© 2012 Pearson Education, Inc. PowerPoint ® Lecture Slides Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College C H A P T E R 6 The.

© 2012 Pearson Education, Inc. Characteristics of Muscles Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber) Contraction and shortening of muscles is due to the movement of microfilaments All muscles share some terminology Prefixes myo and mys refer to “muscle” Prefix sarco refers to “flesh”

© 2012 Pearson Education, Inc. Comparison of Skeletal, Cardiac, and Smooth Muscles CharacteristicSkeletalCardiacSmooth Body locationAttached to bone or skin (for some facial muscles) Walls of the heartMostly in walls of visceral organs (other than the heart) Cell shape and appearance Single, very long, cylindrical, multinucleate cells with very obvious striations Branching chains of cells, uninucleate, striations, intercalated discs Single, fusiform, uninucleate, no striations Connective tissue components Endomysium, perimysium, and epimysium Endomysium

© 2012 Pearson Education, Inc. Comparison of Skeletal, Cardiac, and Smooth Muscles CharacteristicSkeletalCardiacSmooth Regulation of contraction VoluntaryInvoluntary Speed of contraction Slow to fastSlowVery slow Rhythmic contractions NoYesYes, in some

© 2012 Pearson Education, Inc. Connective Tissue Wrappings of Skeletal Muscle Cells are surrounded and bundled by connective tissue Endomysium—encloses a single muscle fiber Perimysium—wraps around a fascicle (bundle) of muscle fibers Epimysium—covers the entire skeletal muscle Fascia—on the outside of the epimysium

© 2012 Pearson Education, Inc. Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment Tendons—cord-like structures Mostly collagen fibers Often cross a joint due to toughness and small size Aponeuroses—sheet-like structures Attach muscles indirectly to bones, cartilages, or connective tissue coverings

© 2012 Pearson Education, Inc. Cardiac Muscle Characteristics Striations Usually has a single nucleus Branching cells Joined to another muscle cell at an intercalated disc Involuntary Found only in the walls of the heart

© 2012 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Sarcolemma—specialized plasma membrane Myofibrils—long organelles inside muscle cell Sarcoplasmic reticulum—specialized smooth endoplasmic reticulum

© 2012 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Myofibrils are aligned to give distinct bands I band = light band Contains only thin filaments A band = dark band Contains the entire length of the thick filaments

© 2012 Pearson Education, Inc. Figure 6.3b (b) Myofibril or fibril (complex organelle composed of bundles of myofilaments) Z disc H zone Z disc I band A band I band M line Thin (actin) filament Thick (myosin) filament

© 2012 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Sarcomere—contractile unit of a muscle fiber Organization of the sarcomere Myofilaments Thick filaments = myosin filaments Thin filaments = actin filaments

© 2012 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Thick filaments = myosin filaments Composed of the protein myosin Has ATPase enzymes Myosin filaments have heads (extensions, or cross bridges) Myosin and actin overlap somewhat Thin filaments = actin filaments Composed of the protein actin Anchored to the Z disc

© 2012 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle At rest, within the A band there is a zone that lacks actin filaments Called either the H zone or bare zone Sarcoplasmic reticulum (SR) Stores and releases calcium Surrounds the myofibril

© 2012 Pearson Education, Inc. Stimulation and Contraction of Single Skeletal Muscle Cells Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus Contractility—ability to shorten when an adequate stimulus is received Extensibility—ability of muscle cells to be stretched Elasticity—ability to recoil and resume resting length after stretching

© 2012 Pearson Education, Inc. The Nerve Stimulus and Action Potential Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that neuron

© 2012 Pearson Education, Inc. Neuromuscular junction Association site of axon terminal of the motor neuron and muscle The Nerve Stimulus and Action Potential PLAY A&P Flix™: Events at the Neuromuscular Junction

© 2012 Pearson Education, Inc. The Nerve Stimulus and Action Potential Synaptic cleft Gap between nerve and muscle Nerve and muscle do not make contact Area between nerve and muscle is filled with interstitial fluid Action potential reaches the axon terminal of the motor neuron Calcium channels open and calcium ions enter the axon terminal

© 2012 Pearson Education, Inc. Transmission of Nerve Impulse to Muscle Calcium ion entry causes some synaptic vesicles to release their contents (acetylcholine, a neurotransmitter) by exocytosis Neurotransmitter—chemical released by nerve upon arrival of nerve impulse in the axon terminal The neurotransmitter for skeletal muscle is acetylcholine (ACh)

