Specify which muscles are pulling on which bones and what types of joints are involved in stepping up on the step. Next, specify which muscles are pulling on which bones and what types of joints are involved to reach up above your head to the shelf.

To determine the muscles involved in these movements and the types of joints involved, we can break down each action step by step:

1. Stepping up on a step:
When you step up on a step, several muscles work together to produce the necessary movements. The primary muscles involved in this action include:
- Quadriceps group: The quadriceps femoris muscles, including rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, contract to extend the knee joint.
- Hamstrings group: The hamstrings, including the biceps femoris, semimembranosus, and semitendinosus, help to control knee flexion and stabilize the hip joint.
- Gluteus maximus: This muscle extends the hip joint, helping to lift the leg and stabilize the body on the step.
- Gastrocnemius and soleus: These calf muscles help to maintain balance and provide a forceful push-off from the toes.

The primary joints involved in stepping up on a step are:
- Knee joint: It is a hinge joint that allows flexion and extension.
- Hip joint: It is a ball-and-socket joint that permits flexion, extension, abduction, adduction, and rotation.
- Ankle joint: It is a hinge joint that allows dorsiflexion (lifting the foot upwards) and plantarflexion (pushing off the toes).

2. Reaching up above your head to the shelf:
When reaching up above your head to the shelf, numerous muscles work together to accomplish the movement. The main muscles involved in this action include:
- Deltoid: The deltoid muscles, located in the shoulder, contract to raise the arm.
- Trapezius: This muscle stabilizes the shoulder girdle and assists in shoulder elevation.
- Biceps brachii: The biceps muscle flexes the elbow joint, assisting in bending the arm.
- Brachialis and brachioradialis: These muscles in the upper arm assist with elbow flexion.
- Latissimus dorsi: This large back muscle contributes to shoulder extension and adduction.

The primary joints involved in reaching up above your head to the shelf are:
- Glenohumeral joint: It is a ball-and-socket joint formed between the humerus bone and the scapula, allowing movement in multiple directions.
- Elbow joint: It is a hinge joint that permits flexion and extension of the forearm.

Remember, these are just the primary muscles and joints involved in these actions, and other muscles may also play a supporting role.