Ch. 9 Muscular System

Question 1

Skeletal muscle structure

Answer 1

• fasciculus
• perimyseum
• epimysium
• muscular fascia

Question 2

Fasciculus

Answer 2

bundled muscle fibers

Question 3

Perimyseum

Answer 3

-heavy connective tissue layer that surrounds fasciculus

Question 4

Epimysium

Answer 4

-surrounds the entire muscle (dense collagenous connective tissue)

Question 5

Muscular fascia

Answer 5

• superficial to the epimysium

- separates or compartmentalizes invidual muscles or groups of muscles

Question 6

Muscle fibers

Answer 6

• sarcolemma
• endomysium
• transverse tubules
• sarcoplasmic reticulum
• sarcoplasm
• myofibrils

Question 7

Sarcolemma

Answer 7

-plasma membrane

Question 8

Endomysium

Answer 8

• superficial, thicker layer outside of sarcolemma
• reticular fibers
• surrounds muscle fibers

Question 9

T-tubules

Transverse tubules

Answer 9

• tubelike invaginations along surface of sacrolemma

- little tunnels that enter into the cell (fiber)

Question 10

Sarcoplasmic reticulum

Answer 10

• modified endoplasmic reticulum

- maze of organelles inside sarcoplasm

Question 11

Sarcoplasm

Answer 11

• cytoplasm of muscle cell (fiber)

- muscles contain very little of this

Question 12

Myofibrils

Answer 12

• inside muscle fiber and sarcoplasm

- bundles of protein filaments

Question 13

Myofilaments

Answer 13

• the protein filaments that are inside a myofibril

- actin and myosin

Question 14

Actin

Answer 14

-thin myofilament

Question 15

Myosin

Answer 15

-thick myofilament

Question 16

Sacromeres

Answer 16

• basic unit of contraction
• actin
• myosin
• titin
• cross bridging
• Z disks

Question 17

Actin

Answer 17

• structural framework of sacromere

- contains g actin, f actin, tropomyosin, troponin

Question 18

G-actin

Answer 18

• each round molecule within actin

- contains the active site

Question 19

F-actin

Answer 19

-long chains of g-actin

Question 20

Tropomyosin

Answer 20

-double strand rope that wraps around double f-actin strand

Question 21

Troponin

Answer 21

-long portion binds to tropomyosin which opens active site so that myosin can bind

Question 22

Myosin

Answer 22

• motor protein
• molecules are bundled together (golf club shaped)
• brings Z disks together (contracts)
• the two heavy chains (rods) are wrapped around each other
• light chains (heads) are molecules located on the globular heads

Question 23

Titin

Answer 23

• begins at one Z disk and goes to the other Z disk
• holds Z disk together under tension
• largest single protein known
• allows sacromere to extend and contract

Question 24

Z-disks

Answer 24

-actin myofilament is attached to this

Question 25

Cross-bridge

Answer 25

-where heads of myosin bind with active sites on actin

Question 26

I band

Answer 26

-includes Z disk and extends from each side of the Z disk to the ends of the myosin myofilaments

Question 27

A band

Answer 27

-extends the length of the myosin myofilaments within a sacromere

Question 28

H zone

Answer 28

-center of A band where myosin and actin do not overlap

Question 29

Membrane potentials

Answer 29

- resting membrane potential | - action potential

Question 30

Resting membrane potential

Answer 30

- when the inside of cell is more negatively charged (-85 mv) and the outside of the cell is positively charged - inside plasma membrane: high K+ concentration - outside plasma membrane: high Na+ concentration - plasma membrane is more permeable to K+ than Na+

Question 31

Action potentials

Answer 31

- chemical signal communication | - caused by depolarization, repolarization, threshholds and propagation

Question 32

Threshold

Answer 32

- considered point of no return | - once met, Na+ flows into cell (depolarization)

Question 33

Depolarization

Answer 33

-Na+ flow inside of cell causing the charge to become positive (+20 mv)

Question 34

Repolarization

Answer 34

- return of membrane potential to its resting value (-85 mv) | - K+ flow out of cell

Question 35

Propagation

Answer 35

- action potentials that travel across the plasma membrane because of stimulation - the spreading over membrane of voltage gates opening (think domino effect)

Question 36

Neuromuscular junction

Answer 36

- where axon branch interdigitates with sarcolemma - one neuromuscular junction centrally located per muscle fiber - include presynaptic terminal, synaptic cleft, synaptic vesicles, neurotransmitters, acetylcholinesterase

Question 37

Presynaptic terminal

Answer 37

-each axon terminal

Question 38

Synaptic cleft

Answer 38

-space between the presynaptic terminal and sarcolemma of muscle fiber

Question 39

Postsynaptic terminal (motor end plate)

Answer 39

-muscle plasma membrane (sarcolemma) in the area of the junction

Question 40

Synaptic vesicles

Answer 40

- storage of neurotransmitters | - spherical sacs inside presynaptic terminal

Question 41

Neurotransmitter

Answer 41

- substance released from a presynaptic membrane that diffuses across the clet and alters the activity of the postsynaptic cell - acetylcholine: inside synaptic vesicles; organic molecule of acetic acid and choline

Question 42

Acetylcholinesterase

Answer 42

- enzyme that breaks down ACH to acetic acid and choline | - breaks down ACH so that it does not accumulate in cleft causing a constant stimulus