muscle

myofilament > myofibril > muscle fiber/cell > muscle fascicle

series of sarcomeres linked together like "beads on a string", align w/ bands above and below

• muscle cell
• multinuc w/ eccentric nuc

paraxial mesoderm (forms somites) and somitomeres in developing head of embryoblast

ends of nerve endings interact w/ muscle fibers at motor end plates

• multinuc, eccentric nuc
• long fibers (but not as long as muscle itself)
• voluntary control (innervated by cholinergic nerve endings)
• contraction results from shortening sarcomeres

CT w/in muscle or CT tendons at each end of muscle

• (I band) "monorefringent"- plane of polarized light is not bent
• light in color
• bisected by Z disc
• made of only thin actin filaments

• (A band) birefringent: plane of polarized light is bent
• made of thick and thin filaments (depends on your XS as to what the composition is)

• (H band); thick filaments only
• btw thin filaments of A band; at center of A band

made of only thick myosin filaments w/ cross connections of myomesin

bisects I band

area btw 2 Z disks; basic contractile unit of striated muscle

• G actin monomers that comprise filamentous F actin
• two F actins intertwine to form a helix

occupies shallow grooves btw actin helices; masks myosin-binding sites on G actin

• located on tropomyosin molecules; 3 subunits:
• troponin T: binds troponin to tropomyosin
• troponin C: binds Ca2+ which causes conformational change in tropomyosin and exposure of myosin binding site on G actin
• troponin I: binds to actin to prevent actin-myosin interaction

• two globular heads on two helices that intertwine
• heads have ATPase activity

holds myosins together

connects ends of myosin molecules to Z line

sER in muscle cells; stores intracellular Ca2+ and release

cell membrane of striated muscle cells

invaginations of sarcolemma into interior of muscle fiber; occur at A-I junction in skeletal muscle and Z-intercalated disk in cardiac muscle

aka TM prots

gene mut or deletion in lamins of dystroglycans

due to mut in Type 1 red muscle fibers

due to mut in type 2 white fibers

gene mut or deletion in sarcoglyans

• cisternae of sarcoplasmic reticulum which parallel T tubule
• two, one for each side of T tubule; forms a triad in skeletal muscle and diad in cardiac muscle

have Ca2+ stored in it, released after deplolarization from AP; Ca2+ causes troponin to relieve tropomyosin inhibition

at A-I junction; v closely assoc w/ myofibrils for best contraction

release calcium once receives signal and re-uptakes calcium right after releasing it so that contractions do not continue to happen

if levels of Ca2+ become too high or ATP levels become depleted (actin and myosin become cross-linked)

via dystrophin protein to TM proteins that are linked to basal lamina; maintains muscle integrity during contraction

dystrophin is lg prot so lots of chances for mutations (duschennes and beckers)

• lots of myoglobin and oxidative enz
• -"slow twitch", sustained force, weight-bearing, enduring
• -sm diameter
• -NADH dk staining (bc of myoglobin)
• -abundant lipids
• -minimal glycogen
• -one motor neuron innervates many muscle fibers (less precise control)
• -located in limb muscles and long back muscles

• -"fast twitch", sudden movements; purposeful motion; easily fatigued
• -less myoglobin
• -NADH light staining
• -minimal lipids
• -abundant glycogen
• -few mit
• -one motor neuron innervates few muscle cells (precise control)
• -located in extraocular muscles, digits

ind myocytes

bundles of muscle cells (fascicles)

entire muscle; many fascicles

Ach; uses cholinergic (nicotinic) receptors

multipolar neuron from ventral horn of gray column synapses on ind fibers (motor end plate)

• bundle of skeletal muscle fiber innervated by single motor neuron
• myelinated
• every muscle fiber receives a nerve terminal

stem cells--->myoblasts--->new muscle fibers

new cell has a more central nuc (bc from myoblast) whereas an original cell has an eccentric nuc

centrally; mononucleated

same as skeletal muscle cells

junctional complex that connects sequential cardiocytes; creates lots of attachment and communication sites for gap junctions

• maculae adherens (desmosomes)-attachment of intF
• fascia adherens-attachment of actin thin filaments
• gap junctions-ion transport to synchronize heart contraction

bridge between layers of cardiocytes; allows heart to contract at once

elongated around the myofibrils; lots bc need lots ATP for heart

less well-developed; diads; located at Z disks (but not intercalated disks)

• lots of cytoplasmic glycogen
• secretory granules in atria contain ANP

• when the atria is stretched (bc of too much H20), cardiocytes in atria release ANP:
• osmotic balance
• distention atrial wall
• stimulates diuresis (counters ADH)
• relaxes cardio channels

• modified cardiocytes; lgr than regular cardiocytes w/ central nuc and less myofibrils peripherally located
• binucleate; lots of glycogen granules

subendocardium

nodes and bundles

to facilitate conduction of contractile stimulus (not actually contract as skeletal...more of a transmitter to rest of heart)

replaced w/ fibrous CT

• organized as bundles or sheets of cells
• spindle shaped
• involuntary control
• non-striated
• stains "frosty pink" color
• organelles (golgi and sec granules) around each end of nuc

• elastin (tunica media cells of elastic arteries)
• type 4 and 3 collagen (tunica intima cells of blood vessels)
• lamin and proteoglycans (CTs)
• renin (juxtaglomerular cells in kidneys)

to act synchronously

• nonmyelinated, ANS
• no specialized synapse
• only a few cells are innervated
• has gap junctions to allow concerted contractions

(ICC): highly specialized pacemaker cells that modulate autonomic stimulation of smooth muscle cells and are important in frequency of rhythmic contraction (i.e. peristalsis)

• sliding filament mechanism w/ actin-myosin
• Ca2+ dep

Ca2+ induces calmodulin dep act of myosin light chain kinase...initiates actin-myosin interaction

• slow
• contractions are sustained (little ATP req)

undergo mitosis

SA-AV-His-Purkinje

vagus nerve-slows down heart contraction

• speeds up contraction at SA
• stim cardiac muscle cells to contract harder
• goes to each node and cell

bare nerve terminal of smooth muscle cells where NE is dumped onto