Anatomy and Physiology Chapter 9

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Questions and Answers

What are the three types of muscle tissue?

Skeletal, cardiac, smooth

What is skeletal muscle?

Organs that attach to/cover bony skeleton; rapid contraction, but tires easily; striations; voluntary

What is cardiac muscle?

In the heart; involuntary; striated; steady and constant rate of contraction

What is smooth muscle?

In walls of visceral organs; involuntary; no striations; slow, sustained rate of contraction Signup and view all the answers

What is another name for muscle cells?

Muscle fibers Signup and view all the answers

What are the two types of myofilaments?

Actin, myosin Signup and view all the answers

What is a myofilament?

Long strands of muscle Signup and view all the answers

What are the four characteristics of muscle tissue?

Excitability, contractility, extensibility, elasticity Signup and view all the answers

What is the ability to receive and respond to a stimulus in muscle tissue?

Excitability Signup and view all the answers

What is the definition of conductivity in muscle tissue?

Response; generation of electrical impulse that passes along plasma membrane of muscle cell and causes cell to contract Signup and view all the answers

What is contractility in muscles?

Ability to shorten forcibly when stimulated Signup and view all the answers

What does extensibility refer to in muscle tissue?

Ability to be stretched or extended Signup and view all the answers

What is elasticity in muscles?

Ability of a muscle cell to recoil and resume resting length after being stretched Signup and view all the answers

What are the functions of muscles?

Producing body movement, maintaining posture, stabilizing joints, generating heat Signup and view all the answers

What connects each muscle to its nerve, artery, and more than one vein?

Each muscle is served by one nerve, artery, and more than one vein. Signup and view all the answers

Why do muscles have a rich blood supply?

They use huge amounts of energy and need to remove numerous amounts of metabolic wastes. Signup and view all the answers

What is endomysium?

Whisky fine areolar connective tissue sheath around each individual muscle fiber. Signup and view all the answers

What is perimysium?

Layer of fibrous connective tissue around each fascicle. Signup and view all the answers

What is a fascicle?

Muscle fibers grouped together and wrapped in perimysium. Signup and view all the answers

What is the insertion of a muscle?

The moveable part when the muscle contracts. Signup and view all the answers

What is the origin of a muscle?

The immovable part when the muscle contracts. Signup and view all the answers

What are direct or fleshy attachments?

Epimysium of muscle fuses to periosteum of bone or perichondrium of cartilage. Signup and view all the answers

What are steroids in relation to muscles?

Synthetic male hormones. Signup and view all the answers

What are indirect attachments?

Muscle's connective tissue extends as tendon or aponeurosis anchors to bone/cartilage/other muscle fascia. Signup and view all the answers

What are tendons?

Tough collagen fibers that withstand tough bony projections. Signup and view all the answers

What is myosin?

Most abundant muscle protein; one molecule is made of two twisted protein strands with globular crossbridges that project outward. Signup and view all the answers

How many myosin molecules make up a myosin filament?

Many myosin molecules make up a myosin filament. Signup and view all the answers

What are cross bridges in muscle contraction?

In the presence of Ca ions, they react with actin filaments and shorten the myofibrils - contraction. Signup and view all the answers

What is actin?

1/4 total protein in skeletal muscle; globular structure with myosin binding sites attached to surface. Signup and view all the answers

How are actin molecules arranged?

In a double helix to form an actin filament. Signup and view all the answers

What two proteins are associated with actin filament?

Tropomyosin, troponin Signup and view all the answers

What is tropomyosin?

Rod shaped; in longitudinal grooves of actin helix. Signup and view all the answers

What is troponin?

Attached to tropomyosin surface. Signup and view all the answers

What happens at rest with tropomyosin and troponin?

They inhibit active sites on actin so linkages between actin and myosin cannot be formed. Signup and view all the answers

What is needed for muscle contraction?

High concentration of Ca ions Signup and view all the answers

What happens when Ca ions bind to troponin?

It changes the position of the tropomyosin and exposes the active sites of actin. Signup and view all the answers

What is the sarcoplasmic reticulum?

"Endoplasmic reticulum" of a muscle fiber; membranous channels that run parallel to and surround each myofibril. Signup and view all the answers

What are transverse tubules?

"T-tubules"; membranous channels that go from the sarcolemma all the way through the muscle fiber. Signup and view all the answers

What functions do the sarcoplasmic reticulum and transverse tubules provide?

To activate the muscle contraction mechanism. Signup and view all the answers

What are terminal cisternae?

Enlarged portions of the sarcoplasmic reticulum where calcium ions are stored. Signup and view all the answers

What is a triad in muscle physiology?

Sarcoplasmic reticulum, transverse tubules, terminal cisternae. Signup and view all the answers

What is a neuromuscular junction?

Site where motor nerve fibers and muscle fibers meet; also called myoneural junction. Signup and view all the answers

What causes muscle contraction?

Stimulation from motor nerve fibers. Signup and view all the answers

What is a motor end plate?

