Myofilaments and Muscle Contraction

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Questions and Answers

Which type of muscle is controlled consciously and attached to the skeleton?

Skeletal muscle (correct)

Smooth muscle

Cardiac muscle

None of the above

Which type of muscle is found in the walls of blood vessels and internal organs?

Skeletal muscle

Smooth muscle (correct)

Cardiac muscle

None of the above

Which type of muscle is only found in the heart?

Skeletal muscle

Smooth muscle

Cardiac muscle (correct)

None of the above

Which property of muscles allows them to be stretched or lengthened beyond their resting length?

Extensibility Signup and view all the answers

Which property of muscles allows them to return to their original shape after being stretched or contracted?

Elasticity Signup and view all the answers

Which property of muscles enables them to generate tension by contracting or shortening?

Contractility Signup and view all the answers

Which organelle is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber?

Sarcoplasmic reticulum Signup and view all the answers

What is the function of T-tubules in a muscle fiber?

Allow for rapid transmission of the action potential into the cell Signup and view all the answers

Which protein is responsible for binding both ATP and actin in a muscle fiber?

Myosin Signup and view all the answers

Which component of a myosin filament forms cross-bridges with actin to shorten the sarcomere?

Myosin heads Signup and view all the answers

Which protein complex is composed of actin, tropomyosin, and troponin in a muscle fiber?

Thin filament Signup and view all the answers

Which type of muscle fiber has more mitochondria and is responsible for slow-twitch contractions?

Red fibers Signup and view all the answers

Which type of muscle fiber has a high aerobic capacity and fatigue resistance?

Type I Signup and view all the answers

Which type of muscle fiber has a moderate aerobic capacity and high anaerobic capacity?

Type IIa Signup and view all the answers

Which type of muscle fiber has a low aerobic capacity and high anaerobic capacity?

Type IIb Signup and view all the answers

What is the primary function of satellite cells in skeletal muscles?

Repair damaged muscle fibers Signup and view all the answers

What is the primary function of myostatin in muscle biology?

Regulate muscle growth and development Signup and view all the answers

Which type of muscle action is responsible for elbow flexion?

Agonists Signup and view all the answers

Which property is not associated with muscle fibers?

Elasticity Signup and view all the answers

What is the primary function of skeletal muscles?

To enable movement of the body Signup and view all the answers

What is the role of the epimysium?

To surround the entire muscle Signup and view all the answers

What is the basic contractile unit of striated muscle fibers?

Sarcomeres Signup and view all the answers

What is the function of the T-tubules in muscle cells?

To invaginate into the sarcoplasm Signup and view all the answers

What are the two types of muscle fibers?

Slow fibers and Fast fibers Signup and view all the answers

According to the Sliding Filament Model of Muscle Contraction, how does a muscle shorten or lengthen?

The thick and thin filaments change length Signup and view all the answers

What happens when calcium ions bind to the troponin-tropomyosin complex?

The cross bridge is formed Signup and view all the answers

What is the source of energy for muscle action?

ATP Signup and view all the answers

What causes the actin filaments to slide toward the M line during muscle contraction?

The myosin heads bend toward the center of the sarcomere Signup and view all the answers

What type of muscle fibers have high aerobic endurance and are suited to low-intensity endurance activities?

Type I (Red) Signup and view all the answers

What type of muscle fibers are better for anaerobic or explosive activities?

Type II (White) Signup and view all the answers

Which type of stimuli can smooth muscle respond to?

All of the above Signup and view all the answers

What type of nervous system signals does smooth muscle receive?

Both sympathetic and parasympathetic nervous system signals Signup and view all the answers

How is smooth muscle organized?

Into sheets Signup and view all the answers

What are the physical dimensions of smooth muscle determined by?

All of the above Signup and view all the answers

Which of the following is NOT a factor that smooth muscle can respond to?

Hydrogen gas levels Signup and view all the answers

What is the primary function of smooth muscle?

To regulate digestion Signup and view all the answers

Which type of muscle is smooth muscle?

Involuntary muscle Signup and view all the answers

What are the dimensions of smooth muscle determined by?

All of the above Signup and view all the answers

Which type of muscle receives nerve signals from the autonomic nervous system?

All of the above Signup and view all the answers

What enables coordinated contractions in smooth muscle?

