Lecture 18 Flashcards
Where is acetylcholine released in the neuromuscular junction
motor end plate
What is another name for neuromuscular junction
• Also known as NMJ or
myoneural junction
where is the NMJ located
Site where an axon and
muscle fiber meet
What are the parts at NMJ
- Motor neuron
- Motor end plate
- Synapse
- Synaptic cleft
- Synaptic vesicles
- Neurotransmitters
What is the use of motor unit
• All muscle fibers controlled by motor neuron •As few as four fibers • As many as 1000’s of muscle fibers
How is the muscle stimulated to contract
• Acetylcholine (ACh) • Nerve impulse causes release of ACh from synaptic vesicles • ACh binds to ACh receptors on motor end plate • Generates a muscle impulse • Muscle impulse eventually reaches the SR and the cisternae
What are the muscle coverings
- Muscle coverings:
- Epimysium
- Perimysium
- Endomysium
Names of the muscles from the most surface layer to the smallest part of the muscle
Muscle > Fascicles > muscle fibers (cells) > myofibrills > thick and thin filaments
What are the thick and thin myofilaments made of
- Actin and myosin proteins
* Titin is an elastic myofilament
What is the triad in muscle fibers
Triad
• Cisternae of SR
• T tubule
What is sarcomere
the combination of myofilaments • I band (thin) • A band (thick and thin) • H zone (thick) • Z line (or disc) • M line
What is wrapping around the actin molecule like a DNA
tropomyosin
What is the bulb attached to the tropomyosin
troponin
What is the protruding part of the myosin
cross-bridges
What is the cross–bridges made of
the head of the myosin molecule with actin-binding site and myosin ATPase site
What is connecting the myosin head to the tail
hindges
What does troponin have
Ca2+ binding site
How does muscle impulses have an impact on calcium ions
• Muscle impulses cause SR to
release calcium ions into cytosol
• Calcium binds to troponin to
change its shape
What happens when calcium binds to tropinin
• Calcium binds to troponin to change its shape • The position of tropomyosin is altered • Binding sites on actin are now exposed • Actin and myosin molecules bind via myosin cross-bridges
how does muscle contract
Exposed binding sites on actin molecules allow the muscle contraction cycle to occur.
2. cross bridges bind actin to myosin
3. cross-bridges pull thin filament (power stroke), ADP and P released from myosin
4. New ATP binds to myosin, releasing linkages
5 ATP splits, which provides power to cock the myosin cross-bridge
Where does the Ca2+ comes from
sacroplasmic reticulum, a lateral sac
What can Ca2+ do
Ca2+ binding to troponin removes blocking action of tropomyosin
What are the Cross Bridge Cycling steps
• Myosin cross-bridge attaches to actin binding site • Myosin cross-bridge pulls thin filament • ADP and phosphate released from myosin • New ATP binds to myosin • Linkage between actin and myosin cross-bridge break • ATP splits • Myosin cross-bridge goes back to original position
What happens during relaxation of the muscle
• Acetylcholinesterase – rapidly decomposes Ach remaining in
the synapse
• Muscle impulse stops
• Stimulus to sarcolemma and muscle fiber membrane ceases
• Calcium moves back into sarcoplasmic reticulum (SR)
• Myosin and actin binding prevented
• Muscle fiber relaxes
How can muscle contraction be observed
Muscle contraction can be observed by removing a
single skeletal muscle fiber and connecting it to a device
that senses and records changes in the overall length of
the muscle fiber.
What is the use of acetylcholinesterase
to break down acetylcholine to acetic acid and choline. To help to terminate the ligand binding channels. so muscle will be able to relax
What is the epimysium for
wrap around all of the muscle together
What is perimysium
wraps around the bundle fasicles
What is the endomysium for
placed inbetween all the muscle fibers and wraps individual muscle fiber
Sarcolemma
muscle membrane
What is the energy stored in the myosin from the ATP
the myosin head
what is the three role of calcium in muscle contraction
- used in the neuron presynapse to release vesicles of acetylcholine
- used in unblocking myosin binding site in actin for contraction by attaching to troponin
- used in muscle relaxation by removing from actin back to sarcolemma
What are the 3 things that ATP is used in muscle contraction
- movement of the myosin for contraction
- attaching to the myosin head which then relax the muscle, breaking the bond of ATP to ADP
- using to move the calcium back into SR, using calcium ATPase pump
When Recording a Muscle Contraction what is a twitch
- Latent period
- Period of contraction
- Period of relaxation
