27 Questions
What is the role of Acetylcholinesterase (AChE) in neuromuscular transmission?
Degradation of ACh in the synaptic cleft
What occurs when the t-tubules are depolarized?
Conformational change in the ryanodine receptor
Where does coupling of electrical activity and calcium release for muscle contraction occur?
Triads
What happens when the action potential propagates to the triads?
Release of calcium from the sarcoplasmic reticulum
Which component is responsible for converting electrical signals into chemical signals at the triads?
Ryanodine receptor
What is the final step in the Power Stroke in Skeletal Muscle and Rigor cycle?
Binding of ATP to myosin HC
What is the first step in the sequence of events at the neuromuscular junction for skeletal muscle contraction?
Excitation
What occurs when calcium binds to the myofibrils during skeletal muscle contraction?
Powerstroke occurs
What happens when the EPP spreads across the muscle fiber at the neuromuscular junction?
Depolarization and firing of an action potential
What is the role of nicotinic receptors at the motor-end plate in the neuromuscular junction?
Binding ACh and allowing ion flux
What is the role of calmodulin in smooth muscle contraction?
Activating myosin light chain kinase
How does calcium enter the cytoplasm in smooth muscle?
From the extracellular compartment or the SR
Which neurotransmitters are involved in activating GPCR pathways in the autonomic nervous system?
Acetylcholine and norepinephrine
What is the main function of myosin light chain kinase (MLCK) in smooth muscle contraction?
Phosphorylating regulatory light chains on myosin
What role does Ca2+-CaM play in smooth muscle contraction?
Activating myosin light chain kinase
What role does Myosin light chain phosphatase (MLCP) play in smooth muscle relaxation?
Decreases Myosin ATPase activity
Why does smooth muscle have the ability to prolong muscle contraction without using large amounts of ATP?
Latch state allows for minimal energy utilization
What characteristic of the latch state allows smooth muscle to maintain tone with minimal ATP use?
Slow crossbridge dissociation
How does the latch state contribute to the prolonged tension in smooth muscle?
By reducing energy expenditure
Why does maximal velocity directly depend on cross-bridge phosphorylation in smooth muscle?
To speed up contraction and relaxation
What mechanism allows smooth muscle to maintain force for long periods without extensive energy utilization?
Latch state with slow crossbridge dissociation
Why does the heart operate at sarcomere lengths lower than the optimal?
To increase the force of contraction needed to eject blood
Where is smooth muscle located in the body?
Vascular system, gastrointestinal tract, urinary system, reproductive system, and eye
What is a characteristic of single-unit smooth muscle?
It requires neural or hormonal input for contraction to occur
How do thick filaments in smooth muscle differ from skeletal muscle?
They are stabilized by dense bodies
What is pharmacomechanical coupling in smooth muscle contraction?
Contraction coupled to changes in membrane potentials or ligand binding
Why do some smooth muscles not require an action potential for contraction?
Because they have pacemaker cells that spontaneously fire action potentials
Discover the physiology of smooth muscle, its functions in maintaining homeostasis in various body systems, and the contractile patterns in different locations such as the blood vessels, gastrointestinal tract, urinary system, reproductive system, and the eye.
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