2) Exercising Muscle: Structure and Function Flashcards
Types of Muscle
Label the image
Skeletal Muscle is Striated/Unstriated and Voluntary/involuntary
Cardiac muscle is Striated/Unstriated and Voluntary/involuntary
Smooth muscle is Striated/Unstriated and Voluntary/involuntary
Skeletal Muscle is Striated and Voluntary
Cardiac muscle is Striated and involuntary
Smooth muscle is Unstriated and involuntary
Four properties of Muscle
1. ?: capacity of muscle to respond to a stimulus
2. ?: Ability of muscle to shorten and generate pulling force
3. ?: Muscle can be stretched back to its original length
4. ?: Ability of muscle to recoil to original resting length after stretched
Four properties of Muscle
1. Excitability: capacity of muscle to respond to a stimulus
2. Contractility: Ability of muscle to shorten and generate pulling force
3. Extensibility: Muscle can be stretched back to its original length
4. Elasticity: Ability of muscle to recoil to original resting length after stretched
Four properties of Muscle
1. Excitability: ?
2. Contractility: ?
3. Extensibility: ?
4. Elasticity: ?
Four properties of Muscle
1. Excitability: capacity of muscle to respond to a stimulus
2. Contractility: Ability of muscle to shorten and generate pulling force
3. Extensibility: Muscle can be stretched back to its original length
4. Elasticity: Ability of muscle to recoil to original resting length after stretched
Skeletal muscle
3 Functions of Skeletal Muscle
- Production of force for movement and breathing
- Production of force for postural support
- Heat production during cold
Label the Skeletal Muscle
Red =
Orange =
Yellow =
Green =
Blue =
Gold =
Purple =
Pink =
Red = Muscle
Orange =Perimysium
Yellow = Epimysium
Green = Fascicles
Blue = Muscle Fibers
Gold = Fascicle
Purple = Muscle Fibers
Pink = Perimysium
Fascicles = Bundle of muscle fibers within a muscle // supplied by nerves and blood vessels and enclosed in a fibrous perimysium separating it from neighboring fascicles
What is a Fascicle?
Fascicle = ? within a muscle
- supplied by ? and ?
- enclosed in a ? separating it from neighboring fascicles
Fascicle = Bundle of muscle fibers within a muscle - supplied by nerves and blood vessels
- enclosed in a fibrous perimysium separating it from neighboring fascicles
What separates neighbouring fascicles?
Fibrous Perimysium
Label the Muscle Fiber
Red =
Orange =
Yellow =
Green =
Label the Muscle Fiber
Red = Sarcolemma
Orange = Z-disc
Yellow = Myofibrils
Green = Myofilaments
What is A muscle Fiber?
- ?
- appearance?
- Enclosed in a specialized Plasma membrane (?)
- Contains densely packed bundles (?) of ?
- Multiple ? immediately beneath the sarcolemma
- Extensive network of specialized smooth endoplasmic reticulum (?)
- Enclosed in a thin fibrous sleeve called ?
Muscle Fiber:
- Single muscle cell
- Slender, elongated, threadlike
- Enclosed in a specialized Plasma membrane (SARCOLEMMA)
- Contains densely packed bundles (Myofibrils) of contractile protein filaments
- Multiple nuclei immediately beneath the sarcolemma
- Extensive network of specialized smooth endoplasmic reticulum (Sarcoplasmic Reticulum)
- Enclosed in a thin fibrous sleeve called endomysium
Label the Myofibril
Red
Orange
Yellow
Green
Red = Z-disc
Orange = T tubule
Yellow = Sarcoplasmic Reticulum
Green = Myofilaments (thick and thin)
Myofibril:
- Bundle of ? within a ?
- Fills most of the ?
- Surrounded by ? and ?
- Has a banded (striated) appearance due to orderly overlap of ?
Myofibril:
- Bundle of protein myofilaments within a muscle fiber
- Fills most of the cytoplasm
- Surrounded by sarcoplasmic Reticulum and mitochondria
- Has a banded (striated) appearance due to orderly overlap of protein myofilaments
Label the Sarcomere
Red
Orange
Yellow
Red = Z-disc
Orange = Thick Filament (myosin)
Yellow = Thin Filament (Actin)
What is A Sarcomere?
Segment of myofibril from one ? to the next in the fiber’s striation pattern
Hundreds of sarcomeres end to end compose a ?
