Muscular System Vocabulary

Muscular System Vocabulary
Aer – air; aerobic An – not; anaerobic Bi – two; biceps Caput – head Di – two Ergon – work; synergist Fasciculus - a bundle; fascicle Gaster – stomach Iso – equal; isometric Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Kneme – knee Lemma – husk; sarcolemma Metron – measure; isometric Mys – muscle; epimysium Platys – flat; platysma Sarkos – flesh; sarcoma Syn - together; synergist Tetanos – convulsive tension; tetnus

Tonos – tension; isotonic Trope – a turning; tropomyosin -trophy – nourishing; atrophy

What do YOU know about the muscular system?

Overview of Muscular System
Types of Muscle Tissue Skeletal - Under voluntary control * muscular system Cardiac - Under involuntary control * heart wall Smooth - Under involuntary control * visceral organs Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Skeletal Muscles Skeletal muscles attach to bones directly or indirectly Perform five functions Produce movement of skeleton – contractions pull on tendons to produce movement Maintain posture and body position – continuous muscle contractions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Skeletal Muscles 3. Support soft tissues
4. Guard entrances and exits – encircle openings to the digestive and urinary tracts 5. Maintain body temperature – heat released by energy produced during contractions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles
Gross Anatomy: Connective tissue organization Three Layers Epimysium Fibrous covering of whole muscle Separates the muscle from surrounding tissue Perimysium Fibrous covering of fascicle (bundle) Contains blood vessels and nerve cells Endomysium Fibrous covering of a single cell (a muscle fiber) Contains stem cell Tendons (or aponeurosis) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Organization of a Skeletal Muscle Figure 7-1

Microanatomy of a Muscle Fiber Much fiber different than a “typical” cell can be very long (60 cm or 24”) / equal to the entire length of that specific muscle multinucleated (can have hundreds of nuclei)

The Organization of a Single Muscle Fiber Figure 7-2(a)

Microanatomy of a Muscle Fiber Transverse tubules (T tubules) narrow tubes filled w/extracellular fluid which form a passageway through a muscle fiber Myofibrils (contraction organelle) cylindrical structures encircled by T-tubules hundreds to thousands Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Microanatomy of a Muscle Fiber Sarcolemma Muscle cell membrane surrounding the cytoplasm Sarcoplasm Muscle cell cytoplasm Sarcoplasmic reticulum (SR) Like smooth ER Contains high concentration of Ca+ ions which are actively pumped in Contraction begins when Ca+ is released into the sarcoplasm

Sarcomere — Repeating structural unit of the myofibril Are responsible for muscle contraction by shortening the entire cell Components of a sarcomere Myofilaments made of the proteins actin & myosin arranged in thin and thick bands Thin filaments (actin with an active site capable of interacting w/ myosin) Thick filaments (myosin)

Anatomy of the Muscular System
An Overview of the Major Skeletal Muscles Figure 7-11(a)

An Overview of the Major Skeletal Muscles Figure 7-11(b)

Origins, Insertions, and Actions Origin Muscle attachment that remains fixed Insertion Muscle attachment that moves Action What joint movement a muscle produces Almost all skeletal muscle either originate or insert on the skeleton (where it begins) (where it ends) (what it does) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Primary Action Categories – Muscles in Action! Agonist (Prime mover) Main muscle whose contraction produces a movement in an action Antagonist Opposed muscle to a muscle in action Synergist Helper muscle to a muscle in action

Muscle Terminology Names of muscles provide clues to location, orientation, or action Axial musculature—Muscles with origins on the axial skeleton that position and Appendicular musculature—Muscles that stabilize move head, spine, rib cage or move appendicular components Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Axial Muscles of the Trunk Thoracic region External intercostals Origin - inferior border of rib Insertion - on superior border of next rib elevates ribs Internal intercostals Origin - superior border of each rib Insertion - inferior border of preceding rib Depresses the ribs Diaphragm separates the thoracic cavity from the abdominal cavity Important in (costal = ribs) respiration Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Abdominal region Rectus abdominis depresses ribs and flexes vertebral column External oblique compresses abdomen, depresses ribs, flexes or laterally vertebral column Internal oblique Transversus abdominis Compresses abdomen (rectus= straight, parallel) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Oblique and Rectus Muscles and the Diaphragm Figure 7-15(a)