Specialized part of sarcolemma/muscle at the neuromuscular junction. Signup and view all the answers

What are synaptic vesicles?

Tiny bubbles that contain neurotransmitters. Signup and view all the answers

What are synaptic clefts?

Recesses of muscle fiber that motor fiber branches into. Signup and view all the answers

What is a motor unit?

A motor neuron and the muscle fiber it controls. Signup and view all the answers

How many muscle fibers does one motor nerve fiber connect to?

One motor nerve fiber is connected to many muscle fibers. Signup and view all the answers

What is acetylcholine?

A neurotransmitter made in cytoplasm at distal end of a motor neuron and stored in synaptic vesicles. Signup and view all the answers

What are the steps for muscle contraction?

<ol> <li>Acetylcholine released and diffuses across gap at neuromuscular junction. 2. Sarcolemma is stimulated, muscle impulse travels deep into fiber through t-tubules to sarcoplasmic reticulum. 3. Ca ions from SR are released into sarcoplasm and bind to troponin molecules. 4. Tropomyosin molecules move and expose binding (active) sites on actin. 5. Linkages form between actin and myosin; actin filaments slide inward along myosin filaments; muscle fiber shortens - contraction.</li> </ol> Signup and view all the answers

What is cholinesterase?

An enzyme that decomposes acetylcholine, located at neuromuscular junction. Signup and view all the answers

What are the steps for muscle relaxation?

<ol> <li>Cholinesterase decomposes acetylcholine so sarcolemma is no longer stimulated. 2. Ca ions are actively transported back into the SR. 3. Linkages between actin and myosin are broken. 4. Troponin and tropomyosin molecules inhibit the binding (active) sites of actin. 5. Actin and myosin filaments slide apart; muscle fiber lengthens - relaxation.</li> </ol> Signup and view all the answers

What is the source of energy for muscle contractions?

ATP Signup and view all the answers

What is the equation for the formation of ATP?

ATP → ADP + P + energy Signup and view all the answers

What is ATPase?

An enzyme in myosin that breaks ATP into ADP and P so energy is released. Signup and view all the answers

What does anything that ends in 'ose' represent?

Sugar Signup and view all the answers

What does anything that ends in 'ase' represent?

Enzymes Signup and view all the answers

What is creatine phosphate?

High energy molecule stored in muscles; tapped to regulate ATP while metabolic pathways adjust to higher demands for ATP; short-lived. Signup and view all the answers

What is the equation for creating phosphate?

Creatine phosphate + ADP → creatine + ATP Signup and view all the answers

In what form is glucose stored?

Glycogen Signup and view all the answers

What is cellular respiration?

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Signup and view all the answers

How many ATP does a glucose molecule provide?

36 Signup and view all the answers

What is the formula for cellular respiration?

Glucose + oxygen → carbon dioxide + water + ATP or C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy/ATP Signup and view all the answers

What are the two steps of cellular respiration?

<ol> <li>Glycolysis (2 ATP); 2. Aerobic respiration (34 ATP: Citric Acid Cycle (Krebs) - 2 ATP; Electron Transport Chain - 32 ATP)</li> </ol> Signup and view all the answers

What is glycolysis?

Anaerobic; the first phase of cellular respiration that breaks glucose down into two pyruvic acid molecules and two ATP. Signup and view all the answers

What is aerobic respiration?

Aerobic; a sequence of chemical reactions in which the bonds of fuel molecules are broken and the energy released is used to make ATP. Signup and view all the answers

What is the citric acid cycle?

Produces 2 ATP; waste: carbon dioxide. Signup and view all the answers

What is the electron transport chain?

Produces 32 ATP; waste: water. Signup and view all the answers

What is lactic acid formation?

Occurs when not enough oxygen is available to send pyruvic acid into aerobic respiration. Signup and view all the answers

What is oxygen deficit/debt?

When have less than the amount of oxygen a body must take in for restorative process. Signup and view all the answers

What is muscle fatigue?

State of physiological inability to contract even though the muscle still may be receiving stimuli. Signup and view all the answers

What are contractures?

State of continuous contractions; e.g., writer's cramp. Signup and view all the answers

What is a byproduct of cellular respiration?

Heat Signup and view all the answers

What percentage of energy from cellular respiration is lost as heat?

75% Signup and view all the answers

What is slow twitch/red muscle?

"Dark meat"; lots of myoglobin and lots of mitochondria. Signup and view all the answers

What is fast twitch/white muscle?

Few mitochondria and less myoglobin; gets most of its ATP through creatine phosphate and glycolysis. Signup and view all the answers

Muscles can have both slow twitch and fast twitch fibers.

True (A) Signup and view all the answers

What is hypertrophy?

Increase in size/muscle mass; working out or exercising. Signup and view all the answers

What is atrophy?

Decrease in size/muscle mass. Signup and view all the answers

What are myoblasts?

