Muscle Mechanics

epithelial, connective, muscle, nervous

what are the 4 major types of tissue in the human body

40%

what % of body weight is made up of skeletal muscle?

50-75%

what % of all proteins in the body is contained in skeletal muscle

synthesis and degredation

muscle mass is dependent on a balance of protein...

maintain posture

initiate/ alter/maintain motion

manage external loads

what is the function of skeletal muscle

stimulus generator (brain)

nerve

muscle

joint

what are the requirements for human motion

proximal attachment

where is the origin usually located

distal attachment

where is the insertion usually located

muscle structure and architecture

fiber types

excitation-contraction coupling

energy release

force, power, movement

what things impact how muscle contracts

muscle cells

muscle fibers are another name for...

myofilaments, sarcomeres, regulatory proteins, structural proteins

what are the architectural components of muscle

the proteins (actin and myosin) that cause contraction

myofilaments

thin filament with double helix strands

actin is what type of filament, what is its structure

thick filament with globular heads that protrude from the myosin to form cross bridges with actin

what type of filament is myosin, what is it's unique structural appendage

sarcomere

the smallest contractile unit made of actin and myosin

sarcoplasm

cytoplasm of a muscle fiber

6

how many actin filaments surround a myosin filament

3

how many myosin filaments surround an actin filament

troponin and tropomyosin

what are the regulatory proteins in muscle

nebulin and titin

titin is elastic

what are the structural proteins, which one is elastic?

A band

which area of the sarcomere has both thick and thin filaments and stretches the length of myosin (doesn't change shape during contraction)

I band

which area of the sarcomere only has thin filaments and gets smaller with contraction

H zone

which part of the sarcomere has thick filaments and gets smaller with contraction

m line

part of the sarcomere in the middle of myosin filaments

z disc

part of a sarcomere where actin is anchored, marks the boundaries of the sarcomere

Endomysium: covers each muscle fiber

perimysium: covers muscle fascicles

epimysium: covers the entire skeletal muscle

muscles are covered in CT with collagen and elastin fibers, what are the layers and what do they cover

tendon

tension developed in a muscle is transmitted to the...

the parallel elastic component

the middle region of a muscle contains both the contractile component and connective tissue, this connective tissue is...

series elastic components

tendons on either end of the muscle are the...

active tension

contraction or shortening of the muscle creates force called...

endo, peri, epi-mysiums

what are the parallel elastic components

tendons and titin

what are the series elastic components of a muscle?

pasive tension

stretching the elastic components creates a force called...

active tension

what type of tension starts movement

calcium, ATP, ATPase

what molecules are needed for muscle contraction

the motor neuron, its axon and all the muscle fibers it innervates

what makes up a motor unit?

each muscle fiber is innervated by one motor neuron, but one motor neuron can innervate many muscle fibers

what is the relationship between muscle fibers and motor neurons

all of them are activated

when a motor unit is activated, what happens to the muscle fibers it innervates

finer control of muscle

muscles with smaller motor units (less number of fibers innervated by 1 motor neuron) are used for...

creating large movements

muscles with larger sized motor units are used for

type 1 and type 2 (A and X)

what are the muscle types

biochemical, mechanical, metabolic

what are the phenotypes of skeletal muscle that give it its variability

denervation, corticosteroids, hormonal levels, aging, inactivity, and disease

what are factors that impact muscle performance

combination

skeletal muscle has a __________________ of muscle fiber types

ATP production, motor neuron innervation and type of myosin heavy chain expressed

what are the two main types of fibers classified by?

evaluating the myosin ATPase activity

how is fiber type established

fast twitch will have increased activity and slow twitch will have decreased

in alkaline conditions, how do the fiber types activity change?

fast twitch decreases and slow twitch increases

in acidic conditions, how do the muscle fiber types activities cange

type 1

what type of muscle fiber is fatigue resistant

they have small motor units leading to a low innervation ratio

the purpose is prolonged low intensity work

what is the size of type 1 muscle fibers? what is the purpose of this?

