Review 3
label myofibril with sacromeres
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aerobic pathways of ATP generation
*aerobic respiration* within mitochondria, pyruvic acid, fatty acids and amino acids are used to produce ATP via aerobic respiration, an oxygen requiring set of reactions -protein is not first choice for energy
anaerobic pathways of ATP generation
*anaerobic glycolysis* breakdown of muscle glycogen into glucose and production of pyruvic acid from glucose via glycolysis produce both ATP and lactic acid. -anaerobic pathway because no oxygen is needed takes place in sarcoplasm -glucose is primary fuel for skeletal muscle
importance of motor unit contraction
*at neuromuscular junctions* a single somatic motor neuron makes contact with an average of 150 skeletal muscle fibers, all of the fibers in one motor unit contract in unison -consists of a somatic motor neuron plus all of the muscle fibers it stimulates
describe the factors associated with fatigue
*inability of muscle to maintain force of contraction after activity* -inadequate release of Ca++ from sarcoplasmic reticulum: resulting in decline of Ca 2+ in sarcoplasm -depletion of creatine phosphate -insufficient oxygen -glycogen depletion -buildup of lactic acid & ADP -failure of motor neuron to release ACh
Type 2b: fast glycolytic
-few mitochondria and capillaries=white -contract strongly and quickly -fatigue quickly *intense movements of short duration: weightlifting, throwing a ball*
Type 1: slow oxidative
-many mitochondria and capillaries= dark red -mainly use aerobic respiration -slow speed of contraction -resistant to fatigue, capable of prolonged, sustained contractions for many hours *maintaining posture, endurance activities(marathons)*
Type 2a: fast oxidative-glycolytic
-many mitochondria and capillaries= dark red/red-pink -use aerobic and anaerobic -faster speed of contraction -reach peak tension quicker than SO fibers but are shorter in duration *contribute to walking, sprinting, etc.*
identify and define structures that comprise neuromuscular junction
-motor neuron(axon terminal) -synaptic end bulbs:@ end of axon terminals, break into synaptic vesicles -synaptic vesicles:contain Ach -neurotransmitter(Ach):chemical messenger that crosses synaptic cleft -synaptic cleft: small gap that separates the 2 cells from touching(reason for neurotransmitters) -motor end plate: region of sarcolemma opp. of synaptic bulb, contains -receptor sites: for Ach
neuromuscular junction steps
1. *action potential* causes Ca++ channels to open: Ca++ enters end bulb 2. synaptic vesicles move to synaptic cleft: *release ACh* 3. Ach binds to receptor sites: *ACh receptors activated*: Na+ channels open 4. Na+ enters muscle fiber: *muscle action potential*
explain events of sliding filament mechanism of muscle contraction
1. ATP hydrolysis: myosin heads hydrolize ATP and become reoriented and energized 2. Myosin heads bind to actin: form cross-bridges 3. power stroke: myosin head folds to grab more actin 4. detachment of myosin from actin
3 ways muscle fibers produce ATP
1. creatine phosphate: unique to muscle fibers 2. anaerobic glycolysis 3. aerobic respiration
contraction and relaxation of skeletal muscle fibers
1. depolarization of motor end plate of sarcolemma 2. Ca++ released from sarcoplasmic reticulum into sarcoplasm 3. Ca++ binds to troponin 4. troponin moves tropomyosin away from myosin binding sites on actin 5. myosin binding sites are free
describe factors that influence a muscle's ability to generate force
1. motor units: all-or-none, spread out, recruitment 2. nutrient and oxygen availability 3. frequency of stimulus 4. length tension relationship
describe role of calcium in excitation-contraction coupling
1: during relaxation, the level of Ca2+ in the sarcoplasm is low, because calcium ions are pumped into the reticulum by Ca2+ active transport pumps 2: a muscle action potential along a transverse tubule opens Ca2+ release channels in the sarcoplasmic reticulum, calcium ions flow and contraction begins *an increase in Ca2+ level in the sarcoplasm starts the sliding of thin filaments. When the level of Ca2+ in the sarcoplasm declines, sliding stops.*
describe how a muscle is stimulated to contract by a neuron
Impulse/stimulus from neuron is carried down axon to neuromuscular junction.
three types of muscle fibers
Type 1: slow oxidative Type 2a: fast oxidative-glycolytic Type 2b: fast glycolytic
sarcomere
basic functional unit of myofibril
transverse tubules
between terminal cisterns, allows communication of internal environment with outer -muscle action potentials travel through tubes allowing all parts of muscle fibers to be excited at once
myofibril
contractile organelles of skeletal muscle, extend entire length of a muscle fiber -contain sarcomere -make entire skeletal muscle fiber appear striated
sarcoplasm
cytoplasm of a muscle fiber within sarcolemma -watery mix where chemical reactions take place/ where energy is made for muscle contraction
A-band (label and define)
darker middle part of sarcomere, extends entire length of thick filaments -toward each end is a *zone of overlap* where thick and thin filaments are side by side -*actin and myosin*(appears light and dark)
terminal cisternae
end sacs of sarcoplasmic reticulum -on both sides of T tubule -form triad with T tubule -release of Ca2++ from terminal cistern of sarcoplasmic reticulum triggers muscle contraction
creatine phosphate
formed from ATP while muscle is relaxed, transfers a high-energy phosphate group to ADP, forming ATP during muscle contraction
cardiac muscle
heart -pump blood through heart - branched, single nucleus, *striated*, intercalated discs *involuntary*
I-band (label and define)
lighter, less dense area that contains the rest of the thin filaments but no thick filaments. -z disc passes through the center of each band -*only actin*(appears light)
myosin (label and define)
main component of thick filaments and functions as a motor protein for all three types of muscle tissue -thicker structures in center of sarcomere
actin (label and define)
main component of thin filaments, form an actin filament which has myosin binding sites for myosin heads -thin attachment to z discs
relationship between muscle fiber, myofibril and myofilament
muscle fiber ^^^^^^^^ myofibril ^^^^^^^^ myofilaments
Z-disc (label and define)
narrow plate @ end of sarcomeres, separate sarcomeres from eachother -thin attachment(actin) attaches here
H-zone (label and define)
narrow, in the center of each A band, contains thick but not thin filaments -*only myosin*(appears dark)
skeletal muscle
skeleton -motion, posture, heat production, protection -long cylindrical, *striated*, multinucleated *voluntary*
describe muscle tone
small amount of tautness or tension in muscle due to weak involuntary contractions motor units -to sustain muscle tone, small groups of motor units are alternatively active and inactive -even at rest, skeletal muscle has muscle tone -when muscle tone lost= flaccid: state of limpness
myofilaments
smaller structures within myofibril, do not extend length of muscle fiber -arranged in compartments called sarcomeres(z disc-z disc) thin filaments-mainly actin thick filaments-mainly myosin
define and explain significance of neuromuscular junction
synapse between asomatic motor neuron and skeletal muscle fiber *stimulates skeletal muscle fibers to contract*
isometric muscle contraction
tension generated is not great enough to exceed the resistance of the object to be moved and muscle does not change length -maintain posture, stabilize joints
isotonic muscle contraction
tension in muscle remains constant -body movements, moving objects 1. concentric: develop tension while muscle shortens-lifting a book 2. eccentric: develop tension while muscle lengthens, will slow down a movement to control it-putting a book down
sarcoplasmic reticulum
tubes important in calcium transport within cell -terminal cisterns at ends
smooth muscle
walls of hollow organs(iris of eye) -motion, moving materials in tubes -spindle-shaped cell, *non-striated*, gap junctions *involuntary*
