What is seen only in lab setting or with neuromuscular problems, but not in normal muscle

what vary strength of contraction for different demands

What is required for proper control of skeletal movement

Changing frequency of stimulation

changing strength of stimulation

What changes in stimulus frequency

What results in single single contractile response (i.e, muscle twitch)

a second stimulus delivered after relaxation is complete does not produce summation

What results if two stimuli are received by a muscle in rapid succession

Where does muscle fibers do not have time to complexly relax between stimuli so twitches increase in force with each stimulus

Where does additional Ca2+ that is released with second stimulus stimulates more shortening in

Additional stimuli delivered before relaxation is complete produce temporal (wave) summation

What happens if stimuli frequency increases

What causes muscle to progress to as sustained, quivering contraction referred to as unfused (incomplete)tetanus)

What does higher stimulation frequency result in

contractions “fuse” into one smooth sustained contraction plateau

What leads to muscle fatigue which is particularly exacerbated in the continuous contraction of fused tetanus

at even higher stimulus frequencies, there is no relaxation at all between stimuli.

What occurs when the stimulus is sent to more muscle fibers, leading to more precise control

what is subthreshold stimulus, threshold stimulus, maximal stimulus involved in

the stimulus not strong enough, so no contraction seen

the stimulus is strong enough to cause first observable contraction

When what has been recruited further stimuli will not be able to recruit more what

What works on size principles

Motor units with what kinds of muscle fibers are recruited first

Motor units with what kinds of muscle fibers are recruited as stimulus intensity increases

What motor units are activated only for the most powerful contractions

What the muscle usually contract asynchronously

Some fibers contract while others rest

Helps prevent fatigue

is the constant, slightly contracted state of all muscles

Due to spinal reflexes

Groups of motor units are alternately activated in response to input from stretch receptors in muscles

Keeps muscles firm, healthy, and ready to respond

the muscle changes in length and moves load

what can be either concentric or eccentric

the muscle shortens an does work

Example: biceps contract to pick up a bro

the muscle lengthens and generates force

Example: laying a book down causes biceps to lengthen while generating a force

The load is greater than the maximum tension muscle can generate, so the muscle neither shortens nor lengthens

What is the same in isotonic or isometric contractions but the results are different

where does actin filament shorten and cause movement

cross bridges generate force, but actin filaments do not shorten

Myosin heads “spin their wheels” on same actin- binding site

What does ATP supply the energy needed for muscle fibers to

What is the only source of energy for contractile activities; therefore, it must be regenerated quickly

What is the first step in glucose breakdown

does not require oxygen

Glucose is broken into 2 pyruvic acid molecules

2 ATPs are generated for each glucose broken down

What prevent pyretic acid from entering aerobic respiration phase

What three mechanisms is ATP regenerated by

What is a unique molecule located in muscle fibers that donates a phosphate to ADP to instantly form ATP

is an enzyme that carries out transfer of phosphate

What can also be generated by breaking down and using energy stored in glucose

What enters mitochondria to start aerobic respiration phase; however, at high intensity activity, oxygen is not available

Bulging muscles compress blood vessels, impairing oxygen delivery

What is referred to as anaerobic glycolysis, pyretic acid is converted to lactic acid

Diffuses into bloodstream

Used as fuel by liver, kidneys, and heart

Converted back into pyruvic acid or glucose by liver

What yields only 5% as much ATP as aerobic respiration, but produces ATP 2½ times faster

What Produces 95% of ATP during rest and light-to-moderate exercise

slower than anaerobic pathway

what Consists of a series of chemical reactions that occur in mitochondria and require oxygen

Breaks glucose into CO2, H2O, and large amount ATP (32 can be produced)

Which respiration has the fuel used include glucose from glycogen stored in the muscle fiber, then bloodborne glucose, and free fatty acids

What is the main fuel after exercise

What are the energy systems used during sports?

Length of time muscle contracts using aerobic pathways

Light-to-moderate activity, which can continue for hours

point at which muscle metabolism converts to anaerobic pathway

is the physiological inability to contract despite continued stimulation

Is this a possible cause of fatigue:

ionic imbalance

Is this a possible cause of fatigue:

Levels of K+, Na+ and Ca2+ can change disrupting membrane potential of muscle cell

Is this a possible cause of fatigue:

Increased inorganic phosphate (Pi) from CP and ATP breakdown may interfere with calcium release from SR or hamper power

Is this a possible cause of fatigue:

Decreased ATP and increased magnesium

Is this a possible cause of fatigue:

Decreased ATP and increased magnesium

Is this a possible cause of fatigue:

