3) Exercising Muscle - Muscle Fiber Types Flashcards
What does the image show?
Differences in fiber number and type proportion within fascicles.
(Muscle fibers in a fascicle are NOT all the same)
Muscle fibers can be classified by several characteristics:
Biochemical properties
- ?
–Number of capillaries, mitochondria, amount of myoglobin
- ?
–Speed of ATP degradation
Contractile properties
- ?
–Force per unit of cross-sectional area
- ?
–Myosin ATPase activity
- ?
Muscle fibers can be classified by several characteristics:
Biochemical properties
- Oxidative capacity
–Number of capillaries, mitochondria, amount of myoglobin
- Type of myosin ATPase
–Speed of ATP degradation
Contractile properties
- Maximal force production
–Force per unit of cross-sectional area
- Speed of contraction
–Myosin ATPase activity
- Muscle fiber efficiency
Muscle fibers can be classified by several characteristics:
Biochemical properties
- Oxidative capacity
–Number of ?, ?, amount of ?
- Type of myosin ATPase
–Speed of ?
Contractile properties
- Maximal force production
–Force per unit of ?
- Speed of contraction
–? activity
- Muscle fiber ?
Muscle fibers can be classified by several characteristics:
Biochemical properties
- Oxidative capacity
–Number of capillaries, mitochondria, amount of myoglobin
- Type of myosin ATPase
–Speed of ATP degradation
Contractile properties
- Maximal force production
–Force per unit of cross-sectional area
- Speed of contraction
–Myosin ATPase activity
- Muscle fiber efficiency
Characteristics of Type 1 and Type II Fibers
Myosin ATPase:
- Different ? due to different forms of myosin-ATPase
- Type II fibers → ? splits ATP more rapidly, resulting in faster ?
Sarcoplasmic reticulum (SR):
- Type II fibers:
–More developed SR than ?
–Can deliver ? more effectively into muscle cell
–? greater due to ?
Motor units:
- Type I motor unit: α-motor neuron has ? cell body; innervates ? muscle fibers
- Type II motor unit: α-motor neuron has ? cell body; innervates ? muscle fibers
- ? muscle fibers reach peak tension faster, generate more force
Myosin ATPase:
- Different speeds of contraction due to different forms of myosin-ATPase
- Type II fibers → fast ATPase splits ATP more rapidly, resulting in faster cross-bridge cycling
Sarcoplasmic reticulum (SR):
- Type II fibers:
–More developed SR than type I fibers
–Can deliver calcium more effectively into muscle cell
–Power greater due to faster shortening velocity
Motor units:
- Type I motor unit: α-motor neuron has small cell body; innervates ≤ 300 muscle fibers
- Type II motor unit: α-motor neuron has larger cell body; innervates ≥ 300 muscle fibers
- Type II muscle fibers reach peak tension faster, generate more force
Characteristics of Type 1 and Type II Fibers
Sarcoplasmic reticulum (SR):
- Type II fibers:
–More developed SR than ?
–Recall: SR stores ? therefore more developed SR would result in ? as seen in Type II fibers
–Can deliver ? more effectively into muscle cell
–Power greater due to ?
Motor units:
- Type I motor unit: α-motor neuron has ? cell body; innervates ? muscle fibers
- Type II motor unit: α-motor neuron has ? cell body; innervates ? muscle fibers
- ? muscle fibers reach peak tension faster, generate more force
Myosin ATPase:
- Different ? due to different forms of myosin-ATPase
- Type II fibers → ? splits ATP more rapidly, resulting in faster ?
Sarcoplasmic reticulum (SR):
- Type II fibers:
–More developed SR than type I fibers
–Can deliver calcium more effectively into muscle cell
–Recall: SR stores Calcium therefore more developed SR would result in Increased Ca++ delivery → Increased Power of Contraction as seen in Type II fibers
–Power greater due to faster shortening velocity
Myosin ATPase:
- Different speeds of contraction due to different forms of myosin-ATPase
- Type II fibers → fast ATPase splits ATP more rapidly, resulting in faster cross-bridge cycling
Motor units:
- Type I motor unit: α-motor neuron has small cell body; innervates ≤ 300 muscle fibers
- Type II motor unit: α-motor neuron has larger cell body; innervates ≥ 300 muscle fibers
- Type II muscle fibers reach peak tension faster, generate more force
Characteristics of Type 1 and Type II Fibers
Motor units:
- type? neurons innervate Skeletal muscle cells
- Each muscle cell (ie ?) is innervated by ?how many/neuron type (one neuron may innervate ?how many? muscle cell(s)
Type I motor unit:
- Type of Neuron,
- Size of cell body
- Innervates how many muscle fibers
Type II motor unit:
- Type of Neuron
- Size of cell body
- Innervates how many muscle fibers
Type? muscle fibers reach peak tension faster, generate more force
(ie how does innervation relate to force of contraction?)
