The action of lifting an arm can seem like a thoughtless movement, however, there is complex and intricate process that goes on within the human body to make that small movement happen. It involves bones, muscles, and nerves to complete this process, but it would not be able to start without a certain subconscious thought beforehand. Lateral abduction of the arm is defined as raising the humerus, radius, and ulna bones to ninety degrees, parallel to the ground, with the elbow extended, and wrist and fingers locked in place.
Lateral Abduction of the ArmExtension of Humeroulnar and Radioulnar Joints
The bones involved in this movement are all the bones of the shoulder and arm, all of these bones are connected and without all of them working together they would not be able to complete this movement. The Pectoral Girdle, which is the basis of the shoulder joint, is connected to the axial skeleton by the sternoclavicular joint. It also holds the clavicle, which is connected to the axial skeleton, the scapula, which stabilizes the shoulder and the humerus together. However, the humerus is also connected to the scapula at the glenohumeral joint, which is a ball and socket joint, and allows the movement of the shoulder. The humerus is then connected to the humeroulnar and Radiohumeral joints, known as the elbow joint, where the trochlear notch fits into the olecranon fossa of the humerus. Moving farther down the arm, the ulna is connected to the humerus at the humeroulnar joint, and the radius right next to it is connected to the ulna at the proximal radioulnar joint. The biaxial joint, is the last part of the arm that works in lateral abduction, it is connected to the radius at the distal articular surface. The Intercarpal joints, between the proximal and distal row of carpals, are what help contribute to wrist movement.
The Term Paper on The Anthem Of The Civil Right’s Movement: A Rhetorical Criticism Of “We Shall Overcome”
Introduction The American traditional “We Shall Overcome,” is the song of the Civil Right’s struggle. From its roots in early spirituals to its re-imagination in twentieth century gospels, “We Shall Overcome” encompasses the history of the civil rights movement. Its collective longevity and deep roots in the African American community make it the perfect song for the movement. From performances by ...
Glenohumeral JointHumerus (red), Scapula (blue), Clavicle (purple)
Though, the bones would not be able to move if it wasn’t for the muscles contracting and moving them into place. There are many different muscles that have to work together to make such a simple movement occur, the bones and muscles have to work together for it to be possible. Each muscle has an origin, insertion, and action. The origin is the anchor point of the muscle on the bone, whenever the origin is contracts, it pulls the muscle. The insertion point is at the opposite end of the origin, whenever a muscle contracts, the insertion point pulls the bone into place. Lastly the action of a muscle is simply what the muscle does in reference to the body. To be able to make the glenohumeral joint rotate and move into place, the deltoid, pectoralis major, and latissimuss dorsi are all responsible. The deltoid is the mover of the humerus during extension, its action is to abduct the arm—its origin is the lateral part of the clavicle and the spine of the scapula. The pectoralis major medially rotates the arm, its insertion points are the clavicular head of the clavicle, the sternocostal manubrium and sternum, and the six upper costal cartilages. The insertion point for this muscle is the bicipital groove of the humerus and the lip of the deltoid; the sternal and abdominal fibers are what extend to flex the joint of the shoulder. Lastly the latissimus dorsi is one of the most important, it extends the humerus. It does this by its insertion point at the bicipital groove on the humerus and its origin, which is located on the lumbar and sacral vertebrae of the spine.
The next group of muscles to work together includes the infraspinatus, supraspinatus, the teres major, and the subscapularis. These muscles form a rotator cuff around the head of the humerus and allow major movements of the joint to occur. To be able to move the radioulnar joint, the triceps brachii and anconeus muscles work closely together, the triceps are a principle extensor with the insertion point on the ulna, and the anconeus assists in the function of the triceps. Finally, the muscles to move the biaxial joint and the hand work to straighten the wrist and lock it in place, while also extending the phalanges. The extensors of the wrist and fingers come from the lateral epicondyle and upper parts of the bone, which then insert into the metacarpals. The interosseous membrane of the forearm creates an extensor compartment which contains all the extensors of the deep and superficial layer in the hand. Even though there are a small variety of muscles used, they all must work together in order to complete any action.
