• Understand why we need muscle (cardiac, smooth, skeletal).
• Know the structure and molecular components of skeletal muscle and their interaction.
• Know the structure and molecular components of motor unit (neuromuscular junction).
• Understand the mechanism of contraction
Skeletal muscle is essential for movement, posture, and heat generation.
Answer
True
False
Question 2
Question
A muscle cell is made of myofilaments, and the sarcomeres within it are made of myofibrils.
Answer
True
False
Question 3
Question
Myofibrils have around 30,000 sarcomeres.
Answer
True
False
Question 4
Question
[blank_start]Sarcoplasmic Reticulum[blank_end]: The ER of the muscle. Stores calcium.
[blank_start]T-tubule(Transverse tubule)[blank_end]: invaginated sarcolemma, enhances calcium transport.
[blank_start]Triad[blank_end]: T-tubule in between two SR.
Answer
Sarcoplasmic Reticulum
T-tubule(Transverse tubule)
Triad
T-tubule(Transverse tubule)
Triad
Sarcoplasmic Reticulum
Triad
Sarcoplasmic Reticulum
T-tubule(Transverse tubule)
Question 5
Question
Troponin and tropomyosin attach to myosin, making them part of the thick filament.
Answer
True
False
Question 6
Question
If a motor neuron innervates a large number of muscle fibres, the action is precise.
If a motor neuron innervates a small number of muscle fibres, the action is unprecise.
Answer
True
False
Question 7
Question
Choose the correct statements.
Answer
A muscle fibre is innervated by multiple motor neurons.
A motor neuron always innervates only one muscle fibre.
The more muscle fibres innervated by a neuron, the more precise the movement.
None of these are correct.
Question 8
Question
The mechanism of contraction of skeletal muscles begins with [blank_start]excitation[blank_end]. Here, the [blank_start]neuronal[blank_end] action potential is transferred to a [blank_start]muscular[blank_end] action potential via the neurotransmitter ACh. (This ACh is diffused through the NMJ when [blank_start]Ca++[blank_end] channels opening in the neuron trigger the release of vesicles.)
Next, [blank_start]contraction[blank_end] occurs. ACh receptors open voltage gated [blank_start]Na+[blank_end] channels, which depolarises the muscle membrane ([blank_start]sarcolemma and T-tubules[blank_end]). Ca++ is released from the [blank_start]SR[blank_end] and diffuses into the firstly the [blank_start]sarcoplasm[blank_end], and then the [blank_start]myofilaments[blank_end]. Here it forms crossbridges with the myofilaments, allowing them to interdigiate.
After, the muscle [blank_start]relaxes[blank_end] when Ca++ is taken up into the SR and the crossbridges [blank_start]uncouple[blank_end].
Answer
excitation
neuronal
muscular
Ca++
contraction
Na+
sarcolemma and T-tubules
SR
sarcoplasm
myofilaments
relaxes
uncouple
Question 9
Question
Choose the incorrect statement.
Answer
When Ca++ binds to the troponin-tropomyosin complex, it changes its composition, to open the binding site for myosin.
Myosin is in an energised state before Ca++ enters.
ATP is released when the myosin moves in its power stroke.
Myosin binding to the open site on actin is the formation of the crossbridge.
Question 10
Question
The sarcolemma depolarises when no new AP innervates it.
Answer
True
False
Question 11
Question
Ca++ ions diffuse back into the SR when the muscle relaxes, and can no longer bind to troponin.
Answer
True
False
Question 12
Question
When Ca++ leaves the myofilaments, they uncouple passively.