11.2 Movement Flashcards
What are exoskeletons?
External skeletons that surround and protect most of the body surface of animals such as crustaceans and insects
How do bones and exoskeleton facilitate movement?
By providing an anchorage for muscles and by acting as levers
How do bones and exoskeleton facilitate movement?
By providing an anchorage for muscles and by acting as levers
How can levers change?
They change in the size and direction of forces
What are the 3 main components of a lever?
- effort force (muscle)
- fulcrum (pivot point)
- resultant force (body weight)
What determines the class of lever?
The relative position of the eoffrt force, fulcrum and resultant force
What is the difference between a first, second and third class lever?
What is the effort force, resultant force and pivote point for each?
What is the class of each of these levers?
How does a grasshoppers leg acts as a third class lever?
Fulcrum is at the body end
effort force is between the fulcrum and the resultant force
How does a grasshoppers leg acts as a third class lever?
Fulcrum is at the body end
effort force is between the fulcrum and the resultant force
When skeletal muscles work in pairs, what does that tell us?
They are antagonistic
What does antagonistic muscles produce?
opposite movements at a joint
How are biceps and triceps antagonistic muscles?
the triceps extend the forearm while the biceps flex the forearm
In a pair of antagonist muscles, which is the agonist and which is the antagonist?
Agonist - one that is contracting
Antagonist - one that is relaxing
How many pairs of appendages does a grasshopper have?
3
What is the hindlimb of a grasshopper specialized for?
Jumping
What are the 3 main parts of a grasshoppers hindlimb?
- below the joint is referred to as the tibia
- at the base of the tibia is another join below which is the tarsus
- above the join is the femur
Where are relatively massive muscles found on the hindleg of a grasshopper?
femur
What happens to the muscles of a grasshopper when they jump?
- flexor muscles contract
- brings the tibia and tarsus into a position where they resemble the letter Z
- the femur and tibia are brough closer
- this is refered to as flexing
- the extensor muscles relax during this phase
- the extensor muscles will then contract extending the tibia and producing a powerful propelling force
When flexing, what muscles contract and relax?
Flexor muscle contract
Extensor muscle relax
What is an example of a synovial joint?
The human elbow
Where can you find a joint?
The point where bones meet
What do joints allow for?
Allow the bones to move in relation to each other - this is called articulation
What do most articulated joints have in comon?
Similar structure, including cartilage, synovial fluid and joint capsule
What is cartilage and what does it do?
- tough, smooth tissue that covers the regions of bone in the jiont
- it prevents contact between regions of bone that might otherwise rub together
- helps to prevent friction
- absorbs shocks that might cause bones to fracture
What is the synoial fluid and what does it do?
- fills a cavity in the joint between the cartilage on the ends of the bones
- it lubricates the joint and so helps to prevent the friction that would occur if the cartilages were dry and touching
What is the joint capsule and what does it do?
- a tough ligamentous covering to the joint
- seals the join
- holds in the synovial fluid
- prevent dislocation
Annotate the diragram of the human elbow
What is the humerus bone?
to which the biceps and triceps are attached
what is the triceps?
muscle that extends the joints
what are biceps?
muscle that flexes the joint
What is the joint capsule?
seals the joint and helps to prevent dislocation
What is the synovial fluid?
- lubriates the joint to reduce friction
- Provides oxygen and nutrients for the cartilage
What is the ulna bone?
bone to which the triceps is attached
Acts as a lever for lowering the forearm using the triceps
What is the radius bone?
Bone to which the biceps is attached to
Acts as a lever for raising the forearm using the biceps
On top when holding thumbs up (can make a radius of a circle to remember)
What determines the movements that are possible in a joint?
The structure of a joint
What joint can a knee act as?
Hinge joint - which only allows two movements
* flexion (bending) and extension (straightening)
Pivot joint - when flexed
* the knee has a greater range of movement when it is flexed than when it is extended
Where is the hip joint?
between the pelvis and the femur
What joint is the hip joint?