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Muscles of the Arm
Nevertheless, the muscles would not be able to contract if it weren’t for nerves within the arm to stimulate them. The main nerves of the arm to complete this specific reaction are the: bracial plexus, axillary, musculocutaneous, median, ulnar, and radius. Beginning with the most medial of the nerves, the brachial plexus is formed from the anterior rami of the spinal nerves, then splitting into other nerves of the arm. The axillary nerve runs though the deltoid, teres minor, and head of the triceps brachii, effectively supplying the muscles of the upper arm. The musculocutaneous nerve supplies the anterior arm muscles and also the cutaneous in the forearm. However, the median nerve is what supplies the rest of the forearm muscles on the anterior side. The ulnar and radius nerves run closely together, however the radius supplies the brachioradialis and posterior forearm, while the ulnar supplies some forearm muscles and the most intrinsic muscles of the hand.
To make these nerves work and send off impulses, a subconscious thought process must occur in advance. The thought process begins in the Central Nervous System (CNS); the neurons start off by synapsing in the Thalamus gland, this is done when motor information is sent through sensory neurons to the cerebrum of the brain for processing. Once the neurons reach the cerebrum, they are sent to the lateral part of the Primary Motor Cortex by motor neurons. Motor neurons are used to conduct motor commands from the CNS to the muscles of the body. The impulse then leaves the Cortex through upper level neurons where it will enter the spinal cord at the Corticospinal Tracts, it will then be carried though lower level neurons from the ventral horns of the spinal cord and into skeletal muscles to make them contract.
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Motor Neuron
The way the nerves work can be very complex, however for each action it goes through there are very specific steps. Since efferent (motor) neurons are used to conduct motor commands from the CNS to the muscles of the body, it must take the impulse from the start of the process through it all. It first conducts the impulse from the cell body in the CNS through axons until they eventually lead out of the system. The axons, which are the threadlike pathways which impulses are conducted on, travel within the spinal cord. The signal is then carried out though a nerve branch, the axillary nerve, and into the arm. The axons are divided into branches, they go until they read a motor end plate within the muscle and at that point the neurotransmitter is released and causes the muscle cell to shorten or contract.
Spinal cordEfferent Neuron
For the actual movement of the muscle to occur, the impulse must move through the nerves until it reaches a motor end plate within a muscle. When it reaches this point, the neurotransmitter is released thus making the muscle fibers shorten or contract. The impulse first reaches the brachial plexus, from there it goes out to the main nerves of the arm: the axillary, median, radial, and ulnar nerves. The axillary nerve takes it to the deltoid and teres minor, at that point it stimulates the muscle fibers by releasing chemicals from the motor neuron. This causes the muscle to contract and the humerus to abduct, the humerus makes this movement because the insertion point of the deltoid is on the middle of the humerus. The impulse moves through the musculocutaneous nerve and reaches the triceps brachii and anconeus, which make up the elbow joint. When the neurotransmitters are released, the muscles contract and make the elbow joint extend. Since it is a hinge joint, it simply straightens out and is held in place by the recently contracted muscles. More support is given to this joint by the triceps and brachioradialis muscles when they contract about the elbow; they are supplied by the radial nerve and stimulate the posterior forearm muscles.
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Hinge JointMovement of Radioulnar and Humeroulnar Joints In order for the biaxial joint to straighten, the anterior forearm muscles must contract—this is done by the impulses traveling through the median nerve and stimulating the muscles thus making them lock the joint in place. The last movement necessary for the arm to become completely straight is for the phalanges to extend and lock into place. The ulnar nerve leads the impulses to the muscles of the hand and stimulates them, making the muscles contract and help lock the wrist in place, at the same time supinating the fingers and holding them straight as well.
Bixial Joint and Hand DiagramExtension of fingers
While the muscles may do the work to make the bones move, in order for the arm laterally abduct, the bones must move in a certain manner. Since the pectoral girdle is attached to the axial skeleton by the sternoclavicular joint, it is unmoving. However, it is made up of the clavicle, scapula, and humerus, which are all important to making this specific movement. The clavicle is what connects the arm to the axial skeleton, it is held in place by the pectoralis major. The scapula is the bone to lock the shoulder in place once it has been anchored; it then connects to the humerus at the glenohumeral joint.
Both of these joints are immobile, but are still vital in making the movement of the arm. The humerus is then connected to the elbow joint at the trochlear notch—when the triceps brachii and anconeus contract, the humeroulnar and radioulnar joints rotate (straighten) and lock in place. When these joints rotate it causes the ulna, which is connected to the humerus at the humeroulnar joint, to move into place and extend. This also happens to the radius; however it is connected to the ulna at the proximal radioulnar joint and moves into place the same time that the ulna does. Lastly the biaxial and intercarpal joints are supinated and locked into place. By each of these movements happening, the arm is then laterally abducted away from the body, being parallel from the floor.