Hf 1 Stauber Basics Of Skeletal Muscle Function

Front 1

What are the four physiological functions of skeletal muscle?

Back 1

Thermogenesis, Protein stores, psychological, and biomechanical

Front 2

Muscle function: Thermogenesis

Back 2

refers to non-purposeful, skeletal muscle activity which is important in the maintenance of body temperature - the twitching of skeletal muscles during shivering

Front 3

Muscle function: Protein stores

Back 3

Basically, muscles are extremely labile. If you don't exercise for a long time they will atrophy

Front 4

Muscle function: Psychological

Back 4

It has an effect on an individual's self-esteem. Especially if it is missing or in a decreased amount

Front 5

Muscle function: Biomechanical

Back 5

Muscles can directly convert chemical energy into mechanical energy. They can also absorb shock

Front 6

Sarcolemma

Back 6

This is the cell membrane that surrounds muscle fibers. It is closely associated with a basal lamina composed of glycoproteins stuck to the cell surface and covered by type IV collagen

Front 7

What substance adds stability to the sarcolemma?

Back 7

type IV collagen

Front 8

What is an invagination in the sarcolemma called and why is it useful?

Back 8

T-tubule. Invagination allows electrolytes and nutrients to have ample diffusion area.

Front 9

Myofibrils

Back 9

several hundred to several thousand myofibrils make up each myofiber. These are composed of actin and myosin and are arranged in a structure referred to as the sarcomere

Front 10

Myofiber

Back 10

muscle fiber. can range anywhere from 45 -120 um

Front 11

Sarcomere

Back 11

The smallest functional unit of skeletal muscle. It is defined as all structures between the 2 Z lines.

Front 12

A band

Back 12

The portion of a sarcomere which contains myosin filaments (and some actin)

Front 13

H zone

Back 13

area of the sarcomere in the A band where no actin filaments overlap

Front 14

Zones in muscles that shorten

Back 14

HI (say HI to the muscle)

Front 15

Sarcoplasm

Back 15

the cytoplasm not related to the contractile process. Contains electrolytes, ribosomes, mitochondria, and glycogen, etc.

Front 16

Sarcoplasmic Reticulum

Back 16

composed of the 2 lateral cisternae and the longitudinal tubules. Release of calcium occurs from the lateral cisternae

Front 17

Which of the two muscle types contains more lateral cisternae and why?

Back 17

Type II muscles because they need to contract and relax more rapidly

Front 18

T-tubules

Back 18

This structure separates the 2 lateral cisternae in the Sarcoplasmic reticulum

Front 19

Type I fibers

Back 19

slow twitch, red oxidative fibers

Front 20

Type II fibers

Back 20

IIa - fast twitch, oxidative
IIb - fast twitch, glycolytic

Front 21

What are the four major proteins in the sarcomere?

Back 21

myosin, actin, tropomyosin, and the troponin complex

Front 22

Myosin is the ___ filament and Actin is the ____ filament.

Back 22

Myosin is the Thick filament and Actin is the Thin filament

Front 23

What are the three proteins contained in the troponin complex?

Back 23

Troponin T, Troponin I, and Troponin C

Front 24

What determines force in a contraction?

Back 24

The number of cross-bridges

Front 25

What are three important features of the contractile process?

Back 25

1.) Hydrolysis of ATP
2.) "" "" which is associtated with a physical-chemical phenomenon resulting in muscle shortening and tension development
3.) Interaction 1 and 2 must be controlled by calcium

Front 26

Describe calcium after depolarization as it relates to the contractile process.

Back 26

Depolarization of T-tubule causes the release of Ca++ from the SR and activates the contraction process. Removal of Ca++ results in relaxation

Front 27

Low ATPase in muscles results in what velocity of muscle shortening? High ATPase? What types of muscles are these found in?

Back 27

Type I muscle - low ATPase, slow
Type IIb muscle - high ATPase, fast

Front 28

How many G-actin molecules are there per half turn on the F-actin polymer?

Back 28

7

Front 29

Where does the tropomyosin lie within the sarcomere?

Back 29

in the "groove" between the 2 actin helices, such that there is a tropomyosin molecule in contact with every actin molecule

Front 30

Troponin I

Back 30

the interaction inhibitor protein

Front 31

Troponin T

Back 31

the tropomyosin-binding molecule binds to tropomyosin

Front 32

Troponin C

Back 32

the calcium-binding component

Front 33

Describe the Troponin Complex's organization within the sarcomere.