Motor units:
- α-motor neurons innervate Skeletal muscle cells
- Each muscle cell (ie muscle fiber) is innervated by ONE α-motor neuron (one neuron may innervate multiple muscle cell(s)
Type I motor unit:
- Type of Neuron: α-motor neuron
- Size of cell body: small
- Innervates how many muscle fibers: ≤ 300
Type II motor unit:
- Type of Neuron: α-motor neuron
- Size of cell body: larger
- Innervates how many muscle fibers: ≥ 300
Type II muscle fibers reach peak tension faster, generate more force
(ie The more muscle fibers innervated by a single alpha motor neuron the stronger the contraction)
Myosin ATPase:
- Different speeds of contraction due to different forms of myosin-ATPase
- Type II fibers → fast ATPase splits ATP more rapidly, resulting in faster cross-bridge cycling
Sarcoplasmic reticulum (SR):
- Type II fibers:
–More developed SR than type I fibers
–Can deliver calcium more effectively into muscle cell
–Power greater due to faster shortening velocity
How does Fiber Diameter relate to function of muscle fibers?
How does structure relate to function of muscle fibers?
- Fiber Diameter?
Type? have smallest diameter = smallest force
Type? fibers have intermediate diameter = intermediate force
Type? fibers have largest diameter = Large force
As the cross-sectional area (diameter) increases in size, the fibers have more surface tension and become capable of generating higher amounts of force.
Muscles with a larger cross-sectional area (diameter) of individual muscle fibers are capable of producing greater amounts of force
Type I fibers have smallest diameter = smallest force
Type IIa fibers have intermediate diameter = intermediate force
Type IIx fibers have large diameter = Large force
How does structure relate to function:
Capillary Density:
Type I muscle fibers have ? capillary density and thus have ? oxidative capacity
- capable of Aerobic Phosphorylation?
Type IIa muscle fibers have ? capillary density = ? oxidative capacity
- capable of Aerobic Phosphorylation?
Type IIx muscle fibers have low capillary density and thus have low oxidative capacity
- capable of Aerobic Phosphorylation?
Higher capillary density = Increased oxygen delivery = increased oxidative capacity (ie ability to make ATP from oxygen)
Type I muscle fibers have high capillary density and thus have high oxidative capacity.
- Capable of Aerobic phosphorylation? Yes
Type IIa muscle fibers have High capillary density = high oxidative capacity
- Capable of Aerobic phosphorylation? Yes
Type IIx muscle fibers have low capillary density and thus have low oxidative capacity
- Capable of Aerobic phosphorylation? No, Anaerobic only
Structure vs Function of Muscle Fiber Types
- Color?
The colour of the muscle fiber relates to the ? density and concentration of ?
Higher Capillary Density = Red in colour
Higher [myoglobin] = Red in colour (Myoglobin bound to O2 is Red]
Type IIx fibers are white/pale pink in colour due to:
- ? level of myoglobin
- ? capillary density
- They produce ATP at a ? rate by ? metabolism and ? very quickly
- Fastest to ?
Type IIa muscle fibers are Reddish-pink in colour due to:
- ? Capillary Density
- ? [myoglobin]
- Less ? than type I fibers because: bigger size dilutes the colour
- They manufacture and split ? at a fast rate (slower to ?)
Type I muscle fibers are Red in colour due to :
- ? capillary density
- ? [myoglobin]
- Slowest to ?
The colour of the muscle fiber relates to the capillary density and [myoglobin]
Higher Capillary Density = Red in colour
Higher [myoglobin] = Red in colour (Myoglobin bound to O2 is Red]
Type IIx fibers are white/pale pink in colour due to:
- low level of myoglobin
- low capillary density
- They produce ATP at a slow rate by anaerobic metabolism and break it down very quickly.
