This is known as the bicep. The muscle that extends the lower arm is known as the tricep.
The brachialis is a muscle in the upper arm that flexes the elbow joint.
latissimus dorsi
Sternocleidomastoid
The biceps muscle flexes and the triceps extends.
Pectoralis major
your tricep flexes at the elbow when you straighten your arm
The triceps brachii.
your bicep (upper arm muscle) gets smaller/ contracts and pulls the lower arm up
the musle at the front of your upper arm contracts to pull up your lower arm
The biceps brachii muscle will contract, pulling the lower arm up.
The biceps brachii muscle will contract, pulling the lower arm up.