© 2012 Pearson Education, Inc. Transmission of Nerve Impulse to Muscle Acetylcholine attaches to receptors on the sarcolemma of the muscle cell In response to the binding of ACh to a receptor, the sarcolemma becomes permeable to sodium (Na + ) Sodium rushes into the cell generating an action potential and potassium leaves the cell Once started, muscle contraction cannot be stopped

© 2012 Pearson Education, Inc. Figure 6.5, step 1 Synaptic vesicle containing ACh Axon terminal of motor neuron Mitochondrion Ca 2+ Synaptic cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm of muscle fiber Folds of sarcolemma Ca 2+ ACh receptor ACh Action potential reaches axon terminal of motor neuron. 1

© 2012 Pearson Education, Inc. Figure 6.5, step 2 Synaptic vesicle containing ACh Axon terminal of motor neuron Mitochondrion Ca 2+ Fusing synaptic vesicle Sarcoplasm of muscle fiber Folds of sarcolemma Ca 2+ ACh receptor ACh Sarcolemma Synaptic cleft Action potential reaches axon terminal of motor neuron. Calcium (Ca 2+ ) channels open and Ca 2+ enters the axon terminal. 1 2

© 2012 Pearson Education, Inc. Figure 6.5, step 3 Synaptic vesicle containing ACh Axon terminal of motor neuron Mitochondrion Ca 2+ Fusing synaptic vesicle Sarcoplasm of muscle fiber Folds of sarcolemma Ca 2+ ACh receptor ACh Sarcolemma Synaptic cleft Action potential reaches axon terminal of motor neuron. Calcium (Ca 2+ ) channels open and Ca 2+ enters the axon terminal. Ca 2+ entry causes some synaptic vesicles to release their contents (acetylcholine, a neurotransmitter) by exocytosis. 1 2 3

© 2012 Pearson Education, Inc. Figure 6.5, step 4 Action potential reaches axon terminal of motor neuron. Calcium (Ca 2+ ) channels open and Ca 2+ enters the axon terminal. Ca 2+ entry causes some synaptic vesicles to release their contents (acetylcholine, a neurotransmitter) by exocytosis. Acetylcholine diffuses across the synaptic cleft and binds to receptors in the sarcolemma. Synaptic vesicle containing ACh Axon terminal of motor neuron Mitochondrion Ca 2+ Fusing synaptic vesicle Sarcoplasm of muscle fiber Folds of sarcolemma Ca 2+ ACh receptor ACh 1 2 3 4 Sarcolemma Synaptic cleft

© 2012 Pearson Education, Inc. Figure 6.5, step 5 ACh binds and channels open that allow simultaneous passage of Na + into the muscle fiber and K + out of the muscle fiber. More Na + ions enter than K + ions leave and this produces a local change in the electrical conditions of the membrane (depolarization), which eventually leads to an action potential. 5 Ion channel in sarcolemma opens; ions pass. Na + K+K+

© 2012 Pearson Education, Inc. Figure 6.5, step 6 ACh effects are ended by its breakdown in the synaptic cleft by the enzyme acetylcholinesterase. 6 Ion channel closed; ions cannot pass. Acetylcholinesterase Na + Degraded ACh ACh K+K+

© 2012 Pearson Education, Inc. Figure 6.6a-b Small twig Match flame Flame ignites the twig. Flame spreads rapidly along the twig. Neuromuscular junction Nerve fiber Striations Muscle cell or fiber Na + diffuses into the cell. Action potential spreads rapidly along the sarcolemma. (b) 1 2 1 2 (a)

© 2012 Pearson Education, Inc. The Sliding Filament Theory of Muscle Contraction Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere This continued action causes a sliding of the myosin along the actin The result is that the muscle is shortened (contracted)

© 2012 Pearson Education, Inc. Figure 6.8a Protein complex Myosin myofilament Actin myofilament (a) In a relaxed muscle cell, the regulatory proteins forming part of the actin myofilaments prevent myosin binding (see a). When an action potential (AP) sweeps along its sarcolemma and a muscle cell is excited, calcium ions (Ca 2+ ) are released from intracellular storage areas (the sacs of the sarcoplasmic reticulum).

