Chapter 9: Muscular System

Question 1

What are the three types of muscle tissue?

Answer 1

Skeletal, smooth, cardiac

Question 2

Characteristics of skeletal muscle

Answer 2

-multinucleated
-many mitochondria
-transverse tubules
-myofibrils and sarcomeres
-sarcolemma
-sarcoplasm
-sarcoplasmic reticulum

Question 3

Sarcolemma

Answer 3

Plasma membrane
-contains T tubules

Question 4

Transverse (T) tubules

Answer 4

Aid in muscle contraction; associated with sarcolemma

Question 5

Sarcoplasm

Answer 5

Cytoplasm

Question 6

Sarcoplasmic reticulum

Answer 6

Smooth ER

Question 7

Myofibrils

Answer 7

Functional unit of muscle fibre
-composed of thin and thick filaments in cylindrical bundles

Question 8

What is the function of a myofibril?

Answer 8

Gives skeletal and cardiac muscle their characteristic striated appearance

Question 9

Thick filaments

Answer 9

Composed of myosin

Question 10

What composes a myosin molecule?

Answer 10

Two large, intertwined polypeptide heavy chains

Question 11

What forms a cross bridge?

Answer 11

Globular heads at the end of myosin heavy chains

Question 12

What is the function of a cross bridge?

Answer 12

Makes contact with thin filament

Question 13

What is the function of the two light chains on the globular heads of myosin?

Answer 13

Inherent ATP-ase activity
-one attaches to the thin filament, one attaches to ATP

Question 14

Thin filaments

Answer 14

Composed of actin, nebulin, troponin, tropomyosin

Question 15

What in the thin filament serves as the binding site for myosin?

Answer 15

Actin molecules

Question 16

Tropomyosin

Answer 16

Blocks myosin binding site on actin filament
-rod shaped molecule composed of two intertwined polypeptides

Question 17

Troponin

Answer 17

Regulates Ca2+
-composed of three subunits (I, T, C)
-holds tropomyosin in its blocking position

Question 18

Sarcomere

Answer 18

Thick and thin filaments together
-from z band to z band

Question 19

Terminal cisternae

Answer 19

Enlarged regions on SR that contains a large amount of Ca2+

Question 20

Calsequestrin

Answer 20

Binding protein in terminal cisternae, helps hold a lot of calcium

Question 21

What lies between terminal cisternae of adjacent segments of SR?

Answer 21

T-tubule

Question 22

Contraction

Answer 22

Refers to actin fibres sliding past myosin fibres

Question 23

What always follows a contraction force?

Answer 23

Relaxation

Question 24

Motor unit

Answer 24

Motor neuron and all the skeletal muscle fibres it innervates

Question 25

Describe the axon of a motor neuron.

Answer 25

Myelinated, largest diameter

Question 26

Neuromuscular junction

Answer 26

Axon terminal junction of motor endplate

Question 27

Motor end plate

Answer 27

Muscle fibre plasma membrane lies directly under the terminal portion of the axon

Question 28

What is one factor of all neuromuscular junctions?

Answer 28

All are excitatory.

Question 29

Function of acetylcholinesterase

Answer 29

Breaks down ACh

Question 30

Describe troponin and tropomyosin in a resting muscle fibre.

Answer 30

Block the interaction of cross-bridges with the thin filament

Question 31

What happens when Ca2+ binds to troponin?

Answer 31

Induces a shape change, relaxes inhibitory grip on tropomyosin, moves away from myosin binding site

Question 32

Dihydropyridine (DHP) receptor

Answer 32

Modified voltage-sensitive Ca2+ channel on T-tuble

Question 33

Ryanodine recpetor

Answer 33

Protein embedded in SR that forms Ca2+ channel

Question 34

Sliding filament mechanism

Answer 34

Generative force behind muscle contraction; involves overlapping thick and thin filaments within each sarcomere

Question 35

In the shortening of a sarcomere during a muscle contraction, is there a change in length of the filaments?

Answer 35

Thick and thin filaments do not change length, only their amount of overlap

Question 36

Cross bridge

Answer 36

Forms between actin and myosin due to Ca2+ increase

Question 37

What is released from myosin when cross bridges bind to actin?

Answer 37

ADP and Pi, producing angular movement

Question 38

How do cross bridges on myosin dissociate from actin?

Answer 38

ATP binds to myosin, breaking linkage to actin

Question 39

How is the myosin cross bridge reenergized after cross bridge to actin dissociates?

Answer 39

ATP binds to the cross bridge

Question 40

Tension

Answer 40

Force exerted on an object by contracting a muscle

Question 41

Load

Answer 41

Force exerted on a muscle by an object

Question 42

Twitch

Answer 42

Mechanical response of muscle fibre to a single action potential

Question 43

Latent period

Answer 43

Period of time between action potential and onset of contraction

Question 44

Contraction time

Answer 44

Beginning of tension development at the end of latent period to peak tension

Question 45

Relaxation time

Answer 45

Peak tension until tension declines to 0

Question 46

Isometric contraction

Answer 46

When a muscle develops tension but does not shorten or lengthen; supports load in constant position

Question 47

Isotonic contraction

Answer 47

Contraction in which the muscle changes length while the load on the muscle remains constant

Question 48

How is it possible that a second action potential can be initiated during a period of mechanical activity?

Answer 48

action potential lasts 1-2 ms, but the twitch last for 100+ ms

Question 49

Summation

Answer 49

Increase in muscle tension from successive action potentials occurring during a phase of mechanical activity

Question 50

Tetanus

Answer 50

Maintained contraction in response to repetitive stimulation

Question 51

Fused tetanus

Answer 51

Full muscle contraction

Question 52

Unfused tetanus

Answer 52

Sporadic stimulus