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145 Cards in this Set

  • Front
  • Back

What are the cells of muscle tissue highly specialized for?


What are the 3 types of muscle tissue?




What does skeletal muscle tissue move?

the body

What does cardiac muscle tissue move?

blood through the body

What does smooth muscle tissue move?

fluids and objects through the digestive system and several other functions

List the functions of skeletal muscle tissue.

i. Producing skeletal movement by pulling on the bones of the skeleton.

ii. Maintain posture and body position.

iii. Supporting soft tissues.

iv. Guarding entrances and exits.

v. Maintaining body temperature.

vi. Store nutrient reserves.

What is the name of the connective tissue surrounding the entire muscle that separates it from other tissues and organs?


What connective tissue surrounds each fascicle? (or divides the muscle into compartments)


What is a bundle of muscle fibers known as?


What is the connective tissue that surrounds each muscle fiber?


What are the embryonic stem cells that function in muscle tissue repair?

Satellite cells

The epimysium, perimysium, and Endomysium come together at the ends of the muscle to form?


What is an aponeurosis?

Broad tendinous sheet

What are the tendon fibers that are interwoven into the periosteum of bones providing strong attachment?

Perforating fibers (Sharpey's fibers)

What do the epimysium and perimysium contain?

Abundant blood vessels and nerves.

Skeletal muscle fibers are longer than typical cells.


Skeletal muscle fibers are multinucleate.


What is multi-nucleation important in skeletal muscle fibers?

Because the multiple copies of genes can make multiple copies of protein; muscle cells need lots of proteins for high metabolic turnover

What are myoblast?

Embryonic cells that fuse together to form the muscle fibers.

Where do satellite cells come from?

Unfused embryonic cells, assist in regenerating muscle tissue.

What is the cell membrane of a muscle fiber known as?


What is the cytoplasm of a mucsle fiber known as?


What are T tubules are what is there function?

Narrow tubes, continuous with the sarcolemma and extend into the sarcoplasm; Help conduct action potentials (contraction signal) to the sarcoplasm

What is a myofibril?

Cylindrical structures that consists of myofilaments (consist of thin filaments and thick filaments); actively shorten; when they contract the entire muscle cell shortens

What are myofilaments?

Protein filaments that are made of mostly actin and myosin.

What is the endoplasmic reticulum of the muscle cells? What does it store?

Sarcoplasmic reticulum; Ca2+ ions

What is a triad?

Combination of 2 terminal cisternae and a transverse tubule.

The smallest functional units of muscle are?


Muscle contraction comes from interactions of?

Thick and thin filaments

What are the dark bands toward the center of a filament?

A bands

What type of filaments is this band made of?

thick filaments

What is the M line and what is its purpose?

thin filament, proteins stabilize the positions of the thick filament

What is the area that contains thick filaments only?

H zone

What is the zone of overlap?

area where thin filaments are found between the thick filaments

What are the light colored bands?

I bands

What type of filament is contained in this band?

thin filaments only

What is the boundary between the sarcomeres?

Z lines

Why do muscles appear banded?

keeps thin and thick filaments in alignment

What is titin and what are the functions?

protein that extends from the tip of the thick filament to the attachment site at Z line; helps prevent extreme stretching.

What is desmin and what are the functions?

protein that make the intermediate filaments that surround Z line; interconnect sarcomeres

What is the progressive muscular weakness and deterioration caused by abnormal genes that code for structural and functional proteins in muscle fibers?

Muscular dystrophies

What type of filament is attached to the Z line?

Thin filament

What is tropomyosin and what is its function?

Protein strands that prevent actin-myosin interaction by covering the active sites

What is troponin and what is its function?

Made of three globular subunits; 1st subunit locks the subunit to tropomyosin; 2nd subunit holds the troponin-tropomyosin complex in position; 3rd subunit has receptors to bind Ca+2.

A change in the position of troponin-tropomyosin complex that exposes the active sites of F actin is necessary for a contraction.

What is the main thin filament that interacts with myosin?


What is the thick filament?

Consist of a pair of myosin molecules, each consisting of an elongated tail and a cross-bridge.

What is the sliding filament theory?

Explains how the relationship between thick and thin filaments changes as the muscle contracts and shortens.

Skeletal Muscle fibers contract only under the control of the?

Nervous system

What is the expanded branch end of an axon?

Synaptic terminal

What is acetylcholine?

ACh; neurotransmitter that changes the membrane potential of other cells.

What is the gap that separates the synaptic terminal of a neuron and the motor end plate?

Synaptic cleft

Where is the motor end plate? What does it contain?

Surface of the sarcolemma; has junctional folds - deep creases that increase the surface area and the number of ACh receptors.

What is the enzyme that breaks down ACh?


Describe the steps of skeletal muscle contraction from neural stimulation to myosin reactivation and relaxation.

Active-site exposure - Ca+2 ions bind to troponin, which changes position and moves tropomyosin away from the active sites of actin. Cross-bridge attachment - cross-bridges of myosin heads then bind to actin. Pivoting - each myosin head pivots at its base, pulling the actin filament toward the center of the sarcomere (power stroke); ADP and phosphate group are released. Cross-bridge detachment; active site is exposed again. Myosin reactivation

Describe excitation-contraction coupling.