© 2012 Pearson Education, Inc. Figure 6.8b Myosin-binding site Ca 2+ Upper part of thick filament only (b) The flood of calcium acts as the final trigger for contraction, because as calcium binds to the regulatory proteins on the actin filaments, the proteins undergo a change in both their shape and their position on the thin filaments. This action exposes myosin-binding sites on the actin, to which the myosin heads can attach (see b), and the myosin heads immediately begin seeking out binding sites.

© 2012 Pearson Education, Inc. Contraction of Skeletal Muscle Muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Graded responses—different degrees of skeletal muscle shortening

© 2012 Pearson Education, Inc. Types of Graded Responses Summing of contractions One contraction is immediately followed by another The muscle does not completely return to a resting state due to more frequent stimulations The effects are added

© 2012 Pearson Education, Inc. Types of Graded Responses Unfused (incomplete) tetanus Some relaxation occurs between contractions but nerve stimuli arrive at an even faster rate than during summing of contractions Unless the muscle contraction is smooth and sustained, it is said to be in unfused tetanus

© 2012 Pearson Education, Inc. Types of Graded Responses Fused (complete) tetanus No evidence of relaxation before the following contractions Frequency of stimulations does not allow for relaxation between contractions The result is a smooth and sustained muscle contraction

© 2012 Pearson Education, Inc. Muscle Response to Strong Stimuli Muscle force depends upon the number of fibers stimulated More fibers contracting results in greater muscle tension Muscles can continue to contract unless they run out of energy

© 2012 Pearson Education, Inc. Energy for Muscle Contraction Initially, muscles use stored ATP for energy ATP bonds are broken to release energy Only 4–6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP

© 2012 Pearson Education, Inc. Energy for Muscle Contraction Direct phosphorylation of ADP by creatine phosphate (CP) Muscle cells store CP CP is a high-energy molecule After ATP is depleted, ADP is left CP transfers a phosphate group to ADP, to regenerate ATP CP supplies are exhausted in less than 15 seconds About 1 ATP is created per CP molecule

© 2012 Pearson Education, Inc. Energy for Muscle Contraction Aerobic respiration Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP) A series of metabolic pathways occur in the mitochondria This is a slower reaction that requires continuous oxygen Carbon dioxide and water are produced

© 2012 Pearson Education, Inc. Energy for Muscle Contraction Anaerobic glycolysis and lactic acid formation Reaction that breaks down glucose without oxygen Glucose is broken down to pyruvic acid to produce about 2 ATP Pyruvic acid is converted to lactic acid This reaction is not as efficient, but is fast Huge amounts of glucose are needed Lactic acid produces muscle fatigue

© 2012 Pearson Education, Inc. Muscle Fatigue and Oxygen Deficit When a muscle is fatigued, it is unable to contract even with a stimulus Common cause for muscle fatigue is oxygen debt Oxygen must be “repaid” to tissue to remove oxygen deficit Oxygen is required to get rid of accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

© 2012 Pearson Education, Inc. Types of Muscle Contractions Isotonic contractions Myofilaments are able to slide past each other during contractions The muscle shortens and movement occurs Example: bending the knee; rotating the arm Isometric contractions Tension in the muscles increases The muscle is unable to shorten or produce movement Example: push against a wall with bent elbows

© 2012 Pearson Education, Inc. Effect of Exercise on Muscles Exercise increases muscle size, strength, and endurance Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue Makes body metabolism more efficient Improves digestion, coordination Resistance (isometric) exercise (weight lifting) increases muscle size and strength

© 2012 Pearson Education, Inc. Five Golden Rules of Skeletal Muscle Activity 1. With a few exceptions, all skeletal muscles cross at least one joint. 2. Typically, the bulk of a skeletal muscle lies proximal to the joint crossed. 3. All skeletal muscles have at least two attachments: the origin and the insertion. 4. Skeletal muscles can only pull; they never push. 5. During contraction, a skeletal muscle insertion moves toward the origin.

