Nervous and Musculosketal Systems

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Nervous and Musculosketal Systems
2011-03-01 17:10:18
IB Biology Nervous Musculoskeletal Systems

IB Biology Study Guide Answers
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  1. The Nervous system consists on the central nervous system and peripheral nerves, and is composed of ells called _______ that can carry rapid electrical impulses.
  2. Draw and label a diagram of the structure of a motor neuron.
  3. Nerve impulses are conducted from receptors to the CNS by _________, with the CNS by ________, and from the CNS to effectors by ___________.
    sensory neurons, relay neurons, motor neurons
  4. Define the resting potential and action potential
    Resting Potential is the difference in charge between inside and outside of a neuron created by the imbalance between K+ and Na+

    • Action potential is an electrical impulse that travels down an axon. The response is triggered by a stimulus strong enough to produce a depolarization that reaches the threshold. Once a threshold is reached, all gates open.
  5. Explain how a nerve impulse passes along a non-myelinated neuron.
    Because the sodium-potassium pump moves three sodium out for every two ions, there is a higher concentration of sodium on the outside and a higher concentration of potassium on the inside. This, together with negatively charged proteins and chloride ions inside the cell, creates a negative charge on the inside, and a positive charge on the outside. When a rapid change in the membrane potential surpasses the threshold, caused by a stimulus strong enough to trigger depolarization, voltage-gated sodium ion channels open, followed quickly by the opening of the potassium channels. When the gates open, sodium and potassium go down their concentration gradients. The sodium gates open first, creating the rising phase. Then the pottasium gates open, which leads to the falling phase, culminating in an undershoot. This has to be resolved by the sodium-pottasium pump in order to restore the resting potential (repolarizing)
  6. Explain the principles of synaptic transmission
    When the action potential reaches the synaptic terminal of an axon, it causes the membrane to become more permeable to Ca2+. This causes an influx of calcium ions which causes the synaptic vesicles to fuse with the presynaptic cleft by exocytosis. Then, the neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic membrane which also function as channels. This opens the channels, increasing the membrane to permeability to sodium, triggering the action potential in the postsynaptic cell. The neurotransmitter is broken down by a specific enzyme in the synaptic cleft (ex) acetylcholinesterase breaks down the neurotransmitter acetylcholine. The breakdown products are absorbed by the pre-synaptic neuron by endocytosis and used to re synthesize more neurotransmitter, using energy from the mitochondria. This stops the synapse from being permanently on.
  7. State the roles of bones, ligaments, muscles, tendons and nerves in human movement
    • Bones: act as a rigid framework for muscles to pull against, muscles attachments and joint configuration determine direction of movement
    • Muscles: Pull on the bones, producing movement
    • Ligaments: join bone to bone
    • Tendons: attach muscles to bones
    • Nerves: stimulate and coordinate muscle contractions
    • a. humerus
    • b. synovial membrane (joint capsule)
    • c. synovial fluid
    • d. ulna
    • e. cartilage
    • f. ligaments
    • 1) humerus
    • 2) biceps
    • 3) tendon
    • 4) elbow joint
    • 5) ulna
  8. Outline the functions of the structures in the human elbow joint
    Humerus forms a hinge joint with the ulna and the radius forms a pivot joint with the ulna. The bicepts and triceps are attached to the humerus near the shoulder. The bicep is attached to the radius, and the triceps is attached to the ulna. The capsule wraps around the joint and prevents leakage of the synovial fluid. The synovial fluid provides a joint lubricant, which reduces friction and damage to the bone. The cartilage provides a smooth surface that reduces friction as well. Ligaments attach bone to bone to keep the joint stable. The tendons attach the triceps and biceps to bones.
  9. Compare the movement of the hip joint and the knee joint
    • The hip joint is a ball and socket joint, able to emovie in many planes and in several directions (an arc)
    • The knee joint is a hinge joint, able to move in a single plane
  10. Describe the structure of striated muscle fibers.
    • Striated muscle fibers contain many myofibrils, and each myofibril is composed of units called sarcomeres. Protein filaments form the contractile unit of the sarcomere. Thin filaments are composed of actin and thick filaments are myosin. Within each sarcomere there are light and dark bands due to the partial overlap of filaments. The dark regions are regions of overlapping thick and thin filaments, and the light regions are only actin or myosin.
    • Each muscle cell has many nuclei, because of the fusion of many cells into one. It also has many mitochondria to produce ATP required for the sliding filament action
    • The sarcoplasmic reticulum stores calcium ions. When an action potential reaches a motor endplate (synapse with the muscle cell), it s transferred via the neurotransmitter acetylcholine to the sarcolemma. It travels along the sarcolemma down the T-tubule until it reaches the sarcoplasmic reticulum. This triggers the release of calcium ions, which free up the myosin binding sites on actin. This allows the myosin head to bind to the actin, allowing the sliding-filament action
    • Once the myosin binding sites are exposed, myosin heads bind to the actin forming a crossbridge. ATP attaches to the myosin head.
  11. Draw and label a diagram to show the structure of a sarcomere
  12. Analyse electron micrographs to find the state of contraction of muscle fibers.