Lesson 7. MUSCULAR SYSTEM PDF

The Legazpi Thomasian Prayer The Legazpi Thomasian Prayer MUSCULAR SYSTEM  Three basic Muscle types  Three basic Muscle types  Microscopic Anatomy of Skeletal Muscle Sarcolemma—specialized plasma membrane Myofibrils—long organelles inside muscle cell Light (I) bands Dark (A) ba...

The Legazpi Thomasian Prayer The Legazpi Thomasian Prayer MUSCULAR SYSTEM  Three basic Muscle types  Three basic Muscle types  Microscopic Anatomy of Skeletal Muscle Sarcolemma—specialized plasma membrane Myofibrils—long organelles inside muscle cell Light (I) bands Dark (A) bands give the muscle its striated (banded) appearance © 2018 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle © 2018 Pearson Education, Inc. Microscopic Anatomy of Skeletal Muscle Banding pattern of myofibrils I band = light band Contains only thin filaments Z disc is a midline interruption A band = dark band Contains the entire length of the thick filaments H zone is a lighter central area M line is in center of H zone © 2018 Pearson Education, Inc. Figure 6.3c Anatomy of a skeletal muscle fiber (cell). Sarcomere M line Z disc Z disc Thin (actin) myofilament Heads, “cross Thick (myosin) bridges” myofilament Contain ATPase enzymes (c) Sarcomere (segment of a myofibril) Sarcomere—contractile unit of a muscle fiber Structural and functional unit of skeletal muscle © 2018 Pearson Education, Inc. “Sliding Filament Theory”  Sarcoplasmic reticulum (SR) Specialized smooth endoplasmic reticulum Surrounds the myofibril Stores and releases calcium Stimulation and Contraction of Single Skeletal Muscle Cells © 2018 Pearson Education, Inc. How do muscles contract?  Axon terminals at neuromuscular junctions Spinal cord Motor Motor unit 1 unit 2 Skeletal muscles must Nerve be stimulated Motor Axon of motor by a motor neuron neuron cell bodies neuron (nerve cell) to contract Muscle Muscle fibers (a) © 2018 Pearson Education, Inc. The Nerve Stimulus and Action Potential Figure 6.5 Events at the Nerve Myelinated axon of motor neuron ▪ When a nerve impulse neuromuscular reaches the axon terminal of junction. impulse Nucleus Axon terminal of neuromuscular junction Sarcolemma of the motor neuron, the muscle fiber Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion Ca2+ Ca2+ Synaptic cleft Sarcolemma Step 1: Calcium channels open, Fusing synaptic vesicle and calcium ions enter the axon Sarcoplasm ACh of muscle fiber terminal ACh Folds of receptor sarcolemma  Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm ACh of muscle fiber ACh Folds of receptor sarcolemma Step 2: Calcium ion entry causes some synaptic vesicles to release acetylcholine (ACh)  Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm 3 Ca2+ entry causes some ACh of muscle fiber synaptic vesicles to release their Folds of contents (the neurotransmitter ACh receptor sarcolemma acetylcholine) by exocytosis. Step 3: ACh diffuses across the synaptic cleft and attaches to receptors on the sarcolemma of the muscle cell  Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm 3 Ca2+ entry causes some ACh of muscle fiber synaptic vesicles to release their Folds of contents (the neurotransmitter ACh receptor sarcolemma acetylcholine) by exocytosis. 4 Acetylcholine diffuses across the synaptic cleft and binds to receptors in the sarcolemma. Step 4: If enough ACh is released, the sarcolemma becomes temporarily more permeable to sodium ions (Na+) Potassium ions (K+) diffuse out of the cell More sodium ions enter than potassium ions leave Establishes an imbalance in which interior has more positive ions (depolarization), thereby opening more Na+ channels  Ion channel in 5 ACh binds and opens channels Na+ K+ sarcolemma opens; that allow simultaneous passage ions pass. of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ions leave, producing a local change in the electrical conditions of the membrane (depolarization). This eventually leads to an action potential. Step 5: Depolarization opens more sodium channels that allow sodium ions to enter the cell An action potential is created Once begun, the action potential is unstoppable Conducts the electrical impulse from one end of the cell to the other Step 6: Acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and choline AChE ends muscle contraction A single nerve impulse produces only one contraction The Nerve Stimulus and Action Potential © 2018 Pearson Education, Inc.  