Occurs as the passage of an action potential reaches the triads; triggers the release of Ca+2 from the cisternae of the SR; the Ca+2 concentration is 100X that of the resting level; the active sites along the thin filaments are exposed by the binding of Ca+2 to troponin; start of contraction cycle.

What happens in Botulism?

Bacterial toxin prevents the release of ACh at the synaptic terminals; can be fatal.

What happens in Myasthenia gravis?

Progressive muscular paralysis that occurs when the immune system attacks the ACh receptors and reduces them.

What is Rigor mortis and why does it happen?

Physical state in which the body becomes very "stiff"; all muscles are locked into a contraction because there is no ATP to detach the myosin cross-bridges; lasts 15-25 hours.

What 3 things determine the duration of contraction?

i. The length of stimulation at the neuromuscular junction.

ii. AChE breaks down ACh.

iii. Limits the duration of stimulation.

What 2 mechanisms return Ca ion concentration back to normal?

i. Active Ca+2 transport across the cell membrane into the extracellular fluid.

ii. Active Ca+2 transport into the sarcoplasmic reticulum

What happens when Ca ion concentrations in the sarcoplasm fall?

i. Ca+2 ions detach from troponin.

ii. Troponin returns to its original position.

iii. Active sites covered by tropomyosin.

The amount of tension produced by an individual muscle fiber ultimately depends on what?

The number of pivoting cross bridges

What is the all or none principle?

Muscle fiber is either "on" -- producing tension or "off" -- relaxed.

What does the number cross-bridges depend on?

Degree of overlap between thick and thin filaments within sarcomeres.

What are the only myosin heads that can interact with the active sites?

Zone of overlap

What happens when thick filaments are jammed against Z-lines?

No tension produced

What happens when thin filaments extends across the center of the sarcomere or overlap thin filaments from opposite sides?

Little tension produced

When is the highest tension produced?

Optimal range is where maximum number of cross-bridges can form.

What prevents extreme compression or extensive stretching?

The arrangement of skeletal muscles, connective tissues, and bones.

What is a twitch?

Frequency of stimulation; a single stimulus produces a single contraction.

What is a graph of tension development in muscle during a twitch contraction?


What are the 3 phases of a twitch?

Latent period

Contraction phase

Relaxation phase

What phase begins at stimulus?

Latent period

In which phase does the action potential sweep across the sarcolemma and SR releases Ca ions?

Latent period

In which phase does tension rise to a peak?

Contraction phase

In which do Ca ions bind to troponin, active sites exposed, and cross bridge interactions occur?

Contraction phase

In which phase do Ca levels fall?

Relaxation phase

In which phase do active sites get covered and cross bridges decline?

Relaxation phase

If a skeletal muscle is stimulated a second time immediately after relaxation phase ends, what is this called? What is this due to?

Treppe; Gradual increase in Ca ion concentration.

The addition of one twitch plus another is?

Summation of twitches or wave summation

If stimulation continues and muscle is never allowed to relax completely this is known as?

Incomplete tetanus (tension peaks)

When stimulation is increased until relaxation phase is eliminated, this is known as?

Complete tetanus

The amount of tension produced in the skeletal muscle as a whole is determined by what two things?

i. Internal and external tension produced by the stimulated muscle fibers.

ii. The total number of muscle fibers stimulated.

What generates the internal tension?

The myofibrils in the muscle fibers.

Where is the internal tension applied?

To the extracellular fibers.

Where is external tension?

The tension in the extracellular fibers

What happens to extracellular fibers as external tension rises?

External tension does not climb as fast as internal tension upon concentrations.

What are these extracellular fibers called?

Series elastic elements (fat rubber bands)

What climbs faster internal or external tension?

Internal tension

What is a motor unit?

All of the muscle fibers controlled by a single motor neuron.

What does the size of a motor unit indicate?

How fine the control of movement can be.

The smooth, steady increase in muscle tension produced by the increasing number of active motor unit is called?

Recruitment or multiple motor unit summation

What is asynchronous motor unit summation?

During sustained titanic contractions, motor units are activated on a rotating basis - some are resting and recovering while other are contracting - relay team.

Resting tension in skeletal muscle is known as?

Muscle tone

What does muscle tension cause?

In skeletal muscle, some motor units are always contracting, even when entire muscle is not contracting.

When tension rises and the skeletal muscle length changes, this is known as?

Isotonic contractions

When muscle tension exceeds the resistance and the muscle shortens, this is known as a?

Concentric contraction

When the peak tension developed is less than the resistance, and the muscle elongates owing to the contraction of another muscle or the pull of gravity, this is known as?

Eccentric contraction

A contraction where tension rises and does not exceed the resistance and the length of the muscle remains constant is known as?

Isometric contractions

What 3 things elongate the muscle fiber after the contraction is over?

1. Series elastic elements recoil.

2. Opposing muscle contractions.

3. Gravity.

What is the function of ATP?

