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.
Are you going to start from the superior portion of the precentral gyrus or are you going to include sensory input to determine the need to step up?
I searched Google under the key words "motor neurons precentral gyrus" to get these possible sources:
http://en.wikipedia.org/wiki/Primary_motor_cortex
(Broken Link Removed)
http://www.statemaster.com/encyclopedia/Precentral-gyrus
http://www.csuchico.edu/~pmccaffrey/syllabi/CMSD%20320/362unit4.html
(Broken Link Removed)
There are other sites available. In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.
Part one: The nerve impulse and muscle contraction
1. The process begins in the brain when you decide to step up on a step or reach for an object on a high shelf.
2. The brain sends an electrical signal or nerve impulse down the spinal cord.
3. The nerve impulse then reaches the specific section of the spinal cord associated with leg movement.
4. From the spinal cord, the nerve impulse travels along a motor neuron, which is a specialized nerve cell that carries signals from the central nervous system to the muscles.
5. At the end of the motor neuron, there is a tiny gap called the synapse.
6. The nerve impulse crosses the synapse by releasing chemical messengers known as neurotransmitters.
7. The neurotransmitters, such as acetylcholine, bind to receptors on the muscle fiber's membrane.
8. This binding triggers a series of reactions within the muscle fiber, causing calcium ions to be released from specialized compartments called the sarcoplasmic reticulum.
9. Calcium ions then bind to a molecule called troponin, which is located on the thin filaments within the muscle fiber.
10. The binding of calcium to troponin causes a conformational change in the structure of the thin filament, exposing binding sites for another molecule called myosin.
11. Myosin, which is located on the thick filaments within the muscle fiber, can now bind to the exposed sites on the thin filament.
12. This binding initiates the sliding filament theory, in which the myosin heads pull the thin filaments towards the center of the sarcomere, the basic functional unit of a muscle.
13. As the sarcomeres within the muscle fiber shorten, the entire muscle fiber contracts, generating force and tension.
14. The contraction of multiple muscle fibers within a muscle leads to the movement of bones and joints.
Part two: Muscles, bones, and joints involved
To step up on a step:
- Muscles involved: The primary muscles involved in stepping up on a step are the quadriceps (specifically, the rectus femoris) in the front of the thigh and the calves (specifically, the gastrocnemius and soleus) in the back of the lower leg.
- Bones involved: The main bones involved in the step-up motion are the femur (thigh bone), tibia (shinbone), and foot bones.
- Joint involved: The knee joint is mainly responsible for extending the leg, while the ankle joint allows for plantar flexion, ensuring stability during the step-up motion.
To reach for an object on a high shelf:
- Muscles involved: The muscles primarily involved in reaching for an object on a high shelf are the deltoid and trapezius muscles in the shoulder, the biceps brachii in the upper arm, and the muscles in the forearm, such as the brachioradialis and flexor carpi radialis.
- Bones involved: The bones involved in reaching for a high shelf include the clavicle (collarbone), scapula (shoulder blade), humerus (upper arm bone), radius and ulna (forearm bones), and the bones of the hand.
- Joint involved: The shoulder joint (glenohumeral joint) is primarily responsible for the movement involved in reaching up, while other joints, such as the elbow and wrist, assist in fine-tuning the motion.