A&P Chapter 10
slow oxidative fibers functional characteristics
•capacity for generating ATP is high and done by aerobic respiration •rate of ATP hydrolysis by myosin ATPase is slow •slow contraction velocity •high fatigue resistance •lowest amount of creatine kinase •low glycogen stores •first in recruitment •fibers are abundant in postural muscle such as those of neck •primary functions of fiber is to maintain posture and aerobic endurance activities
fast oxidative glycolytic fibers functional characteristics
•capacity for generating ATP is intermediate and done by both aerobic respiration and anaerobic glycolysis •fast rate of ATP hydrolysis by myosin ATPase •fast contraction velocity •intermediate muscle resistance •intermediate amount of creatine kinase •intermediate glycogen stores •second in order of recruitment •location where fibers are abundant is lower limb muscles •primary functions of fiber is walking, sprinting
fast glycolytic fibers
•capacity for generating ATP is low and done by anaerobic glycolysis •fast rate of ATP hydrolysis by myosin ATPase •fast contraction velocity •low fatigue resistance •highest amount of creatine kinase •high glycogen stores •third in order of recruitment •location where fibers are abundant is extra ocular muscles •primary functions of fiber is rapid, intense movements of short duration
slow oxidative fibers structural characteristics
•large amount of myoglobin content •many mitochondria •many capillaries •red color
Fast oxidative-glycolytic fibers structural characteristics
•large amount of myoglobin content •many mitochondria •many capillaries •red-pink color
regeneration of muscle tissue
•mature skeletal muscle fibers cannot undergo mitosis •skeletal muscle fibers cannot divide and have limited powers of regeneration; cardiac muscle fibers can regenerate under limited circumstances; and smooth muscle fibers have the best capacity for division and regeneration
skeletal muscle
•microscopic appearance and features: long cylindrical fiber with many peripherally located nuclei; unbranched; striated •location: most commonly attached by tendons to bones •fiber diameter: very large (10-100) •connective tissue components: endomysium, perimysium, and epimysium •fiber length: very large (100 um-30cm=12 inches) •contractile proteins organized into sarcomeres: yes •sarcoplasmic reticulum: abundant •transverse tubules present: yes, aligned with each A-I band junction •junctions between fibers: none •auto
fast glycolytic fibers structural characteristics
•small amount of myoglobin content •few mitochondria •few capillaries •white (pale) color
H zone
Narrow region in center of each A band that contains thick filaments but no thin filaments
Filaments (myofilaments)
Contractile proteins within myofibrils that are of two types: thick filaments composed of myosin and thin filaments composed of actin, tropomyosin, and troponin; sliding of thin filaments past thick filaments produces muscle shortening.
I band
Lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band.
muscle fiber (cell)
Long cylindrical cell covered by endomysium and sarcolemma; contains sarcoplasm, myofibrils, many peripherally located nuclei, mitochondria, transverse tubules, sarcoplasmic reticulum, and terminal cisterns. The fiber has a striated appearance.
functions of muscular tissue
Producing body movements, stabilizing body positions, storing and moving substances within the body, and generating heat.
Tropomyosin
Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin.
On the basis of their structure and function, skeletal muscle fibers are classified as
Slow oxidative (SO) fibers Fast oxidative-glycolytic (FOG) fibers Fast glycolytic (FG) fibers
Most skeletal muscles contain ________.
a mixture of all three fiber types. their proportions vary within the typical action of the muscle
troponin
a regulatory protein that is a component of the thin filament. When calcium ions (Ca2+) bind to troponin, it undergoes a change in shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin
Actin
contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction
excitation-contraction coupling
This concept connects the events of a muscle action potential with the sliding filament mechanism
Myosin
contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filament during muscle contraction
Myofibril
Threadlike contractile elements within sarcoplasm of muscle fiber that extend entire length of fiber; composed of filaments.
Muscle proteins
contractile, regulatory, structural
A band
dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments
Properties of Muscular Tissue
electrical excitability, contractility, extensibility, elasticity
what fiber does a shot putter most heavily rely on?
fast glycolytic fibers
what fiber does a soccer player most heavily rely on?
fast oxidative glycolytic fibers?
cardiac muscle
location: heart function: pump blood appearance: one nucleus/ striated/ intercalated discs control: involuntary
skeletal muscle
location: skeletal function: move bones appearance: multi-nucleated/ striated control: voluntary
Visceral (SMOOTH) muscle
location: various organs (GI tract) functions: various functions (peristalsis) appearance: one nucleus/ NO striations control: involuntary
contractile proteins
myosin and actin
Z disc
narrow, plate-shaped regions of dense material that separate one sarcomere from the next
muscle contraction
occurs because cross-bridges attach to and "walk" along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the center of a sarcomere. As the thin filaments slide inward, the Z disc come closer together, and the sarcomere shortens
skeletal muscle
organ made up of fascicles that contain muscle fibers (cells), blood vessels, and nerves: wrapped in epimysium
M line
region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere
Contraction and relaxation of skeletal muscle fibers
section ⬇️
with few exceptions, muscles develop from mesoderm
skeletal muscles of the head and limbs develop from general mesoderm. other skeletal muscles develop from the mesoderm of somites
3 types of muscle tissue
skeletal, cardiac, smooth
what fiber type does a marathoner most heavily rely on?
slow oxidative fibers?
contraction cycle
the repeating sequence of events that causes the filaments to slide 1. Myosin ATPase hydrolyzes ATP and becomes energized 2. the myosin head attaches to actin, forming a cross-bridge 3. the cross-bridge generates force as it rotates toward the center of the sarcomere (power stroke) 4. binding of ATP to the myosin head detached it from actin. the myosin head again hydrolyzes the ATP, returns to it's original position, and binds to a new site on actin as the cycle continues
structural proteins
titin, nebulin, alpha-actin, myomesin, dystrophin
Why do you continue to breathe heavily for a period of time after stopping exercise?
to "pay back" your oxygen debt The extra oxygen goes toward: 1. replenishing CP stores 2. converting lactate into pyruvate 3. reloading O2 onto myoglobin
regulatory proteins
troponin and tropomyosin
Muscles constitute about ____ our body weight
40-50%
Actinin
Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules.
Titin
Structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.
Myomesin
Structural protein that forms M line of sarcomere; binds to titin molecules and connects adjacent thick filaments to one another.
Dystrophin
Structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons.
Nebulin
Structural protein that wraps around entire length of each thin filament; helps anchor thin filaments to Z discs and regulates length of thin filaments during development.
The NMJ
The events at the NMJ produce a muscle action potential: •voltage-gated calcium channels in a neurons synaptic end bulb open, resulting in an influx of calcium. this causes exocytosis of a neurotransmitter into the synaptic cleft • NT binds to ligand-gated Na+ channels on the motor endplate, which causes an influx of Na+ into the muscle • this depolarizer the muscle and results in Ca2+ release from the sarcoplasmic reticulum •NT (neurotransmitter) gets broken down by acetylcholinesterase
length-tension relationship
The force of a muscle contraction depends on the length of the sarcomeres prior to the contraction
Motion results from
alternating contraction (shortening) and relaxation of muscles
Fascicle
bundle of muscle fibers wrapped in perimysium