BIO 220 CH 10 Muscle Tissues

3 types of muscle tissue

Skeletal, Cardiac, Smooth

Skeletal muscle Pulls on skeletal __________ contraction

bones, Voluntary

Cardiac muscle Pushes ________ through arteries and veins_____ contractions

blood, Rhythmic

Smooth muscle Pushes fluids and solids along the _____ tract, for example_______ contraction

digestive, Involuntary

Muscle tissue

- Cells are specialized for ________

- Skeletal muscles move the body by pulling on bones

- Cardiac and smooth muscles control movements inside the body

contraction

Muscle tissue Common properties include

Excitability, Contractility, Extensibility, Elasticity

Excitability

responsiveness

Contractility

ability of cells to shorten

Extensibility

stretching

Elasticity

recoil

Functions of skeletal muscle

- Producing ________

- Maintaining posture and body position

- Supporting soft tissues

- ________ body entrances and exits

- ___________ body temperature

- Storing nutrients

movement, Guarding, Maintaining

Skeletal muscles contain

- Skeletal muscle tissue (________)

- _________ tissues

- Blood vessels

- Nerves

primarily, Connective

Skeletal muscles have three layers of connective tissue

- Epimysium

- Perimysium

- Endomysium

Epimysium

- Layer of _________ fibers that surrounds the muscle

- Connected to deep fascia

- Separates muscle from surrounding ______

collagen, tissues

Perimysium surrounds

muscle fiber bundles (fascicles)

Perimysium contains

• Collagen fibers

• Elastic fibers

• Blood vessels

• Nerves

Endomysium surrounds

individual muscle cells (muscle fibers)

Endomysium contains

• Capillary networks

• Myosatellite cells (stem cells) that repair damage

• Nerve fibers

Collagen fibers of epimysium, perimysium, and endomysium come together

- At ends of muscles to form

• A _______ (bundle)

• Or _________ (sheet)

- To attach skeletal muscles to bones

tendon, aponeurosis

muscle fiber

muscle cell

tendon

bundle that connects muscle to bone

Aponeurosis

strong sheet of tissue that acts as a tendon to attach muscles to bone

Skeletal muscle fibers are

enormous compared to other cells

Skeletal muscle fibers contain

hundreds of nuclei (multinucleate)

Skeletal muscle fibers develop by

fusion of embryonic cells (myoblasts)

Skeletal muscle fibers also known as

striated muscle cells due to striations

Sarcolemma

- Plasma membrane of a ________ fiber

- Surrounds the __________ (cytoplasm of a muscle fiber)

- A sudden change in __________ _________ initiates a contraction

muscle, sarcoplasm, membrane potential

Transverse tubules (T tubules)

• Tubes that extend from surface of _______ _____ deep into __________

• ________ action potentials from sarcolemma into cell interior

• Action potentials trigger _________

muscle fiber, sarcoplasm, Transmit, contraction

Sarcoplasmic reticulum (SR)

- A tubular network surrounding each _______

- Similar to smooth ___________ __________

myofibril, endoplasmic reticulum

Sarcoplasmic reticulum (SR)

- Forms chambers (________ _______) that attach to T tubules

• _____ terminal cisternae plus a __ ______ forms a triad

terminal cisternae, Two, T tubule

Sarcoplasmic reticulum (SR)

- Specialized for storage and release of _______ _______

• Ions are actively transported from ________ into _______ _______

calcium ions, cytosol, terminal cisternae

2 types of myofilaments

thin filaments (actin) and thick filaments (myosin)

Myofibrils

- Responsible for muscle ___________

- Made of bundles of protein filaments (___________)

contraction, myofilaments

Myofilaments

bundles of protein filaments

Thin filaments

actin

Thick filaments

myosin

Sarcomeres

- _________ functional units of a muscle fiber

- Interactions between ________ produce contraction

- Arrangement of _________ accounts for striated pattern of myofibrils

• Dark bands (A bands)

• Light bands (I bands)

Smallest, filaments, filaments

Dark bands

A bands

Light bands

I bands

A band contains

M line, H band, and zone of overlap

M line

• In center of A band

• Proteins stabilize positions of thick filaments

H band

• On either side of M line

• Has thick filaments but no thin filaments

Zone of Overlap

Dark region where thick and thin filaments overlap

I bands contains

- Contains thin filaments but no thick filaments

- Z lines

- Titin

Z lines

• Bisect I bands

• Mark boundaries between adjacent sarcomeres

Titin

• ________ protein

• Extends from tips of _____ filaments to the __ line

• Keeps filaments in proper ________

• Aids in restoring resting ________ length

Elastic, thick, Z, alignment, sarcomere

Thin filaments contain

F-actin, tropomyosin, and troponin proteins

Filamentous actin (F-actin)

