Chapter 50 (Motor Mechanism)

Question 1

skeletal muscle

Answer 1

moves bones and the body and is characterized by a hierarchy of smaller and smaller units. consists of a bundle of long fibers, each a single cell, running along the length of the muscle

Question 2

Myofibrils

Answer 2

Each muscle fiber (cell) is itself a bundle of smaller myofibrils arranged
longitudinally

Question 3

Muscle cell contraction relies on what interaction

Answer 3

interaction between thin filaments, composed mainly of actin, and thick filaments, staggered arrays of

Question 4

Myoblast

Answer 4

Mononucleated, undifferentiated muscle precursor cell. A skeletal muscle cell is formed by the fusion of multiple myoblasts.

Question 5

sliding-filament model

Answer 5

thin and thick filaments ratchet past each other longitudinally, powered by the myosin molecules

Question 6

The regulatory protein tropomyosin and the troponin complex

Answer 6

a set of additional proteins, bind to actin strands on thin filaments when a muscle fiber is at rest. This prevents actin and myosin from interacting

Question 7

what has to happen for a muscle fiber to contract

Answer 7

myosin-binding sites must be exposed. This occurs when calcium ions (Ca2+) bind to the troponin complex and expose the myosin-binding sites

Question 8

What does Ca2+ have to do with the contraction of muscle fiber

Answer 8

Contraction occurs when the concentration of Ca2+is high; muscle fiber contraction stops when the concentration of Ca2+is low

Question 9

What is the stimulus leading to contraction of a muscle fiber

Answer 9

an action potential in a motor neuron that makes a synapse with the muscle fiber. The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine

Question 10

How does the neurotransmitter Acetylcholine affect our muscles

Answer 10

depolarizes the muscle, causing it to produce an

action potential. The action potential causes the sarcoplasmic reticulum (SR) to release Ca2+

Question 11

Sarcoplasmic reticulum

Answer 11

is a specialized endoplasmic reticulum that regulates the Ca2+ concentration in the cytosol of muscle cell.

Question 12

Actin Filaments

Answer 12

Slide past mycosin, causing contraction

Question 13

Myosin Filaments

Answer 13

pull actin filaments by means of cross-bridges; are enzymatic and split ATP

Question 14

Ca2+

Answer 14

Needed for mycosin to bind to actin

Question 15

motor unit

Answer 15

consists of a single motor neuron and all the muscle fibers it controls

Question 16

Myasthenia gravis

Answer 16

is an autoimmune disease that attacks acetylcholine

receptors on muscle fibers

Question 17

Amyotrophic lateral sclerosis (ALS)

Answer 17

formerly called Lou Gehrig’s disease, is a fatal degenerative disease characterized by the death of
neurons which signal muscle contraction.

Question 18

Botulinum toxin

Answer 18

inhibits presynaptic release of acetylcholine. Untreated botulism is typically fatal because muscles required for breathing fail to contract when acetylcholine release is blocked.

Question 19

Tetnus

Answer 19

is an infection caused by bacteria called Clostridium tetani. Tetanus neurotoxin binds to the presynaptic membrane of the neuromuscular
junction and blocks release of GABA, inhibitory neurotransmitter inducing paralysis.

Question 20

Ligaments

Answer 20

Connect bone to bone

Question 21

Tendon

Answer 21

Connects muscle to bone

Question 22

paired muscles work cooperatively

Answer 22

Can only pull, cannot push. When one muscle contracts, it stretches its antagonistic partner

Question 23

Three Types of Joints

Answer 23

1) Ball and Socket Joint
2) Hinge Joint
3) Pivot Joint

Question 24

Osteoblasts

Answer 24

bone-forming cells, Synthesize new matrix

Question 25

Osteoclasts

Answer 25

Break down bone, remove worn cells, deposit calcium in

the blood

Question 26

Osteocytes

Answer 26

mature bone cells, become caught in the matrix

Question 27

OSTEOPOROSIS

Answer 27

silent disease: it does not produce symptoms until fracture occurs. Is a bone disease that leads to an increased risk of fracture. The form of osteoporosis most common in women after menopause