Muscular System Part 1 4/23/2019 SAP2b

Muscle Functions Movement of bones or fluids (e.g., blood) Maintaining posture and body position Stabilizing joints Heat generation (especially skeletal muscle) arrector pili muscles-hairs stand up-insulate body

Smooth Muscle

Cardiac Muscle

Characteristics of Muscle Tissue Excitability (responsiveness or irritability): ability to receive and respond to stimuli Contractility: ability to shorten when stimulated Extensibility: ability to be stretched Elasticity: ability to recoil to resting length SAP2b

Levels of Organization Insertion/Origin Attachments Tendons & aponeurosis tissue that covers & forms the terminations and attachments of various muscles 4/23/2019 SAP2b

Origin and Insertion Origin: immovable end of muscle Insertion: movable end of muscle **when a muscle contracts the insertion is moved toward the origin The biceps brachii has two origins (or two heads).

When muscles attach to bones one end becomes Origin and the other becomes Insertion Point of attachment that connects to a stationary bone Insertion Point of attachment on the moving bone

Skeletal muscles work in groups Terms describing roles of muscles carrying out actions: Agonist: (prime mover) muscle that causes an action Antagonist: muscle that works against the action Synergists: muscles that contribute to an action by helping the agonist. 4/23/2019 SAP2b

Most common types of movement Flexion: decreases the angle of the joint and brings two bones closer together (bending knee or elbow; bending forward at hip) Extension: opposite of flexion; increases the angle or distance between two bones (straitening knee or elbow) Rotation: movement of a bone around its longitudinal axis (ball & socket joints; shaking your head “no”) Abduction: moving a limb away from the midline; also applies to fanning movement of fingers and toes Adduction: opposite of abduction; limbs moves toward the midline Circumduction: combination of flexion, extension, abduction, and adduction; movement in a cone-shaped pattern (rotating around at shoulder)

Flexion You will need to know the action or movement performed for each of the muscles we study. The first type of movement is called flexion. Note the lower leg is being flexed in this diagram. During flexion the angle of joint is decreased. As the knee is flexed, the angle between the lower leg and the thigh is decreased. Flexion of the upper arm is also illustrated in this diagram. Here the angle between the arm and the frontal plane is decreased.

Extension Extension is the opposite of flexion. In extension the angle of a joint is increased. Extension of the lower leg causes an increased angle between the lower leg and the thigh.  

Hyperextension Flexion and extension also apply to the neck. When a joint is extended past the anatomical position the movement is called hyperextension.

Abduction, Adduction & Circumduction Abduction refers to moving away from the median plane of the body. Adduction is the opposite movement to abduction. It is moving toward the medial plane. Circumduction refers to inscribing a circle while moving a limb.

Rotation Rotation is turning a bone on its own axis. Moving the head back and forth to indicate “no” is an example of rotation. Note the difference between medial and lateral rotation. In lateral rotation the limb is rotated the lateral side of the body. Medial rotation rotates the limb toward the medial side of the body.

Muscle Attachment Tendon Strong connective tissue Attaches muscle to bone Achilles Tendon which attaches Gastrocnemius muscle of the calf to the heel

Muscle Attachment Fascia Tough sheet-like connective tissue Covers & protects muscle tissue Lumbodorsal Fascia-surrounds deep muscle of the back

Skeletal muscle anatomy Epimysium: a tougher overcoat of connective tissue which wraps many fascicles together Tendons: strong cord- like bundles of the blended epimysia Aponeuroses: sheet-like bundles which attach muscle indirectly to bones, cartilage, or connective tissue coverings of each other

Skeletal muscle anatomy Perimysium: more coarse fibrous membrane that wraps several sheathed muscle fibers Endomysium: delicate connective tissue sheath which encloses each muscle fiber Fascicle: the bundle of muscle fibers

Connective Tissue Components Fascia--thin sheets of fibrous connective tissue that hold muscle fibers together Epimysium--fascia that surrounds the entire muscle Perimysium--separates muscles into bundles (10 to 100 muscle fibers) Endomysium--fascia that surrounds each muscle fiber Tendon—a cord of dense regular connective tissue composed of collagen that attaches muscle to periosteum to bone 4/23/2019 SAP2b

Table 9.1

Connective tissue wrappings of skeletal muscle 4/23/2019 SAP2b

Nerve and Blood Supply Supplied w/ nerves and blood vessels Related directly to muscle contractions Utilizes a great deal of ATP Large amounts of nutrients and oxygen required An artery and 1 or 2 veins accompany each nerve Within the endomysium, capillaries are found in each muscle fiber 4/23/2019 SAP2b