topic 11.2 - movement Flashcards
function of bones and exoskeletons
provide anchorage for muscles and act as levers
define exoskeletons
external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects
describe a first class lever and give an example
E (down), F, R (up)
Example - when a person nods their head backwards
describe a second class lever and give an example
F, R, E (down)
Example - someone walking, the moment where they stand on their tiptoes.
describe a third class lever and give an example
F, E (up), R (down)
Example - flexing forearm down
skeletal muscles are
antagonistic
define antagonistic muscles
when one muscle contracts, the other relaxes - they thus produce opposite movements at a joint
give a example of an antagonistic muscle pair
in the elbow, the triceps extends the forearm while the biceps flex the forearm
give an example of antagonistic pairs of muscles in an insect
in the leg of a grasshopper, which is specialised for jumping.
- when the grasshopper prepares to jump, the flexor muscles will contract
- this will bring the tibia and tarsus into a position where they resemble the letter Z and the femur and tibia are brought closer together (flexing). extensor muscles relax during this phase
- extensor muscles contract extending the tibia and producing a powerful propelling force.
draw a diagram of insect legs and their antagonistic muscle pairs
478
draw a diagram of a human flow as an example of a synovial joint
define a synovial joint
a freely moveable joint that allows a wide range of movement (articulation)
cartilage
- tough, smooth tissue that covers the regions of bone in the joint
- prevents contact between regions of bone that might otherwise rub together, helping prevent friction
- absorbs shocks that might cause bones to fracture
synovial fluid
- fills a cavity in the joint between the cartilages on the ends of the bones
- lubricates the joint so helps to prevent the friction that would occur if the cartilages were dry and touching
joint capsule
- tough ligamentous covering to the joint
- seals the joint and holds in the synovial fluid
- helps prevent dislocation
radius bone
to which the biceps is attached
biceps
flexes the joint
humerus bone
to which the biceps and triceps are attached
triceps
extends the joint
ulna bone
to which the triceps is attached
synovial joints allow
certain movements but not others
what determines the movements that are possible in a body part?
the structure of a joint, including the joint capsule and the ligaments
the knee joint can act as
a hinge joint, which allows only flexion (bending) and extension (straightening). It can also act as a pivot joint when flexed, which is when it has a greater range of movement
the hip joint can act as
a ball and socket joint that can flex and extend, rotate, and move sideways (abduction) and back (adduction).
state the three types of muscle
- striated (skeletal muscle)
- smooth muscle
- cardiac muscle
function of striated/skeletal muscle
muscles attached to bones that are used to move the body
what is striated muscle composed of?
bundles of muscle cells known as muscle fibres
state the main features of muscle fibres
- sarcolemma
- many nuclei
- sarcoplasmic reticulum
- mitochondria
- myofibrils
sarcolemma
single plasma membrane that surrounds each muscle fibre
why are muscle fibres much longer than typical cells and contain many nuclei?
embryonic muscle cells fuse together to form muscle fibres
what is the sarcoplasmic reticulum and what does it do?
it is a modified version of the endoplasmic reticulum and wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once. It also stores calcium.
where are mitochondria stored?
between the myofibrils
muscle fibres contain many…
myofibrils
describe a myofibril
- alternating light and dark bands, which give striated muscle its stripes
- in the centre of each light band is a disc-shaped structure (Z-line)
each myofibril is made up of…
contractile sarcomeres.
define a sarcomere
the functional unit of a myofibril, located between one Z-line and the next.
what is the pattern of light and dark bands in sarcomeres due to?
a precise and regular arrangement of two types of protein filament - thin actin filaments and thick myosin filaments
location of actin filaments
attached to a Z line at one end
location of myosin filaments
interdigitated with actin filaments at both ends and occupy the centre of the sarcomere
describe the ratio of actin to myosin filaments and their function
each myosin filament is surrounded by six actin filaments and forms cross-bridges with them during muscle contraction.
draw a labelled diagram of the structure of a sarcomere
p481
how is the contraction the skeletal muscle achieved?
by the sliding of actin and myosin filaments; the myosin filaments pull the actin filaments inwards during the centre of the sarcomere. this shortens each sarcomere and therefore the overall length of the muscle fibre
what causes the sliding motion of actin and myosin filaments?
myosin filaments: they have heads that can bind to special sites on actin filaments, creating cross-bridges, through which they can exert a force, using energy from ATP
how is it that many cross-bridges can form at once?
the myosin heads are regularly spaced along the actin filaments
what is the M-line?
another line in the centre of the sarcomere
what is the visible difference between a relaxed and a contracted sarcomere?
in a relaxed sarcomere, there is a more visible light band on either side of the M-line
what controls muscle contractions?
calcium ions and the proteins tropomyosin and troponin
describe how calcium ions, tropomyosin and troponin work to control muscle contractions
- in a relaxed muscle, tropomyosin (a regulatory protein) blocks the binding sites on actin
- when a motor neuron sends a signal to a muscle fibre to make it contract, the sarcoplasmic reticulum releases calcium ions
- Ca ions bind to troponin which causes tropomyosin to move, exposing actin’s binding sites.
describe the process of muscle contraction
- 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 sites
- ATP is hydrolysed to ADP and phosphate, causing the myosin 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 sarcomere than the previous sites
- the ADP and phosphate are released and the heads push the actin filament inwards towards the centre of the sarcomere (called the power stroke)
