Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 7: Muscles

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Overview The word muscle can refer to an organ or a tissue Muscles –Make up 40-50% of body weight –Can contract on conscious command –Are responsible for movement

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Functions of Muscles Muscles convert chemical energy into mechanical force: –Move body parts –Maintain body posture and stabilize joints –Adjust the volume of hollow structure (e.g., bladder) –Move substances within the body (e.g., pump blood) –Produce heat

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Three Types of Muscle SkeletalCardiacSmooth Other namesSomaticMyocardialVisceral StriatedYes No ContractionQuick Slow Voluntary Yes; some involuntary (reflexive) No Subject to fatigue YesNo

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Three Types of Muscle (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! Adult muscle stem cells are called satellite cells; they produce myoblasts, which fuse to form skeletal muscle fibers.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Structure of Skeletal Muscle

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Motor Units

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Steps in Muscular Contraction An electrical signal in the somatic motor neuron A chemical signal (acetylcholine) in the synapse An electrical signal in the sarcolemma A chemical signal (calcium) in the sarcoplasm

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chemical Synapses

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Myofibrils and Myofilaments

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Myofibrils and Myofilaments (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! During muscle contraction –sarcomeres and myofibrils shorten – myofilaments do not change in length

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Thick and Thin Filaments

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! Levels of Skeletal Muscle Organization Muscle Fascicle (bundle of muscle fibers) Muscle fiber (muscle cell) Myofibril (bundle of myofilaments) Myofilament (stands of contractile proteins) Contractile protein smallest

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Contraction

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Contraction and Relaxation

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Contraction and Relaxation (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Relaxation Relaxation is the reverse of contraction –Acetylcholine release stops –Nicotinic receptor channels close and sarcolemma repolarizes –SR calcium channels close; Ca 2 + ions taken into SR –Tropomyosin covers binding sites –Myosin no longer binds actin; sarcomere returns to resting length

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Energy Production ATP stores energy in chemical bond used by muscles ATP + H 2 O  ADP + H 2 O + PO 4 + Energy Glycolosis is the fastest method of generating ATP from nutrients. Mitochondria generate ATP from glucose and fatty acid molecules.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Energy Production (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! ATP binding causes the cross-bridge to release. The energy from ATP cleavage is necessary for the power stroke.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Aerobic vs. Anaerobic Muscle Function Aerobic muscle functionAnaerobic muscle function Mitochondria provide ATP Glycolitic fibers provide quick energy kick Oxygen is requiredOxygen is not required Jogging = endurance activityLactic acid leads to fatigue

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! The terms anaerobic metabolism and glycolysis are often used synonymously, but erroneously. Glycolysis is the necessary first step in both aerobic metabolism and anaerobic metabolism.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Fiber Types

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Energy Metabolism

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Fatigue Muscle fatigue: loss of the ability to respond to nerve stimulation after vigorous exercise –Peripheral –Central

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Mechanics of Muscle Contraction

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Mechanics of Muscle Contraction (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! In an everyday contraction at a given fiber length, contraction of individual muscle fibers is all-or-none, as the fiber contracts in incomplete tetanus.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Mechanics of Muscle Contraction The force an individual muscle exerts depends on –The force exerted by each contracting fiber –The number of motor units contracting

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Types of Contractions Isotonic contraction: dynamic shortening of muscle tissue that maintains constant force; e.g., chewing food Concentric contraction: myofilaments slide; sarcomeres, fibers, muscles shorten; movement occurs; e.g., biceps curl Eccentric contraction: myosin heads grab actin filaments to slow movement; e.g., lowering weight Isometric contraction: force is generated and muscle tenses, but myofibrils do not slide and length is unchanged; e.g., maintaining upright body posture

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Types of Contractions (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! The thing common to all muscle contraction is force, not movement.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Smooth Muscle vs. Skeletal Muscle Smooth MusclesSkeletal Muscles Have short, plump cells Built on intermediate filaments Connected by dense bodies Layered in sheets, so can stretch in many directions Ca++ ions come through cell membrane and regulate myosin, not actin Have long, thin cells (fibers) Built in bundles; have length- tension relationship Anchored by Z disc Have striations Ca++ ions come from SR and T-tubules; control access to binding sites

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Remember This! Intermediate filaments form the scaffolding of a smooth muscle cell, and myofilaments contract the cell. The myosin heads are regulated in smooth muscle; the binding sites on actin molecules are regulated in skeletal muscle.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Smooth Muscle

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Smooth Muscle Regulation

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Origin and Insertion

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Superficial Muscles, Anterior View

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Superficial Muscles, Posterior View

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles of Facial Expression

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles Controlling the Jaw and Moving the Head

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles Controlling the Jaw and Moving the Head (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles of the Thorax

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles of the Thorax (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles of the Thorax (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles of the Perineum

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move and Stabilize the Pectoral Girdle

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Arm (Humerus) at the Shoulder Joint

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Arm (Humerus) at the Shoulder Joint (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Forearm, Hand, and Fingers

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Forearm, Hand, and Fingers (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Forearm, Hand, and Fingers (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Thigh and Leg

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Thigh and Leg (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Thigh and Leg, (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Foot and Toes

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Foot and Toes (cont’d)

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscles that Move the Foot and Toes (cont’d)