Muscle Flashcards
Three types of muscle
Skeletal, cardiac, smooth
Skeletal muscle
Striated, voluntary, attached to bone
Smooth muscle
Not striated, involuntary, hollow organs
Flexor muscle
Brings bones together
Extensor muscle
Moves bones away
Flexor and extensor muscles are
Antagonistic muscle groups
Example of antagonistic muscle pair
Bicep (flexor), tricep (extensor)
Muscle organization
Fiber –> muscle fascicle (bundle of fibers) –> skeletal muscle –> tendon
Composition of skeletal muscle
Connective tissue, muscle fascicles, blood vessels, nerves
Muscle fascicles
Composed of individual muscle fibers
Sarcomere length
Z-disc to Z-disc
Z discs
Attachment sites for thin filaments
I bands
Lightest color bands, thin filaments only , divided by z disc
A bands
Darkest bands, thick filaments with thin filament overlap
H zone
Lightest region of A band, thick filaments only
M line
Attachment of thick filaments, divides A band
Contractile proteins
Myosin, actin
Myosin
Thick filaments
Actin
Thin filaments
Contraction regulatory proteins
Tropomyosin, troponin
Thick filament anatomy
Myosin heads, hinge regions, myosin tail
Thin filament anatomy
Twisted chains of tropomyosin and g-actin molecules
Nebulin
Inelastic proteins that align actin filaments
Titin
Elastic proteins that stretch between M line and Z disc
Function of sarcoplasmic reticulum
Stores Ca2+
Contraction
Creation of tension in muscle, ATP dependent, shortening of sarcomere
Contraction coupling
Ach release from motor neuron initiates action potential in muscle fiber which triggers calcium release from sarcoplasmic reticulum –> contraction
Muscle twitch
Single contraction-relaxation cycle
Fatigue
Reversible condition in which a muscle is no longer able to generate or sustain the expected output; central and peripheral
Central fatigue
From CNS –> psychological, reflexes
Peripheral fatigue
Fatigue at neuromuscular junction, excitation-contraction coupling, Ca2+ signaling –> decreased neurotransmitter release, change in membrane potential, Ca2+ leak channels, depletion of ATP
Causes of muscle fatigue during extended submaximal exercise
Depletion of glycogen stores
Causes of muscle fatigue during short duration maximal exertion
Increased levels of inorganic phosphate, slows Pi release from myosin, decrease calcium release
Causes of muscle fatigue during maximal exercise
K+ leaves muscle fiber, leading to increased concentration that decreases Ca2+
Muscle fiber types
Slow oxidative, fast oxidative-glycolytic, fast glycolytic
Slow oxidative muscle fibers
High resistance to fatigue; smallest diameter, high capacity to generate ATP, red, slow consumption ATP
Fast oxidative-glycolytic muscle fibers
Moderate resistance to fatigue; intermediate diameter, intermediate capacity to generate ATP, red-pink, fast consumption ATP
Fast glycolytic muscle fibers
Low resistance to fatigue; low capacity to generate ATP, largest diameter, white, fast consumption ATP
Rigor mortis
Metabolism stops, ATP supplies are exhausted –> actin and myosin cannot be released, muscles in state of contraction indefinitely
Isotonic contraction
Create force, move load –> concentric and eccentric
Isometric contraction
Create force, no movement –> shortening of sarcomeres without change in length (elastic elements stretch)
Concentric action
Shortening
Eccentric action
Lengthening
Load-velocity relationship
More load = slower movement of muscle
Which muscle type has the longest contractions
Smooth muscle
Which muscle type uses less energy?
Smooth muscle
Which muscle type maintains force for long periods?
Smooth muscle
Which muscle type has low oxygen consumption?
Smooth muscle
What controls smooth muscle?
Hormones, paracrines, neurotransmitters –> multiple pathways for contraction and relaxation
Single vs. multi-unit smooth muscle cells
Single= no innervation, Multi-unit= innervation (with varicosity)
Smooth muscle compared to skeletal
Smaller fibers, longer actin and myosin filaments, activity much slower, not arranged in sarcomeres, less sarcoplasmic reticulum
Stretch-activated calcium channels
Open when pressure or other force distorts cell membrane, smooth muscle
Smooth muscle control
Antagonistic control, dual innervation from parasympathetic and sympathetic
