MUSCULAR SYSTEM Flashcards
7 functions of the muscular system
body movement
posture maintenance
respiration
production of body heat
communication
constriction of organs and blood vessels
contraction of heart
3 types of muscles
skeletal muscle
smooth muscle
cardiac muscle
long, cylindrical type of muscle
skeletal
has spindle-shaped cells type of muscle
smooth muscle
has branched and cylindrical cells type of muscle
cardiac muscle
special cell-to-cell attachment of smooth muscle
gap junctions
special cell-to-cell attachments of cardiac muscle
intercalated disks
where is the nuclei of skeletal muscles located
periphery (multinucleated)
which type of muscle has no striations
smooth muscle
which type of muscle is capable of voluntary control
skeletal muscle
which muscle type can be found in the walls of hollow organs, blood vessels, glands, and skin
smooth muscle
4 general properties of muscle tissue
contractility
excitability
extensibility
elasticity
ability of muscle to respond to stimulus
excitability
ability of muscle to shorten forcefully
contractility
ability of muscle to stretch beyond its normal resting length
extensibility
ability of muscle to recoil
elasticity
3 connective tissue coverings within the muscle
epimysium (outer)
perimysium (fascicles)
endomysium (muscle fibers)
this connective tissue sheath surrounds each skeletal muscle
epimysium
this connective tissue covering surrounds each muscle fascicle within the skeletal muscle
perimysium
this connective tissue covering surrounds each individual muscle fiber within fascicles
endomysium
2 main aspects of muscle contraction
electrical component (sarcolemma, t tubules, sarcoplasmic reticulum)
mechanical component (myofibril, myofilaments)
these are bundles of protein filaments
myofibrils
2 types of myofilaments that make up myofibrils
actin
myosin
structural and functional units of skeletal muscles
sacromeres
3 proteins of actin myofilament
actin
troponin
tropomyosin
this is composed of many elongated myosin molecules shaped like golf clubs
myosin filaments
shape of myosin molecules
golf club
TRUE OR FALSE:
The rods of myosin molecules break down ATP releasing energy
FALSE (rods –> heads)
this is the parallel arrangement of myofilaments that cause muscle contraction
sliding filament model
TRUE OR FALSE
during muscle contraction, sarcomeres lengthen
FALSE
TRUE OR FALSE
muscle fibers are electrically excitable
TRUE
TRUE OR FALSE
the basis of the electrical properties of skeletal muscle cells is the movement of ions across the cell membrane
TRUE
2 types of ion channels
leak ion channels
gated ion channels
in resting cells, ______ ion channels allow for the slow leak of ions down their concentration gradient
leak
in ___________ cells, gated ion channels are the most important
stimulated
this is the charge difference in an unstimulated cell
resting membrane potential
the resting membrane potential results in 3 factors:
- K concentration is higher inside the cell membrane
- Na concentration is higher outside the cell membrane
- cell membrane is more permeable to K than Na
this occurs when the excitable cell is stimulated
action potential
2 phases of action potential
depolarization
repolarization
when action potential is generated, the inside of the cell membrane becomes ____________ charged
(positive or negative)
positive
an action potential is triggered when depolarization causes the cell membrane to reach ____________
threshold
this phase of the action potential is a brief period where the inside of the cell membrane becomes positively charged
depolarization
this phase of the action potential is a brief period where Na channels close and K channels open; the membrane potential returns to its resting value
repolarization
what happens when the cell becomes more positively charged that stops depolarization and leads to repolarization
the voltage change causes additional permeability
release of _________ from the sarcoplasmic reticulum triggers muscle contraction
Calcium (Ca2+)
release of _____________ at the neuromuscular junction produces an action potential in the sarcolemma
acetylcholine
this occurs when acetylcholine is no longer released at the neuromuscular junction
muscle relaxation
this keeps acetylcholine from accumulating within the synaptic cleft
acetylcholinesterase
this is the mechanical component of muscle contraction (attachment of myosin to actin)
cross-bridge movement
this is the response of a muscle fiber to a single action potential along its motor neuron
muscle twitch
3 phases of muscle twitch
lag phase
contraction phase
relaxation phase
the gap between the time of stimulus application to the motor neuron and the beginning of contraction in muscle twitch
lag phase
this occurs once Ca2+ is released from the sarcoplasmic reticulum, initiating cross-bridge formation and cross-bridge cycling (in muscle twitch)
contraction phase
TRUE OR FALSE
contraction phase is longer than the relaxation phase
FALSE (it’s the other way around)
types of muscle contractions
isometric
isotonic
muscle contraction where the muscle does not shorten
isometric
muscle contraction where the muscle shortens
isotonic
types of isotonic contraction
concentric
eccentric
isotonic contraction where:
tension > opposing resistance
concentric
isotonic contraction where:
tension < opposing resistance (muscle length increases)
eccentric
2 major types of skeletal muscle fibers
slow-twitch muscle fibers (type I)
fast-twitch muscle fibers (type II)
muscle fiber type with more blood supply, more mitochondria, high myoglobin content, and contract more slowly
slow-twitch oxidative muscle fibers (SO; type I)
muscle fiber type that has fewer blood supply and mitochondria, and have myosin heads with a fast form of enzyme to breakdown ATP, resulting in faster muscle contraction
fast-twitch muscle fibers (type II)
this is the temporary state of reduced work capacity of the msucle
muscle fatigue
mechanisms underlying muscle fatigue
acidosis and ATP depletion
oxidative stress
local inflammatory reactions
this is the build up of excess reactive oxygen species that causes muscle fatigue
oxidative stress
TRUE OR FALSE
highly repetitive concentric muscle contractions produce pain more readily than eccentric muscle contractions
FALSE (repetitive eccentric MC produce more pain and soreness)
TRUE OR FALSE
smooth muscles contain less actin and myosin than skeletal muscles
TRUE
TRUE OR FALSE
smooth muscles contract faster than skeletal muscles
FALSE (they contract more slowly)
what connects muscles to bones
tendons
points of attachment ng muscles
origin
insertion
the most stationary/fixed end of the muscle (attachment)
origin
the end of the muscle attached to the bone undergoing the greatest movement (attachment)
insertion
this is a specific body movement caused by a muscle contraction
action
muscles that play a major role in accomplishing a desired movement
prime mover
muscles that hold one bone in place relative to the body while a usually more distal bone is moved
fixators
3 fascicle arrangements
circular
convergent
parallel
