Unit 2: Muscular System Flashcards
-movement
-stability
-control of body opening/passages
-heat production
functions of skeletal muscle
-responsiveness to stimulus
-exhibits electrical and mechanical responses
excitability
electrical excitation is conducted throughout the entire plasma membrane
conductivity
unique characteristic of shortening when stimulated
contractility
can stretch without breaking
extensibility
has ability to return to original length after stretching
elasticity
shortening and lengthening of a muscle through a complete range of motion
isotonic
muscle shortening with contraction
concentric
muscle lengthening with contraction
eccentric
contracts the muscle statically without a change in muscle length
isometric
resistance is given at a fixed velocity with accommodating resistance
isokinetic
surrounds entire muscle
epimysium
surrounds bundles of the muscle fibers
perimysium
surrounds individual muscle fibers
endomysium
muscle fascicle
-multi-nucleated muscle cell
-contains dozens to hundreds of myofibrils
-each myofibril is divided further
-arranged in a highly structured pattern
muscle fibers
contracting strands within sarcoplasm made up of a long series of sarcomeres
myofibrils
muscle filaments
-connective tissue attaching muscle to bone
-improve leverage
-economize space
-make it possible for the muscle to act from a distance
tendons
tendon fibers that penetrate into the bone
sharpey’s fibers
muscle cell membrane
sarcolemma
storage site for calcium
sarcoplasmic reticulum
enlarged lateral sacs of sarcoplasmic reticulum next to transverse tubule
terminal cisternae
-channels that extend deep within the muscle cell
-bring action potential deep and throughout muscle cell
transverse tubules
-thin filaments
-contractile proteins
actin
-thick filaments
-contractile proteins
-(looking at #13)
myosin
-attached on the actin filament
-both involved in regulating muscle contraction
-regulate myosin and actin binding
-regulatory proteins
troponin and tropomyosin
-individual segments of the myofibrils
-extends from z-line to z-line
sarcomere
(looking at D)
A band
(looking at C)
I band
H zone
M line
Z line (disc)
-all muscle fibers within a motor unit are the same type
-if the threshold value for neuron firing is reached, all muscle fibers within a motor unit contract maximally
-smaller motor units offer fine movement control
-larger motor units offer more gross control
motor unit characteristics
the special synapse between a branch of a motor neuron and the sarcolemma of a skeletal muscle fiber
neuromuscular junction
- AP proceeds to synapse
- Ca2+ enters nerve
- Vesicles move to membrane
- Vesicles fuse with membrane
- ACh released into cleft
- ACh binds receptor on post-synaptic membrane
- Na+ enters muscle
- AP continues down sarcolemma
- ACh removed from cleft
Activities at the synapse
- AP enters muscle through t-tubules
- Ca2+ is released when “triad” region depolarizes
- Ca2+ binds troponin
- Troponin removes tropomyosin from “active site”
- Myosin strongly binds the active site
- Muscular contraction begins
Excitation-Contraction sequence
- ACh released from vesicles in terminal axon
- Action potential depolarizes t-tubules
- Depolarization causes Ca2+
to be released from SR - Ca2+
binds to
troponin-
a) tropomyosin moves exposing the binding sites
b) Myosin heads bind with actin - Myosin heads bind to actin and myosin ATPase releases energy and produces movement
- ATP binds to myosin head “breaking”
crossbridge
bond - Crossbridge
activation continues with presence of Ca2+ (maintains open sites on actin) - Lack of AP causes Ca2+ to move back to SR (terminal cisternae)
- Actin & myosin remain in disassociated site in presence of ATP
steps to muscle contraction
-in a stretched muscle, there are less cross-bridge formations due to less overlap of the contractile filaments
-refers to optimizing cross-bridging
-length of muscle affects cross-bridging
length-tension relationship
-does not require oxygen
-phosphagen system
-glycolysis
-i.e. kicking a football
anaerobic
-requires oxygen
-occurs in mitochondria
-oxidative phosphorylation
-i.e. 10,000m run
aerobic
fast twitch oxidative glycolytic
Type IIa
fast twitch glycolytic
Type IIx or IIb
Slow twitch oxidative
Type I
-increase in muscle size
-2 types: sarcoplasmic and myofibrillar
hypertrophy
-result in major adaptations in strength during initial weeks of resistance training
-due to increases in neural activation of muscle and better coordination of muscles involved in movement
neural adaptations
decrease in fiber size after training is stopped
atrophy
if stimulus triggers action potential, all fibers in motor unit will contract
all or none principle
-The orderly recruitment of motor units is due to variations in motor neuron size
-As force increases, motor units with larger neurons are recruited
size principle
is the principle muscle producing a motion or maintaining a posture
agonist
muscle must cross a joint to move that joint
mover rule
produces the opposite effect as the agonist
antagonist
muscles that assist the agonist and contract at the same time
synergist
prevent unwanted movement in a joint
stabilizers/fixators
-detect dynamic and static changes in muscle length
-stretch reflex
muscle spindle
-monitor tension developed in muscle
-prevents damage during excessive force generation
golgi tendon organs
attachment to stationary part of the skeleton
origin
attached to moveable portion of the skeleton
insertion
muscle fibers aligned parallel to line of pull
fusiform
muscle fibers arranged at an angle to the line of pull
pennate
two pinnated muscle fibers aligned in opposite directions and angled to line of pull
bipennate
fibers fan out from a large origin/insertion to a smaller insertion/origin
multipennate