- Fastest to fatigue
Type IIa muscle fibers are Reddish-pink in colour due to:
- High Capillary Density
- High [myoglobin]
- Less red than type I fibers because bigger size dilutes the colour
- They manufacture and split ATP at a fast rate (slower to fatigue)
Type I muscle fibers are Red in colour due to :
- High capillary density
- High [myoglobin]
- Slowest to fatigue
How does MIT density relate to fxn of dif types of muscle fiber?
The density of mitochondria is directly related to ?
- Low mito = ? oxidative capacity = ?
- High Mito = ? oxidative capacity = ?
Type I Muscle fibers have ? MIT density = ? oxidative capacity
Type IIa Muscle fibers have ? MIT density = ? oxidative capacity
Type IIx Muscle fibers have ? MIT density = ? oxidative capacity
The density of mitochondria is directly related to oxidative capacity as oxidative phosphorylation takes place in the Mitochondria
- Low mito = low oxidative capacity = anaerobic
- High Mito = High oxidative capacity = Aerobic
Type I Muscle fibers have High MIT density = High oxidative capacity
Type IIa Muscle fibers have Intermediate to high MIT density = Intermediate to high oxidative capacity
Type IIx Muscle fibers have Low MIT density = Low oxidative capacity
How does Glycogen relate to fxn of dif types of muscle fiber?
The amount of Glycogen (large polymers of ?) in a muscle fiber is related to the ability of said muscle fiber to ?
Type I Muscle fibers have ? Glycogen
- Anaerobic/Aerobic/Both?
Type IIa Muscle Fibers have ?
- Anaerobic/Aerobic/Both?
Type IIx Muscle Fibers have ? glycogen
- Anaerobic/Aerobic/Both?
The amount of Glycogen (large polymers of glucose) in a muscle fiber is related to the ability of said muscle fiber to produce ATP in the absence of oxygen (Anaerobic)
Type I Muscle fibers have Low Glycogen and are Aerobic only
Type IIa Muscle Fibers have Moderate glycogen and can produce ATP Anaerobically
- Have int-high MIT, high myoglobin and high capillary density == can also produce ATP aerobically
Type IIx Muscle Fibers have High glycogen and are Anaerobic only
Glycogen has traditionally been viewed as a key substrate for muscle ATP production during conditions of high energy demand and considered to be limiting for work capacity and force generation under defined conditions
Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g)
How does [Myoglobin] relate to fxn of dif types of muscle fiber?
Concentration of myoglobin is related to ?.
Myoglobin is responsible for ?
Therefore, in fiber types with more myoglobin, the ? will be increased
Type I have ? [myoglobin]
- Impact on metabolism?
Type IIa have ? [myoglobin]
- Impact on metabolism?
Type IIx have ? myoglobin
- Impact on metabolism?
Concentration of myoglobin is related to oxidative capacity.
Myoglobin is responsible for shuttling oxygen from the capillary to the mitochondria
Therefore, in fiber types with more myoglobin, the oxidative capacity will be increased
Type I have High [myoglobin]
- High Oxidative Capacity (Aerobic)
Type IIa have High [myoglobin]
- Aerobic (and Anaerobic)
Type IIx have low myoglobin
- Low oxygen storage/shuttling capacity
- Anaerobic metabolism
oxidative capacity = ability to make ATP from oxygen
Characteristics of Type 1 and Type II Fibers
Type I motor unit:
- Type of Neuron:
- Size of cell body
- Innervates how many muscle fibers
Type II(a/x) motor units:
- Type of Neuron
- Size of cell body
- Innervates how many muscle fibers
Type? muscle fibers reach peak tension faster, generate more force
(ie how does innervation relate to force of contraction?)
Type I motor unit:
- Type of Neuron: α-motor neuron
- Size of cell body: small
- Innervates how many muscle fibers: ≤ 300
Type II motor unit:
- Type of Neuron: α-motor neuron
- Size of cell body: larger
- Innervates how many muscle fibers: ≥ 300
Type II muscle fibers reach peak tension faster, generate more force
(ie The more muscle fibers innervated by a single alpha motor neuron the stronger the contraction)
Type I muscle fibers are also called ? or ?