A ball and socket joint
How does the hip joint offer more range of movement than the knee joint?
It can flex and extend, rotate, move sideways and back
What is it called when the movement to move sideways and back called?
Abduction and adduction
Fill in the gaps
What are the 6 types of synovial muscles?
- Ball and socket (hip)
- Saddle (thumb)
- Condyloid (wrist)
- pivot (neck)
- Hinge (knee, elbow)
- plane joint (ankle)
*from most to least movement
What are the 3 types of muscle?
- caridac muscle (unique to the heart)
- Skeletal muscle (attached to the bone)
- Smooth muscle
What are the characteristics of a smooth muscle?
- contracts slowly and regularly
- dont tire quickly
- controlled by the autonomic nervous system (involuntary)
- Found in the walls of internal tubular structures (e.g. small intestine, oesphagus, iris, blood vessels)
- Arranged in longitudinal and circular layers that are perpendicular to each other and ‘squeeze’ the contents along
What do smooth muscle look like?
tapered cells with one nucleus
What do longitudinal and circular muscles do?
Squeeze conent along
Why does cardiac muscle have long fibres that to branch to form cross-bridges?
to ensure electrical stimulation spreads evenly over the walls of chambers allowing a squeezing motion
Why are skeletal muscles also called striated muscles?
When their structure is viewed sing a microscope, stripes are visible
What is the cardiac muscle contraction controlled by?
By SAN (SA node)
What is a intercalated disc?
Where plasma membranes of adjacent fibres fuse, leaving small gap junctions to allow the movement of ions between fibres
Which types of muscle are voluntary and which are involuntary?
Voluntary - skeletal
Involuntary - smooth, cardiac
What does skeletal muscle need a lot of?
ATP
How do sleletal muscle contract?
- very rapidly and powerfully
- fatigues quickly
What are striated muscle composed of?
Bundles of muscle cells known as muscle fibres
What surrounds each muscle fibre?
A single plasma membrane called the sarcolemma
What are some features of a striated muscle?
- many nuclei present
- muscle fibres are much longer than typical cells
These features are due to the fact that embryonic muscle cells fuse together to form muscle fibres
What fuse together to form muscle fibres?
Embryonic muscle cells
What extends throughout the muscle fibre?
the sarcoplasmic reticulum
What is the sarcoplasmic reticulum?
- a modified version of the endoplasmic reticulum
- it extends throughout the muscle fibre
- it wraps around every myofibril, conveying the signal to contrat to all parts of the muscle fibre at once
- stores calcium
What wraps around every myofibril?
Sarcoplasmic reticulum
What can be found between the myofibril?
Large numbers of mitochondria, which provide ATP needed for contractions
What is the sarcoplasm?
The muscle fibre cytoplasma
What does the sacroplasm contain?
many mitochondria and the sarcoplasmic reticulum
What are myofibrils?
parallel, elongated structures within each muscle fibre
What gives striated muscle its strips?
Myofibrils have alternating light and dark bands
What is in the centre of each light band?
A disc-shaped structure, referred to as the Z-line
What is the functional unit of the myofibril?
the sarcomere
What are sarcomeres?
The part of a myofibril between one Z-line and the next
* myofibrils are arranged into subunits called sarcomeres that contain actin and myosin filaments
What is the pattern of light and dark bands in sarcomeres due to?
due to a precise and regular arrangement of two types of protein filaments - thin actin filaments and thick myosin filaments
What are the two types of protein filament?
thin actin filaments and thick myosin filaments
What are actin filaments attached to?
Z-line at one end
Where can you find myosin filaments
They are interdigitated with actin filaments at both ends and occupy the centre of the sarcomere
What is each myosin filament surrounded by?
6 actin filaments and forms cross-bridge with them during muscle contraction
Fill in the gaps
What happens during muscle contraction?
- Myosin filaments pull the actin filaments inwards towards the cenre of the sarcomere
- this shortens each sarcomere and therefore the overall length of the muscle fibre
The contraction of skeletal muscle occurs by what?