Back 33

1 troponin for every 7 actin molecules. Stable without Ca++
Ca++ causes transformation of Troponin which results in tropomyosin moving away from the binding sites on actin

Front 34

T/F Binding of Ca++ to the troponin complex at troponin C effects 7 actin, the one it was directly covering and three adjacent actins on both sides of the original actin

Back 34

True

Front 35

Describe the reaction mechanism of contraction. Six steps.

Back 35

1. ATP Hydrolysis
2. Formation of Active Complex
3. Phosphate release
4. Power stroke
5. Product dissociation (rate limiting step)
6. Dissociation of Actin and Myosin

Front 36

Why does rigor mortis occur?

Back 36

It occurs because there is no more ATP to Dissociate the Actin and Myosin

Front 37

Excitation-Contraction Coupling - describe how Ca++ can be quickly used and removed.

Back 37

SR stores Ca++ and the diffusion distance to Troponin C is short.

Longitudinal SR can also transport calcium back into storage rapidly for relaxation

Front 38

Excitation-Contraction Coupling - discuss the mechanical coupling occuring between the voltage change in the T-tubule and the opening of the calcium release channel in the SR of the skeletal muscle

Back 38

At a relaxed state cytoplasmic calcium levels are at about 1x10^7 molar.

T-tubule has DHPR, the voltage receptor, and SR has RyR1 (ryanodine receptor), which allows for rapid release of calcium that quickly reaches the troponins

Front 39

Describe calcium removal by the SR.

Back 39

Uses SERCA (sarco(endo)plasmic reticulum which is a Ca2+ - ATPase

Front 40

Compare Ca++ uptake rates by SERCA in type I and Type II skeletal muscles

Back 40

Type II faster than Type I

Front 41

Creatine Phosphate

Back 41

This is the major storage form of high-energy phosphates in muscle and greatly exceeds the amount of ATP. It rephosphorylates ATP. CP stores last for about 30 seconds of maximal exercise

Front 42

Generation of Chemical energy in skeletal muscle contraction can be by which two major pathways?

Back 42

Anaerobic - results in lactic acid, which weakens the muscle

Aerobic - by oxidative phosphorylation makes LOTS of ATP

Front 43

Which does are body use first for energy in the muscles, fat or sugars?

Back 43

sugars

Front 44

Type I fibers use primarily the ____ pathway and Type IIa primarily use ____ pathway and Type IIb uses the ____ pathway

Back 44

Type I, aerobic
Type IIa, aerobic
Type IIb, anaerobic

Front 45

T/F Distribution of Type I and Type II skeletal muscles altered by training

Back 45

FALSE - Type I and Type II skeletal muscle distribution is genetically determined

Front 46

Skeletal Muscles:
What is Twitch?

Back 46

the response to a single AP is a sharp rise and fall in force (related to crossbridge binding)

Front 47

Skeletal Muscles:
What is summation?

Back 47

Increased force production by a muscle due to repetitive stimulation

Front 48

Tetanic Contractions

Back 48

Increased frequency of AP by stimulation results in greater tension developed by the muscle

Front 49

Rate Coding

Back 49

Form of force summation in skeletal muscles that is controlled by the CNS

Front 50

Recruitment (skeletal muscles)

Back 50

Increasing the number of Motor Units recruited increases the amount of force

Front 51

Isometric Contraction

Back 51

No change in length

Front 52

Total Tension

Back 52

the observed tension when a muscle is maximally stimulated at a fixed length

Front 53

Passive Tension

Back 53

the tension developed in the muscle when not stimulated adn results from the passive elastic properties of the muscle

Front 54

Active tension

Back 54

the difference between the total tension and the passive tension. Tension produced by the sarcomeres (specifically the # of cross-bridge interactions

Front 55

Isotonic muscle contraction

Back 55

muscle changes length as a result of the force of the contraction. When muscle force is greater than the attached load, the muscle shortens and moves the load.

Front 56

Concentric muscle action

Back 56

shortening of muscle as a result of isotonic muscle contractionj

Front 57

Preload

Back 57

This is the amount of force that muscle exerts to equal the opposing force

Front 58

Energy consumption for muscle consumption (3 components)

Back 58

Isometric energy (internal shortening or tension required to hold the load, isometric phase)

Energy to perform the work (move the load)

Energy for the rate of moving of the load (velocity of shortening of the muscle)

Front 59

Velocity of shortening

Back 59

When this is smaller, we are able to exert maximal force. We sacrifice force as we increase this velocity

Front 60

Afterload

Back 60

additional resistance not directly related to the load. Added tension that requires slowed down movement

Front 61

Eccentric muscle actions

Back 61

muscle tension developed while lengthening or being stretched - greater forces are developed here than in concentric muscle actions