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88 terms

Muscular System

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Excitability
ability to receive/respond to electrical stimulus
Contractility
generate force when sufficient stimulus is received
Extensibility
can contract when stretched
Elasticity
resume resting length after being stretched
Functions of Muscle
Motion, Posture Maintenance, Generate Heat, Stabilizes joints
Types of Muscle Tissue
Smooth, Skeletal, Cardiac
Skeletal Muscle
long, cylindrical, striations, voluntary control
Skeletal Muscle
this muscle type has rapid contractions and tires easily
Cardiac Muscle
intercalated disc, striated, gap junctions, involuntary
Cardiac Muscle
this muscle type has a steady rate of contraction and is the internal pacemaker
Smooth Muscle
spindle shaped, no striations, gap junctions, involuntary
Smooth Muscle
this muscle type is found in the walls of organs thus maintaining the internal environment with slow sustained contractions
Endomysium
CT around each muscle cell
Perimysium
CT around fascicles
Epimysium
CT around entire muscle
Fascicle
muscle fiber bundles
Indirect Attachment to Bone
CT wrappings extend beyond the muscle as a tendon or aponeurosis
Direct Attachment to Bone
epimysium fuses to periosteum of a bone
Sarcolema
plasma membrane of muscle
Sarcoplasm
surrounds myofibrils and stores calcium
Myoglobin
binds oxygen
T Tubules
invaginations toward center of cell
Terminal Cisterns
enlarged cross channels at the end portions of the SR that release calcium
Triad
T-tubules + 2 terminal cisterns of SR
Triad
Located at A/I band junction and zipped together via integral proteins
Myofibrils
Proteins that run length of muscle fiber
Myofilaments
overlap of thick and thin types
Sarcomere
basic contractile unit of muscle
I Band
thin filaments only
H Zone
thick filaments only
Myosin
thick filament
Actin
thin filament
Head of Mysoin
associated with ATPase, bonding site for ATP, interacts with actin, forms cross bridges
Crossbridges
Link actin and myosin during contraction
Z Disc
anchor actin
Contractile Proteins/Myofilaments
Actin, Myosin
Regulatory proteins
Tropomyosin, Troponin
Tropomyosin
blocks myosin binding site, loosely attached to actin
Troponin
3 polypeptide subunits
Troponin I
which subunit binds to actin
Troponin C
which subunit binds to calcium
Troponin T
which subunit binds to tropomyosin
Titin
elastic structural protein that stabilizes thick filaments
Shortens During Muscle Contraction
H Zone and sarcomere
To Contract A Muscle
Stimulate neuron, Increase calcium, propagate electrical current along sarcolemma
Neuromuscular Junction
Axonal endings contain sacs (synaptic vesicles) of special chemicals
Motor End Plate
part of the sarcolemma that helps form the NMJ
Synaptic Cleft
Space between axonal ends and muscle fibers
Depolarization
inside of membrane becomes less negative than RMP
Repolarization
membrane returns to RMP
Hyperpolarization
inside of membrane becomes more negative than RMP
Depolarization
Na+ gates are opened; K+ gates are closed
Repolarization
Na+ gates close, K+ gates open: K+ exits cell
Hyperpolarization
K+ still open: excessive efflux of K+
High-Energy Configuration
energy from hydrolysis of ATP cocks the myosin head
Power Stroke
myosin head pivots and pulls actin filament toward center of the sarcomere
Roles of ATP During Contraction
energy, release crossbridges, brings intracellular calcium back into the sarcoplasmic reticulum
Ways to Stop Contraction
No nerve impulses, Ach-ase, remove calcium, block myosin binding site, ATP binds to myosin head, ATPase inhibition
All-or-None Principle
Individual muscle fibers contract completely or not at all
Motor Unit
Motor neuron and all the muscle fibers it stimulates
Small Motor Unit
Muscles with precise movements, fine control, fewer fibers per neuron
Large Motor Unit
Gross movements, less precise, many fibers per neuron
Twitch
Response of a muscle to a single, brief threshold stimulus
Phases of Muscle Twitch
Latent, Contraction, Relaxation
Latent Period
period where you would find excitation contraction coupling & Release of calcium in response to nerve stimulation
Contraction Period
period of cross bridge activity & Increase in muscle tension, muscle shortening
Relaxation Period
period when calcium is returned to SR & Muscle tension decreases
Refractory Period
period of temporary lost of excitability where muscle can't respond to stimulus
Complete Tetanus
no relaxation (additive effects of calcium), Maximum frequency reached, no more increase in tension
Incomplete Tetanus
Increase frequency of stimulation more
Heart
this organ cannot achieve tetanus
Temporal Summation
stimuli from one source, 2nd stimulus arrives after refractory period, before end of relaxation; 2nd contraction is greater than 1st (more calcium)
Spatial Summation
stimuli from many sources which occur at same time from different motor units
Recruitment Pattern
recruit small to large
Types of Contraction
Isotonic, Isometric
Isotonic
muscle shortens during contraction, muscle tension is greater than load thus there is movement
Isometric
tension increases but muscle doesn't shorten; load is greater than muscle thus there is no movement
Ways to Generate More ATP
creatine phosphate, glycolysis, oxidative phosphorylation (aerobic respiration)
Aerobic Endurance
length of time a muscle can continue to contract
Anaerobic Threshold
point where muscle metabolism converts to anerobic glycolysis
Muscle Fatigue
inability to contract
Muscle Contraction Force Factors
increase calcium, recruitment, relative muscle size, muscle length
Sarcoplasmic Reticulum
store and release calcium
Agonist
prime mover
Antagonist
opposes movement
Synergist
add/reduces force
Fixators
stabilize muscles`
Aponeuroses
muscles attach to each other or directly to bone