• Twisted strand composed of two rows of globular __-actin molecules

• Active sites on __-actin bind to ________

G, G, myosin

Tropomyosin

• Covers active sites on G-actin

• Prevents actin-myosin interaction

Troponin

Binds tropomyosin, G-actin, and Ca2+

Thick filaments each contains about

300 myosin molecules

Thick filaments

- Each myosin molecule consists of

Tail and Head

Myosin Tail

Binds to other myosin molecules

Myosin Head

- Made of two globularprotein subunits

- Projects toward nearestthin filament

Thick filaments core of titin

recoils after stretching

Initiating Contraction

- Ca2+ binds to receptor _______ molecule

- Troponin-tropomyosincomplex changes

- Exposes active site of _____

ontroponin, actin

During contraction, myosin heads:

- Interact with actin filaments, forming _____-______

- _____, producing motion

cross, bridges, Pivot

Sliding-filament theory

- During a contraction,

1. H bands and I bands ______

2. Zones of overlap ______

3. __ lines move closer together

4. Width of __ band remains constant

- Thus, thin filaments must slide toward center of sarcomere

narrow, widen, Z, A

Excitable membranes

- Are found in ________ muscle fibers and ________

- Depolarization and repolarization events produce _________ ________ (electrical impulses)

skeletal, neurons, action potentials

Skeletal muscle fibers contract due to stimulation by ______ ________

motor neurons

Neuromuscular junction (NMJ)

- Synapse between a ______ and a _______ muscle fiber

- Axon terminal of the motor neuron releases a neurotransmitter into the synaptic _______

• The neurotransmitter is ________ (ACh)

neuron, skeletal, cleft, acetylcholine

Events at the Neuromuscular Junction

1. Nerve impulse arrives at axon terminal

2. Ach released into synaptic cleft

3. Ach diffuses across cleft and binds with receptors on sarcolemma

4. Electrical events

5. Generation of action potential

Excitation-contraction coupling

- Action potential travels down T tubules to triads

• Ca2+ is released from ________ _______ of SR

- Ca2+ binds to _______ and changes its shape

- Troponin-tropomyosin complex changes position

• Exposes active sites on ______

- _________ cycle is initiated

terminal cisternae, troponin, actin, Contraction

Contraction cycle

1. Contraction cycle begins

2. Active-site ________

3. Cross-bridge ________ (myosin binds to actin)

4. Myosin head _______ (power stroke)

5. Cross-bridge ________

6. ______ reactivation

exposure, formation, pivoting, detachment, Myosin

Rigor mortis

Fixed muscular contraction after death

Rigor mortis results when

• ATP runs out and ion pumps cease to _______

- leaving myosin cross-bridges attached to actin

• Calcium ions build up in _______

function, cytosol

Duration of a contraction depends on:

