Human Anatomy and Physiology Chapter 9 Flashcards

Questions and Answers

What are concentric contractions?

Isotonic contractions in which muscle shortens and does work like picking up a book.

What are eccentric contractions?

Isotonic contractions in which muscle generates force as it lengthens.

What does isometric mean in muscle contraction?

No movement; no shortening of muscle; cannot move a load.

What is muscle tone?

Even relaxed muscles are almost always slightly contracted. Signup and view all the answers

What role does phosphorylation play in muscle contraction?

High energy storage molecule called creatine phosphate gives up phosphate to ADP to form ATP. Signup and view all the answers

What is Anaerobic Respiration?

Respiration that occurs without oxygen present. Signup and view all the answers

What occurs during Aerobic Respiration?

Glycolysis breaks down glucose and pyruvic acid enters mitochondria for complete breakdown. Signup and view all the answers

What leads to muscle fatigue?

ATP use exceeds ATP production and excessive accumulation of lactic acid. Signup and view all the answers

What are the requirements for the resting state of muscles?

Oxygen reserves must be replenished, lactic acid must be converted, glycogen stores replaced, and ATP reserves resynthesized. Signup and view all the answers

What factors determine the force of muscle contraction?

Number of muscle fibers stimulated, relative size of fibers, frequency of stimulation, and degree of muscle stretch. Signup and view all the answers

What characterizes slow oxidative fibers?

Slow contracting muscle that produces ATP through aerobic pathway and resists fatigue. Signup and view all the answers

What are fast glycolytic fibers?

Muscle fibers that use anaerobic pathways and tire quickly. Signup and view all the answers

What happens during aerobic exercise?

Increases number of mitochondria within muscle fibers and synthesizes more myoglobin. Signup and view all the answers

What is disuse atrophy?

Muscle gets too small due to lack of use. Signup and view all the answers

What is peristalsis?

Alternating contraction and relaxation of smooth muscle layers. Signup and view all the answers

What are varicosities in smooth muscle?

Bulbous swellings of nerve fibers that release neurotransmitters. Signup and view all the answers

Describe the NMJ of smooth muscle.

Varicosities have neurotransmitters with clefts for many areas of reception. Signup and view all the answers

What does the sarcoplasmic reticulum of smooth muscle lack?

No sarcomeres, no T tubules. Signup and view all the answers

What characterizes smooth muscle contraction?

Calcium binds to calmodulin and activates myosin light chain kinase. Signup and view all the answers

How is smooth muscle contraction regulated?

Autonomic nerves release different neurotransmitters; some excite and some inhibit. Signup and view all the answers

What is the definition of excitability?

It can respond to a stimulus. Signup and view all the answers

What does contractibility mean?

If stimulated, it shortens and thickens. Signup and view all the answers

Define extensibility.

It has the ability to stretch past its normal length. Signup and view all the answers

What is meant by elasticity in muscle tissue?

It can convert back to its normal shape and size if extended or contracted. Signup and view all the answers

Which of the following describes smooth muscle?

Involuntary and found in hollow organs. Signup and view all the answers

What characterizes cardiac muscle?

Involuntary with striations and intercalated disks. Signup and view all the answers

What are the main functions of muscle tissue?

Generating heat and moving bones. Signup and view all the answers

What is the composition of skeletal muscle?

Skeletal muscle fibers, blood vessels, nerve fibers, connective tissue. Signup and view all the answers

Define direct attachment of muscle.

Either periosteum or perichondrium does the attachment. Signup and view all the answers

What is an indirect attachment of muscle?

Connective tissue extending beyond the end of the muscle to the bone. Signup and view all the answers

What is a tendon?

A rope-like extension of connective tissue. Signup and view all the answers

What is an aponeurosis?

Connective tissue that is flat sheet-like. Signup and view all the answers

What does the term 'origin' refer to in muscle attachment?

Attachment to an immovable bone. Signup and view all the answers

Define epimysium.

An overcoat of dense irregular connective tissue that surrounds the whole muscle. Signup and view all the answers

What is the function of the perimysium?

Surrounds each fascicle of muscle fibers. Signup and view all the answers

Describe the endomysium.

A wispy areolar connective tissue sheath surrounding each individual muscle fiber. Signup and view all the answers

What is a fascicle?

A collection of muscle fibers that bundles together to make a muscle. Signup and view all the answers

What does sarcolemma refer to?

The plasma membrane of a muscle cell. Signup and view all the answers

Define sarcoplasm.

Cytoplasm of a muscle cell containing glycosomes and myoglobin. Signup and view all the answers

What are myofibrils?

Rod-like structures running parallel to the muscle fiber's length. Signup and view all the answers

What are glycosomes?

Vesicles that contain glycogen as a storage medium. Signup and view all the answers

What is the function of the sarcoplasmic reticulum?

Regulates intracellular levels of ionic calcium. Signup and view all the answers

Describe the H Zone.

A lighter region at the midsection of a dark A band. Signup and view all the answers

What does the M Line represent?

It vertically bisects each H zone and is formed by proteins. Signup and view all the answers

What is a Z disc?