Oblique and Rectus Muscles and the Diaphragm Figure 7-15(b)

Oblique and Rectus Muscles and the Diaphragm Figure 7-15(c)

Selected Muscles of the Head Frontalis Raises eyebrows, wrinkles forehead Orbicularis oris Compresses lips Buccinator Compresses cheeks Masseter Elevates mandible Temporalis Pterygoids Elevate, protract, and/or move mandible side to side

Muscles of the Head and Neck Figure 7-12(a)

Muscles of the Head and Neck Figure 7-12(b)

Muscles of the Head and Neck Figure 7-12(c)

Selected Muscles of the Neck Platysma Origin - from cartilage on 2nd rib to scapula Tenses neck of skin and depress mandible Digastric Depresses mandible and/or elevates larynx Mylohyoid Elevates floor of mouth and hyoid, and/or depresses mandible Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Stylohyoid Elevates the larynx Sternocleidmastoid Lets break it down! sterno = sternum cleido = clavicle mastos = breast oid = breast-like Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Sternocleidmastoid Based on the definition where might it originate and insert origin = superior margins of sternum and clavicle insertion = mastoid region of the skull Both sides together flex the neck; alone one side bends the head towards the shoulder and turns the face to the opposite side Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles of the Anterior Neck Figure 7-13

Selected Muscles of the Spine Splenius capitis Two sides work together to extend the neck: either alone rotates and laterally flexes head to that side Semispinalis capitis Two sides work together to extend the neck: either alone rotates and laterally flexes head to that side Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Selected Muscles of the Spine Erector spinae groups Spinalis group Two sides work together to extend vertebral column; either alone extend neck and laterally flexes head or vertebral column to that side Longissimus group Two sides work together to extend vertebral column; either alone rotates laterally flexes head or vertebral column to that side Iliocostalis group Extends vertebral column or laterally to that side: moves ribs (Spinal Extensors) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Selected Muscles of the Spine Quadratus lumborum Together they depress ribs, flex vertebral column; one side acting alone produces lateral flexion Spinal Flexor Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles of the Spine Figure 7-14

The Appendicular Muscles Two functionally distinct groups Muscles of the shoulder and upper limbs Muscles of the pelvic girdle and lower limbs Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Selected Shoulder Muscles Trapezius Origin = occipital bone and spinous processes of thoracic vertebrae Insertion = clavicle and scapula Action = depends on active region May elevate, adduct, depress, or rotate scapula and/or elevate clavicle Can also hyperextend neck Rhomboid Action = Adducts and laterally rotates scapula (downward) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Selected Shoulder Muscles Levator scapulae Action = elevates scapula Serratus anterior Origin = anterior and superior margins of ribs 1-9 Action = Protracts shoulder, abducts and medially rotates scapula (upward) Pectoralis minor Origin = anterior of ribs 3-5 Action = Depresses and protracts shoulder, rotates scapula laterally (downward); elevates ribs if scapula is stationary Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles of the Shoulder Figure 7-17(a)

Muscles of the Shoulder Figure 7-17(b)

Muscles the Move the Arm Deltoid Origin = clavicle and scapula Insertion = humerus Action = abducts the shoulder Supraspinatus (rotator cuff muscle) Origin = scapula Subscapularis (rotator cuff muscle) Action = medial rotation of the shoulder Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Teres major Origin = scapula Insertion = humerus Action = adduction and medial rotation of the shoulder Infraspinatus (rotator cuff muscle) Action = medial rotation of the shoulder Teres minor (rotator cuff muscle) Action = lateral rotation of the shoulder as Benjamin Cummings