- The ?, ? unit of the muscle fiber
Segment of myofibril from one Z disc to the next in the fiber’s striation pattern
Hundreds of sarcomeres end to end compose a myofibril
- The functional, contractile unit of the muscle fiber
Chemical Composition of Muscle
What is myoglobin?
Red protein containing heme which carries and stores oxygen in myscle cells
Skeletal muscle releases myoglobin when damaged
Myoglobin in urine indicates muscle damage
Presence of what protein in urine is indicative of muscle damage?
Myoglobin
- Protein containing heme
- Released by skeletal mm in response to damage
6 proteins in muscle
- Myosin
- Actin
- Tropomyosin
- troponin
- Titin
- myoglobin
Why is skeletal muscle multinucleated?
- The formation and growth of multinucleated myofibers or myotubes occur through a process known as myogenesis.
- During myogenesis, mononucleated myoblasts withdraw from the cell cycle, initiate muscle specific gene expression, and subsequently fuse with one another to form nascent, multinucleated myofibers
- They are multi-nucleated because they are formed from the fusion of embryonic myoblasts.
Each nucleus regulates the metabolic requirements of the sarcoplasm around it.
Satellite cells are myogenic stem cells responsible for muscle regeneration throughout the lifespan. Given their capacity to expand, differentiate, and provide a new source of nuclei to growing myofibres, their role in muscle adaptation to exercise was inferred.
What are three types of Connective tissue found in skeletal muscle
(from outermost to innermost)
- Epimysium
- Perimysium
- Endomysium
Epimysium:
- surrounds entire muscle
- Separates muscle from surrounding tissues/organs
- Connected to deep fascia
Perimysium:
- Collagen and elastic fibers surrounding a group of muscle fibers (ie fascicle)
Endomysium:
- sheath of Connective tissue covers each individual muscle fiber
Connective tissue
Epimysium:
- surrounds ?
- Separates muscle from ?
- Connected to ?
Perimysium:
- ? and ? surrounding a group of muscle fibers (ie ?)
Endomysium:
- sheath of Connective tissue covers ?
Epimysium:
- surrounds entire muscle
- Separates muscle from surrounding tissues/organs
- Connected to deep fascia
Perimysium:
- Collagen and elastic fibers surrounding a group of muscle fibers (ie fascicle)
Endomysium:
- sheath of Connective tissue covers each individual muscle fiber
Label and describe:
Muscle fiber: ?
Myofibril: ?
Tendon: ?
Fascicles: ?
Muscle fiber = a muscle cell
Myofibril: any of the longitudinal parallel contractile elements of a muscle cell
- Myofilaments: actin and myosin
Tendon: Attaches Muscle to Bone
Fascicles: Small bundles of muscle fibers wrapped in a connective tissue sheath
Structure of a single muscle fiber
What is the Sarcolemma
Sarcolemma:
- ?
Function?
- Series of ? when fiber is contracted or in resting state; ? disappear on stretching
– Muscle fiber can stretch without disrupting ?
- Junctional folds at ? aid in transmission of ?
- Transport ? from capillary blood into muscle fiber
Sarcolemma:
- Plasma membrane
Function?
- Series of shallow folds when fiber is contracted or in resting state; folds disappear on stretching
– Muscle fiber can stretch without disrupting sarcolemma
- Junctional folds at motor end plate aid in transmission of action potential
- Transport metabolites from capillary blood into muscle fiber
The triad is a skeletal muscle substructure responsible for the regulation of excitation-contraction coupling. It is formed by the close apposition of the T-tubule and the terminal sarcoplasmic reticulum.
Sarcoplasm:
- ?-like substance that fills spaces within and between ?; the ? of muscle fiber
- Contains stored ?, ?, ? and ?
Sarcoplasm:
- Gelatin-like substance that fills spaces within and between myofibrils; the cytoplasm of muscle fiber
- Contains stored glycogen, fat, enzymes and oxygen-binding myoglobin
Transverse-tubules
- Transverse tubules (t- tubules): ? system that synchronizes the release of ? ion ? from the ? of the sarcoplasmic reticulum
- Extensions of ?
- Carry “?”, ? and ? deep into cell
– Rapid transmission of ? to individual ?
Transverse-tubules
- Transverse tubules (t- tubules): duct system that synchronizes the release of Ca2+ from the terminal cisternae of the sarcoplasmic reticulum
- Extensions of sarcolemma/surface membrane
- Carry “ions”, nutrients and action potentials deep into cell
– Rapid transmission of nerve impulses to individual myofibrils
Sarcoplasmic reticulum:
Network of ?
