Anatomy ch 10

• 1. Skeletal - striated, voluntary - move bones of skeleton
• 2. Cardiac - striated, involuntary - forms heart wall
• autorhythmicity - built-in rhythem of the heart
• 3. Smooth - nonstriated (smooth), involuntary - walls of hollow internal structures, such as blood vessels, airways, and most organs in the abdominopalvic cavity

• 1. produce body movement
• 2. stabilizing body position
• 3. storing and moving substances within the body
• 4. Generating heat (thermogenesis)

• 1. Electrical excitability - ability to respond to electrical stimuli
• 2. Contractility: ability to contract fully when stimulated
• 3. Extensibility: ability to stretch without being damaged
• 4. Elasticity: ability to return to original shape after contraction or extension

alternating light and dark protein bands are seen when the tissue is examined with a microscope

a muscle cell - called muscle fibers because of their elongated shape

• superficial fascia - separates muscles from skin - areolar CT and adipose tissue
• Deep fascia - holds muscles with similar functions together - dense irregular CT

• Epimysium: surrounds whole muscle
• perimysium: surrounds muscle bundles of 10 to 100 muscle fibers called fascicles
• endomysium: surrounds individual muscle fiber (muscle cell)

all three CT extend beyond the muscle fibers and form a tendon- dense irregular CT that attach muscle to the periostium of the bone

tendon sheaths - certain tendons (esp wrist & ankle) are enclosed by tubes of fibrous CT

tendon that extends off muscle tissue as a broad, flat layer

ex. epocranial aponeurosis

• somatic motor neuron - the nerve endings that supply each muscle fiber - connected at the neuromuscular joint
• muscle tissue has high O₂ requirements so is well supplied with arteries
• 1 artery and 1 or more veins for each muscle
• blood vessels and nerve fibers enter central part of muscle and branch

growth in muscle tissue by an increase in the number of fibers

hypertrophy - an enlarging of existing muscle cells (growth in infancy)

satellite cells - cells that retain the capacity to fuse with one another or with damaged muscle fibers to regenerate functional muscle fibers

the replacement of muscle fibers by fibrous scar tissue due to skeletal muscle damage or degeneration

• the plasma membrane of the muscle cell
• T tubules - tunnel in from the surface toward the center ir each muscle fiber (open to the outside of the fiber and are filled with interstitial fluid)
• sarcoplasm - cytoplasm of a muscle fiber
• Myoglobin - red-colored protein in the sarcoplasm - found only in muscle cells - binds O₂ that diffuse into the muscle fiber from interstitial fluid

• contractile organelles of skeletal muscle - in the sarcoplasm
• 

• SR - fluid-filled system of membranous sacs that encircle each myofibril
• terminal cisterns - end sacs of the SR that butt against the T tubules from both sides
• triad - a T tubule and two terminal cisterns on either side of it

• myo
• sarco

• short protein structures arranged into sarcomeres (short sections)
• Two types:
• Actin - thin filaments
• Myosin - thick filaments

• Functional - Contractile - units of skeletal muscle - short sections of filaments
• Z disks: separate one sarcomere from the next
• A bands: appear dArd - runs entire length of thick filament (thick and thin) in three zones
• 1) H Zone: (Heavy) thick but no thin filaments
• 2) Zone of Overlap - both thick and thin
• 3) M line - in middle of sarcomere
• I bands: appear lIght - contains only thin filaments - extends across Z disk from A band of one sarcomere to A band of next sarcomere
• 

• contain mostly Myosin - Have head (crossbridges) and tails - two gold clubs
• Functions as a Motor protein - drives the action of cells
• 

• mostly Actin - have myosin binding sites - concave area on actin where myosin binds to it
• Tropomyosin - covers binding site when muscle is relazed
• Troponin - holds tropomyosin in place
• 

• Contractile proteins
• Myosin - think filaments
• Actin - thin filaments
• Regulatory Proteins
• Tropomyosin - when skeletal muscle is relaxed tropomyosin covers myosin binding site on actin
• Troponin - when Ca²⁺ (calcium ion) bind to troponin it changes shape and pulls propomyosin away from myosin binding site - uncovers it
• Structural proteins
• Titin - connects to the Z disk and M line of a sarcomere- helps to stabilize the position of the thick filament - accounts for elasticity and extensibility of the myofibrils
• Nebulin - wraps around length of each thin filament - helps anchor thin filament to Z disks
• Myomesin - forms the M line of the sarcomere
• Dystrophin - links thin filaments of the sarcomere to integral proteins of the sarcolemma

• 1. ATP hydrolysis - ATP that is bound to myosin head and is hydrolized into ADP - causes tropomyosin to move leaving binding site open
• 2. Attachement of myosin to actin to form crossbridges
• 3. Power stroke - ADP is released crossbridges act like tiny ratchets to propel thin filament towards center of sarcomere - each crossbridge attaches and detaches several times during contraction
• 4. Detachment of myosin form actin - APT binds to myosin head causing it to detatch from actin

muscle contracion occurs becuase myosin heads attach to and walk along the thin filaments at both ends of a sarcomere - pulling the thin filaments toward the M line - Z disks come closer together and sarcomere shortens - length of individual thick and thin filaments does not change

the events involved from excitation (receiving and propagating a stimulus) to contraction (actual sliding of the filaments)

• channels in the SR that open and let Ca²⁺ flow out into cytosol around the thick and thin filaments
• calsequestrin - calcium-binding protein that enables calcium to be stored withing the SR

