Trace the impulse, listing the steps in as much detail as possible, from which your brain sends the message to the appropriate muscles to lift a glass of water to drink. Detail the steps involved in the transmission of the neural impulse to the muscle fiber and then the steps involved in the sliding filament theory. Then, specify which muscles are pulling on which bones and what type of joints are involved in lifting the glass
When your brain sends a message to lift a glass of water, it begins with the activation of neurons in the primary motor cortex, which is responsible for initiating voluntary muscle movement.
1. The neural impulse starts at the primary motor cortex in the brain. This area of the brain is responsible for planning, executing, and controlling voluntary movements.
2. The impulse travels down the spinal cord through descending tracts, specifically the corticospinal tract.
3. As the impulse reaches the spinal cord, it passes through the appropriate segment that corresponds to the muscle group involved in lifting the glass.
4. The impulse then branches off into motor neurons in the ventral horn of the spinal cord.
5. The motor neurons carry the signal to the muscles involved in lifting the glass.
6. At the neuromuscular junction, the motor neurons release acetylcholine, a neurotransmitter, which binds to receptors on the muscle fiber membrane.
7. The binding of acetylcholine triggers an action potential in the muscle fiber membrane and initiates muscle contraction.
At this point, let's dive into the sliding filament theory, which explains the mechanism of muscle contraction:
8. Within the muscle fiber, there are units called sarcomeres which consist of thick and thin protein filaments, known as myosin and actin respectively.
9. The action potential in the muscle fiber triggers the release of calcium ions from the sarcoplasmic reticulum, a specialized network for calcium storage.
10. The released calcium ions bind to troponin molecules on the actin filaments, causing a conformational change that allows myosin heads to bind to actin.
11. The myosin heads then undergo a series of chemical reactions, powered by ATP (adenosine triphosphate), causing them to change shape and pull the actin filaments towards the center of the sarcomere.
12. This repeated binding and release of myosin heads, known as cross-bridge cycling, results in the sliding of actin filaments over the myosin filaments, shortening the sarcomeres.
By understanding the muscle groups involved in the action of lifting a glass, we can determine the muscles and joints involved:
13. The muscles primarily responsible for lifting a glass of water involve the biceps brachii and the deltoids.
14. The biceps brachii muscle, located in the upper arm, contracts and flexes the forearm at the elbow joint.
15. The deltoids, located in the shoulder region, contract to stabilize and elevate the arm, aiding in the lift.
16. The elbow joint and the shoulder joint are involved in lifting the glass. The elbow joint is a hinge joint that allows flexion and extension of the forearm, while the shoulder joint is a ball-and-socket joint that permits a wide range of motion and rotation.
So, when you lift a glass of water, the neural impulse activates the biceps brachii and deltoid muscles, which contract to flex the forearm at the elbow joint and stabilize and elevate the arm at the shoulder joint.