EXAM 2 Module 4 Flashcards
striated muscles (striped pattern perpendicular to their long axis)
skeletal and cardiac
skeletal muscle structures
connective tissue
blood vessels
striated muscle fiber (single muscle cell)
sarcomere between two Z lines
thick filament
myosin
thin filament
actin
muscle contraction:
thick filament cross bridges are composed of ______ proteins
myosin
muscle contraction:
myosin proteins contact thin filaments and use the energy of ______ to pull on the thin filaments
ATP
muscle contraction:
in the absence of ATP, myosin attaches to _____
actin
explains what happens at sarcomere level
sliding-filament mechanism
in the sliding filament mechanism at the sarcomere level, the ______ move closer together
Z lines
sliding filament mechanism:
- the lengths of the thick filaments (A band) and thin filaments ______ change
- rather, the thin filaments are ________ around the thick filaments
- this does reduce the length of the _____ and ____
do not;
pulled in closer;
H zone; I band
cross-bridge cycling in skeletal and cardiac muscle:
- when Ca2+ inside the cell is low, _______ keeps the tropomyosin in a position that blocks cross-bridge binding to the ______
- muscle is ______
troponin; actin;
relaxed
cross-bridge cycling in skeletal and cardiac muscle:
- when Ca2+ inside the cell is high, it binds to troponin, which allows ________ to move away from the cross-bridge binding sites
- cross-bridges ______ and muscle is _______
tropomyosin;
form; contracted
3 sources of ATP production in muscle (in general order in which they are used during muscle contraction)
- creatine phosphate
- oxidative phosphorylation
- glycolysis
synapse where motor neuron AP communicates with muscle fiber to trigger muscle contraction
neuromuscular junction
EC coupling in skeletal muscle pathway
AP motor neuron
T tubules
DHP receptors
muscle contraction
after ______ flows into the cytoplasm, it binds troponin to allow cross-bridge formation and subsequent muscle contraction
Ca2+
EC coupling in cardiac muscle pathway
difference to skeletal muscle is no DHP receptors, instead there are voltage-gated L-type Ca2+ channels
muscle type with no striations
smooth muscle
smooth muscle structures
thick myosin filaments
thin actin filaments (anchored to plasma membrane or dense bodies)
tropomyosin
NO troponin
in smooth muscle, the thick and thin filaments slide past each other, and when the contraction happens, the entire cell ______ and ______
shortens; thickens
smooth muscle specialized structures
relaxed spindle-shaped
contracted blob
smooth muscles that respond to stimuli as a single unit, cells are connected by gap junctions
single-unit smooth muscles
smooth muscles that respond to stimuli independently, fewer gap junctions
multi-unit smooth muscles
two things that are lacking in smooth muscle contraction
troponin
sarcomere
smooth muscle contraction pathway:
1. increased cytosolic Ca2+ binds and activates _____
2. active calmodulin activates _______
3. myosin light-chain kinase ________ smooth muscle myosin
4. _______ can form
5. cross-bridge cycling can occur as long as _______ is phosphorylated
calmodulin;
myosin light-chain kinase;
phosphorylates;
cross-bridges;
myosin
thick and thin filaments
skeletal, smooth, cardiac
sarcomeres - banding pattern
skeletal, cardiac
transverse (T) tubules
skeletal, cardiac
sarcoplasmic reticulum
high skeletal, low smooth, medium cardiac
gap junctions between cells
smooth (more in single-unit, few in multi-unit), cardiac
source of activating Ca2+
skeletal: SR
smooth: SR and extracellular
cardiac: SR and extracellular
site of Ca2+ regulation
skeletal: troponin
smooth: myosin
cardiac: troponin
speed of contraction
skeletal: fast-slow
smooth: very slow
cardiac: slow
spontaneous production of action potentials by pacemakers
single-unit smooth, few specialized cardiac
tone (low levels of maintained tension in the absence of external stimuli)
single-unit smooth
effect of nerve stimulation
skeletal: excitation
smooth: excitation or inhibition
cardiac: excitation or inhibition
physiological effects of hormones on excitability and contraction
smooth, cardiac
stretch of cell produces contraction
single-unit smooth
once-common viral disease that can destroy motor neurons, leading to paralysis of skeletal muscle
poliomyelitis
involuntary tetanic contraction of skeletal muscles
muscle cramps
involuntary tetanic contraction of skeletal muscles that occurs when the extracellular Ca2+ concentration decreases to about 40% of its normal value
hypocalcemia tetany
common genetic disease, associated with progressive degeneration of skeletal and cardiac muscle fibers, more common in men
muscular dystrophy
what causes muscular dystrophy
the absence or defect of one or more proteins that make up the costameres in striated muscle
sex-linked recessive disorder caused by a mutation in a gene on the X chromosome that codes for the protein dystrophin
Duchenne muscular dystrophy
neuromuscular disorder characterized by muscle fatigue and weakness that progressively worsen as the muscle is used
myasthenia gravis
