2 ' Muscle Physiology Flashcards Preview

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Flashcards in 2 ' Muscle Physiology Deck (61):
1

Muscular system is comprised of three types of muscle tissue:

Skeletal, cardiac, and smooth

2

Skeletal

Striated muscle attached to the skeleton used to facilitate movement by applying force to bones and joints via contractions

3

Cardiac

Involuntary, mononucleated, striated muscle found exclusively within the heart

4

Smooth

Non-striated muscle found within the "walls" of hollow organs such as the bladder, uterus, and GI tract

5

Signals initiated in the brain stimulate the nervous system, causing muscles to contract and produce tension

True

6

Motor information is carried via actin potentials from the central nervous system (CNS)

True

7

Action potential

Wave-like change in the electrical properties of a cell membrane that results from the difference in electrical charge between the inside and outside of the membrane and causes the muscle call to contract

8

Capillaries

Ting blood vessels that connect arteries and veins, forming an intricate network around body tissues in order to distribute oxygen and nutrients to the cells and remove waste substances

9

Myofibrils

Cylindrical structures containing the myofilaments actin (thin filament) and myosin (thick filament)

10

Surrounding myofibrils are a calcium-housing network called the sarcoplasmic reticulum (SR), tube-like structures that transfer signals called T-tubules, and mitochondria, which are used to produce energy

True

11

SR

A tubular network that surrounds each individual myofibril and acts as a storage site for calcium within the skeletal muscle

12

T-tubules

Tubules that pass in a transverse manner from the sarcolemma across a myofibril of striated muscle passing signals within the cell

13

Tension is created in a group of muscle fibers by initiation of the action potential

True

14

The action potential travels via an electrical current through the spinal cord and is transferred to the peripheral nervous system (PNS)

True

15

The current runs through outer levels of muscle tissue to very small nerve fibers called motor neurons which connect to the particular fibers to be contracted

True

16

Motor unit

Motor neuron and all the muscle fibers it innervates

17

Inside the muscle fiber, the following must occur to allow for a contraction (sliding filament theory):

5 actions

18

Action potent ion travels down the T-tubules and stimulates the SR

True

19

Calcium is released from the SR, acting as a key to unlock the bond between the thin contractile filament and troponin

True

20

Troponin molecule moves, rotating the tropomyosin molecule away from binding site

True

21

Myosin is free to attach to actin for in a cross-bridge

True

22

Adenosine triphosphate (ATP) is split at the myosin/actin attachment site and energy is released, allowing the muscle fiber to contract and produce force

True

23

A muscle fiber is either in a state of producing maximum tension or not productive any tension at all; this is known as the "all of none" principle

True

24

Motor units are stimulated within the desired muscle to produce movement

True

25

The greater the number of motor units stimulated, the more fibers recruited, producing more tension

True

26

Total skeletal muscle force dictates how many muscle fibers are recruited for the concentration

True

27

Two type of motor unit firing patterns:

Synchronized firing and Asynchronous firing

28

Synchronized firing

Employed during high-output demands involving fast-twitch fibers and warranting significant fiber recruitment m

29

Asynchronous firing

Employed during endurance activities involving slow-twitch fibers which conserve motor unit potential, allowing prolonged work

30

The ability to increase force production within a muscle through training is dependent on adaptations that occur to both:

Muscle fibers (size) and the nervous system (recruitment, firing rate, firing synchronicity)

31

Force production improvements can occur without the addition of new muscle due to efficiency changes related to motor unit recruitment

True

32

Inability to produce force, most notably due to intensity of exercise occurs in the CNS and PNS

True

33

Disrupts the motor units ability to produce force

True

34

As the rate of motor unit fatigue increases, performance proportionately declines

True

35

Rest interval or rest period

Period of time between repeated actions in an exercise; energy system specified and based on physical condition

36

Muscle cell recovery is dependent on the return of intracellular energy supply; circulatory-based, cellular by-product removal; and the delivery of O2

True

37

Recovery period is a Period of time between exercise bouts, during which muscle fibers will

Replenish their energy reserves, repair any damage resulting from the production of force, and fully return to normal pre-exertion levels

38

Two types of isotonic contractions involve lengthening or shortening of a working muscle

Eccentric contraction and Concentric contraction

39

Eccentric contraction

Muscle lengthens; negative work is produced; movement is decelerated

40

Concentric concentration

Muscle shortens; positive work is produced; movement is accelerated

41

Isometric contractions

Mostly used for stability; represent tension in the muscle that helps maintain position but does not cause acceleration or deceleration forces

42

Employed by stabilizing muscles to control movements and prevent undesirable actions

True

43

Type of muscle fiber recruited to produce a contraction depends on the amount of force needed

True

44

Three types of skeletal muscle fibers

Type IIb, type IIa and type I

45

Type IIb

High force-producing fibers, or face glycolytic fibers

46

Type IIa

Intermediate force-producing fibers, or fast oxidative/glycolytic fibers

47

Type I

Low force-producing fibers, or slow oxidative fibers

48

Fast-twitch fiber characteristics

Large diameter size, high force output but quick to fatigue (30-50g per motor unit), densely picked myofibrils, large glycogen reserves, preferentially recruited for high-power output activities, increases in size and strength when trained under conditions of short duration and high intensity and preferentially function using anaerobic metabolic systems

49

Slow-twitch fiber characteristics

50% smaller than fast-twitch fibers, produce low amounts of force (5g per motor unit), primarily use aerobic metabolic systems, better suited for endurance activities - fatigue-resistant, extensive capillary network and high mitochondrial density and higher amounts of myoglobin, increasing oxygen reserves in cells

50

Myoglobin

O2-transporting protein of muscle; resembles blood hemoglobin in function

51

Type IIa intermediate fiber characteristics

Used for activities requiring prolonged duration and/or elevated force, composition of both fast- and slow-twitch fiber characteristics, and adaptations support both anaerobic and aerobic activities

52

Genetically predetermined; training will not change concentrations of fibers within segments of the body

True

53

Postural muscles maintain a higher concentration of slow- twitch fibers

True

54

Soleus, deep muscles of the back, and the rectus abdominis must contract continuously to maintain upright posture and is not designed for rapid, high-force output; experience limited improvements in power/hypertrophh

True

55

Slow-twitch fibers do not convert to fast-twitch fibers (or vice versa), but muscle can become better suited to training stimulus due to the following changes:

Neural stimulation, capillary and mitochondrial density and enzyme concentration

56

Muscle tone

Some motor units in a muscle are always active even when the muscle is not contracting

57

Two primary proprioceptors used to manage the tonicity of muscle tissue

Muscle spindles and golgi tendon organs

58

Muscle spindles

Intrafusal fibers that lie parallel to normal muscle fibers which relay information to sensory neurons regarding changes in tissue length and tension

59

When rapidly stretched, they respond with a stretch reflex to initiate a concentration that limits an overstretch and potential damage to the muscle

True

60

Golgi tendon organs

Sensory receptors found within muscle tendons that communicate information to motor neurons regarding the presence of excessive tension that may cause damage

61

If tension in a muscle is too great, they send inhibitory signals to reduce motor neuron activity and thereby reduce the force of muscular contraction

True