© 2012 Pearson Education, Inc. Muscles and Body Movements Movement is attained due to a muscle moving an attached bone Muscles are attached to at least two points Origin Attachment to a immoveable bone Insertion Attachment to an movable bone

© 2012 Pearson Education, Inc. Types of Body Movements Flexion Decreases the angle of the joint Brings two bones closer together Typical of bending hinge joints like knee and elbow or ball-and-socket joints like the hip Extension Opposite of flexion Increases angle between two bones Typical of straightening the elbow or knee Extension beyond 180° is hypertension

© 2012 Pearson Education, Inc. Types of Body Movements Rotation Movement of a bone around its longitudinal axis Common in ball-and-socket joints Example is when you move atlas around the dens of axis (shake your head “no”)

© 2012 Pearson Education, Inc. Special Movements Dorsiflexion Lifting the foot so that the superior surface approaches the shin (toward the dorsum) Plantar flexion Depressing the foot (pointing the toes) “Planting” the foot toward the sole

© 2012 Pearson Education, Inc. Special Movements Supination Forearm rotates laterally so palm faces anteriorly Radius and ulna are parallel Pronation Forearm rotates medially so palm faces posteriorly Radius and ulna cross each other like an X

© 2012 Pearson Education, Inc. Types of Muscles Prime mover—muscle with the major responsibility for a certain movement Antagonist—muscle that opposes or reverses a prime mover Synergist—muscle that aids a prime mover in a movement and helps prevent rotation Fixator—stabilizes the origin of a prime mover

© 2012 Pearson Education, Inc. Naming Skeletal Muscles By location of the muscle’s origin and insertion Example: Sterno (on the sternum) By shape of the muscle Example: Deltoid (triangular) By action of the muscle Example: Flexor and extensor (flexes or extends a bone)

© 2012 Pearson Education, Inc. Figure 6.15 (g) Unipennate (f) Bipennate Orbicularis oris Deltoid (d) Circular (a) Convergent Biceps brachii (a) (c) (b) Fusiform Sartorius (g) (c) Parallel (d) (e) Multipennate (e) (b) (f) Extensor digitorum longus Rectus femoris Pectoralis major

© 2012 Pearson Education, Inc. Head and Neck Muscles Facial muscles Frontalis—raises eyebrows Orbicularis oculi—closes eyes, squints, blinks, winks Orbicularis oris—closes mouth and protrudes the lips Buccinator—flattens the cheek, chews Zygomaticus—raises corners of the mouth Chewing muscles Masseter—closes the jaw and elevates mandible Temporalis—synergist of the masseter, closes jaw

© 2012 Pearson Education, Inc. Figure 6.16 Cranial aponeurosis Orbicularis oris Orbicularis oculi Frontalis Zygomaticus Buccinator Platysma Temporalis Occipitalis Masseter Sternocleidomastoid Trapezius

© 2012 Pearson Education, Inc. Muscles of Trunk, Shoulder, Arm Anterior muscles Pectoralis major—adducts and flexes the humerus Intercostal muscles External intercostals—raise rib cage during inhalation Internal intercostals—depress the rib cage to move air out of the lungs when you exhale forcibly

© 2012 Pearson Education, Inc. Muscles of Trunk, Shoulder, Arm Muscles of the abdominal girdle Rectus abdominis—flexes vertebral column and compresses abdominal contents (defecation, childbirth, forced breathing) External oblique—flex vertebral column; rotate trunk and bend it laterally Internal oblique—flex vertebral column; rotate trunk and bend it laterally Transversus abdominis—compresses abdominal contents

© 2012 Pearson Education, Inc. Muscles of Trunk, Shoulder, Arm Posterior muscles Trapezius—elevates, depresses, adducts, and stabilizes the scapula Latissimus dorsi—extends and adducts the humerus Erector spinae—back extension Quadratus lumborum—flexes the spine laterally Deltoid—arm abduction

© 2012 Pearson Education, Inc. Muscles of Trunk, Shoulder, Arm Muscles that arise from the shoulder girdle and cross the shoulder joint to insert into the humerus include: Pectoralis major Latissimus dorsi Deltoid PLAY A&P Flix™: Movement at the glenohumeral joint: An overview. PLAY A&P Flix™: Muscles that cross the glenohumeral joint. PLAY A&P Flix™: Muscles of the pectoral girdle. PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview.

© 2012 Pearson Education, Inc. Figure 6.18a Olecranon process of ulna (deep to tendon) Triceps brachii Latissimus dorsi Occipital bone Sternocleidomastoid Trapezius Deltoid (a) Spine of scapula Deltoid (cut) Humerus

© 2012 Pearson Education, Inc. Muscles of the Upper Limb Biceps brachii—supinates forearm, flexes elbow Brachialis—elbow flexion Brachioradialis—weak muscle; elbow flexion Triceps brachii—elbow extension (antagonist to biceps brachii) PLAY A&P Flix™: Movement at the elbow joint. PLAY A&P Flix™: Muscles of the elbow joint. PLAY A&P Flix™: The elbow joint and forearm: An overview.

