Anatomy Chapter 9 Flashcards

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Questions and Answers

Describe the difference between a tendon and an aponeurosis.

A tendon is a projection of connective tissue beyond the ends of the muscle that attaches to bone. An aponeurosis is a broad fibrous sheet of connective tissue that connects muscles to adjacent muscles.

Describe how connective tissue is part of the structure of a skeletal muscle.

Muscle fibers are grouped together in fascicles that are surrounded by endomysium. The fascicles are bundled together and surrounded by perimysium. The entire muscle is covered by epimysium.

Distinguish among deep fascia, subcutaneous fascia, and subserous fascia.

Deep fascia surrounds and penetrates muscles. Subcutaneous fascia lies just beneath the skin. Subserous fascia forms the connective tissue layer of serous membranes covering organs.

Identify the major parts of a skeletal muscle fiber and describe the functions of each.

A muscle fiber has a sarcolemma (cell membrane), sarcoplasm (cytoplasm), myofibrils (threadlike proteins), sarcomeres (segments of myofibrils), sarcoplasmic reticulum (network of channels), and transverse tubules (invaginations for stimulation). Signup and view all the answers

Describe the neuromuscular junction.

The neuromuscular junction is the site where a nerve fiber communicates with a muscle fiber, allowing for muscle contractions via stimulation. Signup and view all the answers

Describe the neural control of skeletal muscle contraction.

A neurotransmitter is released into the gap at the motor end plate when stimulated, which stimulates the muscle fiber to contract. Signup and view all the answers

Identify the major events that occur during skeletal muscle fiber contraction.

Skeletal muscle contraction involves the sliding movement of actin and myosin filaments due to muscle parts and chemical substances. Signup and view all the answers

Explain how ATP and creatine phosphate function in skeletal muscle fiber contraction.

ATP supplies energy for muscle contraction, while creatine phosphate acts as an energy reservoir for ADP. Signup and view all the answers

Describe how oxygen is supplied to skeletal muscle.

Oxygen is carried by hemoglobin in the blood and transferred to myoglobin in muscle fibers. Signup and view all the answers

Describe how oxygen debt may develop.

Oxygen debt occurs when skeletal muscles exceed their oxygen reserves, leading to anaerobic respiration and lactic acid accumulation. Signup and view all the answers

Explain how a muscle may become fatigued, and how a person's physical condition may affect tolerance to fatigue.

Muscle fatigue occurs from prolonged strenuous exercise, often due to lactic acid accumulation, diminished blood supply, or acetylcholine depletion. Signup and view all the answers

Define threshold stimulus.

The threshold stimulus is the minimal strength of stimulus required to trigger a muscle fiber response. Signup and view all the answers

Distinguish between a twitch and a sustained contraction.

A twitch is a single muscle fiber contraction, while sustained contraction involves multiple action potentials leading to increasing contraction strength. Signup and view all the answers

Define motor unit and explain how the number of fibers within a unit affects muscular contractions.

A motor unit consists of a motor neuron and the muscle fibers it controls; fewer fibers allow for more precise movements. Signup and view all the answers

What is recruitment of motor units?

Recruitment is the increase in the number of activated motor units as stimulation intensity increases. Signup and view all the answers

Explain how a skeletal muscle can be stimulated to produce a sustained contraction.

A muscle can sustain contraction when stimuli increase in frequency to prevent complete relaxation before the next stimulus. Signup and view all the answers

Distinguish between a complete tetanic contraction and muscle tone.

Tetanic contraction is a sustained forceful contraction without relaxation, while muscle tone maintains posture through small, repeated contractions. Signup and view all the answers

Distinguish between isotonic and isometric contractions.

Isotonic contractions involve muscle shortening, while isometric contractions occur with tension without movement. Signup and view all the answers

Distinguish between fast- and slow-twitch muscle fibers.

Fast-twitch fibers contract rapidly and fatigue quickly, while slow-twitch fibers are fatigue-resistant, supporting prolonged activity. Signup and view all the answers

Distinguish between multiunit smooth muscle and visceral smooth muscle.

Multiunit smooth muscle consists of separate fibers and requires nerve impulse stimulation, while visceral smooth muscle has interconnected fibers capable of stimulating each other. Signup and view all the answers

Define peristalsis and explain its function.

Peristalsis consists of alternating contractions and relaxations of muscle fibers, forcing contents along a tube. Signup and view all the answers

Compare the characteristics of skeletal and smooth muscle cell contractions.

Both types use actin and myosin, triggered by membrane impulses, but skeletal muscle uses acetylcholine, while smooth muscle uses both acetylcholine and norepinephrine. Signup and view all the answers

Compare the characteristics of skeletal and cardiac muscle cell contractions.

Skeletal muscle contracts individually, while cardiac muscle works in a coordinated network and occurs only in the heart. Signup and view all the answers

Describe a lever, and explain how its parts may be arranged to form first-class, second-class, and third-class levers.

A lever has a rigid rod, fulcrum, resistance, and force. First-class: resistance-fulcrum-force; Second-class: fulcrum-resistance-force; Third-class: resistance-force-fulcrum. Signup and view all the answers

Explain how limb movements function as levers.

Limb movements act as levers by utilizing rigid bars, pivots, resistance, and force. Signup and view all the answers

Describe three aging-related changes in the muscular system.

