Podcast
Questions and Answers
What is the role of IP3 in GPCR signaling?
What is the role of IP3 in GPCR signaling?
- It inhibits the action of Rho-kinase in smooth muscle contraction.
- It directly phosphorylates myosin light chains.
- It leads to increased intracellular calcium by binding to IP3 gated channels. (correct)
- It acts as a secondary messenger to activate PKC.
Which mechanism directly allows for smooth muscle contraction to sustain with minimal energy expenditure?
Which mechanism directly allows for smooth muscle contraction to sustain with minimal energy expenditure?
- The latch mechanism of myosin heads onto actin filaments. (correct)
- Phosphorylation of calmodulin leading to increased MLCK activity.
- Cross-bridge cycling between actin and phosphorylated myosin.
- Increased ATP hydrolysis by myosin heads.
What effect does the calcium-calmodulin complex have after its formation?
What effect does the calcium-calmodulin complex have after its formation?
- It re-stimulates GPCR activation leading to more calcium influx.
- It activates MLCK and inhibits calcium inhibitors like calponin. (correct)
- It directly phosphorylates myosin light chains, bypassing MLCK.
- It inhibits MLCK activity, reducing muscle contraction.
What initiates the process of muscle contraction in smooth muscle cells?
What initiates the process of muscle contraction in smooth muscle cells?
Which component is NOT involved in the activation of MLCK?
Which component is NOT involved in the activation of MLCK?
What is the primary function of DAG in the signaling cascade?
What is the primary function of DAG in the signaling cascade?
What triggers the smooth muscle relaxation process?
What triggers the smooth muscle relaxation process?
What is a common point of calcium signaling differentiation between smooth and skeletal muscle?
What is a common point of calcium signaling differentiation between smooth and skeletal muscle?
How does Rho-kinase affect muscle contraction?
How does Rho-kinase affect muscle contraction?
Which protein plays a critical role in the inhibition of actin-bound myosin ATPase during contraction?
Which protein plays a critical role in the inhibition of actin-bound myosin ATPase during contraction?
What initiates contraction in smooth muscle cells?
What initiates contraction in smooth muscle cells?
Which channel type is primarily responsible for calcium entry in smooth muscle cells?
Which channel type is primarily responsible for calcium entry in smooth muscle cells?
How does calcium-induced calcium release (CICR) occur in smooth muscle cells?
How does calcium-induced calcium release (CICR) occur in smooth muscle cells?
What differentiates contraction in skeletal muscle from contraction in smooth muscle?
What differentiates contraction in skeletal muscle from contraction in smooth muscle?
What role do varicosities play in smooth muscle contraction?
What role do varicosities play in smooth muscle contraction?
Which of the following factors does NOT stimulate smooth muscle contraction?
Which of the following factors does NOT stimulate smooth muscle contraction?
Smooth muscle relaxation primarily involves the dephosphorylation of which protein?
Smooth muscle relaxation primarily involves the dephosphorylation of which protein?
What is the primary messenger that mediates the action of hormones in smooth muscle?
What is the primary messenger that mediates the action of hormones in smooth muscle?
Which component is less developed in smooth muscle compared to skeletal muscle?
Which component is less developed in smooth muscle compared to skeletal muscle?
Which of the following correctly describes the function of calcium in smooth muscle?
Which of the following correctly describes the function of calcium in smooth muscle?
What is the primary consequence of a decrease in intracellular Ca²⁺ levels in smooth muscle?
What is the primary consequence of a decrease in intracellular Ca²⁺ levels in smooth muscle?
Which mechanism primarily contributes to the calcium influx necessary for smooth muscle contraction?
Which mechanism primarily contributes to the calcium influx necessary for smooth muscle contraction?
How do natural remedies such as peppermint oil help in alleviating symptoms of intestinal disorders?
How do natural remedies such as peppermint oil help in alleviating symptoms of intestinal disorders?
In contrast to skeletal muscle, smooth muscle excitation-contraction coupling primarily relies on which of the following?
In contrast to skeletal muscle, smooth muscle excitation-contraction coupling primarily relies on which of the following?
What role does inositol trisphosphate (IP3) play in smooth muscle contraction?
What role does inositol trisphosphate (IP3) play in smooth muscle contraction?
Which of the following best describes the function of myosin phosphatase (MLCP) in smooth muscle relaxation?
Which of the following best describes the function of myosin phosphatase (MLCP) in smooth muscle relaxation?
What is the effect of calcium-induced calcium release (CICR) in smooth muscle?
What is the effect of calcium-induced calcium release (CICR) in smooth muscle?
How does smooth muscle differ from striated muscle in terms of contraction mechanisms?
How does smooth muscle differ from striated muscle in terms of contraction mechanisms?
What role does Myosin Light Chain Kinase (MLCK) play in smooth muscle contraction?
What role does Myosin Light Chain Kinase (MLCK) play in smooth muscle contraction?
Smooth muscle relaxation occurs when calcium levels decrease. What is the immediate result of this decrease?
Smooth muscle relaxation occurs when calcium levels decrease. What is the immediate result of this decrease?
