Smooth Muscle Physiology

Play an AI-generated podcast conversation about this lesson

What is the role of Acetylcholinesterase (AChE) in neuromuscular transmission?

Degradation of ACh in the synaptic cleft (correct)

Generating the action potential at the neuromuscular junction

Promoting muscle contraction by releasing calcium into the cytosol

Converting electrical signals into chemical signals

What occurs when the t-tubules are depolarized?

Conformational change in the ryanodine receptor (correct)

Initiation of muscle contraction

Coupling of electrical activity and calcium release

Release of ADP stabilizing myosin-actin interaction

Where does coupling of electrical activity and calcium release for muscle contraction occur?

T-tubules

Triads (correct)

Sarcoplasmic reticulum (SR)

Myofibrils

What happens when the action potential propagates to the triads?

Release of calcium from the sarcoplasmic reticulum Signup and view all the answers

Which component is responsible for converting electrical signals into chemical signals at the triads?

Ryanodine receptor Signup and view all the answers

What is the final step in the Power Stroke in Skeletal Muscle and Rigor cycle?

Binding of ATP to myosin HC Signup and view all the answers

What is the first step in the sequence of events at the neuromuscular junction for skeletal muscle contraction?

Excitation Signup and view all the answers

What occurs when calcium binds to the myofibrils during skeletal muscle contraction?

Powerstroke occurs Signup and view all the answers

What happens when the EPP spreads across the muscle fiber at the neuromuscular junction?

Depolarization and firing of an action potential Signup and view all the answers

What is the role of nicotinic receptors at the motor-end plate in the neuromuscular junction?

Binding ACh and allowing ion flux Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

Activating myosin light chain kinase Signup and view all the answers

How does calcium enter the cytoplasm in smooth muscle?

From the extracellular compartment or the SR Signup and view all the answers

Which neurotransmitters are involved in activating GPCR pathways in the autonomic nervous system?

Acetylcholine and norepinephrine Signup and view all the answers

What is the main function of myosin light chain kinase (MLCK) in smooth muscle contraction?

Phosphorylating regulatory light chains on myosin Signup and view all the answers

What role does Ca2+-CaM play in smooth muscle contraction?

Activating myosin light chain kinase Signup and view all the answers

What role does Myosin light chain phosphatase (MLCP) play in smooth muscle relaxation?

Decreases Myosin ATPase activity Signup and view all the answers

Why does smooth muscle have the ability to prolong muscle contraction without using large amounts of ATP?

Latch state allows for minimal energy utilization Signup and view all the answers

What characteristic of the latch state allows smooth muscle to maintain tone with minimal ATP use?

Slow crossbridge dissociation Signup and view all the answers

How does the latch state contribute to the prolonged tension in smooth muscle?

By reducing energy expenditure Signup and view all the answers

Why does maximal velocity directly depend on cross-bridge phosphorylation in smooth muscle?

To speed up contraction and relaxation Signup and view all the answers

What mechanism allows smooth muscle to maintain force for long periods without extensive energy utilization?

Latch state with slow crossbridge dissociation Signup and view all the answers

Why does the heart operate at sarcomere lengths lower than the optimal?

To increase the force of contraction needed to eject blood Signup and view all the answers

Where is smooth muscle located in the body?

Vascular system, gastrointestinal tract, urinary system, reproductive system, and eye Signup and view all the answers

What is a characteristic of single-unit smooth muscle?

It requires neural or hormonal input for contraction to occur Signup and view all the answers

How do thick filaments in smooth muscle differ from skeletal muscle?

They are stabilized by dense bodies Signup and view all the answers

What is pharmacomechanical coupling in smooth muscle contraction?

Contraction coupled to changes in membrane potentials or ligand binding Signup and view all the answers

Why do some smooth muscles not require an action potential for contraction?

Because they have pacemaker cells that spontaneously fire action potentials Signup and view all the answers