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Questions and Answers
What is the primary function of skeletal muscles?
What is the primary function of skeletal muscles?
- To enable voluntary body movements (correct)
- To pump blood throughout the body
- To line the digestive tract
- To facilitate involuntary movements in organs
Which of the following is a characteristic of smooth muscles?
Which of the following is a characteristic of smooth muscles?
- Involuntary control and non-striated appearance (correct)
- Specialized to contract rapidly and fatigue quickly
- Striated appearance and voluntary control
- Highly vascularized and multinucleated fibers
What role does cardiac muscle play in the body?
What role does cardiac muscle play in the body?
- Pumps blood through the circulatory system (correct)
- Controls voluntary movements of limbs
- Supports the movement of air in the lungs
- Facilitates digestion by moving food
What is the action of actin and myosin in muscle contraction?
What is the action of actin and myosin in muscle contraction?
Which statement regarding cardiac muscle is true?
Which statement regarding cardiac muscle is true?
What is the primary role of myoglobin in muscle fibres?
What is the primary role of myoglobin in muscle fibres?
Which component regulates the entry and exit of materials in muscle fibres?
Which component regulates the entry and exit of materials in muscle fibres?
What is the function of the sarcoplasmic reticulum in muscle contraction?
What is the function of the sarcoplasmic reticulum in muscle contraction?
What occurs when myosin heads attach to actin during muscle contraction?
What occurs when myosin heads attach to actin during muscle contraction?
What initiates the sliding process of actin and myosin during muscle contraction?
What initiates the sliding process of actin and myosin during muscle contraction?
What prevents contraction when a muscle is relaxed?
What prevents contraction when a muscle is relaxed?
Which proteins block myosin attachment sites on actin when muscle contractions are not occurring?
Which proteins block myosin attachment sites on actin when muscle contractions are not occurring?
The shortening of the muscle occurs due to which mechanism during contraction?
The shortening of the muscle occurs due to which mechanism during contraction?
What structure within muscle fibres contains organized bundles of myofilaments?
What structure within muscle fibres contains organized bundles of myofilaments?
When calcium ions are released from the sarcoplasmic reticulum during contraction, what is the consequence?
When calcium ions are released from the sarcoplasmic reticulum during contraction, what is the consequence?
Flashcards
What is the primary function of skeletal muscle?
What is the primary function of skeletal muscle?
Skeletal muscles are responsible for voluntary movement, which allows us to walk, run, talk, and perform other conscious actions. They also play a role in maintaining posture and stabilizing joints.
What are the main characteristics of skeletal muscle?
What are the main characteristics of skeletal muscle?
Skeletal muscles are characterized by their striated appearance, meaning they have a striped pattern under a microscope. They are also voluntary, meaning we can consciously control their movements.
Where is smooth muscle found and what type of contractions does it have?
Where is smooth muscle found and what type of contractions does it have?
Smooth muscles are found in the walls of internal organs like the stomach, intestines, blood vessels, and bladder. Their contractions are involuntary, meaning we don't consciously control them.
What are the unique features of cardiac muscle?
What are the unique features of cardiac muscle?
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Describe the mechanism of muscle contraction and heat production.
Describe the mechanism of muscle contraction and heat production.
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Muscle Fiber
Muscle Fiber
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Myoglobin
Myoglobin
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Sarcolemma
Sarcolemma
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Sarcoplasm
Sarcoplasm
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Sarcoplasmic Reticulum
Sarcoplasmic Reticulum
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Myofibrils
Myofibrils
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Thick Myofilament (Myosin)
Thick Myofilament (Myosin)
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Thin Myofilament (Actin)
Thin Myofilament (Actin)
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Tropomyosin
Tropomyosin
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Troponin
Troponin
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Study Notes
Types of Muscle Tissue
- Skeletal muscles are responsible for movement of the skeleton.
- Smooth muscles are found in internal organs and blood vessels.
- Cardiac muscles are found in the heart.
Traits of Skeletal Muscles
- Voluntary control
- Striated appearance
- Multi-nucleated cells
- Responsible for locomotion and movements of the skeleton
Traits of Smooth Muscles
- Involuntary control
- Non-striated appearance
- Single-nucleated cells
- Responsible for involuntary movements in internal organs
Traits of Cardiac Muscles
- Involuntary control
- Striated appearance
- Single-nucleated cells
- Responsible for pumping blood throughout the body
Skeletal Muscle Structures and Functions
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Muscle fiber: Single muscle cell responsible for muscle contractions.
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Myoglobin: Stores oxygen for muscle contractions.
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Sarcolemma: Membrane of the muscle fiber, regulates material exchange.
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Sarcoplasm: Cytoplasm of a muscle fiber, site of cellular processes and stores glycogen (energy source).
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Sarcoplasmic Reticulum: Smooth endoplasmic reticulum in muscle fiber, stores calcium ions.
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Myofibrils: Bundles of myofilaments, cylindrical structures within muscle fibers, containing protein filaments responsible for contractions.
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Myofilament (thick) – Myosin: Protein filaments (~11 nm), bind to actin and cause contractions.
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Myofilament (thin) – Actin: Protein filaments (~5 nm), bind to myosin and cause contractions.
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When muscles contract, they shorten, causing movement.
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Muscles are arranged in antagonistic pairs (e.g., biceps and triceps), where one muscle contracts while the other relaxes.
Mechanism of Muscle Fibre Contraction
Structure of Myofilaments
- Actin Myofilaments: Composed of globular actin proteins; contain tropomyosin (blocks myosin binding sites when needed) and troponin (calcium-binding protein).
- Myosin Filaments: Two polypeptide chains wrapped around each other, with globular heads (myosin heads) protruding at regular intervals, capable of binding to actin and causing motion.
The Sliding Filament Model of Muscle Contraction
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During muscle contraction, the actin filaments slide past the myosin filaments, shortening the muscle fiber.
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Myosin Attach: Myosin heads bind to actin binding sites.
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Myosin Flex: Myosin heads pivot, pulling the actin filaments.
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Myosin Release: Myosin heads detach from actin sites.
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Myosin Reattach: Myosin heads reattach to new actin sites further along the filament.
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The actin filaments are pulled towards the center of the sarcomere, and the Z lines move closer together. The sarcomere shortens, and the muscle fiber contracts.
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The myosin heads are alternately pulling opposite sides of the actin filament.
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Muscle shortening causes change in the arrangement of molecules in the plasma membrane.
Muscle Contraction
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Relaxed muscle: Tropomyosin blocks actin binding sites, preventing myosin interaction.
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Muscle contraction: Calcium ions bind to troponin, causing a shift in the position of tropomyosin, exposing the binding sites on actin for myosin.
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Calcium ions are stored in the sarcoplasmic reticulum. The release of calcium ions is triggered by nerve impulses causing a signal cascade leading to the release.Â
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Calcium ions are released into the sarcoplasm which causes contraction.
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