Situation: You need to step up on a step to reach an object on a high shelf.
Instructions: (Part one) Trace the nerve impulse, listing the steps in as much detail as possible, from which your brain sends the message to the appropriate muscles to step up one step. Include the steps involved in transmitting the impulse from one neuron to another and then to the muscle fiber. Include in this the steps involved in the actual muscle fiber contraction – Sliding filament theory. (Part two) 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.
Part one: The steps involved in the nerve impulse and muscle fiber contraction for stepping up one step are as follows:
1. Sensory receptors in your feet detect the presence of the step and send signals to the sensory neurons.
2. The sensory neurons transmit these signals through the peripheral nervous system to the spinal cord.
3. In the spinal cord, the sensory neurons synapse with interneurons, which integrate the incoming signals and relay them to the motor neurons.
4. The motor neurons carry the signals from the spinal cord to the appropriate muscles responsible for stepping up.
5. At the neuromuscular junction, the motor neurons release a neurotransmitter called acetylcholine into the synaptic cleft, which stimulates the muscle fibers.
6. Acetylcholine binds to receptors on the muscle fibers, generating electrical impulses known as action potentials.
7. The action potentials travel along the muscle fibers through a network of tubules called the transverse tubules.
8. The action potentials cause the release of calcium ions from the sarcoplasmic reticulum, a specialized cellular structure within the muscle fibers.
9. Calcium ions bind to troponin, a protein on the thin filaments of the muscle fibers.
10. This binding causes a conformational change in the troponin-tropomyosin complex, exposing the myosin-binding sites on the actin filaments.
11. Myosin heads on the thick filaments bind to the actin filaments, forming cross-bridges.
12. ATP (adenosine triphosphate) provides the energy for the myosin heads to undergo a series of conformational changes, pulling the actin filaments towards the center of the sarcomere.
13. This sliding of the actin and myosin filaments leads to muscle fiber contraction.
14. Once the action potentials stop, calcium ions are actively pumped back into the sarcoplasmic reticulum, allowing the troponin-tropomyosin complex to return to its resting state.
15. The actin and myosin filaments slide apart, causing the muscle fiber to relax.
Part two: When stepping up on a step, several muscles and joints are involved:
1. Muscles: The muscles involved in stepping up on the step include the quadriceps (located in the front of the thigh) and the gluteus maximus (located in the buttocks). These muscles contract to extend the knee and raise the leg.
2. Joints: The main joint involved in stepping up is the knee joint. The knee joint is a hinge joint that allows flexion and extension of the lower leg. Additionally, the hip joint also plays a role, as it provides stability and assists in raising the leg.
When reaching up above your head to the shelf, different muscles and joints are involved:
1. Muscles: The muscles involved in reaching up above your head include the deltoids (located in the shoulders) and the triceps brachii (located in the back of the upper arm). The deltoids contract to raise the arms, while the triceps brachii help to extend the elbow.
2. Joints: The main joint involved in reaching up is the shoulder joint. The shoulder joint is a ball-and-socket joint that allows a wide range of movement, including abduction, flexion, and extension of the arm. Additionally, the elbow joint is also involved, enabling extension of the forearm.