Storage site for ?
Speeds up ? in skeletal muscle because Ca2+ has shorter distances to diffuse i.e. 0.25 μm opposed to 50 μm (200 x)
Sarcoplasmic reticulum:
Network of tubules
Storage site for calcium
Speeds up contraction in skeletal muscle because Ca2+ has shorter distances to diffuse i.e. 0.25 μm opposed to 50 μm (200 x)
Structure of a single muscle fiber
Terminal cisternae:
- Enlarged area of ? surrounding ?
Compartment from which ? is released following an ?
Triad:
Composed of: ? – ? – ?
Couples ? to ?
Terminal cisternae:
- Enlarged area of sarcoplasmic reticulum surrounding transverse tubules
Compartment from which Ca2+ is released following an action potential
Triad:
Terminal cisternae – t-tubule – terminal cisternae
Couples excitation to contraction
Structure of single muscle fiber
Triad:
Composed of: ? – ? – ?
Couples ? to ?
Triad:
Terminal cisternae – t-tubule – terminal cisternae
Couples excitation to contraction
What are Satellite cells?
Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling.
Mononucleated cells “wedged” between the basement membrane and plasma membrane of the muscle fiber. Act as stem cells and are responsible for the further growth and development of skeletal muscles.
Satellite cells
Function: ? and ? of ?
When muscle hypertrophy occurs cell volume ?
A single nuclei can only maintain/produce proteins for a finite ?
Satellite cells merge with the muscle fiber and become ? for that fiber
Increases the number of ? for the fiber allowing for greater ?
Important for ? to strength training
Satellite cells
Function: Growth and repair of muscle cell
When muscle hypertrophy occurs cell volume increases
A single nuclei can only maintain/produce proteins for a finite volume
Satellite cells merge with the muscle fiber and become new nuclei for that fiber
Increases the number of nuclei for the fiber allowing for greater protein synthesis
Important for adaptations to strength training
Sarcomere
- Striped appearance
- Basic contractile unit of muscle
- Z-line (disk) to Z-line
- Because sarcomeres are joined end to end throughout an entire muscle fiber, their simultaneous contraction shortens the entire muscle
Sarcomere
- Striped appearance
- Basic contractile unit of muscle
- Z-line (disk) to Z-line
- Because sarcomeres are joined end to end throughout an entire muscle fiber, their simultaneous contraction shortens the entire muscle
Label
1. Z-line
2. Titin
3. Thick filament
4. M line
5. Thin filament
6. I band
7. A band
8. H zone
9. Sarcomere
Red = I band
Orange = A band
Yellow = H- Zone
Green = Z-disk
Grey = Titin
Cyan = Thin filament (actin)
Navy = M-line
Purple = Thick filament (Myosin)
Microscopic structure of muscle
What part of the sarcomere is being described:
Dark with slightly lighter region in the center; contains thick and thin filaments
A Band
Dark with slightly lighter region in the center; contains thick and thin filaments
Microscopic structure of muscle
What part of the sarcomere is being described:
Light region in the middle of the A band; contains only thick filaments
H Zone
Light region in the middle of the A band - contains only THICK filaments (ie myosin only)
Microscopic structure of muscle
What part of the sarcomere is being described:
Transverse line in the middle of H zone; composed of proteins that serve as the attachment site of the thick filaments and stabilizes structure of sarcomere; myosin anchor site
M Line
Transverse line in the middle of H zone; composed of proteins that serve as the attachment site of the thick filaments and stabilizes structure of sarcomere; myosin anchor site
Microscopic structure of muscle
What part of the sarcomere is being described:
Light regions; regions of sarcomere where there are thin filaments (no thick filaments)
Actin; troponin, tropomyosin Only
I Bands
Light regions; regions of sarcomere where there are thin filaments (no thick filaments)
Microscopic structure of muscle
What part of the sarcomere is being described:
- Narrow dark line in the middle of the I band;
- site of attachment for titin, thin filaments
Z line
- Narrow dark line in the middle of the I band;
- site of attachment for titin, thin filaments
Microscopic structure of muscle
What part of the sarcomere is being described:
- Narrow dark line in the middle of the I band;
- site of attachment for titin, thin filaments
Z line
- Narrow dark line in the middle of the I band;
- site of attachment for titin, thin filaments
The distance from Z line to Z line is a ?
