
T-tubule
Muscle fiber
Troponin
TropomyosinActin
Z disk
Na+
Ca2+
Ca2+ released
Myosin thick filament
Fig. 12-11
Troponin and tropomyosin
Fig. 12-3
Thin filaments
Tropomyosin
Troponin
Actin chain G-actin molecule
Nebulin
Cross-bridge cycle
Fig. 12-9
ADP ADP
Actinmoves
Cytosolic Ca2+
Tropomyosin shifts,exposing bindingsite on actin
TN
Power stroke
Initiation of contraction
Troponin G-Actin
Tropomyosinblocks binding
site on actin
Myosin head
TN
Relaxed state. Myosin head cocked.
Pi
Pi
1
2 3
4
5
Types of Muscle Fibers
Fig. 12-15
SPINAL CORD
Neuron 1Neuron 2Neuron 3
Motornerve
Muscle fibers
Motor unit 2
Motor unit 1
Motor unit 3
One muscle may havemany motor units ofdifferent fiber types.