11.2– movement Flashcards
what is the general function of bones and exoskeletons?
- provide anchorage for muscles
- act as levers
what are 3 specific functions of the skeletal system?
- provide structural support
- provide protection for organs
- act as attachment points for muslces
how are bones connected to other bones?
by ligaments
ligaments are found in between…
bones
tendons are found in between…
muscles and bones
muscles work in _________ pairs
antagonistic
what are the parts of an insect leg?
femur, tibia, tarsus
what are the muscles involved in the jumping of an insect?
flexor muscle and extensor muscle
how do antagonistic muscle pairs in an insect leg help the insect jump?
- when the flexor muscle contracts, the extensor muscle relaxes
- tibia and femur are brought closer together
- causes retraction of hind quarters -> prepares insect for pushing off the ground
- when the extensor muscle contracts, the flexor muscle relaxes
- tibia is pushed away from femur
- causes extension of the hind quarters -> jump
label a diagram of the human elbow
-
which part of the arm anchors the muscle?
the humerus
what are the parts of the arm that act as a forearm level?
radius for biceps and ulna for triceps
the biceps ______ the forearm
bends/flexes
the triceps ______ the forearm
straightens/extends
what does the joint capsule do?
it seals joint space and limits range of movement to provide stability
the synovial fluid functions to…
provide food, O2 and lubrication to the cartilage
what is the function of the cartilage?
- it reduces friction, allowing smooth movement
- it absorbs shock and distributes load
why are skeletal muscle fibres multinucleated? (short)
- muscle cells fuse together to form a long fibre
- nuclei of the cells do not degenerate -> thus fused muscle fibre contains multiple nuclei
what is the specialised feature of muscle fibres that provides energy?
muscle fibres have a large no. of mitochondria for ATP for contraction
muscle cells have specialised endoplasmic reticulum called _______ which is adapted to store _____
sarcoplasmic reticulum, Ca ions
muscle fibres contain ________
myofibrils
what are the two types of myofilaments?
thin, actin
thick, myosin
what is the continuous membrane surrounding the muscle fibre called?
sarcolemma
sarcolemmas contain…
T tubules
protein myofilaments myosin and actin make up a ______
sacromere
what are the adaptations of a skeletal muscle fibre? (5) (mnemonic: FMSMT)
- made up of Fused skeletal muscle cells
- reduces the need for strong junctions between muscle cells to withstand forces of contraction
- contains large no. of Mitochondria
- to generate ATP for muscle contraction
- contains Sarcoplasmic reticulum
- to store and release Ca ions for muscle contraction
- contains Myofibrils
- w thin actin and thick myosin filaments for muscle contraction
- contains T-tubules
- runs deep into muscle fibre
- allows for action potential to travel down the t-tubule to sarcoplasmic reticulum
what do Z-discs do?
they hold the myofilaments in place
draw a labelled diagram of a sacromere
-
what does tropomyosin do when a muscle is at rest? (short)
- tropomyosin fibres wrap around actin filaments -> preventing myosin heads from binding to actin filaments
- thus no contraction takes place
what are the 4 key steps of muscular contraction?
- depolarisation and Ca ion release
- actin + myosin cross-bridge formation
- sliding mechanism of actin and myosin filaments
- sarcomere shortening = muscle contraction
what triggers the release of acetylcholine into the motor end plate?
the action potential from a motor neuron
how is depolarisation spread throughout muscle fibres?
by the T tubules on the sarcolemma
which part of the sarcomere releases Ca ions?
sarcoplasmic reticulum
what triggers the release of Ca ions by the sarcoplasmic reticulum?
depolarisation
what happens during depolarisation and Ca ion release? (3)
- action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
- acetylcholine initiates depolarisation within the sarcolemma -> spreads through muscle fibre via T tubules
- depolarisation triggers sarcoplasmic reticulum to release stores of Ca ions
what are the binding sites on the myosin heads blocked by?
the troponin and tropomyosin complex
how are the binding sites on myosin heads exposed?
Ca ions bind to troponin on actin, reconfiguring the troponin and tropomyosin complex
the _______________ form a cross bridge with ____________________
myosin heads, actin filaments
what happens during actin and myosin cross-bridge formation? (3)
- on actin, the binding sites for the myosin heads are covered by a blocking complex comprised of troponin and tropomyosin
- Ca ions bind to troponin on tropomyosin -> reconfiguring the complex -> this exposes the binding sites on actin for myosin heads
- the myosin heads then form a cross-bridge with actin filaments
what binds to myosin to break the cross bridge between actin and myosin
ATP
ATP hydrolysis causes myosin heads to _______________ and _________
change balance, swivel
what happens during the sliding mechanism of actin and myosin? (5)
- ATP binds to the myosin head, breaking the cross-bridge between actin and myosin
- ATP hydrolysis causes myosin heads to change position and swivel -> pulls the actin filaments toward the center of the sarcomere -> releases ADP+Pi
- new ATP molecule binds to the myosin head -> causes it to detach from actin filament
- ATP is hydrolysed to ADP+Pi -> myosin head can re-cock back into high energy stage for next cycle
which part is the ‘sliding mechanism’?
the pulling of actin filaments toward the center of the sarcomere by the swivelling of myosin heads
when do the myosin heads return to its original conformation?
when it swivels
how do sarcomeres shorten? (short)
dragging of actin pulls the Z lines closer together, shortening the sarcomere
how do individual sarcomeres lead to muscle contraction? (short)
- individual sarcomeres become shorter in length
- contraction of muscle fibres as a whole
what are the events in muscle contraction? (7)
- action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
- acetylcholine initiates depolarisation within the sarcolemma -> spreads through muscle fibre via T tubules
- depolarisation triggers sarcoplasmic reticulum to release stores of Ca ions
- Ca ions bind to troponin on tropomyosin and cause tropomyosin to move
- exposing binding sites on actin for myosin heads
- Pi released from myosin heads
- myosin heads bind to actin -> forms cross bridge
- myosin heads, having hydrolysed ATP to ADP+Pi, have high energy state
- chemical energy is used for the myosin heads to swivel, pulling the actin filaments toward the center of the sarcomere
- releases ADP
- new ATP molecule binds to the myosin head
- causes it to detach from the actin filament
- ATP is hydrolysed to ADP+Pi
- re-cocks the myosin head into high energy state
- another cycle can begin
in electron micrographs, A bands are ______
darker
the lighter part of electron micrographs are
- I bands
- actin is present, myosin is not
identify if the muscle in the electron micrograph is relaxed or contracted:
-