Myosin Actin Mechanism of Muscle Contraction: The Sliding Filament Theory What causes Z Z H filaments to I A I slide? (a) Relaxed sarcomere Z Z I A I © 2018 Pearson Education, Inc. (b) Fully contracted sarcomere In a relaxed muscle fiber, 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 fiber is excited, calcium ions (Ca2+) are released from intracellular storage areas (the sacs of the sarcoplasmic reticulum). 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 and the myosin heads immediately begin seeking out binding sites. The free myosin heads are “cocked,” much like an oar ready to be pulled on for rowing. Myosin attachment to actin causes the myosin heads to snap (pivot) toward the center of the sarcomere in a rowing motion. When this happens, the thin filaments are slightly pulled toward the center of the sarcomere ATP provides the energy needed to release and recock each myosin head so that it is ready to attach to a binding site farther along the thin filament. The free myosin heads are “cocked,” much like an oar ready to be pulled on for rowing. Myosin attachment to actin causes the myosin heads to snap (pivot) toward the center of the sarcomere in a rowing motion. When this happens, the thin filaments are slightly pulled toward the center of the sarcomere (see c). ATP provides the energy needed to release and recock each myosin head so that it is ready to attach to a binding site farther along the thin filament. How does the power stroke created? Contraction of a Skeletal Muscle as a Whole Graded responses Muscle fiber contraction is “all-or-none,” meaning it will contract to its fullest when stimulated adequately Within a whole 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 By changing the frequency of muscle stimulation By changing the number©of muscle cells being stimulated at one time 2018 Pearson Education, Inc. Contraction of a Skeletal Muscle as a Whole Muscle response to increasingly rapid stimulation Muscle twitch Single, brief, jerky contraction Not a normal muscle function Tension (g) (Stimuli) © 2018 Pearson Education, Inc. (a) Twitch Contraction of a Skeletal Muscle as a Whole In most types of muscle activity, nerve impulses are delivered at a rapid rate As a result, contractions are “summed” (added) together, and one contraction is immediately followed by another © 2018 Pearson Education, Inc. Contraction of a Skeletal Muscle as a Whole When stimulations become more frequent, muscle contractions get stronger and smoother The muscle now exhibits unfused (incomplete) tetanus © 2018 Pearson Education, Inc. Contraction of a Skeletal Muscle as a Whole Muscle response to increasingly rapid stimulation (continued) Fused (complete) tetanus is achieved when the muscle is stimulated so rapidly that no evidence of relaxation is seen Contractions are smooth and sustained © 2018 Pearson Education, Inc. Providing Energy for Muscle Contraction ATP Only energy source that can be used to directly power muscle contraction Stored in muscle fibers in small amounts that are quickly used up After this initial time, other pathways must be utilized to produce ATP ▪ Three pathways to regenerate ATP 1. Direct phosphorylation of ADP by creatine phosphate 2. Aerobic pathway 3. Anaerobic glycolysis and lactic acid formation © 2018 Pearson Education, Inc.  (a) Direct phosphorylation Direct phosphorylation of Coupled reaction of creatine phosphate (CP) and ADP ADP by creatine phosphate Energy source: CP (CP)—fastest – Muscle cells store CP, a high-energy molecule P Creatine ADP – After ATP is depleted, ADP remains Creatine ATP – CP transfers a phosphate group to ADP to regenerate ATP – CP supplies are exhausted in less than 15 seconds Oxygen use: None Products: 1 ATP per CP, – 1 ATP is produced per CP creatine molecule Duration of energy provision: 15 seconds © 2018 Pearson Education, Inc.  (c) Anaerobic pathway Anaerobic glycolysis and lactic acid Glycolysis and lactic acid formation formation Energy source: glucose – Reaction that breaks down glucose without oxygen Glucose (from – Glucose is broken down to pyruvic glycogen breakdown or delivered from blood) acid to produce about 2 ATP Glycolysis – Pyruvic acid is converted to lactic in cytosol acid, which causes muscle soreness 2 ATP Pyruvic acid net gain – This reaction is not as efficient, but it Released Lactic acid to blood is fast Oxygen use: None – Huge amounts of glucose are Products: 2 ATP per glucose, needed lactic acid Duration of energy provision: 40 seconds, or slightly more © 2018 Pearson Education, Inc.  (b) Aerobic pathway Aerobic respiration Aerobic cellular respiration – Supplies ATP at rest and Energy source: glucose; pyruvic acid; free fatty acids from adipose during light/moderate exercise tissue; amino acids from protein catabolism – A series of metabolic Glucose (from pathways, called oxidative glycogen breakdown or delivered from blood) phosphorylation, use oxygen and occur in the mitochondria Pyruvic acid Fatty – Glucose is broken down to acids Aerobic respiration O2 Amino in mitochondria carbon dioxide and water, acids releasing energy (about 32 CO2 32 ATP ATP) H2O net gain per – This is a slower reaction that Oxygen use: Required glucose Products: 32 ATP per glucose, requires continuous delivery of CO2, H2O Duration of energy provision: oxygen and nutrients Hours © 2018 Pearson Education, Inc. Muscle Fatigue and Oxygen Deficit If muscle activity is strenuous and prolonged, muscle fatigue occurs Suspected factors that contribute to muscle fatigue include: Ion imbalances (Ca2+, K+) Oxygen deficit and lactic acid accumulation Decrease in energy (ATP) supply After exercise, the oxygen deficit is repaid by rapid, deep breathing © 2018 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; lifting weights, smiling Isometric contractions Muscle filaments are trying to slide, but the muscle is pitted against an immovable object Tension increases, but muscles do not shorten Example: pushing your palms together in front of you © 2018 Pearson Education, Inc.  Types of Body Movements ▪ Flexion ▪ Decreases the angle of the joint ▪ Brings two bones closer together ▪ Typical of bending hinge joints (e.g., knee and elbow) or ball-and-socket joints (e.g., the hip) ▪ Extension ▪ Opposite of flexion ▪ Increases angle between two bones ▪ Typical of straightening the elbow or knee ▪ Extension beyond 180º is hyperextension © 2018 Pearson Education, Inc. Figure 6.13a Body movements. Flexion Hyperextension Extension Flexion Extension (a) Flexion, extension, and hyperextension of the shoulder and knee © 2018 Pearson Education, Inc.  Figure 6.13b Body movements. Extension Hyperextension Flexion © 2018 Pearson Education, Inc. (b) Flexion, extension, and hyperextension  Types of Body Movements ▪ Rotation ▪ Movement of a bone around its longitudinal axis ▪ Common in ball-and-socket joints ▪ Example: moving the atlas around the dens of axis (i.e., shaking your head “no”) © 2018 Pearson Education, Inc.  Types of Body Movements ▪ Abduction ▪ Movement of a limb away from the midline ▪ Adduction ▪ Opposite of abduction ▪ Movement of a limb toward the midline ▪ Circumduction ▪ Combination of flexion, extension, abduction, and adduction ▪ Common in ball-and-socket joints ▪ Proximal end of bone is stationary, and distal end moves in a circle © 2018 Pearson Education, Inc.  