The distance from Z line to Z line is a Sarcomere (2-3um)
How do sarcomeres in a muscle fiber differ?
They dont
All sarcomeres in a muscle fiber are identical
What is Nebulin? Function?
Anchoring protein for actin; regulatory role in actin and myosin interactions
- helps anchor actin filament to Z disks
Thin filaments contain ? to bind myosin heads
Thin filaments contain active sites to bind myosin heads
Actin:
? proteins (?) in 2 helical strands (?)
Actin:
Globular proteins (G-actin) in 2 helical strands (F-actin)
What is tropomyosin?
Tropomyosin: Tubular protein of two identical alpha helices, shadows the actin double helix
Describe troponin
What are the three types?
Troponin is a heterotrimer
1. TnT = binds to tropomyosin
2. TnC = binds Ca2+ (4 calcium binding sites in skeletal muscle)
3. TnI = Binds to the actin monomer (inhibitory)
Describe the three subunits of troponin:
The troponin complex is a ? composed of:
1. troponin C (TnC): the ? subunit // binds to ?,
2. troponin I (TnI), the ? subunit // binds to ?
3. troponin T (TnT), the ? subunit // binds to ?
The troponin complex is a heterotrimer composed of:
1. troponin C (TnC): the Ca2+-binding subunit,
2. troponin I (TnI): the inhibitory subunit // binds to the actin monomer
3. troponin T (TnT): the Tropomyosin (Tm)-binding subunit.
Thick filaments are ? of proteins (?)
Each myosin molecule is a ? consisting of:
1. Two intertwined ?
2. Two ? light chains
3. Two ? light chains
Thick filaments are polymers of proteins (myosin II)
Each myosin molecule is a double trimer consisting of:
1. Two intertwined heavy chains
2. Two regulatory light chains
3. Two Alkali (essential) light chains
The 2 heavy chains have 3 regions: rod (tail), hinge and head region
Rods (tails) are α helices
Hinge regions flare into two globular heads
Heads:
(i) are cross bridges
(ii) contain binding sites for actin
(iii) contain sites for binding and hydrolyzing ATP
Thick filaments are polymers of proteins (myosin II)
Each myosin molecule is a double trimer consisting of:
1. Two intertwined heavy chains
2. Two regulatory light chains
3. Two Alkali (essential) light chains
- The 2 heavy chains have 3 regions: 1, 2 and 3 region
- ? are α helices
- ? regions flare into two globular heads
-
?:
(i) are cross bridges
(ii) contain binding sites for actin
(iii) contain sites for binding and hydrolyzing ATP
Thick filaments are polymers of proteins (myosin II)
Each myosin molecule is a double trimer consisting of:
1. Two intertwined heavy chains
2. Two regulatory light chains
3. Two Alkali (essential) light chains
- The 2 heavy chains have 3 regions: rod (tail), hinge and head region
- Rods (tails) are α helices
- Hinge regions flare into two globular heads
-
Heads:
(i) are cross bridges
(ii) contain binding sites for actin
(iii) contain sites for binding and hydrolyzing ATP
Thick filaments are polymers of proteins (myosin II)
Each myosin molecule is a double trimer consisting of:
1. Two intertwined heavy chains
2. Two regulatory light chains
3. Two Alkali (essential) light chains
- The 2 heavy chains have 3 regions: rod (tail), hinge and head region
- Rods (tails) are ?
- Hinge regions flare into ?
- Heads:
(i) are ?
(ii) contain binding sites for ?
(iii) contain sites for binding and hydrolyzing ?
Thick filaments are polymers of proteins (myosin II)
Each myosin molecule is a double trimer consisting of:
1. Two intertwined heavy chains
2. Two regulatory light chains
3. Two Alkali (essential) light chains
- The 2 heavy chains have 3 regions: rod (tail), hinge and head region
- Rods (tails) are α helices
- Hinge regions flare into two globular heads
- Heads:
(i) are cross bridges
(ii) contain binding sites for actin
(iii) contain sites for binding and hydrolyzing ATP
Accessory proteins
What is Titin?
Role?
Prevents?
Provides?
Titin:
- large elastic protein
- anchors thick myosin filament to the Z disk
- Prevents overstretching
- Provides elastic recoil
What is alpha-actinin?
Attachment of actin filament to Z-disk