Bundles or sheets Signup and view all the answers

What is the main function of smooth muscle in the gastrointestinal tract?

Peristaltic contraction Signup and view all the answers

Which type of smooth muscle is found in the ciliary muscles of the eyes?

Multi-unit smooth muscle Signup and view all the answers

What is the main difference between smooth muscle and skeletal muscle in terms of actin and myosin arrangement?

Smooth muscle has myosin filaments attached to dense bodies Signup and view all the answers

What is the main source of Ca2+ for smooth muscle contraction?

Extra cellular fluid Signup and view all the answers

Which type of muscle fiber has the highest aerobic capacity and fatigue resistance?

Slow-twitch muscle fibers Signup and view all the answers

What is the main function of the iris muscle in the eyes?

Pupil constriction and dilation Signup and view all the answers

What is the main function of smooth muscle in the walls of blood vessels?

Regulation of blood flow Signup and view all the answers

Which property of smooth muscle allows it to contract as much as 80% of its length?

Side-polar cross-bridges in myosin filaments Signup and view all the answers

What is the main function of smooth muscle in the uterus?

Contraction during childbirth Signup and view all the answers

What is the main function of smooth muscle in the base of hair follicles?

Hair erection Signup and view all the answers

Which organelle is responsible for storing, releasing, and reuptake of calcium ions in smooth muscle cells?

Sarcoplasmic reticulum Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

To regulate the contraction process Signup and view all the answers

Which enzyme is activated by calmodulin in smooth muscle contraction?

Myosin light chain kinase (MLCK) Signup and view all the answers

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

To phosphorylate myosin Signup and view all the answers

What happens when the ion calcium concentration is reduced in smooth muscle cells?

Myosin phosphatase removes phosphate from myosin Signup and view all the answers

Which type of muscle uses calmodulin as a calcium-binding protein to regulate the contraction process?

Smooth muscle Signup and view all the answers

Which component of a myosin filament forms cross-bridges with actin to shorten the sarcomere?

Myosin heads Signup and view all the answers

What is the primary function of satellite cells in smooth muscles?

To repair and regenerate muscle tissue Signup and view all the answers

What is the role of caveolae in smooth muscle cells?

To excite calcium release from the SR Signup and view all the answers

Which type of muscle fiber has a low aerobic capacity and high anaerobic capacity?

Type IIb fibers Signup and view all the answers

Which type of muscle receives nerve signals from the autonomic nervous system?

Smooth muscle Signup and view all the answers

What is the main function of smooth muscle in the uterus?

Childbirth Signup and view all the answers

What are the dimensions of smooth muscle determined by?

Physical factors Signup and view all the answers

What enables coordinated contractions in smooth muscle?

Neural factors Signup and view all the answers

What is the role of caveolae in smooth muscle cells?

Cellular communication Signup and view all the answers

What type of stimuli can smooth muscle respond to?

All of the above Signup and view all the answers

What is the source of energy for muscle action?

ATP Signup and view all the answers

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

Activating myosin cross-bridges Signup and view all the answers

What happens when the ion calcium concentration is reduced in smooth muscle cells?

Muscle relaxation Signup and view all the answers

Which organelle is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber?

Sarcoplasmic reticulum Signup and view all the answers

Which of the following is true about smooth muscle contraction?

Calcium-bound calmodulin activates myosin light chain kinase (MLCK). Signup and view all the answers

Which organelle is responsible for calcium release in smooth muscle cells?

Endoplasmic reticulum (ER) Signup and view all the answers

What is the role of caveolae in smooth muscle cells?

They are small invaginations of the cell membrane. Signup and view all the answers

Which type of muscle uses troponin as a calcium-binding protein?

Skeletal muscle Signup and view all the answers

Which enzyme is responsible for phosphorylating myosin in smooth muscle cells?

Myosin light chain kinase (MLCK) Signup and view all the answers

What happens when myosin is phosphorylated in smooth muscle cells?

Myosin binds to actin, causing muscle contraction. Signup and view all the answers

Which type of muscle fiber has the highest aerobic capacity and fatigue resistance?

Type I fibers Signup and view all the answers

What is the primary function of myosin phosphatase in smooth muscle cells?

To remove phosphate from myosin Signup and view all the answers

Which muscle type uses calmodulin as a calcium-binding protein?

