Chapter 7: Muscular System Flashcards by Amy Guzman

Skeletal Muscles

Attached to bones; striated appearance; BOTH voluntary and involuntary

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Cardiac Muscles

Heart; striated appearance; Involuntary

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Smooth Muscles

Around hollow organs (stomach, blood vessels); non-striated; Involuntary

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Functions of Muscular System

Movement of body
Posture
Respiration
Body heat
Constriction of Organs (smooth muscle)
Contraction of Heart (cardiac muscle)

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What are the 4 functional properties of muscles?

-Excitability
-Contractility
-Elasticity
-Extensibility

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What is Excitability?

capacity of muscle to RESPOND to stimulus

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What is Contractility?

muscle shortens w/ force

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What is Elasticity?

muscle RECOILS back to original length after stretched

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What is extensibility?

muscle can stretch beyond normal resting length and STILL contract (w/out injury)

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Endomysium

loose connective tissue that SEPARATES each individual muscle fiber

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Perimysium

loose connective tissue that SURROUNDS AROUND group of muscle fibers (aka fascicles); AKA passage for blood vessels and nerves

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AGAIN… What are fascicles?

groups or bundles of muscle cells/fibers

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Epimysium

loose connective tissue that SURROUNDS WHOLE muscle (many fasciles)

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What are the 5 electrical components of a muscle?

-Sarcolemma
-Transverse tubules (T-Tubules)
-Sarcoplasmic reticulum (SR)
-Terminal Cisternae
-Triad

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What is the sarcolemma?

cell membrane of muscle cell/fiber (pink)

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What are T-Tubules?

In-foldings of sarcolemma; project into the interior of muscle cell (pink)

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What is the sarcoplasmic reticulum (SR)?

specialized smooth ER (endoplasmic reticulum) that stores/releases calcium…. (is also yellow)

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What is terminal cisternae?

enlarged ends of SR (yellow_

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What is triad?

consists of 2 terminal and 1 T-tubule

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Myofibrils

protein filaments made of myofilaments that cause contraction

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Myofilaments

Arranged into orderly units called sarcomeres

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Myofilaments have 1 thick version… what is it called?

Myosin

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What is myosin?

rod portion (proximal) and myosin head (distal) AKA, binding site …. golf clubs

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What are the 3 thin myofilaments?

-ACTIN (active site for myosin head to bind into)
-TROPOMYOSIN ( twisted blue rope; calcium binding site)
-TROPONIN (red jelly beans; 3 subunits that consists of actin, tropomyosin, and Ca+2)

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What is actin?

myosin head's binding site *purple beads*

What is troponin?

contains (3) calcium, tropomyosin, AND actin binding site *red jelly beans*

What is tropomyosin?

composed of 3 subunits called actin, tropomyosin, and calcium ions *twisted blue rope*

What is the sarcomere?

basic functional unit of muscle fiber; smallest part that can contract; BETWEEN 2 adjacent Z-disks

Z-disk:

filamentous network of protein; serves as attachment for actin myofilaments

Regions of sarcomere:

-M line -H zone -A bands -I bands

What is the M line?

middle of H zone; hold myosin in place (resembles a vertical CHAIN)

What is the H-zone?

portion of thick myofilament that doesn't overlap with thin myofilament (only contains thick green filament w/ M-Line)

What is the A-Bands?

entire length of thick filament + overlapping of thin filament

What are the I-Bands?

non-overlapping portion, only including thin myofilament and Z-disk

Which 2 regions of sarcomere create dark and light striations? AND WHICH is light & dark!?!

A= dArk striations i= LiGHT striations

When discussing action potential, what can be seen on a graph? (3 parts)

x-axis shows time milliseconds... y-axis measures units of millivolts voltage... AND threshold

What is the x-axis on a graph?

time milliseconds (ms)

What is the y-axis on a graph?

millivolts voltage (mV)

What is a threshold?

minimum amount of energy needed for action potential to happen

Resting membrane potential

no stimulation; cell is under -85 mV

Anything > 0 indicates positive or negative range?

POSITIVE

Anything < 0 (or at RMP) is negative or positive?

negative

What is depolarization?

Upstroke phase sodium ions can open w/ influx (inward movement) & potassium channels are closed

What is Repolarization?

downstroke phase; sodium channel closes & potassium opens w/ efflux (outward movement of ions)

What is hyperpolariization

small repolarized region that is BELOW resting membrane potential

Also, what causes hyperpolarization?

caused by closing of potassium; BTW it's the dip to the right on the graph

So... once cell is fully stimulated by action potential... now what?

it must now go down again and rest; HOWEVER, HOW? it requires both, the Na+/K+ pump with ATP (Na+ goes OUT & k+ goes IN)

What does influx mean?

inward movement of ions (ion goes inside in cell)

What does eflux mean?

outward movement of ions (ions move out of cell)

What 3 channels are used in action potential?

Na+, Ka+, AND Na+/K+ pump

What 4 events lead to muscle contraction (NMJ)?

1. Presypnatic Terminal 2. Synaptic cleft (gap) 3. Postsynaptic terminal 4. Interactions of myofilaments *cross-bridge formation*

Twitch (from muscle)

complete contraction and relaxation of muscle

What are the 2 types of skeletal muscle contraction?

-Isotonic (change in muscle length) -Isometric (no change)

Rigor Mortis

stiffness after death CAUSED BY lack of ATP

Within isotonic contraction, there are 2 terms for muscle lengths?

Concentric: shorten of muscle Eccentric: lengthening of muscle

Smooth muscle

-not striated, -has caveolea (indentation in sarcolemma) -has dense bodies -calcium binds to calmodulin (cross-bridging occurs)

Cardiac Muscle

-found in heart -striated & branched -has intercalated disks & gap junctions -use both Na+ and Ca2+ influx for depolarization

Skeletal Muscle Anatomy

-origin -insertion -belly -agonist -antagonist

What is the origin/head of a muscle?

muscle end attached to 2 bones

What is insertion?

muscle end attached to bone w/ greatest movement

What is the belly of a muscle?

largest portion of muscle BETWEEN origin & insertion

What is the agonist?

contracted muscle that causes an action

What is the antagonist?

muscle working in opposition to agonist

What are muscle names based on?

-Location -Size -Shape -Orientation of fascicles -Origin & Insertion -Number of heads -Function (abductors or adductors)

Muscles of Facial Expression

14 in total (continue page 17)