A cell that builds muscles. Signup and view all the answers

What is another name for a gap junction?

Synaptic clefts Signup and view all the answers

When are skeletal muscle fibers contracting?

Week 7 Signup and view all the answers

What do smooth and cardiac muscle not do?

They don't fuse. Signup and view all the answers

When is the heart pumping blood during development?

Week 3 Signup and view all the answers

How are babies' movements described?

Uncoordinated and reflexive Signup and view all the answers

Which movements precede fine movements?

Gross movements Signup and view all the answers

Where does development in a kid start?

Starts in the head and radiates outward Signup and view all the answers

When is the natural peak of motor control?

Mid adolescence Signup and view all the answers

What percentage of body mass do women's skeletal muscles make up?

36% Signup and view all the answers

What percentage of body mass do men's skeletal muscles make up?

42% Signup and view all the answers

Why are muscles not easily infected?

Rich blood supply Signup and view all the answers

What is muscular dystrophy?

Inherited muscle-destroying diseases that appear in childhood. Signup and view all the answers

What is Duchenne muscular dystrophy?

Sex-linked recessive disease; primarily affects males; symptoms appear around ages 2-7. Signup and view all the answers

What happens to connective tissue and muscle fibers as we age?

Connective tissue increases, and the number of muscle fibers decreases. Signup and view all the answers

What is sarcopenia?

Gradual loss of muscle mass. Signup and view all the answers

By what percentage has muscle strength usually decreased by age 80?

50% Signup and view all the answers

How can elderly individuals regain or maintain muscle strength?

Lightly working out Signup and view all the answers

Study Notes

Types of Muscle Tissue

Three types of muscle tissue: skeletal, cardiac, smooth.
Skeletal muscle: attached to the skeleton, striated, voluntary, rapid contraction but tires easily.
Cardiac muscle: located in the heart, involuntary and striated, maintains a steady contraction rate.
Smooth muscle: found in hollow organs, involuntary, non-striated, slow and sustained contraction.

Muscle Structure and Function

Muscle cells are also known as muscle fibers.
Myofilaments consist of actin and myosin, essential for muscle contraction.
Four characteristics of muscle tissue:
- Excitability: responds to stimuli.
- Contractility: can shorten forcibly.
- Extensibility: can be stretched.
- Elasticity: can recoil to original length after stretching.

Muscle Tissue Functions

Produces body movement, maintains posture, stabilizes joints, generates heat.
Protects inner organs and forms valves (sphincters) in smooth muscle.
Each muscle is supplied by a nerve, an artery, and veins for energy use and waste removal.

Muscle Connective Tissue

Endomysium: fine connective tissue sheath around individual muscle fibers.
Perimysium: connective tissue layer surrounding fascicles.
Fascicles: bundles of muscle fibers grouped together.

Muscle Attachments

Muscle's origin: the immovable attachment point.
Muscle's insertion: the movable attachment during contraction.
Direct attachments: muscle epimysium fuses to periosteum or cartilage.
Indirect attachments: connective tissue extends to form tendons or aponeurosis.

Myofilament Structure

Myosin is the most abundant muscle protein, forming thick filaments.
Actin consists of globular structures with binding sites for myosin, forming a double helix filament structure.
Tropomyosin and troponin are regulatory proteins associated with actin, controlling access to binding sites.

Muscle Contraction Mechanism

Motor nerve stimulation triggers contraction through the neuromuscular junction.
Acetylcholine is released, activating muscle fibers by generating an impulse leading to calcium ion release from the sarcoplasmic reticulum.
Calcium binds to troponin, shifting tropomyosin to expose active sites on actin for myosin binding.

Relaxation and Energy Use

Cholinesterase decomposes acetylcholine to cease stimulation.
ATP is crucial for muscle contraction; produced during cellular respiration.
Creatine phosphate stores energy, quickly converting to ATP when needed.

Types of Muscle Fiber

Slow-twitch (red) fibers are fatigue-resistant, use aerobic respiration, rich in myoglobin.
Fast-twitch (white) fibers fatigue quickly, rely on anaerobic processes and creatine phosphate for quick energy bursts.
Muscles can contain both fiber types, contributing to overall functionality.

Muscle Development and Aging

Muscle mass typically decreases with age, a condition known as sarcopenia.
Peak motor control occurs during mid-adolescence.
Women's skeletal muscles comprise about 36% of body mass, while men's make up about 42%.
Light exercise can help older adults maintain or regain muscle strength.

Muscle Disorders

Muscular dystrophy: genetic disorders leading to muscle degeneration, notably Duchenne muscular dystrophy.
Symptoms typically appear in childhood, progressing to muscle atrophy.
Muscle strength is often reduced by 50% by age 80 due to aging-related changes.

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Test your knowledge on the different types of muscle tissues in this Anatomy and Physiology Chapter 9 quiz. Explore the characteristics and functions of skeletal, cardiac, and smooth muscles. Perfect for students looking to enhance their understanding of muscle anatomy.