11.2 Movement Flashcards
Explain the role of calcium ions in muscle contraction
- Ca2+ ions are released when a nerve impulse arrives at the muscle
- Ca2+ ions are released from a sarcoplasmic reticulum
- binding sites for myosin heads are exposed
- this allows cross bridges between myosin and actin to form
What are antagonistic muscles?
Movement of the body requires muscles to work in antagonistic = opposite pairs. This means one muscle relax (extend) while the other flex/contract (shorten). Eg. Triceps extends when biceps flex.
Explain the role of ATP in the contraction of skeletal muscles
- ATP binds to the myosin head
- ATP binding causes cross-bridges to break/heads detach from binding site
- ATP broken down/hydrolysed to ADP + P (Phosphate) causing myosin heads attach to binding sites on actin filaments further along sarcomere
- head with ADP + P attaches to binding site on the actin that are further from the centre of the sarcomere than the previous site
- The ADP and phosphate are released and the heads push the actin in wards towards centre of the sarcomere (power stroke)
Outline how skeletal muscle contracts (5 marks)
- tropomyosin blocks the binding sites on actin
- calcium ions are released from the sarcoplasmic reticulum (motor neuron signal);
- Calcium ions bind to troponin
- they expose the myosin binding sites (on actin) / cause movement of blocking molecules/troponin;
- ATP hydrolysis into ADP +P;
- cross-bridges form between actin and myosin molecules using ADP +P;
- phosphate released;
- myosin myofilament is used to move the head and pull actin towards centre of sarcomere;
- ADP is released from the myosin head as it moves.
- ATP provides energy to release myosin from binding site;
- action can be repeated further along the molecule;
Explain how nerve impulses are transmitted along and between neurons (9 marks)
- the resting potential of cell is negative inside compared with outside; - stimulation causes depolarization/reversal of charge on each side; - due to Na+ channels opening / Na+ flowing into the cell; - which causes an action potential; - K+ channels open / K+ flows out of the cell; - sodium potassium pump restores resting potential; - transmitted between neurons across a synapse; - neurotransmitter released into synaptic cleft; - diffuse across cleft to postsynaptic membrane; - where they bind to receptors; - influx of Na+ into cell; - which may initiate action potential;
How do bones and exoskeletons facilitate movement?
Provide an anchorage for muscles and by acting as levers
What determines the class of lever?
Effort force, a pivot point called fulcrum, and resultant force
How many pairs of appendages does a grasshopper have?
Three like all insects
Annotate the parts of an insects leg
Tibia, Tarsus, and Fermur with massive muscles
What is point called where the bones meet?
joint
what is articulation?
joints allowing bones to move in relation to one another
What do most articulated joints have?
Cartilage, synovial fluid and joint capsule
What do to biceps do?
Flex the joint
What do triceps do?
Extend the joint
What does synovial fluid do?
Fills a cavaty in the joint between cartilages, lubricates the joint and prevents
What does the joint-capsule do?
Tough ligamentous, that seals the joint and hold in the synovial fluid and prevents dislocation
What are muscle fibres composed of?
Many myofibrils
Draw labelled diagram of structure of sarcomere
- two z-lines
- myosin filaments should with heads
- actin filament should be connected to z-lines
- light and dark band labelled
Annotate a diagram of a human elbow
- ulna
- radius bone
- humerus bone
- triceps
- biceps
- cartilage
- synovial fluid
- joint-capsule