Smooth muscle Signup and view all the answers

What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

To store and release calcium ions Signup and view all the answers

What is the main difference between single-unit smooth muscle and multi-unit smooth muscle?

Single-unit smooth muscle fibers are arranged in sheets or bundles, while multi-unit smooth muscle fibers are discrete and separate Signup and view all the answers

Which muscles are examples of single-unit smooth muscle?

Gastrointestinal tract and bile ducts Signup and view all the answers

How do smooth muscle cells contract?

Through the sliding filament mechanism Signup and view all the answers

What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

It regulates the binding of calcium to calmodulin in smooth muscle cells Signup and view all the answers

What is the function of caveolae in smooth muscle cells?

To regulate the contraction process by binding calcium ions Signup and view all the answers

What is the main function of smooth muscle in the uterus?

Contraction during childbirth and menstruation Signup and view all the answers

What is the main difference between smooth muscle and skeletal muscle in terms of contraction?

Smooth muscle can contract as much as 80% of its length, while skeletal muscle can only contract up to 30% of its length Signup and view all the answers

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

To phosphorylate myosin and initiate cross-bridge cycling Signup and view all the answers

What is the main function of smooth muscle in the gastrointestinal tract?

Peristaltic contraction Signup and view all the answers

What enables coordinated contractions in smooth muscle?

The presence of many gap junctions between muscle cells Signup and view all the answers

Study Notes

Muscle Types

Skeletal muscle is controlled consciously and attached to the skeleton
Smooth muscle is found in the walls of blood vessels and internal organs
Cardiac muscle is only found in the heart

Muscle Properties

Elasticity is the property that allows muscles to be stretched or lengthened beyond their resting length
Elasticity is the property that allows muscles to return to their original shape after being stretched or contracted
Contractility is the property that enables muscles to generate tension by contracting or shortening

Muscle Fiber Components

The sarcoplasmic reticulum is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber
T-tubules are involved in the function of a muscle fiber
Actin and myosin are proteins in a muscle fiber
Myosin is responsible for binding ATP and actin in a muscle fiber
The component of a myosin filament that forms cross-bridges with actin to shorten the sarcomere is the myosin head
Actin, tropomyosin, and troponin form a complex in a muscle fiber

Muscle Fiber Types

Slow-twitch (Type I) muscle fibers have more mitochondria and are responsible for slow-twitch contractions
Fast-twitch (Type II) muscle fibers have a high anaerobic capacity
Intermediate (Type IIa) muscle fibers have a moderate aerobic capacity and high anaerobic capacity

Muscle Functions

The primary function of satellite cells in skeletal muscles is to repair and regenerate muscle tissue
The primary function of myostatin in muscle biology is to inhibit muscle growth and development
The primary function of skeletal muscles is to provide movement, maintain posture, and regulate body temperature
The role of the epimysium is to surround and protect the entire muscle
The basic contractile unit of striated muscle fibers is the sarcomere

Smooth Muscle Functions

Smooth muscle receives nerve signals from the autonomic nervous system
The primary function of smooth muscle is to control the diameter of blood vessels, regulate body temperature, and aid in digestion
Smooth muscle can respond to hormonal, neural, and local stimuli
Smooth muscle is organized into single-unit and multi-unit types
The physical dimensions of smooth muscle are determined by the length and diameter of the muscle fibers
The primary function of smooth muscle in the gastrointestinal tract is to mix food with digestive enzymes
The primary function of smooth muscle in the uterus is to aid in childbirth
The primary function of smooth muscle in the base of hair follicles is to regulate hair growth

Smooth Muscle Contraction

Smooth muscle contraction is regulated by calcium ions and calmodulin
The enzyme myosin light chain kinase (MLCK) is activated by calmodulin to phosphorylate myosin
Phosphorylated myosin then interacts with actin to shorten the sarcomere
The sarcoplasmic reticulum is responsible for storing, releasing, and reuptake of calcium ions in smooth muscle cells
The role of caveolae is to regulate the contraction process by modulating calcium release

Muscle Comparisons

Smooth muscle differs from skeletal muscle in terms of actin and myosin arrangement
Smooth muscle can contract as much as 80% of its length due to its unique properties

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Description

Test your knowledge on myofilaments and their role in muscle contraction with this quiz. Learn about the components of thin and thick filaments, the arrangement of filaments in a sarcomere, and the structure of myosin molecules.