Final answer:
Quadriceps, triceps, and gastrocnemius are types of skeletal muscles responsible for knee extension, forearm extension, and leg flexing/plantarflexing the ankle, respectively.
Step-by-step explanation:
The quadriceps, triceps, and gastrocnemius are all types of skeletal muscle. The quadriceps, located in the anterior compartment of the thigh, is a group comprised of four muscles: the rectus femoris, vastus lateralis, vastus medius, and vastus intermedius. These muscles work together to extend the knee. The triceps brachii, a three-headed muscle in the arm, functions to extend the forearm. The gastrocnemius is a muscle in the posterior compartment of the leg that helps in flexing the leg at the knee and plantarflexing the ankle.
Each of these muscles is involved in specific movements of the body. The quadriceps muscle group is the main agonist for knee extension, while the hamstring group, in the posterior thigh compartment, acts as the antagonist when flexing the knee. Skeletal muscles like these are responsible for voluntary movements and are one of three types of muscles in the body, alongside cardiac and smooth muscles.