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Questions and Answers
Which ion primarily influences smooth muscle action potential?
Which ion primarily influences smooth muscle action potential?
How do smooth muscle action potentials compare to those in skeletal muscle and nerve cells?
How do smooth muscle action potentials compare to those in skeletal muscle and nerve cells?
What initiates spontaneous action potentials in some smooth muscles?
What initiates spontaneous action potentials in some smooth muscles?
Which of the following hormones enhances uterine contractions?
Which of the following hormones enhances uterine contractions?
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What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?
What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?
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What effect does mechanical stretch have on smooth muscle cells?
What effect does mechanical stretch have on smooth muscle cells?
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How many calcium ions can each calmodulin molecule bind?
How many calcium ions can each calmodulin molecule bind?
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Which pathway regulates smooth muscle contraction?
Which pathway regulates smooth muscle contraction?
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What is a key difference between smooth muscle action potentials and those in skeletal muscle?
What is a key difference between smooth muscle action potentials and those in skeletal muscle?
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Which of the following locations does smooth muscle NOT typically regulate?
Which of the following locations does smooth muscle NOT typically regulate?
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Which type of smooth muscle action potential can occur spontaneously in the muscle cells?
Which type of smooth muscle action potential can occur spontaneously in the muscle cells?
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Which component is responsible for activating the contraction cascade in smooth muscle cells?
Which component is responsible for activating the contraction cascade in smooth muscle cells?
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What is the resting membrane potential range for smooth muscle cells?
What is the resting membrane potential range for smooth muscle cells?
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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?
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Which structure initiates slow wave potentials in smooth muscle cells?
Which structure initiates slow wave potentials in smooth muscle cells?
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What happens during the plateau phase of the smooth muscle action potential?
What happens during the plateau phase of the smooth muscle action potential?
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What is the primary characteristic that distinguishes smooth muscle from striated muscle?
What is the primary characteristic that distinguishes smooth muscle from striated muscle?
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Which physiological feature is essential for smooth muscle contraction?
Which physiological feature is essential for smooth muscle contraction?
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What type of smooth muscle has gap junctions that allow for synchronized contraction?
What type of smooth muscle has gap junctions that allow for synchronized contraction?
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Which type of contraction is characterized by maintaining constant tension?
Which type of contraction is characterized by maintaining constant tension?
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What is the effect of the latch mechanism in smooth muscle?
What is the effect of the latch mechanism in smooth muscle?
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What is a key structural feature of smooth muscle cells?
What is a key structural feature of smooth muscle cells?
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How does smooth muscle adapt to prolonged stretching?
How does smooth muscle adapt to prolonged stretching?
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Which of the following factors can influence smooth muscle contraction?
Which of the following factors can influence smooth muscle contraction?
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Study Notes
Smooth Muscle Physiology
- Smooth muscle is a type of muscle tissue found in the walls of internal organs.
- It lacks the striations (sarcomeres) seen in skeletal muscle.
- Contractions are involuntary, slow, and sustained, controlled by the autonomic nervous system and hormones.
Smooth Muscle Structure
- Smooth muscle cells are spindle-shaped, wider in the middle and tapered at the ends.
- Each cell has a single nucleus.
- Cells are smaller in diameter than skeletal muscle cells and are shorter in length.
- Actin and myosin filaments are arranged irregularly, forming dense bodies.
- These dense bodies are similar to Z-discs found in skeletal muscle, anchoring actin filaments.
Smooth Muscle Physiological Features
- Contraction is calcium-dependent.
- Calcium influx into the cell triggers contraction.
- Contraction uses myosin light chain kinase (MLCK) to phosphorylate myosin for contraction.
- Contractions are triggered by an increase in intracellular calcium.
- Calcium binds to calmodulin, which then activates myosin light chain kinase (MLCK).
- MLCK phosphorylates myosin, enabling interaction with actin.
- Contraction is slow and sustained, allowing smooth muscle to perform various functions efficiently.
- Contraction is controlled by the autonomic nervous system.
- Hormonal mechanisms and local factors influence contraction.
- Smooth muscle responds to stretch.
Smooth Muscle Functional Features
- Smooth muscle demonstrates both phasic and tonic contractions.
- Phasic contractions are periodic, like peristalsis.
- Tonic contractions are continuous, like maintaining blood pressure.
- ATP consumption is low during smooth muscle contractions.
- The "latch mechanism" helps maintain prolonged tensions with minimal energy expenditure.
Types of Smooth Muscle
- Single-unit (visceral) smooth muscle: cells are electrically coupled by gap junctions, enabling synchronized contractions. Examples include intestines and uterus.
- Multi-unit smooth muscle: cells are not electrically coupled, allowing for independent and finer control. Examples include iris muscles and arrector pili muscles.
Smooth Muscle Locations
- Smooth muscle is found in blood vessels, digestive system, respiratory tract, and urinary system.
- Also present in the eye (iris and ciliary muscles).
Smooth Muscle Action Potentials
- Smooth muscle action potentials are various.
- They include slow-wave potentials (basal electrical rhythms) and spike potentials.
- Slow waves are spontaneous, rhythmic fluctuations in membrane potential that can trigger action potentials when a threshold is reached, while spike potentials are rapid changes in membrane potential.
Key Players in Smooth Muscle Contraction and Relaxation
- Calcium triggers the contraction cascade.
- Calmodulin binds calcium and activates myosin light chain kinase (MLCK).
- MLCK phosphorylates myosin, allowing for contraction.
- Myosin light chain phosphatase (MLCP) dephosphorylates myosin for relaxation.
Factors Triggering Smooth Muscle Action Potentials
- Neural stimulation (sympathetic and parasympathetic pathways).
- Hormones (e.g., oxytocin, adrenaline).
- Mechanical stretch.
- Local factors like changes in pH or oxygen levels.
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Description
This quiz explores the key features and structure of smooth muscle tissue. It covers aspects such as involuntary contractions, the arrangement of actin and myosin filaments, and the physiological mechanisms involved in contraction. Test your knowledge on the differences between smooth and skeletal muscle.
