Question

1. what observations show that skeletal muscles work in pairs?
2. what is the name of the flexor muscle involved in this activity?
3. name the extensor muscle.
4. where are these muscles attached?
5. at what joint does the movement take place?
6. what must occur in the cells of the biceps when the arm is flexed?
7. what must occur in the cells of the triceps when the arm is flexed?
8. 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 in a pair contracts, the other relaxes. For example, when the biceps (flexor) contracts to bend the arm, the triceps (extensor) relaxes. This complementary action shows skeletal - muscles work in pairs.
2. The flexor muscle involved in bending the arm is the biceps brachii.
3. The extensor muscle for the arm is the triceps brachii.
4. These muscles are attached to bones via tendons.
5. The movement of flexing and extending the arm takes place at the elbow joint.
6. When the arm is flexed, the biceps cells undergo a process called muscle contraction. This involves the sliding - filament theory where actin and myosin filaments slide past each other, powered by ATP.
7. When the arm is flexed, the triceps cells relax.
8. Adenosine triphosphate (ATP) is the chemical molecule that supplies the energy for muscle activity.
9. Cardiac tissue is involuntary and has intercalated discs for synchronized contraction, while skeletal tissue is voluntary and striated.
10. Both cardiac and skeletal muscle are striated due to the arrangement of actin and myosin filaments.
11. Smooth muscle is distinctive as it is involuntary, non - striated, and has a single nucleus per cell.
12. a. Cardiac muscle is found in the heart. b. Smooth muscle is found in the walls of internal organs like the stomach and intestines. c. Skeletal muscle is attached to bones, for example, the quadriceps in the thigh.

Answer:

1. Complementary contraction and relaxation of muscles like biceps and triceps during arm movement show skeletal muscles work in pairs.
2. Biceps brachii.
3. Triceps brachii.
4. Attached to bones via tendons.
5. Elbow joint.
6. Muscle contraction via sliding - filament theory powered by ATP.
7. Relaxation.
8. Adenosine triphosphate (ATP).
9. Cardiac is involuntary with intercalated discs; skeletal is voluntary and striated.
10. Both are striated.
11. Involuntary, non - striated, single nucleus per cell.
12. a. Heart. b. Walls of internal organs (e.g., stomach). c. Attached to bones (e.g., quadriceps in thigh).