Podcast
Questions and Answers
What primarily initiates a slow wave potential in smooth muscle cells?
What primarily initiates a slow wave potential in smooth muscle cells?
- Calcium influx from the ECF
- Intrinsic rhythmic activity of the muscle itself (correct)
- Action potentials from neighboring cells
- Extrinsic neural stimulation
How does calcium primarily enter smooth muscle cells to trigger contraction?
How does calcium primarily enter smooth muscle cells to trigger contraction?
- Endocytosis processes that engulf calcium ions
- Through specialized channels unique to smooth muscle
- Via diffusion through the membrane due to small size (correct)
- Transport proteins that require ATP
What is the result of a slow wave reaching -35 mV in smooth muscle cells?
What is the result of a slow wave reaching -35 mV in smooth muscle cells?
- Causes complete muscle relaxation
- Initiates a full action potential that spreads across the muscle (correct)
- Leads to the generation of a local potential only
- Triggers calcium release from the sarcoplasmic reticulum
What characterizes caveoli in smooth muscle cells?
What characterizes caveoli in smooth muscle cells?
What effect does stretching visceral smooth muscle have on its activity?
What effect does stretching visceral smooth muscle have on its activity?
What type of muscle contraction is characterized by a prolonged, tonic contraction lasting for hours or days?
What type of muscle contraction is characterized by a prolonged, tonic contraction lasting for hours or days?
Which component of smooth muscle plays a role similar to Z discs in skeletal muscle?
Which component of smooth muscle plays a role similar to Z discs in skeletal muscle?
What is a key feature of the cross-bridge cycling in smooth muscle compared to skeletal muscle?
What is a key feature of the cross-bridge cycling in smooth muscle compared to skeletal muscle?
What primarily characterizes the energy requirement of smooth muscle?
What primarily characterizes the energy requirement of smooth muscle?
Which of the following types of smooth muscle is known for its unitary contraction?
Which of the following types of smooth muscle is known for its unitary contraction?
What is the primary function of the protein bridges linking dense bodies in smooth muscle?
What is the primary function of the protein bridges linking dense bodies in smooth muscle?
Which of the following best describes the sustained duration of smooth muscle contraction?
Which of the following best describes the sustained duration of smooth muscle contraction?
How does the abundance of actin and myosin in smooth muscle compare to skeletal muscle?
How does the abundance of actin and myosin in smooth muscle compare to skeletal muscle?
Which neurotransmitter is primarily responsible for stimulating contraction in smooth muscle?
Which neurotransmitter is primarily responsible for stimulating contraction in smooth muscle?
What allows smooth muscle to maintain a full force of contraction with minimal energy consumption?
What allows smooth muscle to maintain a full force of contraction with minimal energy consumption?
What determines whether smooth muscle will be excited or inhibited by a neurotransmitter?
What determines whether smooth muscle will be excited or inhibited by a neurotransmitter?
Which characteristic distinguishes multi-unit smooth muscle from single-unit smooth muscle?
Which characteristic distinguishes multi-unit smooth muscle from single-unit smooth muscle?
Which of the following correctly describes the action potential of visceral smooth muscle?
Which of the following correctly describes the action potential of visceral smooth muscle?
How does smooth muscle compare to skeletal muscle in terms of contraction force?
How does smooth muscle compare to skeletal muscle in terms of contraction force?
What role do calcium channels play in smooth muscle action potentials?
What role do calcium channels play in smooth muscle action potentials?
What structural feature of single-unit smooth muscle contributes to synchronized contraction?
What structural feature of single-unit smooth muscle contributes to synchronized contraction?
Which statement about hormones affecting smooth muscle contraction is accurate?
Which statement about hormones affecting smooth muscle contraction is accurate?
What determines the flexibility of smooth muscle in shortening its length?
What determines the flexibility of smooth muscle in shortening its length?
Which of the following examples best represents multi-unit smooth muscle?
Which of the following examples best represents multi-unit smooth muscle?
What contributes to the reduced need for excitatory signals in smooth muscle contraction?
What contributes to the reduced need for excitatory signals in smooth muscle contraction?
What structure allows ions to flow freely between smooth muscle cells?
What structure allows ions to flow freely between smooth muscle cells?
What is a key feature of the latch phenomenon in smooth muscle physiology?
What is a key feature of the latch phenomenon in smooth muscle physiology?
Which component does NOT play a role in the contraction of smooth muscle?
Which component does NOT play a role in the contraction of smooth muscle?
What initiates the phosphorylation of the myosin light chain in smooth muscle contraction?
What initiates the phosphorylation of the myosin light chain in smooth muscle contraction?
How does smooth muscle respond to being elongated or shortened?
How does smooth muscle respond to being elongated or shortened?
What role does calcium play in smooth muscle contraction?
What role does calcium play in smooth muscle contraction?
In which type of muscle is troponin absent?
In which type of muscle is troponin absent?
Which statement about the action potential in smooth muscle is true?
Which statement about the action potential in smooth muscle is true?
What happens during the power stroke of smooth muscle contraction?
What happens during the power stroke of smooth muscle contraction?
Study Notes
Smooth Muscle Physiology
- Smooth muscle cells are connected via dense bodies that serve a role similar to Z discs in skeletal muscle.
- Contains a higher proportion of actin and much less myosin compared to skeletal muscle.
- Two main types of smooth muscle:
- Multi-unit: Fibers function independently, each innervated by a single nerve ending (e.g., iris and ciliary muscles).
- Single-unit (syncytial): Fibers contract in unison due to many gap junctions, found in walls of viscera like the gut and blood vessels.
Smooth Muscle Contraction Characteristics
- Exhibits prolonged, tonic contraction lasting hours or days compared to the rapid contractions of skeletal muscle.
- Slow cycling of cross-bridges results in longer attachment times between actin and myosin.
- Very low energy requirement makes smooth muscle economical.
- Capable of sustaining contraction force greater than that of skeletal muscle.
- High flexibility in shortening, able to maintain force while shortening a significant percentage of its length.
- The latch mechanism allows maintenance of contraction strength with minimal energy expenditure.
Regulation of Contraction
- Contraction triggered by calcium ions (Ca++), binding to calmodulin, an essential regulatory process.
- Calcium influx through slower-opening calcium channels contributes to unique action potentials in smooth muscle.
- Stress-relaxation allows smooth muscle to adapt its contraction force after being stretched or shortened.
Action Potentials and Calcium Role
- Two types of action potentials exist:
- Spike potential: resembles skeletal action potentials; duration of 10-50 ms; can be induced by various stimuli.
- Action potential with plateau: includes a prolonged depolarization phase, lasting several hundred milliseconds.
- The primary source of Ca++ for contraction is extracellular fluid, facilitated by rudimentary structures like caveoli.
Hormonal Influence and Neural Control
- Hormones can initiate contractions through specific receptors on muscle fibers; some hormones may induce inhibition depending on receptor type.
- Neurotransmitters such as acetylcholine and norepinephrine modulate muscle contraction through diffuse junctions and varicosities.
- The resting membrane potential of smooth muscle is between -50 mV to -60 mV, influencing excitability.
Summary of Key Mechanisms
- Calcium channels in smooth muscle membranes play a vital role in generating action potentials, more so than sodium channels.
- The overall contraction mechanism relies on the synchronized activity among muscle fibers and the regulatory effects of calcium and hormones.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the fundamental concepts of smooth muscle physiology as outlined in the first bimonthly assessment. Participants will explore the structure, function, and importance of smooth muscle in the human body. Enhance your understanding of how smooth muscle contributes to various physiological processes.
