Histo Lecutre 15

• Multinucleated cells
• Cells appear striated at the microscopic level due to orientation of contractile proteins
• Contraction provides voluntary movement

• Epimysium
• Perimysium
• Enodmysium

• Nourishment via rich capillary and lymphatic network
• Protection/organization
• Transmist fores along muscle fibers

• Myofilament
• Myofibril
• Muscle fiber
• Muscle Fasciculus
• Whole muscle

• Protein polymers responsible for contraction
• (e.g. action, myosin)

Grouping of myofilaments within a muscle cell

Muscle cell

Bundle of muscle fibers

• Connection of muscle and tendon
• Infoldings of cell membrane of muscle fibers
• Proides insertion sites for collagen fibers of tendon into muscle fibers

• Myosin (thick)
• Actin (thin)
• Titin

• Large protein polymer
• Assists with transmission of force during contraction
• Limits range of motion of sarcomere in tension
• Provides passive tension in resting muscle
• Maintains appropriate position of actin and myosin (binds Z-disc to M-line)

• Z-line (disk)
• I band
• A band
• H band
• M line

Actin attaches here

area of actin molecules only (staddles Z-line)

Area of mysoin & action overlap

Area of myosin only

• Anchors central area of myosin within each sarcomere
• Contains creatine kinase - enzyme that adds high energy phosphates to ADP to make ATP

Number of myofilaments increases with training while number of muscle fibers stays the same

• Consists of area of ATPase function (globular head)
• Serves as connection site for actin

Consist of helixes of filamentous protein polymers

Functions as an ATPase - enzyme that energies the the process of muscle contraction by fascilitating hydrolysis of ATP to release energy

• Globular protein polymer; bound to myosin at cross-bridges (on light chain of myosin)
• Globular proteins polymerized into long chains

Filamentous protein that exists within the "grooves" of actin filaments

• TnT - binds tightly to tropomyosin
• TnC - contains Ca 2+ at binding site
• Tnl - inhibits actin/myosin interaction

Sarcoplasmic reticulum (terminal cisternae)

Invaginations of the sarcolemma that create a network of membranous tubules at each sarcomere of muscle fibers

• Complex of two terminal cisterns of SR and one T-tubule
• Area where sarcomere depolarization is transmitted to the membrane of SR

• Depolarization is "transmitted" from the sarcolemma to the SR via the T-tubule system of the muscle fiber
• SR depolarization stimulates release of Ca2+ from cisterns
• Released Ca2+ binds to TnC (Allows cross-bridging between action and myosin)
• When depolarization is gone, Ca2+ actively returns from sarcoplasm to SR

• Used reflexively to maintain appropriate muscle tension for posture and regulation of opposing muscle groups
• Within straited muscle fibers

• Intrafusal muscle fibers (modified muscle fibers)
• Bag fibers (dynamic and static stretch)
• Chain fibers (static stretch)

• Velocity and degree of muscle stretch and sends that info to the CNS
• -Transmits info using Ia and II affarent fibers

Stimulate reflexive inhibition of anatagonist muscle to allow agonist muscles to contract without opposition

"sensitivity" of the spindles to stretch

Sensory nerve ending imbedded in the collagen fibers of the myotendinous junction

• Monitors force of contraction of the muscle and sends info to CNS via 1b efferent fibers
• Provides an inhibitory reflex that protects muscles from creating too much tension

• Glycogen - source of glucose for energy
• Myoglobin - Storage site for oxygen for aerobic respiration

• Site of connection between the nerve fiber of a motorneuron and the muscle fibers of skeletal muscle ("motor end plate")
• Each nerve fiber contains terminal branches allowing it to synapse with up to several hundred muscle fibers

• Synaptic trough - invagination of muscle membrane
• Subneural clefts - folds within synaptic trough which increase surface area for NT receptors (Ach)

Create ATP energy for acetylcholine synthesis and vesicle exocytosis

Nicotinic receptors

acetylcholinesterase

• Auto-immune disease in which anti-bodies "attack" Ach receptorsand render them nonfunctional
• Disease creates paralysis due to inability of muscle cell to react to nerve impulses

Acetylcholinesterase inhibitors that reduce Ach degradation and increase Ach binding to remain functional receptors

inhibits acetylcholinesterase and creates tonic muscle contraction

• Alpha motor neuron - Extrafusal muscle fibers (skeletal muscle fibers)
• Gamma motor neuron - Intrafusal muscle fibers (muscle spindle). Generates muscle response to sensory input from muscle spindles
• C motor neuron - Autonomic nervous system fibers to smooth muscle