<ol> <li>Decline in myoglobin, ATP, and creatine. 2) Muscles become smaller and drier. 3) By age 80, half of muscle mass may be atrophied.</li> </ol> Signup and view all the answers

Explain the benefits of exercise for maintaining muscular health while aging.

Exercise can promote muscle growth, maintain blood pressure, and enhance oxygen levels and endurance. Signup and view all the answers

Study Notes

Differences Between Tendons and Aponeuroses

Tendons attach muscle to bone, comprised of connective tissue projections.
Aponeuroses serve as broad, fibrous sheets connecting adjacent muscles.

Connective Tissue in Skeletal Muscle Structure

Muscle fibers are bundled in fascicles, surrounded by endomysium.
Fascicles are encased in perimysium, while the entire muscle is covered by epimysium.

Types of Fascia

Deep fascia surrounds and penetrates muscles, providing structural integrity.
Subcutaneous fascia lies beneath the skin, forming the outer layer.
Subserous fascia is the connective tissue layer for serous membranes covering organs.

Major Components of Skeletal Muscle Fiber

Sarcolemma: cell membrane of a muscle fiber.
Sarcoplasm: cytoplasm of a muscle fiber.
Myofibrils: proteins in parallel arrangement contributing to muscle striations.
Sarcomere: myofibril segment between Z lines, essential for contraction.
Sarcoplasmic reticulum: endoplasmic reticulum network around myofibrils.
Transverse tubules: inward extensions of sarcoplasm for signal transmission.

Neuromuscular Junction

The site where nerve fibers communicate with muscle fibers is crucial for contraction.
It includes the motor end plate, where nerve branches connect and release neurotransmitters.

Neural Control of Muscle Contraction

Neurotransmitters, released into the motor end plate gap, are essential to stimulate muscle contraction.

Events During Muscle Contraction

Involves actin and myosin filament sliding, driven by cross-bridges formed by myosin interacting with actin active sites.

Role of ATP and Creatine Phosphate

ATP is the primary energy source for contractions, provided by mitochondria.
Creatine phosphate stores energy, facilitating the regeneration of ATP but cannot directly supply energy.

Oxygen Supply to Skeletal Muscle

Hemoglobin transports oxygen from lungs to muscles, transferring it to myoglobin within muscle fibers for storage.

Development of Oxygen Debt

Oxygen debt occurs when muscle activity exceeds oxygen reserves, leading to anaerobic respiration and lactic acid accumulation.

Muscle Fatigue and Physical Condition

Muscle fatigue results from prolonged exercise, blood supply interruption, or lactic acid buildup.
Regular exercise enhances capillary growth, improving nutrient and oxygen delivery, thereby reducing fatigue risk.

Threshold Stimulus

The minimum stimulus strength required to elicit a muscle fiber contraction is known as the threshold stimulus.

Twitch vs. Sustained Contraction

A twitch is a brief contraction of a muscle fiber in response to an impulse.
Sustained contraction occurs when multiple action potentials create a stronger, prolonged response.

Motor Unit and Fiber Impact

A motor unit consists of a motor neuron and muscle fibers it controls; fewer fibers allow for more precise movements.

Recruitment of Motor Units

The activation of additional motor units for stronger contractions is termed multiple motor unit summation.

Sustained Muscle Contraction Stimulation

Rapid, successive stimuli prevent complete relaxation, resulting in a sustained contraction.

Complete Tetanic Contraction vs. Muscle Tone

Tetanic contraction is a continuous forceful contraction without any relaxation.
Muscle tone maintains posture through involuntary nerve impulses affecting small muscle fiber groups.

Isotonic vs. Isometric Contractions

Isotonic contractions involve muscle shortening, while isometric contractions maintain tension without movement.

Fast-twitch vs. Slow-twitch Muscle Fibers

Fast-twitch fibers contract quickly but fatigue faster, having less myoglobin and fewer mitochondria.
Slow-twitch fibers sustain longer contractions, equipped with ample myoglobin and mitochondria for aerobic respiration.

Multiunit vs. Visceral Smooth Muscle

Multiunit smooth muscle consists of separate fibers and requires neural stimulation for contraction, seen in the iris and blood vessels.
Visceral smooth muscle is composed of interconnected sheets, contracting rhythmically and facilitating peristalsis in hollow organs.

Peristalsis Function

Peristalsis involves coordinated muscle contractions to move contents through tubular organs.

Skeletal vs. Smooth Muscle Contrasts

Both types rely on actin and myosin but differ in contraction speed and neurotransmitters used. Skeletal muscles contract faster, while smooth muscles maintain longer contractions.

Skeletal vs. Cardiac Muscle Differences

Skeletal muscle can contract independently; cardiac muscle fibers work as a unified network and only occur in the heart.

Lever Mechanics in Limb Movements

Levers consist of a rigid bar, pivot, resistance, and force, functioning to enhance movement efficiency in limbs.

Aging and Muscular Changes

Aging leads to a decline in myoglobin, ATP, and creatine; muscle size reduces, and by age 80, half may atrophy.

Benefits of Exercise in Aging

Regular exercise promotes new muscle development, manages blood pressure, and enhances oxygen levels and endurance.

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Description

This quiz focuses on key concepts from Chapter 9 of anatomy. It covers important definitions and distinctions, such as the differences between tendons and aponeuroses. Test your knowledge of the structure of skeletal muscles and the role of connective tissue within them.