Effector organs

Name the two types of effector organs that execute the body's responses and give a specific example of how each acts in the same dangerous situation.

State whether these structures are muscles, bones, or endocrine glands, and what effector function each performs: biceps, femur, thyroid, diaphragm, adrenal glands.

Explain what hormones are, which organs produce them, and how they reach the target cells they act upon.

Explain what an endocrine gland is and name two examples, indicating the hormone each one produces and its main effect.

Compare the body's muscular response and hormonal response: which is faster, which lasts longer, how the signal arrives in each case, and give an everyday example of each type.

Explain what a joint is and cite two examples of joints in the human body, indicating which movements each one allows.

Name the three parts of the musculoskeletal system and state the general function of each one in movement.

Diagrams A and B represent the same arm with the two muscles that move the forearm, marked with ?: in each case, one appears thickened (contracted) and the other stretched (relaxed). State which muscle (biceps or triceps) is contracted in each diagram and, taking into account that skeletal muscles can only pull and not push, explain why bending and straightening the forearm requires the coordinated action of both and what this type of muscle pair is called.

In an ankle sprain, the joint swells and hurts. Explain which structures of the joint can be damaged when the foot twists and why inflammation appears in the area.

Children's bones bend more before breaking than those of older people. Relate this difference to the composition of bone at each age, and explain which habits in youth help to have strong bones in old age.

To study how the nervous system and the musculoskeletal system interact, three patients with different conditions in one leg are analysed after one month of progression:

• Patient A: has a leg immobilised by a cast following an ankle fracture (the motor nerves and muscles are intact, but the joint does not move).

• Patient B: has suffered a complete severing of the sciatic nerve that innervates the leg muscles (the muscles are disconnected from the spinal cord).

• Patient C: has the same nerve injury as Patient B, but receives daily sessions of external electrical stimulation applied directly to the skin over the muscle, causing it to contract.

1. a) Predict in which of the three patients the most severe and rapid muscle atrophy will occur, and justify why Patient C better preserves muscle mass than Patient B despite having the same neurological injury.
2. b) A student suggests: "To prevent Patient B's atrophy, it would be enough to stimulate the motor area of their brain with electrodes so that it sends stronger commands." Refute this statement by justifying the anatomical pathway of the motor response from the nerve centre to the muscle effector.