As ATP levels drop, magnesium levels increase, and this can interfere with voltage sensitive T tubule proteins

Is this a possible cause of fatigue:

decreased glycogen

Is this a possible cause of fatigue:

lack of ATP is rarely a reason for fatigue, except in severely strength

True or false

In order for muscles to return to its pre-exercise state:

oxygen reserves are replenished

True or false

In order for muscles to return to its pre-exercise state:

Lactic acid is reconverted to pyruvic acid

True or false

In order for muscles to return to its pre-exercise state:

Glycogen stores are replaced

True or false

In order for muscles to return to its pre-exercise state:

ATP and creatine phosphate reserves are resynthesized

what require extra oxygen, so this is referred to as excess postexercise oxygen consumption (EPOC)

Formerly referred to as“oxygen debt

What depends on the number of cross bridges attached

frequency of stimulation

2. number of muscle fibers stimulated (recruitment)

3. Relative size of fibers

4. Degree of muscle stretch

the higher the frequency, the greater the force

the more motor units recruited the greater the force

the more motor units recruited the greater the force

the bulkier the muscle, the more tension it can develop

Muscle cells can increase in size (hypertrophy) with regular exercise

What is muscle fibers with sarcomeres that are 80–120% their normal resting length generate more force

Which statements is true about the degree of muscle stretch

How fast a muscle contracts and how long it can stay contracted is influenced by

What is the speed of contraction and the metabolic pathways used for ATP synthesis two characteristics of

slow or fast fibers according to:

Speed at which myosin ATPases split ATP

Pattern of electrical activity of motor neuron

Oxidative fibers

Glycolytic fibers

What are the three types that skeletal muscle fibers can be classified into

What contain mixture of fiber types, resulting in a range of contractile speed and fatigue resistance

All fibers in one motor unit are the same type

Genetics dictate individual's percentage of each

low-intensity, endurance activities

Example: maintaining posture, running a marathon

medium-intensity activities

Example: sprinting or walking

short-term intense or powerful movements

Example: hitting a baseball

Contract slowly – slow myosin ATPases

Needs high O2 delivery

Thin fibers

Rich capillary supply

Numerous mitochondria

Red – high concentration of myoglobin

Less power because cells are thin = less actin and myosin

Long-lived sustaining energy

Less common

Intermediate diameter and power

Quick but O2 dependent

Rich capillary supply

Numerous mitochondria

Red – high concentration of myoglobin

Intermediate energy

Contract quickly– fast myosin ATPases

Needs low O2 delivery

Thick fibers (large diameter)

Little capillary supply

Few mitochondria

Abundant supply of glycogen

White – low concentration of myoglobin

More power because cells are thick = more actin and myosin

Short lived bursts of energy

such as jogging, swimming, biking leads to increased:

Muscle capillaries

Number of mitochondria

Myoglobin synthesis

Results in greater endurance, strength, and resistance to fatigue

May convert fast glycolytic fibers into fast oxidative fibers

(typically anaerobic), such as weightlifting or isometric exercises, leads to

Muscle hypertrophy

Due primarily to increase in fiber size

Increased myofilaments, glycogen stores, and connective tissue

Increased muscle strength and size

What must be active to remain healthy

(degeneration and loss of mass)

Due to immobilization or loss of neural stimulation

Can begin almost immediately

How much can muscle strength decline a day

What may atrophy to one-fourth the initial size

What replaces lost muscle tissue

What is found in walls of most hollow organs:

Respiratory, digestive, urinary, reproductive, and circulatory (except in smallest of blood vessels and heart)

Not found in heart – heart contains cardiac muscle, not smooth

Most ____ is organized into sheets of tightly packed fibers

Most ____ contain two layers of sheets with fibers oriented at right angles to each other.

fibers run parallel to long axis of organ

Contraction causes organ to shorten

fibers run around circumference of organ

Contraction causes lumen of organ to constrict

mix and squeeze substances through lumen of hollow organs

are spindle-shaped fibers thin and short compared with skeletal muscle fibers which are wider and much longer

Only one nucleus, no striations

Contains the endomysium only that wraps individual cells

What contain varicosities (bulbous swellings) of nerve fibers instead of neuromuscular junctions

What store and release neurotransmitters into a wide synaptic cleft referred to as a diffuse junction

Innervated by the autonomic nervous system

has less elaborate SR, and no T tubules

SR is less developed than in skeletal muscle

SR does store intracellular Ca2+, but most calcium used for contraction has extracellular origins