A darker area that is the midline interruption of a light I band. Signup and view all the answers

Define sarcomere.

The region of a myofibril between two successive Z discs. Signup and view all the answers

What are myofilaments?

Small structures within sarcomeres that contain actin or myosin. Signup and view all the answers

What are thick filaments primarily composed of?

Myosin. Signup and view all the answers

What are thin filaments primarily composed of?

Actin. Signup and view all the answers

What are intermediate (desmin) filaments?

They extend from Z discs and connect each myofibril to the next. Signup and view all the answers

What is the composition of myofilaments?

Primarily composed of myosin, some actin. Signup and view all the answers

Describe myosin's structure.

Each molecule consists of two heavy and four light polypeptide chains. Signup and view all the answers

What happens during a cross bridge formation?

Myosin heads link thick and thin filaments together during contraction. Signup and view all the answers

What does actin provide in muscle cells?

Active sites for myosin heads to attach during contraction. Signup and view all the answers

Define regulatory proteins in thin filaments.

Proteins that help regulate muscle contraction by binding to actin and tropomyosin. Signup and view all the answers

What does the elastic filament do?

Helps maintain organization of A band and spring back into place. Signup and view all the answers

What is the function of T Tubule?

Increase surface area for muscle contraction impulses. Signup and view all the answers

What does the Z line signify?

The end of the sarcomere, shared between two adjacent sarcomeres. Signup and view all the answers

What is the A band?

The entire length of the thick myofilament. Signup and view all the answers

What is the I band?

Where there are only thin myofilaments. Signup and view all the answers

What does the sliding filament theory describe?

Thin myofilaments slide over thick myofilaments during contraction. Signup and view all the answers

What is the neuromuscular junction?

The modification of sarcolemma where muscle fiber is adjacent to a neuron. Signup and view all the answers

What is required for skeletal muscle fiber contraction?

Must generate action potential and increase intracellular calcium levels. Signup and view all the answers

What are synaptic vesicles?

Membranous sacs containing neurotransmitters, such as acetylcholine. Signup and view all the answers

Describe the neuromuscular junction process.

Action potential opens calcium channels, triggering neurotransmitter release. Signup and view all the answers

What is excitation-contraction coupling?

The process where ACh triggers action potential and calcium release. Signup and view all the answers

Define power stroke.

The process where myosin heads pull thin myofilaments toward H zone. Signup and view all the answers

What happens during muscle recovery?

Calcium is pumped back into the sarcoplasmic reticulum, and muscle relaxes. Signup and view all the answers

What is a twitch?

A single, rapid, jerky response to a single stimulus. Signup and view all the answers

What is a graded muscle response?

Variations needed for proper control of skeletal movement. Signup and view all the answers

What is wave or temporal summation?

A phenomenon where rapid successive stimuli lead to stronger contractions. Signup and view all the answers

Define unfused or incomplete tetanus.

Sustained but quivering contraction due to constant stimulation. Signup and view all the answers

What is complete tetanus?

Maximal muscle tension with smooth, sustained contraction. Signup and view all the answers

What does treppe refer to?

Stronger contractions due to incomplete relaxation between stimuli. Signup and view all the answers

What is isotonic contraction?

Muscle contraction that produces movement. Signup and view all the answers

Study Notes

Muscle Tissue Characteristics

Excitability: Muscle tissue can respond to stimuli, primarily nervous impulses.
Contractibility: Muscles can shorten and thicken when stimulated.
Extensibility: Muscles have the ability to stretch beyond their normal length.
Elasticity: Muscles can return to their original shape and size after being stretched or contracted.

Types of Muscle

Smooth Muscle: Involuntary muscle found in the walls of hollow organs; elongated cells without striations.
Cardiac Muscle: Striated, branched muscle with intercalated disks; it is involuntary.
Skeletal Muscle: Long, striated muscle cells arranged in parallel; voluntary and multinucleated.

Functions of Muscle Tissue

Movement and locomotion
Maintaining posture
Stabilizing joints
Generating heat through muscle activity

Structure of Skeletal Muscle

Composed of muscle fibers, blood vessels, nerve fibers, and connective tissue. Requires continuous oxygen and nutrient delivery.
Direct Attachment: Epimysium of muscle fuses with the periosteum of bone or perichondrium of cartilage.
Indirect Attachment: Tendons connect muscle to bone, extending beyond the muscle.
Tendons: Rope-like extensions of connective tissue, while Aponeurosis is a flat sheet-like structure.

Connective Tissue Sheaths

Epimysium: Dense connective tissue surrounding the entire muscle.
Perimysium and Fascicles: Fascicles are bundles of muscle fibers wrapped in perimysium.
Endomysium: Wispy connective tissue sheath surrounding individual muscle fibers.

Muscle Fiber Components

Sarcolemma: Plasma membrane of a muscle cell.
Sarcoplasm: Cytoplasm containing glycosomes (glycogen storage) and myoglobin (oxygen storage).
Myofibrils: Rod-like structures that account for muscle cell volume, containing sarcomeres (contractile units) and myofilaments.

Myofilaments

Thick Filaments: Composed of myosin, extending the entire length of the A band.
Thin Filaments: Consists of actin, extending across the I band.
Cross Bridge: Myosin heads link thick and thin filaments during contraction.

