gainz histo Flashcards
What are characteristics of skeletal muscle?
voluntary control
strong, quick contractions
striated (actin and myosin)
large, elongated, multinucleated cells
What are characteristics of cardiac muscle?
involuntary control strong, quick contractions striated uninucleated cells centrally located nucleus elongated/branched cells joined by intercalated discs
What are characteristics of smooth muscle?
involuntary control weak, slow contractions non striated uninucleated, fusiform cells centrally located nucleus
What are the three types of fibers in skeletal muscle?
type I: slow, red oxidative fibers
type IIa: fast, intermediate oxidative-glycolytic fibers
type IIb: fast, white glycolytic fibers
What are characteristics of type I fibers?
slow, red oxidative fibers
lots of mitochondria and myoglobin
energy from aerobic oxidative phosphorylation of fatty acids
slow, continous contractions (endurance)
What are characteristics of type IIa fibers?
fast, intermediate oxidative-glycolytic fibers
many mitochondria, myoglobin and glycogen
use oxidative phosphorylation and anaerobic glycolysis
rapid contractions, short bursts of energy
What are characteristics of type IIb fibers?
fast, white glycolytic fibers
few mitochondria and myoglobin, LOTS of glycogen
use anaerobic glycolysis
rapid contractions, but fatigue quickly
What color are A bands?
dark
What color are I bands?
light
What runs through I bands?
Z disc
What are the boundaries of a sarcomere?
Z disc to Z disc
What is actin?
thin filament
What is myosin?
thick filament
What fibers are in an A band?
actin (thin) and myosin (thick)
What fibers are in an I band?
only actin (thin)
What is the M line?
in the center of an A band, thick filaments only, myosin fibers tie in with one another
What is the H zone?
Area of an A band where there are only thick (myosin) fibers
What happens during muscle contraction?
Z discs slide closer together
myosin ‘grabs’ actin and pulls Z discs closer together
A band remains same size
I band shrinks
H zone disappears, but M line stays
What are characteristics of the globular heads of myosin?
acting binding
ATP binding
ATPase activity
What blocks myosin binding to actin?
tropomyosin
What are the important subunits of the troponin complex?
TnT: troponin and tropomyosin binding?
TnC: binds calcium
What is the trigger for muscle contraction?
increased Ca2+ concentration in cytosol
What is the role of the sarcoplasmic reticulum in muscle cells?
takes up and stores Ca, will release Ca upon contraction
What is a T tubule and where is it located?
extension of plasma membrane that allows action potentials to reach deep into cells
located between A band/I band junction
What is a terminal cisterna?
enlarged region of sarcoplasmic reticulum located near a T tubule
What is a motor unit?
the motor neuron and all the muscle fibers it innervates
one axon innervates multiple muscle cells
What is an important neurotransmitter in muscle contraction
acetylcholine (ACh)
What are the steps of muscle contraction?
- AP generated, sent down T tubules
- AP triggers Ca release from SR
- Ca ions bind to troponin, removing the blocking action of tropomysosin, actin binding sites exposed
- myosin grabs actin and pulls fibers closer to center of sarcomere
- Ca removed by active transport
- tropomysoin blocks actin binding site again
How do you change myosin heads from low to high energy conformations?
need ATP to change head myosin head conformation.
need ATP to make the myosin head “let go” of actin
need ATPase to get rid of ATP and put head into high energy conformation
(look at pics this is confusing)
What are the connective tissue sheaths associated with skeletal muscle?
endomysium (around individual fibers)
perimysium (around fiber bundles called fasicles)
epipysium (around entire muscle_
What is the difference in T tubules between cardiac and skeletal muscle?
cardiac: one per sarcomere at Z disc (forms diads)
skeletal: two per sarcomere at A-I junctions (forms triads)
What are the components of intercalated discs?
Fascia adherens: links actin filaments
desmosome: links intermediate filaments
gap junctions: communicating junction