By the sliding of actin and myosin filaments
How do actin and myosin filaments slide?
- myosin filaments cause this sliding
- they have heads that can bind to special sites on actin filaments, creating cross-bridges
How do cross bridges exert force?
using energy from ATP
How is it that many cross-bridges can form at once?
The heads of myosin filaments are regularly spaced and the binding sites are regularly spaced along the actin filaments, so many cross-bridges can form at once
What is the use of calcium ions in skeletal muscle contractions?
In the presence of calcium, there will be a formation of cross-bridge
What is tropomyosin?
A regulatory protein in a relaxed muscle that blocks the binding sites on actin
What happens when a motor neuron sends a signal to a muslce fibre to make it contract?
the sarcoplasmic reticulum releases calcium ions
* the calsium ions bind to a protein called troponin which causes tropomyosin to move, exposing actin’s binding sites
What allows myosin heads to bind to actin’s binding site?
- binding sites on actin are blocked by tropomyosin in a relaxed state
- motor neuron sends a signal to a muscle fibre to make it contract
- the sarcoplasmic reticulum releases calcium ions
- calcium ions bind to a protein called troponin which causes tropomyosin to move, exposing actin’s binding site
- now myosin head’s bind and swivel towards the centre of the sarcomere, moving the actin filament a small distance
What must myosin heads do for significant contraction of the muscle?
Myosin heads must carry out this action (binding to actin site) repeatedly
What are the sequence of stages for significant contraction of the muscle?
- myosin filaments have heads which form cross bridges when they are attached to binding sites on actin filaments
- ATP binds to the myosin heads and causes them to break the cross-bridges by detaching from the binding site
- ATP is hydrolysed to ADP and phosphate, causing the yosin heads to change their angle. The heads are said to be ‘cocked’ in their new position as they are storing potential energy from ATP
- The heads attach to binding sites on actin that are further from the centre of the sarcromere than the previous sites
- The ADP and phosphate are released and the heads push the actin filament inwards towards the centre of the sarcomere - this is called the power stroke
Why is ATP needed in muscle contraction?
ATP hydrolysis and cross-bridge formation are necessary for filaments to slide
ATP binds to myosin heads and causes them to break the cross-bridges by detaching from the binding site and the ADP and phosphate causes the myosin heads to change their angle and attaches to another binding site on actin that is further away
Think of tug of war
What happens in the cocking of the myosin head?
Hydrolysis of the ATP to ADP and phosphate provides energy for the myosin heads to swivel outwards away from the centre of the sarcomere
Where are new cross-bridges formed?
New cross-bridges are formed by the binding of myosin heads to actin at binding sites adjcent to the ones previously occupied (each head binds to a site one position further from the centre of the sarcomere)
When is energy stored in the myosin head?
When it was cocked
What does the energy stored in the myosin head when it was cocked do?
Causes it to swivel inwards towards the centre of the sarcomere, moving the actin filament a small distance
Until when does the process of ATP hydrolysis and cross-bridge formation continue until?
Until the motor neuron stops sending signals to the muscle fibre
What happens once the motor neuron stops sending signals to the muscle fibre?
Calcium ions are then pumped ack into the sarcoplasmic reticulum, so the regulatory protein (tropomyosin) moves and covers te binding sites on actin. The muscle fibre therefore relaxes
What do Z lines represent and what do they do?
They are dense protein discs that hold the myofilaments in place
Actin filaments radiate out from the Z discs and help anchor the central myosin filaments in place
What is the A band?
Both actin and myosin filaments
Why is the A band dark?
The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments
What is the I band?
Only actin
What is the I band?
Only actin
Why is the I band light?
The peripheries of the sarcomere appear lighter as only actin is present in this region
Why is the I band light?
The peripheries of the sarcomere appear lighter as only actin is present in this region
What is the H band?
Only myosin
Why is the H band only slightly lighter compared to the I band?
Its not as dark as the A band because it only contains myosin but its darker than the I band because myosin is thicker than actin