Tension depends on the degree of overlap of thin and thick myofilaments

• Lots of overlap = little tension
• some overlap = allows for maximum tension - most binding available
• little overlap = little tension - little possibility of binding
• no overlap = no tension - muscle streatched out - muscle failure

• muscle contractions are controlled by the nervous system via the NMJ
• Neuromuscular Junctions - area of contact between neuron and sarcolemma
• Synapse - Regions where nerve cell communicates with other cell through the release of neurotransmitters called Acetylcholine (ACh)
• Synaptic gap: space between the synaptic terminal and the sarcolemma
• synaptic end bulbs:expanded ends of neuron
• Motor End Plate: area on the sarcolemma where Ach receptors are found - every place you have a NMJ you have a motor end plate
• 

• 1. Release of acetylcholine (ACh):
• --nerve impulses from the axon release ACh via exocytosis into the synaptic cleft
• -- ACh diffuses across synaptic cleft and binds to receptors on sarcolemma - concentration gradient
• 2. Activation of ACh receptors and production of muscle action potential
• -- ACh binding opens sodium ion channels and causes an influx of sodium ions into the sarcoplasm
• --This brings on an ACTION POTENTIAL that spreads all over via T tubules
• -- Sarcoplasmic reticulum releases calcium ions
• --calcium ions bind with troponin and expose myosin binding site
• --Muscle fibers then contract
• 3. Termination of ACh activity and subsequent relaxation of skeletal muscle fibers
• --Release of ACh stops- causes release of calcium to stop
• --Calcium pumped back into SR via active transport
• -- Calcium ions detach from troponin
• --Tropomyosin covers up myosin binding site - crossbridge cant attach - contraction stops

• 1. Excess ATP temporarily converted to and stored as Creatine Phosphate- a high energy molecule that is used to regenerate ATP to supply quick energy bursts
• 2. Anaerobic Cellular Respiration - No oxygen - short burst of energy
• --occurs in sarcoplasm - lactic acid byproduct- small amount of ATP
• 3. Aerobic cellular respiration
• -- occurs in mitochondria - large ATP - provides most of energy for activities that last more than 10 mins

• psysiological inability to contract - spirit is will but the flesh is not
• - caused by insufficient oxygen or calcium
• Motor Unit Recruitment:
• adding motor units as we need more strength
• process in which the number of active motor units increases
• delays onset of muscle fatigue

• 1. Oxygen debt is paid - extra oxygen needed for restoration
• 2, Recovery Oxygen Uptake- better term than oxygen debt
• a. lactic acid removed and recycled (converted to pyruvic acid to be used by mitochondria)
• b. elevated body temp increases rate of chemical reactions
• c. heart and respitory muscles work harder
• d. tissue repair is ongoing

• single neuron and all the muscles fibers it innervates
• -can handle hundreds of muscle fibers
• - each muscle has multiple motor units
• - smaller motor units in muscles for fine movement
• - not all motor units active at same time
• - Recruitment- increasing tension through an increase in active motor units

Muscle twitch is the response of a muscle to a single brief threshold stimulus.

• Phases
• 1). Latent Period - Muscle tension is beginning.
• 2). Period of Contraction - Muscle fibers shorten.
• 3). Period of Relaxation - Ca++ renters the sarcoplasmic reticulum
• 4) refractory period - if you send another electrical signal muscle wont respond - cant contract agian yet

• i).Wave Summation - If 2 stimuli are delivered in rapid succession the second twitch will be greater than the first - increasing intensity
• . ii).Unfused Tetanus- The amount of Ca++ increases in the cytoplasm results in a quivering response- PARTIAL relaxation -
• iii). Fused Tetanus - Stimuli arrice very close - NO RELAXATION possible - occurs in most muscle contractions
• 

• resting tension on a skeletal muscle
• Poor - flaxxid, limp
• Good - firm, solid

• The muscle changes length and moves a load
• .Isotonic contractions- the thin actin filaments are sliding across the myosin
• Concentric isotonic contraction- muscle shortens as tension exceeds resistance
• Eccentric isotonic contraction- muscle lengthens as tension exceeds resistance
• 

• Tension in the muscle increases but the muscle neither shortens or lengthens.
• Isometric contractions the cross bridges are forming and pulling but the actin filament is not moving
• 

• 1. Slow oxidative fibers - dont contract quickly\
• - hydrolisys of ATP takes longer
• - areobic respiration
• - Takes 3 times as long to contract as fast fibers
• - Dont fatigue easily - endurance activities
• - lots of mitochondria, capillaries and myoglobin - appear red
• 2. Fast Oxidative-Glycolytic fibers
• - Gen ATP via aerobic AND anaerobic cellular respiration
• - lots of capillaries and myoglobin
• - aerobic endurance
• 3. Fast Glycolytic Fibers
• - anaerobic respiration
• - contract quick and strong
• - large diameter- lots of myofibrils
• - few mitochondria & capillaries & myoglobin
• - fatigue easily - good for weight lifting

• adding motor units as we need more strength
• process in which the number of active motor units increases
• delays onset of muscle fatigue

• All three types of fibers are present in most muscles - slow oxidative, fast oxidative-glycolytic, and fast glycolitic fibers
• relative proportions differ depending on the action of the muscle, fitness level, and genetics
• distribution of muscle fiber types is genetically determined
• Endurance exercieses can transform some fast glycolytic into fast oxidative-glycolitic
• exercises that focus on guick and strong contractions can increase size and strength of fast glycolitic fibers - more thick than thin - results in hypertrophy

• white - low myglogin - appear lighter
• red - high myglobin - appear red - high mitochondria and more blood capillaries