postural muscles

where are type 1 fibers mostly found

type 2A

which muscle fiber uses fast oxidative glycolytic mechanisms and fatigues at an intermediate time

aerobic and anaerobic

what type of metabolism is done if type 2A fibers

type 2X

which muscle fibers uses fast glycolytic fibers that are fast to fatigue

anaerobic

what type of metabolism is used in type 2x fibers?

type 1 and type 2a

type 2 hybrid has what types of muscle fibers

large and numerous mitochondria

low ATPase activity

slow calcium handling ability (slow shortening speed)

less developed glycolytic capacity

what 4 characteristics are present in type 1 fibers

high transmission of AP

high ATPase activity

fast calcium release and uptake

high cross-bridge turn over

what 4 characteristics are present in type 2 fibers

a motor neuron innervates many muscle fibers

type 2x

what is a high innervation ratio, which type of muscle has this ratio

direct

what is the relationship between innervation ratio and muscle twitch speed

function and genetics

what determines the ratio of muscle fibers that make up a muscle

Type 1:40-55

type2a: 20-30

type 2x: 20-30

what is the average fiber composition of muscle in the normal population

endurance: increases proportion of type 1 fibers

resistance: promotes type 2a instead of 2x

how does training effect muscle fiber composition

slow twitch/type 1

in major muscle groups, what type of fibers would endurance athletes have

fast twitch/type 2

what muscle fiber types dominate in elite sprinters

continuum

current research states that fiber types may be on a ______________________

False

true or false? fiber types can change from FT to ST

excitability

the ability of skeletal muscle to respond to stimulation

elasticity

the ability of muscle to deform and return to original length

extensibility

the ability of a muscle to change in length

contractility

the ability of a muscle to contract in response to stimulation

isometric

activation that results in a constant length

tension in the cross-bridges is equal to the resistance applied

why is length constant in isometric activation

there is no distance change

why is no work done in isometric activation

concentric and eccentric

what are the types of dynamic activation

shortens because the tension within the muscle overcomes resistance applied

what happens to the length of the sarcomere during concentric contraction, why?

positive work because there is movement through the ROM

what work is being done during concentric, why?

it lengthens under load because the tension in the muscle is less than the resistance applied

what happens to the length of the sarcomere during eccentric contraction, why?

negative work because the distance is changing but the work is being done on the muscle

what work is being done during eccentric, why?

concentric

eccentric

which type of activation generates the least tension? most?

muscle torque/load torque

what is the formula for solving for the type of activation

isometric

when MT/TL = 1 what type of contraction is present

eccentric

when MT/TL <1 what type of contraction is present

concentric

when MT/TL >1 what type of contraction is present

recruitment, preload, muscle size, velocity, fiber arrangement, length-tension relationship

what factors affect muscle force production (6)

all or none

how do motor units contract

types of motor units recruited and the number

in what ways can muscle contraction vary?

greater resistance

increased motor neuron recruitment results in

low threshold slow twitch fibers

minimal force

when there is a weak stimulus, what type of fibers are recruited? what type of force is created

higher threshold FOG fibers and then FG fibers

greater force/maximal force (fatigue quickly)

as the stimulus increases in strength, what types of fibers are recruited, what is the resulting force?

asynchronous recruitment

what is the term for the form of recruitment that avoids fatigue by having different motor neurons take turns maintaining muscle tension

direct

what is the relationship between recruitment of motor units and force production

the frequency of stimulation and the number stimulated

how is force production controlled in terms of motor units

there needs to be time for calcium release and binding of myosin to actin

what is the reason that max force does not occur instantaneously in skeletal muscle, it also is the reason that high tension does not occur in early range

preloading

what can help the muscle achieve higher tensions in early range

the amount of contractile proteins

what does the cross sectional area of a muscle reflect?

force generation

increased cross sectional area gives more potential for..

increased speed results in decreased force generation (inverse)

what is the relationship between contraction speed and concentric contraction

increased speed results in increased force (direct)

what is the relationship between contraction speed and eccentric contraction

fusiform and pennate

what are the 2 common muscle shapes