The Muscular System

Muscular system functions Muscle types Muscle movements Essential Question Muscular system functions Muscle types Muscle movements What are the structures of the muscular system?

Abduction vs. Adduction

The Muscular System Comprises nearly half our weight. Over 650 muscles. Each muscle is made up of hundreds or thousands of muscle fibers. Muscles never, ever push… THEY ALWAYS PULL. Flexor versus Extensor.

Flexor vs Extensor Muscles A flexor muscle bends a joint, For example, the muscle at the top and front of the arm, the biceps brachii, flexes or bends the arm at the elbow. An extensor muscle straightens a joint. Example: the muscle at the back of the arm, the triceps brachii, straightens it back out, extending it.

Flexor and Extensor Relastionship flexor is (anatomy) a muscle whose contraction acts to bend a joint or limb while extensor is (anatomy) a muscle whose contraction extends or straightens a limb or body part. 

Agonist and Antagonist Muscles Antagonist and agonist muscles often occur in pairs, called antagonistic pairs. As one muscle contracts, the other relaxes. An example of an antagonistic pair is the biceps and triceps, to contract - the triceps relaxes while the biceps contracts to lift the arm.

Agonist Muscles Agonist muscles and antagonist muscles refer to muscles that cause or inhibit a movement. Agonist muscles cause a movement to occur through their own contraction. For example, the triceps brachii contracts during the up phase of a push-up (elbow extension). During the down phase of a push-up, the same triceps brachii actively controls elbow flexion while relaxing. It is still the agonist, because while resisting gravity during relaxing, the triceps brachii continues to be the prime mover, or controller, of the joint action. Agonists are also interchangeably referred to as "prime movers," since they are the muscles considered primarily responsible for generating a specific movement. This term typically describes skeletal muscles.

Antagonist Muscles Antagonist muscles oppose a specific movement. This controls a motion, slows it down, and returns a limb to its initial position. Antagonism is a role that a muscle plays depending on the motion. If a motion is reversed, agonist and antagonist muscles switch roles. Because a flexor muscle is always a flexor, in flexion it is the agonist, and in extension it is the antagonist.

Synergistic Muscles Synergist muscles perform, or help perform, the same set of joint motion as the agonists. Synergists muscles normally act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. Synergists are muscles that facilitate the fixation action. Fixation of the wrist during full flexion of the fingers in clenching the fist. Try IT Now!!

Voluntary and Involuntary Muscles 15 minutes research and write down the meaning/function of these two terms in your notes, using an example for each and an analogy for each, to share.

The Muscular System: Muscle Fibers Bundles of threadlike structures called myofibrils Composed of: Myosin Actin Form overlapping pattern called sarcomere muscle muscle fiber sarcolemma sarcomere functional unit of muscle movement

Structures of the muscular system Muscles Skeletal Smooth Cardiac Sphincter Connective tissue Tendons Fascia

Structures of the muscular system Types of muscle Skeletal Smooth Cardiac Sphincter Dilator

Structures of the muscular system Types of Muscle Skeletal muscles Attached to bone Striated (striped) appearance Voluntary Multinucleated muscle cell bundles

Structures of the muscular system Types of Muscle Smooth muscles Also known as visceral muscles Involuntary Located in walls of digestive system, uterus & blood vessels

Structures of the muscular system Types of Muscle Cardiac muscle Found only in the heart Striated, branched Involuntary Cells are fused- when one contracts, they all contract, creating the heartbeat

Structures of the muscular system Types of Connective tissue Tendons Fascia

Structures of the muscular system Connective tissue Tendons dense bands that connect skeletal muscle to the bone

Structures of the muscular system Connective tissue Fascia Fibrous connective tissue sheets that wrap around muscle bundles

How do skeletal muscles get their names? Location Location of origin and insertion Size Action flexor Direction Extensor Number of origins Depressor However, not all muscles are named by the above methods!

Head & Neck Muscles

Anterior Torso/Trunk (anterior)

Torso/Trunk (anterior)

Posterior Torso/Trunk (posterior)

Upper extremities

Lower extremities

The Muscular System Review http://www.anatomyarcade.com/games/PAM/PAM.html

The muscular system review Posterior view

Sphincter Muscles A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the human body. But there only about four or five we will discuss. Sphincters relax at death, often releasing fluids.

Any of the ring like muscles surrounding and able to contract or close a bodily passage or opening. One of the most important human sphincter muscles is the sphincter pylori, a thickening of the middle layer of stomach muscle around the pylorus (opening into the small intestine) that holds food in the stomach until it is thoroughly mixed with gastric juices. Other sphincters are involved in excretion of waste: the sphincter ani externus keeps the anal opening closed by its normal contraction, The sphincter urethrae is the most important voluntary control of urination. There is a sphincter in the eye, the sphincter pupillae, a ring of fibres in the iris that contracts the pupil in the presence of bright light. Compare dilator muscle.

Sphincter Hot Topic Total Misconceptions Some say there are millions of microscopically small precapillary sphincters muscles, a band of smooth muscle that adjusts blood flow into capillaries. It is a highly debated topic and some researchers have suggested the term precapillary resistance instead. The muscles of the mouth, is not actually a sphincter, but a complex of four muscles in the lips that encircles the mouth called the orbicularis oris muscles.

Sphincter Muscles: Two Classifications Sphincters can be further classified into functional and anatomical sphincters: Anatomical sphincters have a localized and often circular muscle thickening to facilitate their action as a sphincter. Functional sphincters do not have this localized muscle thickening and achieve their sphincter action through muscle contraction around (extrinsic) or within (intrinsic) the structure. Sphincters can also be voluntarily or involuntarily controlled: Voluntary sphincters are supplied by somatic nerves. Involuntary sphincters are stimulated by autonomic nerves.

the iris dilator (of the eye) muscle Dilator Muscles any of the muscles that widen/dilate a body part, the iris dilator (of the eye) muscle  or the dilator naris  (of the nose) muscle.