Sarcomere Structure

Z Disc: Midline interruption of I band; connects thin filaments.
H Zone: Lighter region in the A band, bisected by the M line.
Sliding Filament Theory: Thin filaments slide over thick filaments during contraction, shortening the muscle.

Excitation-Contraction Coupling

Action potential generation leads to muscle contraction through calcium release from the sarcoplasmic reticulum.
Calcium binds to troponin, allowing myosin heads to attach to actin for contraction.

Muscle Contraction Types

Twitch: Rapid, jerky response; a single contraction follows a single stimulus.
Graded Muscle Response: Variations in muscle movement strength, influenced by stimulus frequency and intensity.
Wave Summation: Successive stimuli cause a stronger contraction due to incomplete relaxation.
Tetanus: Sustained muscle contraction occurs when stimuli frequency increases.

Muscle Contraction Energy Sources

Aerobic Respiration: Generates high ATP through glycolysis and complete breakdown in mitochondria; requires continuous oxygen.
Anaerobic Respiration: Glycolysis leads to lactic acid accumulation in the absence of oxygen; generates less ATP quickly.
Phosphorylation: Creatine phosphate supplies phosphate to regenerate ATP quickly for short-term energy.

Muscle Fatigue and Recovery

Fatigue: Occurs when ATP usage exceeds production, leading to lactic acid buildup and ionic imbalances.
Recovery: Requires replenishing oxygen, converting lactic acid, resynthesizing glycogen, ATP, and creatine phosphate.

Muscle Characteristics

Muscle Tone: Even at rest, muscles maintain slight tension to stabilize joints and posture.
The force of muscle contractions depends on the number of crossbridges, stimulated fibers, fiber sizes, and stimulation frequency.### Muscle Physiology Basics
Muscle contraction strength increases with the number of stimulated fibers.
Larger muscle fibers generate stronger contractions, influenced by training and genetics.
Muscle fiber size can be modified through exercise, though individuals are born with a predetermined number of fibers.
Faster stimulation leads to stronger muscle contractions until optimal stretch is reached; excessive stretching hinders contraction.
Optimal overlap of thick and thin filaments (A) ensures effective contraction, while partial overlap (B) still allows for some contraction.

Muscle Fiber Types

Slow Oxidative Fibers
- Contract slowly, utilize aerobic pathways for ATP production, high endurance, and rich in mitochondria.
- Resilient to fatigue but have less power due to slower ATPase activity.
Fast Oxidative Fibers
- Contract rapidly, also use aerobic pathways, resistant to fatigue.
- Characteristics include a rich supply of myoglobin and capillaries, allowing for quick ATP production.
Fast Glycolytic Fibers
- Rely on anaerobic pathways, produce less ATP quickly, and tire rapidly.
- Characterized by large diameter and minimal mitochondria; suited for brief, intense activities.

Exercise Effects on Muscle

Aerobic Exercise
- Increases mitochondrial numbers and myoglobin synthesis in muscle fibers.
- Primarily enhances slow oxidative fibers, contributing to endurance through angiogenesis (new capillary formation).
Resistance Exercise
- Focuses on anaerobic pathways and intensively loads muscles.
- More significantly increases muscle fiber size than aerobic exercise, promoting hypertrophy.
- Can convert some fast oxidative fibers to fast glycolytic fibers.

Muscle Atrophy

Disuse atrophy occurs when muscles weaken and shrink due to inactivity.
Prolonged disuse can lead to muscle tissue converting to fibrous connective tissue.

Smooth Muscle Structure

Smooth muscle fibers are smaller than skeletal fibers and lack connective tissue sheaths except for the endomysium.
Organized in layers: longitudinal for dilation and circular for constriction of tubes.
Features no motor end plates or structured neuromuscular junctions; uses varicosities to release neurotransmitters.

Smooth Muscle Physiology

Peristalsis
- Smooth muscle layers contract and relax alternately, propelling contents through organ lumens.
Varicosities
- Enlarged nerve fibers release neurotransmitters into synaptic clefts during smooth muscle activation.
Sarcoplasmic Reticulum
- Lacks sarcomeres and T-tubules; instead, features caveoli for calcium concentration.
Myofilaments consist of both thick and thin components, arranged diagonally, and lack troponin.

Smooth Muscle Contraction

Triggered by neurotransmitter-induced action potentials that release calcium.
Calcium interacts with calmodulin, activating myosin light chain kinase to facilitate muscle contraction.
Involves calcium influx from both caveoli and extracellular space, leading to myosin activation and fiber shortening.

Regulation of Smooth Muscle Activity

Controlled by autonomic nerve neurotransmitters causing excitation or inhibition.
Influenced by chemical factors, such as oxytocin in labor and histamine during inflammation.
Somatic motor neurons release solely acetylcholine as a neurotransmitter.

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Description

Explore key concepts from Chapter 9 of Human Anatomy and Physiology with these flashcards. Each card provides essential definitions of important terms, including excitability, contractibility, extensibility, and elasticity. Master these concepts for a deeper understanding of muscle function.