Muscles Flashcards
(23 cards)
5 properties of muscle
- excitability- react to chemical signals
- conductivity- propogate electrical signals
- contractility- ability to contract
- extensibility- ability to stretch without harm
- elasticity- return to shape
skeletal muscle (nucleus status/branch status/mitosis status)
multi nucleated, peripheral/unbranched/non-mitosing
describe the 3 layers of connective tissue in muscle
epi- surrounds entire muscle
peri- separates muscle fasicles
endo- separates muscle fibers
list muscle layers from biggest to smallest
muscle - fasicle - fiber - myofibril - myofilament
why are muscle fibers multinucleated?
immature myoblasts fuse together to form fibers
describe a sarcomere
a-band- dark, myosin and actin overlap i-band- light, actin m-line- myosin CT at the center of a band z line- actin CT at edge h- band- myosin only
how many actin strands are associated with myosin
6/myosin
describe the tropomyosin/troponin complex
tropomyosin- bound to actin, covers active site
troponin C- binds Ca
troponin T- holds everything together
troponin I- binds active site
describe the make up of myosin II
2 heavy (binding) chains, 2 light chains, 2 regulatory light chains. mechanoenzyme- ATPase that uses ATP to release myosin head from actin for recocking
describe the power stroke mechanism in skeletal muscle
- myosin is bound to ATP and cocked in high energy position
- tropomyosin reveals binding site
- myosin binds to binding site
- binding causes the release of ADP and conformational change that takes actin closer to H band
- ATP binds to myosin and cuases release from actin
- ATP hydrolysis recocks myosin head into high energy position
what is a triad? compare to heart/
triad is the junction of a t-tubule with 2 adjacent terminal cisternae of SR. The heart functions in dyads where t-tubule is only adjacent with 1 terminal cisternae.
describe the NMJ
one nerve innervates many muscle fibers- motor unit
one muscle fiber is only innervated by one nerve
motor end plate- NMJ on the side of the muscle w/ many folds to increase surface area and 30 million ACh receptors
cardiac muscle (nuclei status, branching status/mitosis status)
single, centrally located nuclei/branched/extremely limited
what are 2 differences in cardiac t-tubules?
only at z lines. have dyads instead of triads
describe intercalated discs
zig zag w/ different structures on different parts
- longitudinal- gap junctions/desmosomes
- transverse- fascia adherens
smooth muscle (nucleus status/mitosis status)
single, centrally located/ actively mitosing
how does smooth muscle differ in appearance from cardiac and skeleton?
no striations
what doesnt smooth muscle appear striated?
its contractile system is different. actin and myosin connect two dense bodies (IFs) which pull the membrane
describe the role of myosin light chain kinase in muscle contraction
smooth muscle- extracellular Ca enters and binds calmodulin, which then binds MLCK, which frees actin binding sites. contraction is terminated by phosphatase
how is the NMJ different in smooth muscle?
no distinct NMJ, innervating axons contain local varcosities which release NT to the muscle
what is the effect of the type of innervation?
smooth muscle can work in sheets if one nerve innervates a large number, or have more individual characteristics in individually innervated
myoepithelial cells
common around glands and contain contracile properties. found in basement membranes
describe the general characteristics of the 3 types of muscles
skeletal- fast contracting, powerful, voluntary, discontinuous
cardiac- fast contracting, powerful, involuntary, continuous
smooth- slow contracting, weak, involuntary, discontinuous