Which structure in smooth muscle cells is involved in regulating calcium signaling and enhancing contraction?
Which structure in smooth muscle cells is involved in regulating calcium signaling and enhancing contraction?
Which factor has a minor role in calcium influx during smooth muscle contraction compared to voltage-gated channels?
Which factor has a minor role in calcium influx during smooth muscle contraction compared to voltage-gated channels?
What unique feature of the sidepolar model allows smooth muscle myocytes to function effectively during contraction?
What unique feature of the sidepolar model allows smooth muscle myocytes to function effectively during contraction?
In smooth muscle, which protein is absent that distinguishes it from striated muscle regarding contraction modulation?
In smooth muscle, which protein is absent that distinguishes it from striated muscle regarding contraction modulation?
What effect does calcium binding to calmodulin have in smooth muscle cells?
What effect does calcium binding to calmodulin have in smooth muscle cells?
What is the primary structural characteristic of smooth muscle cells that contributes to their ability to contract in multiple directions?
What is the primary structural characteristic of smooth muscle cells that contributes to their ability to contract in multiple directions?
Which signaling pathway is primarily responsible for the activation of smooth muscle cells?
Which signaling pathway is primarily responsible for the activation of smooth muscle cells?
What is the primary function of dense plaques in smooth muscle cells?
What is the primary function of dense plaques in smooth muscle cells?
How does the organization of actin and myosin in smooth muscle contribute to its plasticity during changes in organ volume?
How does the organization of actin and myosin in smooth muscle contribute to its plasticity during changes in organ volume?
Flashcards are hidden until you start studying
Study Notes
Intracellular Calcium Dynamics
- Decrease in intracellular Ca²⁺ levels leads to calcium unbinding from calmodulin.
- Myosin light chain phosphatase (MLCP) dephosphorylates myosin, lowering its affinity for actin.
- Myosin-actin cross-bridges detach, resulting in reduced tension and muscle relaxation.
Irritable Bowel Syndrome (IBS)
- IBS is a gastrointestinal disorder marked by intestinal cramping, increased flatulence, and altered bowel habits.
- Treatment options are limited and may include antispasmodic medications.
- Natural remedies like peppermint oil can help by blocking Ca²⁺ channels in smooth muscle, promoting muscle relaxation.
Excitation-Contraction Coupling in Smooth vs. Skeletal Muscle
- In smooth muscle, excitation-contraction coupling is influenced by multiple competing signals converging on calcium, unlike the actin-mediated coupling in skeletal muscle.
- Three main calcium sources for smooth muscle contraction:
- Ca²⁺ influx across the sarcolemma.
- Calcium-induced calcium release (CICR) from the sarcoplasmic reticulum (SR).
- Inositol trisphosphate (IP3)-mediated Ca²⁺ release from the SR.
Calcium Influx Mechanisms
- Voltage-Gated Calcium Channels (VGCCs): Depolarization opens L-type channels, allowing extracellular Ca²⁺ to enter.
- Receptor-Operated Calcium Channels (ROCs): Aid in depolarization and Ca²⁺ flux, but have a minor influence in smooth muscle contraction.
Calcium-Induced Calcium Release (CICR)
- Initial extracellular Ca²⁺ influx activates ryanodine receptors (RyR) on the SR, releasing more calcium into the cytoplasm and enhancing contraction.
IP3-Mediated Calcium Release
- G-protein-coupled receptor (GPCR) activation generates inositol trisphosphate (IP3), which binds to its receptors on the SR, releasing calcium.
- Multiple signaling pathways involve phospholipase C (PLC) and Rho-kinase, ultimately influencing MLCP inhibition.
Smooth Muscle Contraction Process
- Influx of Ca²⁺ triggers the formation of Ca²⁺-calmodulin complex.
- This complex activates myosin light chain kinase (MLCK), which phosphorylates myosin light chains.
- Phosphorylated myosin interacts with actin, forming cross-bridges that lead to muscle contraction via power strokes.
Muscle Relaxation
- Occurs through stimulus removal, calcium pump activation (primarily SERCA), and removal of Ca²⁺ from the cytoplasm.
Structural Characteristics of Smooth Muscle
- Myocytes: Spindle-shaped, non-striated with a single nucleus, smaller than skeletal fibers.
- Cytoskeleton: Actin and myosin filaments arranged randomly, allowing multidirectional contraction; dense bodies anchor actin similarly to Z-discs in striated muscle.
- Calcium Signaling: Caveolae help concentrate signaling molecules and regulate calcium influx.
Differences in Myocyte Functionality
- Skeletal Muscle: Uses organized sarcomeres; contraction regulated by Ca²⁺ binding to troponin for rapid contractions.
- Smooth Muscle: Lacks sarcomeres; contraction regulated through phosphorylation via calmodulin and MLCK, allowing sustained contractions.
Neuromuscular Junction in Smooth Muscle
- Varicosities along the axon form the sites for neurotransmitter release, controlling contraction via the autonomic nervous system (ANS).
Adaptability of Smooth Muscle
- Capable of maintaining contractility as organ luminal volume changes due to inherent plasticity and structural features like minisarcomeres and dense plaques.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
