Module 4: muscle contraction and factors influencing force Flashcards
how do skeletal muscles power movement?
by converting ATP into mechanical energy
what is the muscle hierachy?
- Muscle Organ
- Fascicle
- Fiber
- myofibril
- sarcomere
- myofiliment
what are the 3 levels of connective tissue?
- epimysium: dense, irregular surrounding entire muscle
- perimysium: surrounding fascicle
- endomysium: surrounding each fiber
does muscular connective tissue create active or massive force?
passive
what is a motor unit?
and alph motor neuron and all of te fibers it innervates
what is a neuromuscular junction?
the connection between the axon terminal and muscle fiber
what neurotransmitter is release at the neuromuscular junction?
Acetlycholine (ACh)
what is the name of the muscle membrane?
sarcolemma
what is End Plate Potential (EPP)?
the local depolarisation of the synapse and the muscle fiber
which direction does the AP travel in EPP?
both directions
is sarcolemma deep or superficial to endomysium?
deep
what is sarcoplasmic reticulum?
the smooth ER in muscle tissue, used for storage of Ca2+
what are the t-tubules attached to?
the sarcolemma
what is the process of muscle contraction?
- AP travels down motor neuron
- ACh is released at the neurotransmitter junction
- AP runs through the sarcolemma of the muscle
- AP runs through the t-tubules of the muscle
- Ca2+ is released from the sarcoplasmic reticulum
- Ca2+ causes actin and myosin to bind
- sarcomeres shorten
- muscle contracts
what is the cross bridge cycle?
when calcium ions binds to troponin, causing tropomyosin to move away from the myosin binding gates on the actin and causing a contraction through the hydrolysis of ATP.
what are the 2 points of attachement for skeletal muscles?
- origin: attachment that is relatively fixed, typically proximal
- insertion: attachment more moveable, usually distal
what is the difference between direct and indirect attachement of skeletal muscles?
- Direct: epimysium fused to perioseum of bone or periochondrium of cartilage
- indirect: connective tissue that wraps or extends beyond muscle as rope like tendons or sheet like aponeurosis
what is aponeurosis?
the sheet like connective tissue that attaches
1. muscle to bone
2. muscle to muscle
3. muscle to fascia
4. muscle to tendon unit
can muscles push?
no, muscles can only pull tendons or bones
what are the 3 functional groups?
- agonist (primary mover)
- antagonist (opposes the agonist
- synergist (assists agonist)
what are the descriptors for muscle terminology?
- muscle location
- location of attachment
- muscle shape
- number of origins
- muscle size
- muscle action
- muscle direction
what is the measurment of force with muscles
Newtons
what is the list of architectures for muscle groups?
- circular
- multipennate
- bipennate
- unipennate
- parrallel
- fusiform
- convergent
describe a circular muscle and give an example
a muscle that makes a dougnut shape (mouth)
describe a multipennate muscle and give an example
a bundle of muscle fibers together to make a muscle organ (shoulder)
describe a bipennate muscle and give an example
a muscle that has a tendon through the middle an the muscle fibers are on either side of the tendon (thigh)
describe a unipennate muscle and give an example
a tendon that has 1 side of muscle fiber attached to it ( shin)
describe a parrallel muscle and give an example
when the muscle runs parallel to the locations
describe a fusiform muscle and give an example
a muscle in a shape of a spindle with a tendon running off the side (bicep)
describe a convergent muscle and give an example
when the muscle has a wide origin and a narrow point (chest)
what is a fascile?
the architecture of the muscle, linked to function
what is pennate in a muscle describing?
higher force
smaller range of motion
higher PCSA
what is parallel in a muscle describing?
lower force
wide range of movement
lower PCSA
what is PCSA?
physiological cross examinational area
what is the formula for PCSA?
PCSA= muscle volume/ fiber lengthe
how do you find muscle volume and length in muscles?
volume: MRI
length: ultrasound
what is the sarcomere length?
the length/tension relaionship
which component other than muscle keeps the muscle attached to the skeleton and passively produces force?
elastic
what is the components of a contractile component?
- muscle fibers
- actin and myosin cross bridges
what is the series elastic compoent? (SEC)
intracellular titin, tendons
what is the parallel elastic component (PEC)
connective tissue, epimysium and perimysium., endo and cross bridge
how does the sarcomere look when the muscle is relaxed?
small overlap of the mysoin and actin
how does the sarcomere look when the muscle is contracted?
lots of overlap of mysoin and actin, little ofrce to be used
what is muscle force influenced my?
- number of neurons recruited
- frequency of motor units discharging AP
what does an AP firing in a muscle cause?
a twitch
what does many twitches firing cause?
tetanus
what are the 3 types of muscle fibers
- slow twitch, light force, fatigue resistant
2a. intermediate twitch
2b. high twitch, large force, fatigues quickly
what is hennemans size principle?
smaller units recruited first
what are the different contraction types?
- static: isometric (same length)
- dynamic: concentric (shortening)
- eccentric: eccentric (lengthening)
what is the load difference, strongest to weakest in contraction types?
eccentric-isometric-concentric