Aerobic or Anaerobic?
Type I muscle fibers are also called slow twitch or red slow oxidative fibers
Aerobic
GENERAL Type 1 Muscle Fibers
Type 1: How does the Structure of Type I (aka: ?; ? muscle fibers relate to function?
- ? fiber diameter:
- ? capillary density:
- ? colour:
- ? MIT density:
- ? [myoglobin]
- ? Glycogen
Anaerobic or Aerobic? Why?
Resistance to fatigue?
Power/force capacity?
Contraction velocity? (type and [myosin-ATPase])
Order of recruitment?
How does the Structure of Type I MM fibers (aka Slow twitch; Red slow oxidative fibers relate to function?
Structure:
Small diameter: Smallest type
- related to force = Low power/force capacity
- Recruited first (size principle)
High capillary density
- High levels of oxygen delivered to muscle = increases oxidative capacity
- Slow to fatigue
Red colour
- indicative of high capillary density and high myoglobin
High MIT density
- Increases oxidative capacity
- Slow to fatigue
Metabolic:
Aerobic ONLY:
- High capillary density
- High MIT density
- High [myoglobin]
- Low glycogen
Low contraction velocity
- Low [myosin-ATPase]
- Slow myosin ATPase
High resistance to fatigue
Low Power/force capacity
- small diameter
- Recruited first
Function:
- Long, slow (several minutes to marathon)
- Postural muscles (antigravity muscles)
Complete image Type I
Type I: How does structure relate to function of Type I mm fibers?
- Fiber Diameter?
- Capillary Density?
- Color?
- MIT density?
- Glycogen?
- [Myoglobin]
How does structure relate to function of Type I mm fibers?
- Fiber Diameter: Small → Weaker contraction
- Capillary Density: High = Lots of Oxygen = High oxidative capacity = Aerobic
- Color: Red = Due to High capillary density and high myoglobin-O2 = can rapidly make ATP = Slower to fatigue
- MIT density: High = High oxidative capacity = rapidly makes ATP
- Glycogen: Low (involved in Anaerobic)
- [Myoglobin]: High = Ability to shuttle high amounts of O2 from Capillary to Mitochondria // Stores O2 during rest
Type IIa Muscle Fibers
Type IIa Mm Fibers are also called ? or ?
Type IIa Mm Fibers are also called Fast Twitch or White fast oxidative fibers
Type IIa Muscle Fibers
Are Type IIa Muscle Fibers Aerobic or Anaerobic?
BOTH
Aerobic
- high capillary density
- high myoglobin
- high mitochondria
All contribute to HIGH oxidative capacity = Aerobic
Anaerobic:
- Moderate glycogen -> Ability to make ATP by glycolysis in absence of O2
glycogen (polymers of glucose) is the fuel for anaerobic ATP production
Type IIa Muscle Fibers
Type IIa: How does the Structure of Type IIa (aka: ?; ? muscle fibers relate to function?
- ? diameter:
- ? capillary density:
- ? colour:
- ? MIT density:
- ? [myoglobin]
- ? Glycogen
Anaerobic or Aerobic? Why?
Resistance to fatigue?
Power/force capacity?
Contraction velocity?
Order of recruitment?
How does the Structure of Type IIa MM fibers (aka Fast twitch; white fast oxidative fibers relate to function?
Structure:
Intermediate diameter
- related to force = intermediate to high power/force capacity
High capillary diameter
- High levels of oxygen delivered to muscle = increases oxidative capacity
Reddish-pinkish colour
- indicative of high capillary density and high myoglobin
Intermediate to high MIT density
- Increases oxidative capacity
Metabolic:
Aerobic:
- High capillary density
- High MIT density
- High [myoglobin]
Anaerobic (glycolysis, creatine phosphate pathway)
- Moderate glycogen = fuel for glycolysis = Anaerobic ATP production
Intermediate to high contraction velocity
- High [myosin-ATPase]
- Fast myosin ATPase
Intermediate to high resistance to fatigue
- 1min < time to fatigue < 30min
Intermediate to high Power/force capacity
- Intermediate diameter
- Recruited second
Function
- Intermediate to short, fast, few minutes long (400m, 800m or 1500m run)
As the diameter increases in size, the fibers have more surface tension and become capable of generating higher amounts of force.