Pectoralis major Origin = cartilage of ribs 2-6, body of the sternum, and clavicle Insertion = humerus Action = abducts the shoulder Latissimus dorsi Origin = spinous process of lower thoracic vertebrae, ribs, & lumbar vertebrae Action = flexion, adduction, and medial rotation of the shoulder Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles that Move the Arm Figure 7-18(a)

Muscles that Move the Arm Figure 7-18(b)

Muscles That Move the Forearm - flexors Biceps brachii Origin = scapula Insertion = radius Action = flexion at shoulder and elbow, supination Brachialis Origin = anterior, distal surface of humerus Insertion = ulna Action = flexion at elbow Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Forearm - extensors Triceps brachii Origin = humerus at the scapula Insertion = ulna Action = extension at elbow Pronators Origin = ulna Insertion = humerus Action = pronation Supinator Origin = scapula Action = supination Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Forearm and Wrist Figure 7-19

Muscles That Move the Wrist Wrist flexors Flexor carpi ulnaris Flexor carpi radialis Palmaris longus Wrist extensors Extensor carpi radialis Extensor carpi ulnaris Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Forearm and Wrist Figure 7-19

Muscles That Move the Thigh Gluteal muscles Action: generally move the hip (extend, lateral and medial rotation as well as abduction and flexion) Thigh adductors Adductor magnus Adductor brevis Adductor longus Thigh flexors Iliopsoas (psoas major + iliacus) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Thigh Figure 7-20(a)

Muscles That Move the Thigh Figure 7-20(b)

Flexors of the Knee 1. Biceps femoris (hamstring muscle) Insertion = tibia Action = flexion at knee, extension and lateral rotation of the hip 2. Semimembranosus (hamstring muscle) 3. Semitendinosus (hamstring muscle) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Extensors of the Knee Quadriceps femoris group 1. Rectus femoris 2. Vastus lateralis 3. Vastus intermedius 4. Vastus medialis All insert into the tibial tuberosity by way of patellar ligament Action: extension at knee (all) Rectus femoris also has flexion at hip Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Leg Figure 7-21

Muscles That Move the Foot Plantar flexion Soleus Gastrocnemius Eversion and plantar flexion Fibularis Dorsiflexion Tibialis anterior Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles That Move the Foot and Toes Figure 7-22(a)

Muscles That Move the Foot and Toes Figure 7-22(b)

Muscles That Move the Foot and Toes Figure 7-22(c)

Muscles That Move the Foot and Toes Figure 7-22(d)

Aging and the Muscular System
Age-Related Reductions Muscle size: fibers become smaller in diameter With the cardiac muscle becoming smaller blood flow to active muscle does not increase as rapidly with exercise Muscle elasticity: develop more fibrous connective tissue making muscle less flexible Muscle strength: decreases Exercise tolerance: decreases in part to reduced thermoregulatory ability Injury recovery ability : repair is limited and scar tissue usually forms Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Sliding Filaments and Cross Bridges
Sliding Filaments: where Sarcomeres Contract Z Line – made of proteins Boundaries of each sarcomere Zone of overlap Move closer together during contraction M Line - made of proteins Connect thick filaments to its neighbors A Band Area containing thick filaments I Band Light region between two successive A bands Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Sliding Filaments and Cross Bridges
Cross Bridges – myosin heads which connect thick and thin filaments When a cross bridge binds to an active site it pivots (moves) towards the center of the sarcomere pulling thin filaments in that direction After it pivots it returns to its original position It can then repeats the cycle of: attach, pivot, detach, and return (like a person pulling a rope one –handed) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Organization of a Single Muscle Fiber Figure 7-2(b)

The Organization of a Single Muscle Fiber Figure 7-2(cde)

Changes in the Appearance of a Sarcomere During Contraction of a Skeletal Muscle Fiber Figure 7-3 (1 of 2)

Changes in the Appearance of a Sarcomere During Contraction of a Skeletal Muscle Fiber

