Question

video 1: your bones do more than you think (scishow)

1. what are the obvious roles of bones, as introduced in the video?
2. the video argues that bones also function as an endocrine organ. what are two hormones or signaling molecules that bone cells produce, and what is their effect in the body?
3. what kinds of cells exist inside bone (beyond osteoblasts/osteoclasts)? name two and briefly describe their roles.
4. explain how bones can influence metabolism (blood sugar/insulin).
5. the video suggests a link between bone health and brain function. what evidence is presented?
6. what implications does this expanded view of bone physiology have for medicine, health, or disease?
7. what question(s) are left unanswered, or what further experiments would help solidify the ideas in the video?

video 2: anatomy of a skeletal muscle (khan academy)

1. what are the hierarchical levels of organization in skeletal muscle (from gross to microscopic)?
2. name three structural components in a muscle fiber (e.g. sarcolemma, myofibril, sarcoplasmic reticulum).
3. how does the sliding filament theory describe muscle contraction? what roles do actin, myosin, atp, and calcium play?
4. describe how nerves and neuromuscular junctions are involved in initiating contraction.
5. what is the role of the sarcoplasmic reticulum in muscle contraction and relaxation?
6. what happens inside the muscle fiber during relaxation (i.e. how does contraction stop)?

Explanation:

For Video 1:

1. Bones provide structural support and protect internal organs.
2. Osteocalcin increases insulin - sensitivity and aids in glucose metabolism; Fibroblast growth factor 23 (FGF23) regulates phosphate and vitamin D metabolism.
3. Osteocytes maintain bone matrix and respond to mechanical stress; Bone - lining cells cover bone surfaces and regulate ion exchange.
4. Osteocalcin produced by bones can increase insulin - sensitivity and affect glucose metabolism.
5. Some studies suggest that bone - derived factors may influence neurotransmitter production or brain cell function.
6. It could lead to new diagnostic and therapeutic approaches for diseases related to metabolism, brain function, and bone health.
7. Questions like the exact molecular mechanisms of bone - brain communication remain unanswered. Further experiments could involve in - depth genetic studies on bone - derived factors and their brain targets.

For Video 2:

1. Muscle, fascicle, muscle fiber, myofibril, sarcomere.
2. T - tubules, sarcoplasm, myofilaments.
3. Actin and myosin filaments slide past each other. ATP provides energy for myosin to bind to actin and pull it. Calcium ions expose binding sites on actin.
4. Nerves release neurotransmitters at neuromuscular junctions which trigger an electrical signal in the muscle fiber leading to contraction.
5. It stores and releases calcium ions which are crucial for muscle contraction and relaxation.
6. Calcium is pumped back into the sarcoplasmic reticulum, myosin detaches from actin, and the muscle relaxes.

Answer:

Video 1:

1. Provide structural support and protect internal organs.
2. Osteocalcin: Increases insulin - sensitivity; FGF23: Regulates phosphate and vitamin D metabolism.
3. Osteocytes: Maintain bone matrix and respond to mechanical stress; Bone - lining cells: Cover bone surfaces and regulate ion exchange.
4. Osteocalcin produced by bones can increase insulin - sensitivity and affect glucose metabolism.
5. Some studies suggest bone - derived factors may influence neurotransmitter production or brain cell function.
6. New diagnostic and therapeutic approaches for metabolism, brain function, and bone - related diseases.
7. Exact molecular mechanisms of bone - brain communication. In - depth genetic studies on bone - derived factors and their brain targets.

Video 2:

1. Muscle, fascicle, muscle fiber, myofibril, sarcomere.
2. T - tubules, sarcoplasm, myofilaments.
3. Actin and myosin filaments slide past each other. ATP provides energy for myosin to bind to actin and pull it. Calcium ions expose binding sites on actin.
4. Nerves release neurotransmitters at neuromuscular junctions which trigger an electrical signal in the muscle fiber leading to contraction.
5. Stores and releases calcium ions for muscle contraction and relaxation.
6. Calcium is pumped back into the sarcoplasmic reticulum, myosin detaches from actin, and the muscle relaxes.