In smooth muscle what contains pouch like inholdings called caveolae

What contain numerous Ca2+ channels that open to allow rapid influx of extracellular Ca2+

Which muscle fibers fibers are usually electrically connected via gap junctions

Which muscle fibers are not directly connected electrically

What is specialized cell connections that allow depolarization to spread from cell to cell

In what muscle are there no striation and no sarcomeres but they do contain overlapping thick and thin filaments

Thick filaments are fewer and have myosin heads along entire length

Ratio of thick to thin filaments (1:13) is much lower than in skeletal muscle (1:2)

Thick filaments have heads along entire length, making smooth muscle as powerful as skeletal muscle

No troponin complex in the thin filaments

Does contain tropomyosin, but not troponin

Protein calmodulin binds Ca2+

What is arranged diagonally

are spirally arranged, causing smooth muscle to contract in corkscrew manner

dense body network

contain lattice-like arrangement of non contractile intermediate filaments that resist tension

During contraction, areas of sarcolemma between dense bodies bulge outward

Make muscle cell look puffy

proteins that anchor filaments to sarcolemma at regular intervals

Correspond to Z discs of skeletal muscle

slow, synchronized contractions

Cells electrically coupled by gap junctions

Action potentials transmitted from fiber to fiber

Some cells are self-excitatory (depolarize without external stimuli)

Act as pacemakers for sheets of muscle

Rate and intensity of contraction may be modified by neural and chemical stimuli

is this how smooth muscle contraction like skeletal muscle contraction or different

Actin and myosin interact by sliding filament mechanism

Final trigger is increased intracellular Ca2+ level

is this how smooth muscle contraction like skeletal muscle contraction or different

ATP energizes sliding process

Contraction stops when Ca2+ is no longer available

is this how smooth muscle contraction like skeletal muscle contraction or different

Some Ca2+ still obtained from SR, but mostly comes from the extracellular space

Ca2+ binds to calmodulin, not troponin

is this how smooth muscle contraction like skeletal muscle contraction or different

Activated calmodulin then activates myosin kinase (myosinlight chain kinase)

Activated myosin kinase phosphorylates the myosin head, activating it

Leads to crossbridge formation with actin

What requires more steps than skeletal muscle

What requires

Ca2+ detachment from calmodulin

Active transport of Ca2+ into SR and extracellularly

Dephosphorylation of myosin to inactive myosin by myosin light chain phosphatase

Slower to contract and relax but maintains contraction for prolonged periods with little energy cost

Slower ATPases

Myofilaments may latch together to save energy

maintain moderate degree of contraction constantly without fatiguing

Referred to as smooth muscle tone

Makes ATP via aerobic respiration pathway

what is controlled by nerves, hormones, or local chemical changes

Neurotransmitter binding causes either graded (local) potential or action potential

Results in increases in Ca2+ concentration in the sarcoplasm

Response depends on neurotransmitter released and type of receptor molecules

One neurotransmitter can have a stimulatory effect on smooth muscle in one organ, but an inhibitory effect in a different organ

Depolarize spontaneously or in response to chemical stimuli that bind to G protein–linked receptors

Chemical factors can include hormones, histamines, prostaglandins, gastrin, high CO2, low pH, low O2

what muscle cells have no nerve supply

respond to both neural and chemical stimuli

Which of the following are the special features of smooth muscle contraction

the stress-relaxation response responds to stretch only briefly, then adapts to new length

Retains ability to contract on demand

Enables organs such as the stomach and bladder to temporarily store contents

the stress-relaxation response responds to stretch only briefly, then adapts to new length

Retains ability to contract on demand

Enables organs such as the stomach and bladder to temporarily store contents

What vary by

fiber arrangement and organization

innervation

responsiveness to various stimuli

Which muscle is categorized by

uniatary and multiunit

Commonly referred to as visceral muscle

found in all hollow organs except the heart

found in all hollow organs except the heart

found in all hollow organs except the heart

Possess all common characteristics of smooth muscle:

Arranged in opposing (longitudinal and circular) sheets

Innervated by varicosities

Often exhibit spontaneous action potentials

Electrically coupled by gap junctions

Respond to various chemical stimuli

Located in large airways in lungs, large arteries, arrector pili muscles, and the iris of eye

Very few gap junctions, and spontaneous depolarization is rare

Like skeletal muscle in some features

Consists of independent muscle fibers

Innervated by autonomic nervous system, forming motor units

Graded contractions occur in response to neural stimuli that involve recruitment

Different from skeletal muscle because, like unitary smooth muscle, it is controlled by autonomic nervous system and hormones