Lab Muscle Physiology

Question 1

Myofiber

Answer 1

skeletal muscle cell/fiber

Question 2

Sarcolemma

Answer 2

plasma membrane of muscle cell/fiber

Question 3

Sarcoplasm

Answer 3

cytoplasm of muscle fiber

Question 4

Mitochondria

Answer 4

packed between Myofibrils; produce ATP which is required for muscle contraction

Question 5

Triad

Answer 5

composed of a Transverse Tubule and Terminal Cisternae

Question 6

Transverse (T) Tubules

Answer 6

tubular interfoldings that penetrate the cell

Question 7

Terminal Cisternae

Answer 7

paired structure on each side of T Tubule; connected to Sarcoplasmic Reticulum

Question 8

Sarcoplasmic Reticulum

Answer 8

smooth endoplasmic reticulum of Myofiber; stores Ca2+ which is required for muscle contraction

Question 9

Thick Filaments

Answer 9

composed of several hundred Myosin molecules.

Question 10

Myosin

Answer 10

formed by two intertwined protein chains that form a tail and head

Question 11

Thin Filaments

Answer 11

composed primarily of two intertwined strands of Fibrous (F) Actin and Globular (G) Actin

Question 12

Globular (G) Actin

Answer 12

contains an active site, which is regulated by Troponin and Tropomyosin, that can bind to the head of Myosin

Question 13

Troponin

Answer 13

bound to Tropomyosin; also binds Ca2+

Question 14

Tropomyosin

Answer 14

covers the active site on G Actin; also bound to Troponin

Question 15

Elastic Filaments

Answer 15

composed of massive protein Titin, which anchors the Z disc to the Thick Filament

Question 16

Contractile Proteins

Answer 16

Myosin and Actin bind, the golf club-shaped heads of Myosin cock to shorten the length of the muscle (i.e. contract)

Question 17

Regulatory Proteins

Answer 17

Troponin binds to Tropomyosin; Tropomyosin is bound to the active site on Actin. Ca2+ binds to the Troponin-Tropomyosin complex which causes a conformational change, and reveals the active site on Actin allowing Myosin to bind. Their conformation determines if the active site will be exposed

Question 18

Myosin and Actin

Answer 18

proteins that occur in all cells, and function in cellular motility, mitosis, and intracellular transport

Question 19

Striations

Answer 19

alternating light and dark bands that are caused by the overlap of the Thick and Thin Filaments. Precisely arranged in Skeletal and Cardiac Muscle

Question 20

A band

Answer 20

dArk band; caused by Thick Filaments, particularly dark where Thin Filaments overlap

Question 21

H band

Answer 21

lighter area of the A band where the thin filaments do not reach

Question 22

M line

Answer 22

protein complex that intersects the H band

Question 23

I band

Answer 23

lIght band; lighter area composed of Thin and Elastic Filaments

Question 24

Z disc

Answer 24

provides anchorage for the Thin and Elastic Filaments

Question 25

Sarcomere

Answer 25

the functional contractile unit of the muscle fiber; the segment of the Myofibril from Z disc to Z disc. As the muscle contracts, the Z discs are pulled closer together. During contraction the length of the filaments do not change, the amount of overlap changes

Question 26

Somatic Motor Neuron

Answer 26

erve cells that innervate skeletal muscles, whose cell bodies are in the brainstem and spinal cord. Their axons, called somatic motor fibers, lead to the muscles.

Question 27

Motor Unit

Answer 27

one nerve fiber and all of the muscle fibers innervated by it

Question 28

Myofibers of a motor unit

Answer 28

Are dispersed throughout a muscle, Contract in unison, Produce contraction over wide areas, Provide ability to sustain long-term contraction as motor units take turns contracting

Question 29

Average motor unit contains how many myofibers per neuron?

Answer 29

~200 myofibers per neuron

Question 30

Small motor units

Answer 30

offer finer degree of control; each neuron controls 3-6 muscles in the eye

Question 31

Large motor units

Answer 31

one neuron may control up to 1000 myofibers

Question 32

Multiple Motor Unit Summation (Recruitment)

Answer 32

the process of stimulating more motor units to contract when given a stronger twitch

Question 33

Maximal Stimulus

Answer 33

stimulus that produces the maximum contraction

Question 34

Length-Tension Relationship

Answer 34

elationship between an overly stretched muscle, an extremely contracted muscle, and a muscle at an optimum resting length

Question 35

Muscle Tone (Tonus)

Answer 35

the partial state of contraction in resting muscles maintained by the central nervous system

Question 36

Treppe “staircase phenomenon”

Answer 36

the pattern of increasing tension with repetitive stimulation

Question 37

Electromyography

Answer 37

the detection, amplification, and recording of changes in skin voltage produced by underlying skeletal muscle contraction

Question 38

Dynamometry

Answer 38

the measurement of power

Question 39

Power

Answer 39

the amount of work done per unit of time

Question 40

Fatigue

Answer 40

the progressive weakness and loss of contractility that results from prolonged use of muscles