Chapter 6 (Locomotion)

Question 1

Describe nematode locomotion.

Answer 1

• movement achieved by redistribution of bodily fluid

- muscle fibers contract on one side of the body and relax on the other side; body bends

Question 2

Describe earthworm locomotion.

Answer 2

• circular muscle contracts to push coelomic fluid forward

- longitudinal muscle contracts to pull posterior body segments forward

Question 3

Describe squid locomotion.

Answer 3

• jet propulsion forces water from body cavity through siphon

Question 4

Differences between white, red and pink muscles in fish

Answer 4

• white muscles: glycolytic, high intensity activity
• red muscle: oxidative, most active during steady state movement
• pink muscle: separates white and red muscles; function is in between the two

Question 5

myotome

Answer 5

• repeating units that make up fish white muscle

Question 6

striated vs. smooth skeletal muscle

Answer 6

• striated: actin and myosin arranged in parallel (sarcomeres); skeletal and cardiac muscle
• smooth: actin and myosin not arranged in parallel (no sarcomeres)

Question 7

A skeletal muscle cell is called a ___, which is composed of many ___.

Answer 7

myofiber; sarcomeres

Question 8

thick filament vs thin filament

Answer 8

• thick filament: polymers of myosin

- thin filament: composed of actin

Question 9

Z disk

Answer 9

• protein plate at the ends of each sarcomere

- point of attachment for thin filament (+ end) (anchored by CapZ)

Question 10

titin

Answer 10

• holds thick filament in position

- anchors thick filament to the Z disk

Question 11

nebulin

Answer 11

• parallels thin filaments

- establishes appropriate length of each thin filament

Question 12

A-band (anisotropic band)

Answer 12

dark region of sarcomere where thick filaments occur

Question 13

I-band (isotropic band)

Answer 13

• narrow region spanning Z disk

- the part of thin filaments that don’t overlap thick filaments (only overlaps titin)

Question 14

M-line

Answer 14

gap between thin filaments

Question 15

sarcomeres arranged in parallel vs. arranged in series

Answer 15

• parallel: shorten only a small amount but generate a lot of force
• series: generate less force but shorten more and shorten faster

Question 16

troponin and tropomyosin

Answer 16

• troponin binds to every 7th actin filament
• tropomyosin spans 7 actin filaments (between troponin)
• forms complex with tropomyosin to block myosin binding site on actin during low Ca2+ levels (will roll out of the way during high Ca2+)

Question 17

Describe the sliding filament model.

Answer 17

• myosin heads detach due to ATP binding
• ATP hydrolyzed into ADP and Pi (remain bound by myosin)
• this hydrolysis causes myosin to re-attach to actin further down
• Pi released, promoting power stroke that moves actin
• ADP released from myosin, ATP binding site on myosin free again

Question 18

unitary displacement

Answer 18

distance that myosin steps after each cross bridge cycle (about 36 nm)

Question 19

neurogenic muscles

Answer 19

muscles that receive signals from a motor neuron

Question 20

nicotinic receptors are involved with which neurotransmitter

Answer 20

acetylcholine

Question 21

What part of the muscle stores and releases Ca2+ during excitation-contraction coupling?

Answer 21

sarcoplasmic reticulum

Question 22

role of Ca2+ in muscle contraction

Answer 22

• binds to troponin complex, causing it to unblock myosin binding site on actin
• allows myosin cross-bridges to bind to actin filaments

Question 23

What triggers the release of intracellular Ca2+ in a muscle cell?

Answer 23

• action potentials conducted deep into the muscle fiber

- depolarization induced Ca2+ release or Ca2+ induced Ca2+ release

Question 24

difference between depolarization induced Ca2+ release and Ca2+ induced Ca2+ release

Answer 24

• depolarization induced Ca2+ release: RyR opening triggered by changes in DHPR structure upon depolarization of plasma membrane
• Ca2+ induced Ca2+ release: RyR opening triggered by elevated cytoplasmic Ca2+ levels cause by depolarization that opens DHPR

Question 25

motor pool

Answer 25

the collection of motor neurons that innervate a muscle

Question 26

asynchronous muscle vs synchronous muscle

Answer 26

• asynchronous muscle contracts more than once for every one nerve signal/action potential
• synchronous muscle contracts only once for every AP