© 2012 Pearson Education, Inc. Figure 6.18a Olecranon process of ulna (deep to tendon) Triceps brachii Latissimus dorsi Occipital bone Sternocleidomastoid Trapezius Deltoid (a) Spine of scapula Deltoid (cut) Humerus

© 2012 Pearson Education, Inc. Muscles of the Upper Limb Muscles of the forearm, which insert on the hand bones and cause their movement include: Flexor carpi—wrist flexion Flexor digitorum—finger flexion Extensor carpi—wrist extension Extensor digitorum—finger extension PLAY A&P Flix™: Movements of the wrist and fingers (b). PLAY A&P Flix™: Movements of the wrist and fingers (a). PLAY A&P Flix™: Muscles that act on the wrist and fingers: An overview.

© 2012 Pearson Education, Inc. Muscles of the Lower Limb Muscles causing movement at the hip joint include: Gluteus maximus—hip extension Gluteus medius—hip abduction, steadies pelvis when walking Iliopsoas—hip flexion, keeps the upper body from falling backward when standing erect Adductor muscles—adduct the thighs PLAY A&P Flix™: Movement at the hip joint: An overview. PLAY A&P Flix™: Muscles that act on the hip joint and femur: An overview.

© 2012 Pearson Education, Inc. Figure 6.20c 12th rib Iliac crest lliopsoas Psoas major lliacus Anterior superior iliac spine Sartorius Rectus femoris Vastus lateralis Vastus medialis Quadriceps Patellar ligament (c) Patella Adductor group 5th lumbar vertebra 12th thoracic vertebra

© 2012 Pearson Education, Inc. Muscles of the Lower Limb Muscles causing movement at the knee joint Sartorius—flexes the thigh Quadriceps group—extends the knee Rectus femoris Vastus muscles (three) PLAY A&P Flix™: Muscles that cross the knee joint: An overview.

© 2012 Pearson Education, Inc. Figure 6.20c 12th rib Iliac crest lliopsoas Psoas major lliacus Anterior superior iliac spine Sartorius Rectus femoris Vastus lateralis Vastus medialis Quadriceps Patellar ligament (c) Patella Adductor group 5th lumbar vertebra 12th thoracic vertebra

© 2012 Pearson Education, Inc. Muscles of the Lower Limb Muscles causing movement at ankle and foot Tibialis anterior—dorsiflexion, foot inversion Extensor digitorum longus—toe extension and dorsiflexion of the foot Fibularis muscles—plantar flexion, foot eversion Soleus—plantar flexion PLAY A&P Flix™: Movements of the ankle and foot. PLAY A&P Flix™: Posterior muscles that act on the ankle and foot. PLAY A&P Flix™: Muscles that act on the ankle and foot: An overview.

© 2012 Pearson Education, Inc. Figure 6.22 Facial Temporalis Masseter Shoulder Trapezius Deltoid Arm Triceps brachii Biceps brachii Brachialis Forearm Brachioradialis Flexor carpi radialis Pelvis/thigh lliopsoas Thigh (Quadriceps) Rectus femoris Vastus lateralis Vastus medialis Leg Fibularis longus Extensor digitorum longus Tibialis anterior Facial Frontalis Orbicularis oculi Zygomaticus Orbicularis oris Neck Platysma Sternocleidomastoid Thorax Pectoralis minor Pectoralis major Serratus anterior Intercostals Abdomen Rectus abdominis External oblique Internal oblique Transversus abdominis Thigh Sartorius Adductor muscle Gracilis Leg Gastrocnemius Soleus

© 2012 Pearson Education, Inc. Figure 6.23 Arm Triceps brachii Brachialis Forearm Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Extensor carpi ulnaris Extensor digitorum lliotibial tract Leg Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon Neck Occipitalis Sternocleidomastoid Trapezius Shoulder/Back Deltoid Latissimus dorsi Hip Gluteus medius Gluteus maximus Thigh Adductor muscle Hamstrings: Biceps femoris Semitendinosus Semimembranosus

© 2012 Pearson Education, Inc. PowerPoint ® Lecture Slides Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College C H A P T E R 6 The.

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© 2012 Pearson Education, Inc. PowerPoint ® Lecture Slides Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College C H A P T E R 6 The.

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