- Duration of neural stimulus

- Presence of free calcium ions in cytosol

- Availability of ATP

As Ca2+ is pumped back into SR and Ca2+ concentration in cytosol falls,

1. Ca2+ detaches from _______

2. Troponin returns to ________ position

3. Active sites are re-covered by tropomyosin and the __________ ends

troponin, original, contraction

Muscle relaxation and the return to resting length

- Elastic forces

• ________ recoil after a contraction

• Helps return muscle fibers to resting length

- Opposing muscle contractions

• Opposing muscles return a muscle to resting length ______

- ________

• Assists opposing muscles

Tendons, quickly, Gravity

The number of contracting sarcomeres in a muscle fiber is fixed

- So, a muscle fiber is either producing _______ or ________

tension, relaxed

The amount of tension produced depends on the

- Frequency of stimulation

- Number of power strokes performed

- Fiber's resting length at time of stimulation

Frequency of stimulation

- A single neural stimulation produces a single contraction, or ______

- Sustained muscular contractions

• Require many repeated _______

- A ________ is a graph showing tension development in muscle fibers

twitch, stimuli, myogram

A twitch's 3 phases

1. Latent Period: depolarize; Ca2+ released

2. Contraction period: cross-bridges form

3. Relaxation period: Ca2+ returns to SR

Twitch Latent period

• Action potential moves across ________

• SR releases ____

sarcolemma, Ca2+

Twitch Contraction phase

• Calcium ions bind to ______ and cross-bridges form

• _______ builds to a peak

troponin, Tension

Twitch Relaxation phase

• _____ levels in cytosol fall

• Cross-bridges detach and tension decreases

Ca2+

Treppe

- A stair-step _______ in tension

- Caused by repeated stimulations immediately after _________ phase

• Produces a series of ________ with increasing tension

- Typically seen in _______ muscle and not skeletal muscles

increase, relaxation, contractions, cardiac

Wave summation

- Increasing tension due to _________ of twitches

- Caused by repeated stimulations before the end of __________ phase

summation, relaxation

Tetanus is

maximum tension

incomplete tetanus

• Muscle produces near-maximum tension

• Caused by rapid cycles of contraction and relaxation

Complete tetanus

• Higher stimulation frequency eliminates relaxation phase

• Muscle is in continuous contraction

• All potential cross-bridges form

Tension production by skeletal muscles depends on the number of stimulated _______ _______

muscle fibers

A motor unit is a _______ _______ and all of the ______ ______ it controls

- May contain a few muscle fibers or thousands

- All fibers in a motor unit contract at the same time

motor neuron, muscle fibers

Recruitment

- Increase in the number of active ______ units

- Produces smooth, _____ increase in tension

- Maximum tension is achieved when all motor units reach complete tetanus

• Can be sustained for a very short time

- Sustained contractions

• Produce less than maximum tension

• Motor units are allowed to ____ in rotation

motor, steady, rest

Generation of muscle tension

- When muscle cells contract, they produce tension (pull)

- To produce movement, tension must overcome the ______ (resistance)

- The entire muscle _______ at the same rate

• Because all sarcomeres contract together

• Speed of shortening depends on ________ rate (number of power strokes per second)

load, shortens, cycling

Muscle tone

- The normal tension and firmness of a muscle at _____

- Without causing movement, motor units actively:

• Stabilize positions of bones and joints

• Maintain balance and posture

- Elevated muscle tone increases resting energy ___________

rest, consumption

ATP (adenosine triphosphate) is the only energy source used ________ for muscle contraction

- Contracting muscles use a lot of ATP

- Muscles store enough ATP to start a contraction

- More ATP must be generated to sustain a contraction

directly

ATP can be generated in three ways

- Direct phosphorylation of ADP by creatine phosphate (CP)

- Anaerobic metabolism (glycolysis)

- Aerobic metabolism (citric acid cycle and electron transport chain)

At rest, ________ muscle fibers produce more ATP than needed

- ATP transfers energy to creatine

- Creating _______ _______ (CP)

• Used to store energy and convert ADP back to ____

skeletal, creatine phosphate, ATP

The enzyme creatine kinase (CK)

Catalyzes the conversion of ADP to ATP using the energy stored in CP

When CP is used up, other mechanisms are used to generate ____

ATP

Glycolysis

- _________ process

- Important energy source for peak muscular activity

- Breaks down glucose from _______ stored in skeletal muscles

- Nets _____ ATP per molecule of glucose

Anaerobic, glycogen, two

Aerobic metabolism (requires oxygen)

- Primary energy source of _______ muscles

• Breaks down fatty acids

- Active muscles utilize glucose

- Produce over ___ ATP

resting, 30

Muscle metabolism

- Skeletal muscles at rest metabolize ______ ____ and store glycogen and CP

- During moderate activity, muscles generate ATP through _______ breakdown of glucose, primarily

- At peak activity, pyruvate produced via glycolysis is converted to _______

fatty acids, aerobic, lactate

Oxygen debt

- Also called excess postexercise oxygen consumption (EPOC)

- After exercise or other exertion

• Body needs more oxygen than usual to normalize __________ activities

• Breathing rate and depth are _________

metabolic, increased

Heat production and loss

- Active skeletal muscles produce _____

• Release up to ___ percent of the heat needed to maintain normal body temperature

heat, 85

Muscle performance is based on

force and endurance

Force

The maximum amount of tension produced

Endurance

The amount of time an activity can be sustained

Force and endurance depend on

• The types of muscle fibers

• Physical conditioning