The Organization of a Single Muscle Fiber Figure 7-2(a)

Control of Muscle Contraction
Steps in Neuromuscular Transmission Motor neuron (nerve cell) with action potential Fine branches with expanded ends called synaptic terminals Acetylcholine (ACh): neurotransmitter Triggers muscle contraction Action potential: electrical impulse in sarcolemma T tubule action potential Calcium release from SR

The Structure and Function of the Neuromuscular Junction

Action potential Axon Synaptic terminal Sarcolemma Vesicles ACh
Arrival of an action potential at the synaptic terminal Axon Arriving action potential Synaptic terminal Sarcolemma Vesicles ACh Synaptic cleft AChE molecules ACh receptor site Muscle fiber Sarcolemma of motor end plate ACh binding at the motor and plate Appearance of an action potential in the sarcolemma Release of acetylcholine Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft. The binding of ACh to the receptors increases the membrane permeability to sodium ions. Sodium ions then rush into the cell. An action potential spreads across the surface of the sarcolemma. While this occurs, AChE removes the ACh. Action potential Na+ Na+ Na+ Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Contraction Process Actin active sites and myosin interact Thin filaments slide past thick filaments Cross-bridges undergo a cycle of movement Attach, pivot, detach, return Troponin-tropomyosin (proteins) control interaction Prevent interaction at rest cross-bridges Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Resting sarcomere Figure 7-5 2 of 7 Myosin head Troponin Tropomyosin
ADP Myosin head + P Troponin Tropomyosin Actin ADP P + Figure 7-5 2 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Resting sarcomere Active-site exposure Figure 7-5 3 of 7 Myosin head
ADP Myosin head ADP + P + Sarcoplasm P Troponin Ca2+ Ca2+ Tropomyosin Actin Active site ADP ADP P + P + Figure 7-5 3 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Cross-bridge formation
Resting sarcomere Active-site exposure Cross-bridge formation ADP Myosin head ADP + P + Sarcoplasm P Troponin ADP + P Ca2+ Ca2+ Ca2+ ADP Ca2+ Tropomyosin Actin Active site P + ADP ADP P + P + Figure 7-5 4 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Resting sarcomere Active-site exposure Cross-bridge formation ADP Myosin head ADP + + Sarcoplasm P P Troponin ADP + P Ca2+ Ca2+ Ca2+ ADP Tropomyosin Actin Active site Ca2+ ADP ADP P + P + P + Pivoting of myosin head ADP + P Ca2+ Ca2+ ADP + P Figure 7-5 5 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Resting sarcomere Active-site exposure Cross-bridge formation ADP Myosin head ADP + P + Sarcoplasm P Troponin ADP + P Ca2+ Ca2+ Ca2+ ADP Tropomyosin Actin Active site Ca2+ P + ADP ADP P + P + Cross bridge detachment Pivoting of myosin head ATP ADP + P Ca2+ Ca2+ Ca2+ Ca2+ ATP ADP + P Figure 7-5 6 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Resting sarcomere Active-site exposure Cross-bridge formation ADP Myosin head ADP + Sarcoplasm P + P Troponin ADP + P Ca2+ Ca2+ Ca2+ ADP Active site Ca2+ Tropomyosin Actin + ADP ADP P P + P + Myosin reactivation Cross bridge detachment Pivoting of myosin head ADP ATP ADP + P + P Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ ADP P + ATP ADP + P Figure 7-5 7 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Summary of Contraction Process Table 7-1

Key Note Skeletal muscle fibers shorten as thin filaments interact with thick filaments and sliding occurs. The trigger for contraction is the calcium ions released by the SR when the muscle fiber is stimulated by its motor neuron. Contraction is an active process; relaxation and the return to resting length is entirely passive. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Mechanics Some Basic Muscle Definitions
Muscle tension—The pulling force on the tendons that muscle cells generate when contracting Muscle twitch—A brief contraction-relaxation response to a single action potential Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Twitch and Development of Tension
Muscle Mechanics The Twitch and Development of Tension Figure 7-6

