Chapter 9

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Is skeletal muscle striated?

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120 Terms

1

Is skeletal muscle striated?

yes it's striated

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2

Is skeletal muscle branched?

no

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3

Is skeletal muscle voluntary or involuntary?

voluntary

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4

Does skeletal muscle need nervous stimulation?

yes

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What is excitability?

ability to receive and respond to stimuli by changing membrane potential

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What is contractility?

ability to shorten forcibly when stimulated

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What is extensibility?

ability to extend or stretch

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8

What is elasticity?

ability to recoil and return to resting length

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9

What are the four functions of muscle?

movement, posture, joint stability, heat production

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10

What is a muscle?

an organ that consists of many muscle cells, connective tissue wrapping, blood vessels, and nerve fibers

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What is a fascicle?

bundle of muscle cells that is separated from the rest of the muscle by a connective tissue sheath

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What is a muscle fiber?

an elongated multinucleate contractile cell, with striated appearance

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13

What is a myofibril?

rodlike structures inside muscle fibers that contain myofilaments

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14

Is cardiac muscle striated?

yes it's striated

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15

Is cardiac muscle branched?

yes

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16

Is smooth muscle striated?

no striations

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17

Is smooth muscle branched?

no

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Is cardiac muscle voluntary or involuntary?

involuntary

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19

Is smooth muscle voluntary or involuntary?

involuntary

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What is a sarcomere?

Contractile unit of striated muscle

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What is the H zone?

segment with no thin filaments (thick only)

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What is the M line?

anchoring site for thick filaments

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What is the Z disc (line)?

anchoring site for thin filaments, aka the dividing line

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What are thick filaments made of?

myosin protein

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What are thin filaments made of?

actin protein

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What happens during the sliding filament theory?

thin filaments slide across thick filaments, H zone disappears with contraction, then z discs get closer to m line with contraction

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stages of skeletal muscle contraction

  1. motor neuron excitation, 2) stimulation by acetylcholine, 3) excitation-contraction coupling, 4) cross-bridge cycling

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Steps of muscle fiber excitation

  1. action potential, 2) voltage-gated calcium channels open, 3) release of acetylcholine, 4) ACh receptors at neuromuscular junction, 5) ACh binds ti receptors, sodium enters, end plate potential, 6) acetylcholinesterase degrades ACh

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What is action potential?

a massive, all-or-none, depolarization of a cell's membrane

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What is excitation-contraction coupling?

events that transmit action potential along sarcolemma lead to sliding of myofilaments

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Steps of Excitation-Contraction Coupling

  1. The action potential (AP) spreads from the cell membrane into the T tubules.

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  1. Voltage-sensitive proteins stimulate release of Ca2+ from SR

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  1. Calcium binds to troponin on thin filaments

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  1. Contraction begins by cross bridge cycling

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steps of cross bridge cycle

  1. Cross bridge formation, high-energy myosin head attaches to actin thin filament active site

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  1. Power stroke, myosin head pivots, pulls thin filaments to M line

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  1. Cross bridge detachment, ATP attaches to myosin head, causing detachment

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  1. Cocking of myosin head, ATP cocks myosin head into high-energy state

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What is a motor unit?

one motor neuron and all the muscle fibers it innervates

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Which muscle fiber type is both involuntary and not branched?

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a) Skeletal muscle

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b) Cardiac muscle

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c) Smooth muscle

c) Smooth muscle

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Which structure of a sarcomere serves as the anchor for thin filaments?

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a) H zone

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b) I band

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c) M line

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d) Z disc

d) Z disc

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Select the true statement about muscle contraction in the sliding filament model.

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a) The A band gets shorter

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b) The Z discs get closer to the M line

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c) Myosin thin filaments pull on the thick filaments

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d) Cross bridges only break when the muscle relaxes

b) The Z discs get closer to the M line

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How does the body stop the stimulation of muscle fibers by acetylcholine?

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a) ACh breakdown by acetylcholinesterase

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b) ACh reuptake by motor neurons

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c) Inactivation of ACh receptors at the end plate of the neuromuscular junction

c) Inactivation of ACh receptors at the end plate of the neuromuscular junction

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What is triggered when the action potential reaches the end of the T tubules?

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a) Calcium is released from the sarcoplasmic reticulum

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b) Sodium flows into the sarcoplasm

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c) Calcium flows into the motor neuron axon terminal

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d) Calcium is moved back into the sarcoplasmic reticulum

a) Calcium is released from the sarcoplasmic reticulum

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What would happen to the cross-bridge cycle if there was no ATP available?

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a) The myosin head would not be able to attach to the actin filament > flaccid muscle

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b) The myosin head would not be able to release from the actin filament > rigid muscle

b) The myosin head would not be able to release from the actin filament > rigid muscle

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From what two sources can higher tension be produced by a skeletal muscle?

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a) Higher frequency stimulation

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b) Lower frequency stimulation

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c) Higher recruitment of motor neurons

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d) Lower recruitment of motor neurons

a) Higher frequency stimulation

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