Muscle Models

Question 1

aponeurosis

Answer 1

like a tendon, connective tissue layer forms a thin, flattened sheet of dense irregular tissue

connect muscle to bone

Question 2

deep fascia

Answer 2

additional expansive sheet of dense irregular connective tissue external to epimysium

separates individual muscles, binds muscles with similar functions, contains nerve, blood, lymph vessels, fill space between muscles

Question 3

endomysium

Answer 3

between fascicles

innermost layer, delicate areolar connective tissue layer surrounds and electrically insulates each muscle fiber

reticular protein fibers help bind neighboring muscle fibers and support capillaries

Question 4

epimysium

Answer 4

wraps muscle

layer of dense irregular connective tissue surrounding whole skeletal muscle

protection

Question 5

fascicles

Answer 5

bundles of many organized muscle fibers (myofibers)

keep together

Question 6

gap junctions

Answer 6

protein pores between sarcolemma of adjacent cardiac muscle cells; provide low-resistance pathway for ion flow allowing action potential to move continuously resulting in synchronous contraction

Question 7

muscle fibers (cells)

Answer 7

in fascicles

skeletal muscle cells, extraordinarily long, mulinucleated because of fused myoblasts

Question 8

myofibrils

Answer 8

long, cylindrical structures composing 80% of volume of a muscle fiber; contain myofilaments

Question 9

perimysium

Answer 9

around fascicles

surrounds fascicles, dense irregular connective tissue sheath contains extensive blood vessels and nerves that branch to supply muscle fibers within each fascicle

Question 10

tendons

Answer 10

thick, cord like structure, dense regular connective tissue, 3 layers as they merge and extend past muscle fibers

attach muscle to bone, skin, or another muscle

Question 11

A bands

Answer 11

central region of sarcomere containing entire thick filament; thin filaments partially overlap on ends

never changes length

Question 12

Actin

Answer 12

protein of thin filaments

contains myosin binding site

Question 13

H zone

Answer 13

no actin, most central portion of A band in a resting sarcomere, no thin filament overlap- only thick

disappears when thin is pulled past thick during maximum muscle contraction

Question 14

I bands

Answer 14

extend from both ends of and are bisected by the Z disc, contain only thin filaments (light)

disappears during contraction as thin filaments are pulled past thick filaments

changes length during contraction

Question 15

M line

Answer 15

thin transverse protein meshwork structure in center of H zone serving as attachment site for thick filaments and keeps thick filaments aligned during contraction/relaxation events

Question 16

motor end plate

Answer 16

specialized region of sarcolemma with numerous folds to increase surface area covered by synaptic knob, vast acetylcholine receptors

Question 17

motor neuron

Answer 17

nerve cells that transmit nerve signals from brain or spinal cord, axon branches to innervate numerous skeletal muscle fibers

Question 18

motor unit

Answer 18

single motor neuron and the muscles it controls

size determines the degree of control

Question 19

myofilaments

Answer 19

bundles of muscle protein fiber

Question 20

myosin

Answer 20

protein makes up thick filaments; 2 strands with globular head and elongated tail

site for ATP to break into ADP and Pi

Question 21

sarcolemma

Answer 21

plasma membrane of a skeletal muscle fiber

Question 22

sarcomere

Answer 22

composed of overlapping thick and thin filaments, repeating microscopic cylindrical units

Question 23

sarcoplasmic reticulum

Answer 23

internal membrane complex similar to smooth endoplasmic reticulum, surround bundles of myofibrils

Question 24

synaptic cleft

Answer 24

extremely narrow fluid-filled spec separating synaptic knob and motor end plate

residing place of acetylcholinesterase (AChE)

Question 25

T tubules

Answer 25

transverse tubules

deep invaginations of sarcolemma extending into muscle fibers as a network of narrow membranous tubules

contain NA/K pumps and channels used for muscle contraction

Question 26

terminal cisterns

Answer 26

blind sacs at ends of individual sections of sarcoplasmic reticulum surrounding t- tubule

serve as reservoirs for Calcium cation

Question 27

thick filaments

Answer 27

about 11 nanometer diameter made of 200-500 myosin protein molecules

Question 28

thin filaments

Answer 28

about 5-6 nanometer diameter made of 2 strands of twisted/helical actin protein

Question 29

tropomyosin

Answer 29

short, thin, twisted filament, “string like” protein

cover actin strands and myosin binding sites

Question 30

troponin

Answer 30

globular/ ball-like protein attached to tropomyosin

binding site for calcium cation

Question 31

Z disc

Answer 31

composed of specialized proteins positions perpendicular to myofilaments and serve as anchors for thin filaments

delineate ends of the sarcomere

Question 32

Order of skeletal muscle

Answer 32

thick- myosin and thin- actin
myofilaments
myofibrils
muscle fiber (wrapped in endomysium)
fascicle (wrapped in perimysium)
skeletal muscle (wrapped in epimysium)