Muscle Mechanics Motor Units
Motor Unit —A motor neuron and all the muscle cells it controls Recruitment—To increase muscle tension by activating more motor units Small motor units provide finer control Motor units are intermixed in the muscle to pull evenly on the tendon Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Mechanics Motor Units Figure 7-8

Muscle Mechanics Key Note
All voluntary (intentional) movements involve the sustained contractions of skeletal muscle fibers organized into distinct motor units. The force generated can be increased by increasing the frequency of action potentials or by recruiting additional motor units. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Mechanics Muscle tone —Tension in a “resting” muscle produced by a low level of spontaneous motor neuron activity. Function of muscle tone Stabilizes bones, joints Prevents atrophy (muscle wasting) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Mechanics Types of Contractions Isotonic contraction
The tension (load) on a muscle stays constant (iso = same, tonic = tension) during a movement. (Example: lifting a baby) Isometric contraction The length of a muscle stays constant (iso = same, metric = length) during a “contraction” (Example: holding a baby at arms length) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Mechanics Muscle Elongation Muscle contract actively
Muscles can only pull Muscles never push Muscle elongates passively Elastic forces Contraction of opposing muscles Effects of gravity Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Energetics of Muscle Contraction
ATP and Creatine Phosphate Reserves Muscle contraction consumes much ATP ATP transfers energy directly to cycling cross-bridges and calcium pumping CP stores energy and regenerates ATP CP transfers its energy to ADP Creatine phosphokinase (CPK) catalyzes ADP (2 “P”s) becomes ATP(3 “P”s) CP levels greatly exceed ATP levels Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

ATP Generation Light activity Aerobic metabolism of fatty acids Storage of glucose as glycogen Moderate activity Breakdown of glycogen to glucose Glycolysis of glucose Peak activity Anerobic breakdown of glucose Production of lactic acid Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Fatigue—When a muscle loses ability to contract due to a low pH (lactic acid buildup), low ATP levels, or other problems Recovery Period—Time after muscle activity that it takes to restore pre-exertion conditions Oxygen Debt—Amount of excess oxygen used during the recovery period Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Key Note Skeletal muscles at rest metabolize fatty acids and store glycogen. During light activity, muscles can generate ATP through the aerobic breakdown of carbohydrates, lipids, or amino acids. At peak levels of activity, most of the energy is provided by anaerobic reactions that generate lactic acid. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Performance Two Types of Skeletal Muscle Fibers
Fast fibers: Large diameter, abundant myofibrils, ample glycogen, scant mitochondria. Produce powerful, brief contractions Slow fibers : Smaller diameter, rich capillary supply, many mitochondria, much myoglobin. Produce slow, steady contractions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Performance Physical Conditioning Anaerobic endurance
Time over which a muscle can contract effectively under anerobic conditions. Hypertrophy Increase in muscle bulk. Can result from anerobic training. Aerobic endurance Time over which a muscle can contract supported by mitochondria. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Performance Key Note
What you don’t use, you lose. When motor units are inactive for days or weeks, muscle fibers break down their contractile proteins and grow smaller and weaker. If inactive for long periods, muscle fibers may be replaced by fibrous tissue. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Cardiac and Smooth Muscle
Cardiac Muscle Tissue Small cells Single nucleus/cell Aerobic metabolism Intercalated discs – double membrane between cells that aids adjacent cell communication Long contraction time Self-exciting (automaticity) No tetanic contraction Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Cardiac Muscle Tissue Figure 7-10(a)

Smooth Muscle Tissue Nonstriated cells (no sarcomeres) Calcium control of contraction different from striated muscle Wide range of operating lengths Involuntary muscle Under hormonal or local control Pacesetter cells Motor neurons often unneeded Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Smooth Muscle Tissue Figure 7-10(b)

Muscular System Vocabulary

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