Question

1. what observations show that skeletal muscles work in pairs? 4. what is the name of the flexor muscle involved in this activity? 5. name the extensor muscle. 6. where are these muscles attached? 7. at what joint does the movement take place? 8. what must occur in the cells of the biceps when the arm is flexed? 9. what must occur in the cells of the triceps when the arm is flexed? 10. what chemical molecule supplies the energy for muscle activity? part 2: 1. look at the slides of the smooth, skeletal and cardiac muscle tissues and sketch on a separate sheet of paper. 2. how does cardiac tissue differ from skeletal tissue? 3. name one similarity between cardiac and skeletal muscle. 4. in what way is smooth muscle distinctive? 5. name one place you would find: a. cardiac b. smooth c. skeletal:

Explanation:

1. When one muscle contracts to bend a joint (flexion), another muscle relaxes, and vice - versa. For example, when flexing the elbow, the biceps contracts and the triceps relaxes.
2. In arm - flexing activity, the biceps brachii is the main flexor muscle.
3. The triceps brachii is the extensor muscle for the arm.
4. Biceps brachii attaches to the scapula and radius. Triceps brachii attaches to the scapula and humerus and ulna.
5. In arm - flexing/extending, the movement occurs at the elbow joint.
6. When the arm is flexed, the biceps cells contract. This involves the sliding - filament theory where actin and myosin filaments slide over each other.
7. When the arm is flexed, the triceps cells relax.
8. Adenosine triphosphate (ATP) supplies the energy for muscle activity.

Part 2:

1. This requires a practical drawing based on microscope observations.
2. Cardiac tissue is involuntary and has intercalated discs for synchronized contraction, while skeletal tissue is voluntary and striated.
3. Both cardiac and skeletal muscle are striated due to the arrangement of myofibrils.
4. Smooth muscle is involuntary, non - striated, and has a single nucleus per cell.

5a. The heart is where cardiac muscle is found.
5b. Smooth muscle is found in the walls of organs like the stomach and intestines.
5c. Skeletal muscle is attached to bones, for example, the biceps and triceps are attached to arm bones.

Answer:

1. When one muscle contracts and another relaxes during joint movement.
2. Biceps brachii
3. Triceps brachii
4. Biceps: scapula and radius; Triceps: scapula, humerus, and ulna
5. Elbow joint
6. Cells contract via sliding - filament theory.
7. Cells relax.
8. ATP

Part 2:

1. Draw based on observations.
2. Cardiac is involuntary with intercalated discs; skeletal is voluntary and striated.
3. Both are striated.
4. Involuntary, non - striated, single nucleus per cell.

5a. Heart
5b. Stomach/intestines walls
5c. Attached to arm bones (e.g., biceps and triceps)