Muscles with a larger cross-sectional area (diameter) of individual muscle fibers are capable of producing greater amounts of force
Type IIx
Type IIx
How does the Structure of Type IIx MM fibers (aka ?; ? relate to function?
Structure:
? diameter
? capillary diameter
? colour
? MIT density
? Glycogen
? [Myoglobin]
Metabolic:
Aerobic or Anaerobic? Explain
? contraction velocity
- Type and concentration of myosin ATPase?
? resistance to fatigue
? Power/force capacity
Function? (ie types of exercise)
Type IIx
How does the Structure of Type IIx MM fibers (aka Fast twitch; White fast Glycolytic fibers relate to function?
Structure:
Large diameter: largest fiber type
- related to force = High power/force capacity
Low capillary diameter
- Low levels of oxygen delivered to muscle = decreases oxidative capacity
White (pale pink) colour
- indicative of low capillary density and low myoglobin
Low MIT density
- Decreases oxidative capacity
High Glycogen
- Make ATP by Glycolysis Primary source of ATP in these fiber types
- Fast ATP production, but produces very little ATP
Low [Myoglobin]
- Low Shuttling/Storage capacity for O2 -> decreases oxidative capacity
Metabolic:
Anaerobic ONLY:
- Low capillary density
- Low MIT density
- Low [myoglobin]
- high glycogen -> fuel for glycolysis = Anaerobic ATP production
High contraction velocity
- High [myosin-ATPase]
- Fast myosin ATPase
Very Low resistance to fatigue
- time to fatigue < 1min
High Power/force capacity
- Large diameter
- Recruited Third
Function
- Short, explosive, brief (100m sprint, throws, hitting baseballs, weights)
Fill in the table:
Fiber type and exercise
Type I fibers:
- High ? capacity (ie dominant energy type)
- Produce ATP from ? of ? and ?
- When are they used?
Type II fibers:
- ? (dominant energy type?)
- ? more easily than type I
- Type IIa: when are they used?
- Type IIx: when are they used?
Type I fibers:
- High aerobic capacity
- Produce ATP from oxidation of carbohydrate and fat
- Low-intensity endurance events (ie. marathons) and daily activities where muscle force requirements are low (ie. walking)
Type II fibers:
- Anaerobic
- Fatigue more easily than type I
- Type IIa: shorter higher-intensity endurance events (ie. running mile)
- Type IIx: highly explosive events (ie. 100 m sprint)
Two types of Contraction:
?:
- Maintain constant tension in the muscle as the muscle changes length
- Joint angle changes
- Two types: Concentric and Eccentric contractions
?
- Muscle contracts but does not change length
- Joint angle does not change
Two types of Contraction:
Isotonic (dynamic): “Same Tension”
- Maintain constant tension in the muscle as the muscle changes length
- Joint angle changes
- Two types: Concentric and Eccentric contractions
Isometric: “Same Length”
- Muscle contracts but does not change length
- Joint angle does not change
All exercises have a type of contraction component and type of contraction component
All exercises have a Concentric component and Essentric component
Concentric contraction (isotonic):
Total length of muscle ? as ? is produced (shorter + contacting)
Produces ? movement (? contractions)
? work
? pulled toward center of sarcomere
Effect on muscle of these contractions?
Example?
Concentric contraction (isotonic):
Total length of muscle shortens as tension is produced (shorter + contacting)
- Produces joint movement (dynamic/isotonic contractions)
- Positive work = Against Gravity
- Thin filaments pulled toward center of sarcomere
What is the effect of these contractions?
With these contractions: Build speed, improve muscle mass and strength
ie. Bicep curl (raising weight), standing back up in a squat, swinging a racquet
Concentric contraction (isotonic):
Total length of muscle shortens as tension is produced (shorter + contacting)
Produces joint movement (dynamic contractions)
Positive work
Thin filaments pulled toward center of sarcomere
ie. Bicep curl (raising weight), standing back up in a squat, swinging a racquet
Build speed, improve muscle mass and strength
What is the concentric phase?