To transfer energy from one location to another.

What is the reaction of ATP + creatine? Importance?

ADP + creatine phosphate; At rest, skeletal muscle fiber produces more ATP than i needs - ATP transfer energy to creatine.

What is the reaction of ADP recharging ATP? Importance?

During contraction, each myosin head breaks down ATP producing ADP and a phosphate group. The energy stored in creatine phosphate is used.

Aerobic metabolism occurs in the?


What percentage of ATP needed by the resting cell is provided by aerobic metabolism?


The substrates from aerobic metabolism absorbed by the mitochondria enter what cycle?

TCA cycle (Tricarboxylic acid cycle)

How many ATP are produced per pyruvic acid?

17 ATP

A resting muscle fiber uses _______ for aerobic metabolism.

Fatty acids

A contracting muscle fiber uses _________ for aerobic metabolism.

Pyruvic acid

The breakdown of glucose to pyruvic acid in cytoplasm is aerobic or anaerobic?


How many ATP does this produce?


What is the primary source of ATP product during peak periods of activity?


Resting Levels

i. Demand for ATP is low.

ii. Aerobic metabolism provides surplus of ATP.

Moderate Levels

i. Demand for ATP increases.

ii. Metabolism can provide most of the necessary ATP to support muscle contractions.

iii. Glycolysis contribution is minor.

Peak Levels

i. The cell relies heavily on the anaerobic process of glycolysis to generate ATP because the mitochondria cannot obtain enough oxygen to meet existing ATP demands.

What are the draw backs to glycolysis?

(1) Produces pyruvic acid faster than can be used by the mitochondria, then pyruvic acid is converted by lactate dehydrogenase (LDH)(enzyme) to lactic acid. (2) lactic acid - organic acid that will lower the intracellular pH; after a while the low pH will change the functional characteristics of important enzymes. (3) inefficient, it only produces 2 ATP (aerobic metabolism can produce 34 more ATP)

When a muscle can no longer contract regardless of continued neural stimulation, this is known as?

Muscle fatigue

What causes muscle fatigue?

(1) Depletion of ATP and CP reserves.

(2) Changes in pH due to buildup of lactic acid. (3) Physical damage to sarcoplasmic reticulum and sarcolemma.

(4) Normal muscle functions require.

What 3 things do normal muscle functions require?

(1) Substantial intracellular energy reserves.

(2) Normal circulatory supply.

(3) Normal blood oxygen concentration.

The time where conditions inside the muscle fibers are returned to preexertion levels is the?

Recovery period.

The shuffling of lactate to the liver and glucose back to muscle cells is the?

Cori cycle

What is the oxygen debt?

The amount of oxygen used in the recovery period to restore normal conditions.

Active skeletal muscles generate and release ______ of heat needed for normal body temperature.


What hormone stimulates the generation of contractile proteins and enlargement of skeletal muscles?

Growth hormone and testosterone

What hormone increases the rate of energy consumption by muscles?

Thyroid hormones

What hormone stimulates muscle metabolism and increases duration of stimulation and force of contraction?

Epinephrine (adrenaline) hormone

The amount of time an individual can perform an activity is?


The maximum amount of tension produced by a specific muscle or muscle group is?


What are the 2 factors that determine muscle performance?

Types of muscles fibers and physical conditioning.

Fast Muscle Fibers

(1) Most of the skeletal muscle fibers. (2) Can contract in .01 sec or less. (3) Large in diameter. (4) Contain densely packed myofibrils. (5) Large glycogen reserves. (6) Relatively few mitochondria. (7) Produce rapid and powerful contractions of relatively brief duration. (8) Fatigue rapidly

Slow Muscle Fibers

(1) Half the diameter of fast fibers. (2) Take 3X as long to contract after stimulation. (3) Abundant mitochondria. (4) Extensive capillary supply. (5) High concentration of myoglobin. (6) Continue contracting for extended periods of time. (7) Dark red in color.

What are similar to fast fibers by having a greater resistance to fatigue?

Intermediate fibers

Muscles that consist of mainly fast fibers are?

White muscles

Muscles that consist of mainly slow fibers are?

Red muscles

What type of fibers do human muscles contain? What determines this?

A mixture of fast, slow, and intermediate fibers so our muscles look pink; The pecentage of slow to fast fibers is genetically

An enlargement of muscle due to an increase in the diameter of individual muscle fibers is?


A reduction in muscle size, tone, and power is?


What type of muscle tissue contracts without neural stimulation?

Cardiac muscle tissue

What type of muscle tissue has no sarcomeres?

Smooth Muscle Tissue

What type of metabolism does cardiac muscle depend on?

Aerobic metabolism

What is the importance of intercalated discs?

Help stabilize positions.

What is the trigger for smooth muscle contraction?

Ca ions moving into cytoplasm

What does calcium interact with in smooth muscle contraction?


What does the plasticity of smooth muscle mean?

Ability to contract over a wide range of lengths.

What is the arrangement of thin and thick filaments in smooth muscle?

Scattered, tension development and resting length are not related.