Biceps Brachii Ebook
Returning to the arm, we can say that the biceps brachii is the main agonist or prime mover for flexion (bending) of the forearm. If this bending movement is to be successfully carried out, however, the opposing muscles that extend (straighten) the forearm must be inhibited or relaxed.
When a related group of forearm flexors (such as the biceps brachii and brachialis muscles) are hit with a severe wasting away of their fibers, then the actions of their antagonists (the forearm extenders) are not opposed. In this example, the forearm would tend to be strongly extended most of the time, and become progressively less able to bend.
The elbow is a hinge joint between the humerus (upper arm bone) and the ulna and radius. The elbow allows you to bend and straighten your arm and to rotate your forearm without moving your upper arm. Your biceps muscle bends the forearm, while your triceps muscle straightens the forearm. The bony projection that forms the point of the elbow is the olecranon. Popularly known as the funny bone, because bumping the nerve (the ulnar nerve) that passes over it produces a familiar tingling sensation, the olecranon prevents overextension of the elbow.
Fusiform8 muscles are thick in the middle and tapered at each end. Their contractions are moderately strong. The biceps brachii of the arm and gastrocnemius of the calf are examples of this type. biceps brachii and brachialis muscles are synergists in elbow flexion. The triceps brachii is an antagonist of those two muscles and is the prime mover in elbow extension. biceps brachii and brachialis muscles are synergists in elbow flexion. The triceps brachii is an antagonist of those two muscles and is the prime mover in elbow extension.
The prime mover (agonist) is the muscle that produces most of the force during a particular joint action. In flexing the elbow, for example, the prime mover is the biceps brachii. 2. A synergist10 (SIN -ur-jist) is a muscle that aids the prime mover. Several synergists acting on a joint can produce more power than a single larger muscle. The brachialis, for example, lies deep to the biceps brachii and works with it as a synergist to flex the elbow. The actions of a prime mover and its 3. An antagonist11 is a muscle that opposes the prime mover. In some cases, it relaxes to give the prime mover almost complete control over an action. More often, however, the antagonist moderates the speed or range of the agonist, thus preventing excessive movement and joint injury. If you extend your arm to reach out and pick up a cup of tea, your triceps brachii is the prime mover of elbow extension and your biceps brachii acts as an antagonist to slow the extension and stop it at the appropriate...
Flexion Biceps brachii Brachialis Biceps brachii Biceps Brachii (BY-seps BRAY-kee-eye) Figure 10.25 Actions of the Rotator Muscles on the Forearm. (a) Supination (b) pronation (c) cross section just distal to the elbow, showing how the biceps brachii aids in supination. Figure 10.25 Actions of the Rotator Muscles on the Forearm. (a) Supination (b) pronation (c) cross section just distal to the elbow, showing how the biceps brachii aids in supination. 21. Identify three functions of the biceps brachii. Biceps brachii Biceps brachii Short head Long head Biceps brachii Biceps brachii
Characteristic 1 Number of muscle heads . We have started out focusing our attention upon a particular muscle - the biceps brachii. The first part of this name, biceps, literally means ''two'' (bi-) ''heads'' (ceps). A head or cep is a major division of a muscle that has its own attached tendon. In Figure 8.2, Biceps femoris - a two-headed muscle of the thigh Biceps femoris - a two-headed muscle of the thigh for instance, we see that the biceps brachii has two heads (ceps) - a long head and a short head. The same is true for another skeletal muscle pictured, the biceps femoris (FEM-or-is). Observe that the two heads of each of these muscles have their own tendons hooking them onto the skeleton. There are muscles with more than two heads. If you study Figure 8.2 again, you see that there is a triceps (TRY-seps) brachii muscle, as well as a quadriceps (QWAD-rih-seps) femoris (FEM-or-is) muscle group. Study suggestion Using your knowledge gained from analyzing the biceps muscles, write...
Most skeletal muscles in the human body are arranged into pairs of antagonists. The biceps brachii forearm flexor versus the triceps brachii forearm extender is one example of an antagonistic muscle pair. ''Can the biceps brachii ever be considered the antagonist '' Yes, it can, if the body movement in question is forearm extension, rather than forearm flexion. In that case, the triceps brachii is the agonist, while the biceps brachii is the antagonist. Therefore, the labels, agonist versus antagonist, are all relative. Their use depends upon what particular body movement is being considered at the time.
Fig. 3.1 The biceps brachii muscle and one of its tendons as a ''little mouse'' below the skin. organ, the biceps (BUY-seps) brachii (BRAY-kee-eye) muscle in the upper arm (brachii). The body or main mass of the biceps brachii does, indeed, closely resemble a ''little mouse,'' doesn't it And how about those tendons (TEN-duns) or tough straps of connective tissue All of the skeletal muscles are anchored to the bones at either end by one or more of these tough, slender tendons. Doesn't one of the tendons of the biceps brachii shown in Figure 3.1 look a lot like a tail of a little mouse (muscul) creeping below the skin
And Figure 3.1 further talked about the biceps brachii muscle in the upper arm as being representative of the approximately 600 different skeletal muscle organs. It depicted the biceps brachii according to the Common English translation of the Latin term, muscular. We know that it literally ''pertains to'' (-ar) a ''little mouse'' (muscul). The tough tendons hooking skeletal muscles onto bones, moreover, were seen to somewhat resemble the tails of mice
The biceps brachii does not have to struggle against or contend with the triceps brachii all by itself. The biceps brachii (unlike many other skeletal muscles) does have a helper Its main helper is the brachialis (bray-kee-AL-is) muscle. Study suggestion Analyze the name, brachialis. For which of the 8 different muscle characteristics is it named Go back to Figure 8.2, and examine it closely. Do you see part of the brachialis muscle peeking out at you, located deep to the biceps brachii The brachialis is a synergist (SIN-er-jist) of the biceps brachii. A synergist is literally ''one that specializes in'' (-ist) working (erg) with (syn-) something else. In general, a synergist is a muscle that works with and assists a particular agonist or prime mover in carrying out some body movement. In the case of forearm flexion, then, the brachialis (synergist) works together with the biceps brachii (agonist) to bend the forearm at the elbow.
To take a simple example when you bend your elbow the biceps muscle contracts and the triceps relaxes. When you straighten it again the opposite happens the biceps relaxes and the triceps contracts. The part of the brain responsible for these movements contains reciprocal control systems. When the nerves to the biceps fire, the nerves to the triceps are inhibited, and vice-versa. This control depends crucially on the construction of the nerve pathways. For example, one set of axon terminal branches activates an excitatory nerve, one an inhibitory nerve51. It also depends on pathway function which neurones become active, which transmitters are released at which synapses. In turn, the control mechanism ensures that some neurones and synapses are active and others are not. Since brain function affects brain structure, the control processes also indirectly affect brain structure. 51 The motor nerves (the ones that actually cause muscle contraction) respond to...
A muscle returns to its resting length with the aid of two forces (1) like a recoiling rubber band, the series-elastic components stretch it and (2) since muscles often occur in antagonistic pairs, the contraction of an antagonist lengthens the relaxed muscle. Contraction of the triceps brachii, for example, extends the elbow and lengthens the biceps brachii.
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