Concentric Contraction: type of Isotonic contraction
- Portion of movement where the target muscle is shortening reaching it’s peak contraction to overcome gravity or some sort of resistance load
- Against Gravity = Positive Work
- Muscle contracts with force greater than resistance and shortens
Concentric contraction (isotonic):
Total length of muscle shortens as tension is produced (shorter + contacting)
Produces joint movement (dynamic contractions)
Positive work
Thin filaments pulled toward center of sarcomere
ie. Bicep curl (raising weight), standing back up in a squat, swinging a racquet
Build speed, improve muscle mass and strength
What is The Isometric Phase?
Transition point of an exercise in which the muscle is stationary following the concentric phase
- Muscle length doesn’t change
eg:
- lifting a heavy box: muscles are contracting but the bos isn’t moving
- Plank
- Wall sit
What is the Eccentric Phase?
Eccentric contraction: type of Isotonic contraction
- Muscle elongates/lengthens while under tension due to an opposing force which is greater than the force generated by the muscle
Eccentric contraction:
Total length of muscle increases as tension is produced (longer + contracting)
Produces joint movement (dynamic contractions)
Negative work
Thin filaments pulled toward center of sarcomere
Muscle challenged by a heavy force and gravity
ie. Bicep curl (lowering weight), standing back up in a squat
Build speed, improve muscle mass and strength
Eccentric contraction:
Total length of muscle ? as ? is produced (longer + contracting)
Produces ? movement (?/? contractions)
? work: with gravity
? pulled toward center of sarcomere
- ?controls extension
- Sarcomere, muscle fiber and muscle are all ?
- ? adds resistance to stretch
These contractions: Build ?, improve muscle ? and ?
Examples?
Eccentric contraction:
Total length of muscle increases as tension is produced (longer + contracting)
Produces joint movement (dynamic/isotonic contractions)
Negative work: with gravity
Thin filaments pulled toward center of sarcomere
- Cross bridge cyclingcontrols extension
- Sarcomere, muscle fiber and muscle are all lengthening
- Titin adds resistance to stretch
These contractions: Build speed, improve muscle mass and strength
eg: Muscle challenged by a heavy force and gravity
- Bicep curl (lowering weight),
- lowering in a squat
Eccentric contraction:
Total length of muscle increases as tension is produced (longer + contracting)
Produces joint movement (dynamic contractions)
Negative work
Thin filaments pulled toward center of sarcomere
Muscle challenged by a heavy force and gravity
ie. Bicep curl (lowering weight), standing back up in a squat
Build speed, improve muscle mass and strength
Eccentric contractions:
- Muscle ? under load to return to ?
Muscular ? or growth
Greater ? at lower ?
Slow down movement to increase ?
Theory: ?
This resistance produces ? without additional ? consumption because potential energy has been stored as ? during the ? phase
Eccentric contractions:
- Muscle lengthened under load to return to starting position
Muscular hypertrophy or growth
Greater forces at lower energy cost
Slow down movement to increase work
Theory: titin
This resistance produces extra force without additional ATP (energy) consumption because potential energy has been stored as elastic recoil during the concentric phase
Isometric (static) contraction:
- Muscle length ? as ? is produced
- ? does not change
- Load force > ?
- Generate LOTS of Tension
Examples
Isometric (static) contraction:
- Muscle length remains static (unchanged; no shortening/lengthening) as tension is produced
- Joint angle does not change
- Load force > muscle force
- Generate LOTS of Tension
ie. Trying to lift a weight that is too heavy (but not able to), holding a static exercise pose (plank; wall sits), gripping an object, postural muscles
What is Flexion?
Fexion: Movement that DECREASE joint angles
Extension: Increase Joint Angles
Flexion: Decrease Joint Angles
Abduction: Move limb AWAY from side of the body
Adduction: Move limb towards side of the body
What is Extension?
Extension = Increase Joint angles
Extension: Increase Joint Angles
Flexion: Decrease Joint Angles
Abduction: Move limb AWAY from side of the body
Adduction: Move limb towards side of the body
What is Abduction?
Moving limb AWAY from side of the body
Extension: Increase Joint Angles
Flexion: Decrease Joint Angles
Abduction: Move limb AWAY from side of the body
Adduction: Move limb towards side of the body
What is Adduction?
Adduction: Moving a limb towards the side of the body
Extension: Increase Joint Angles
Flexion: Decrease Joint Angles
Abduction: Move limb AWAY from side of the body
Adduction: Move limb towards side of the body