Special Movements ▪ Dorsiflexion ▪ Lifting the foot so that the superior surface approaches the shin (toward the dorsum) ▪ Plantar flexion ▪ Pointing the toes away from the head © 2018 Pearson Education, Inc.  Special Movements ▪ Inversion ▪ Turning sole of foot medially ▪ Eversion ▪ Turning sole of foot laterally © 2018 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 © 2018 Pearson Education, Inc.  Special Movements ▪ Opposition ▪ Moving the thumb to touch the tips of other fingers on the same hand © 2018 Pearson Education, Inc.  Interactions of Skeletal Muscles in the Body ▪ Muscles can only pull as they contract—not push ▪ In general, groups of muscles that produce opposite actions lie on opposite sides of a joint ▪ 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 or reduces undesirable movements ▪ Fixator—specialized synergists that hold a bone still or stabilize the origin of a prime mover © 2018 Pearson Education, Inc. Figure 6.17a Clavicle Muscles of the anterior trunk, shoulder, and Deltoid arm. Sternum Pectoralis major Biceps brachii Brachialis Brachio- radialis Naming Skeletal Muscles 1 – Location of the muscle 2 – Shape of the muscle 3 – Size of the muscle 4 – Direction/Orientation of the muscle fibers/cells 5 – Number of Origins 6 – Location of the Attachments 7 – Action of the muscle  Muscles Named by Location File:Tibialis anterior 2.png Location: ⚫ frontalis – frontal bone ⚫ lateralis – lateral or on the side ⚫ tibialis anterior – front of tibia ⚫ fibularis longus – near fibula ⚫ supra – above ⚫ infra – below ⚫ sub - underneath  Muscles Named by Shape 27c99b70a004090a7f651481df1f6c55d3509402e7d266915fe674f09f0bdd382ba4de7b98caab0cfd38734f935c797c13fda2193a9f0859d1f33b391cce133c14d8bce8d6b00d856c3f1d3122a93e0f5bbaf91508ae9e7f231434b2ebcb8a36d1c7fd8de4fb7b3a15120 Shape: ⚫ deltoid – triangle ⚫ Latissimus – wide ⚫ teres - round ⚫ trapezius – trapezoid ⚫ serratus –saw-toothe ⚫ orbicularis – circular  Muscles Named by Size File:Pectoralis major he.png Size: ⚫ maximus – largest ⚫ minimis – smallest ⚫ vastus - huge ⚫ longus – longest ⚫ brevis – short ⚫ major – large ⚫ minor – small Example: Pectoralis Major  Muscles Named by Direction of Fibers Direction/Orientation: File:Rectus abdominis.png ⚫ rectus (straight) - parallel to the muscle’s long axis ex: rectus abdominis ⚫ transversus (transverse) – at right angles to the muscle’s long axis ⚫ oblique – diagonal Muscles Named for Number of Origins Number of Origins: ⚫ biceps – two origins ex: biceps brachii ⚫ triceps – three origins ex: triceps brachii ⚫ quadriceps – four origins  Muscles Named for Origin and Insertion Points Origin and Insertion: sterno = sternum cleiodo = clavicle mastoid = location on the temporal bone sternocleiodomastoid muscle Muscles Named for Action Action: ⚫ flexor carpi radialis – flexes wrist ⚫ abductor magnus – abducts the thigh ⚫ extensor digitorum – extends the fingers ⚫ levator – lifts a structure Figure 6.15 Relationship of fascicle arrangement to muscle structure. (a) (b) (e) (c) (a) Circular (b) Convergent (e) Multipennate (orbicularis oris) (pectoralis major) (deltoid) (d) (f) (f) Bipennate (g) (rectus femoris) (c) Fusiform (d) Parallel (g) Unipennate (biceps brachii) (sartorius) (extensor digitorum longus) © 2018 Pearson Education, Inc.  Figure 6.19 The fleshy deltoid muscle is a favored site for administering intramuscular injections. Deltoid muscle Humerus © 2018 Pearson Education, Inc. Figure 6.20d Pelvic, hip, and thigh muscles of the right side of the body. Inguinal ligament Adductor muscles Sartorius Vastus lateralis (d) © 2018 Pearson Education, Inc. Figure 6.20 Pelvic, hip, and thigh Posterior superior iliac spine muscles of the right side of the body. Iliac crest Gluteus medius Gluteus maximus Safe area in gluteus medius Gluteus maximus Adductor magnus Sciatic nerve Iliotibial tract (b) Biceps femoris Semitendinosus Hamstring group Semimembranosus Gastrocnemius (a) © 2018 Pearson Education, Inc.  Developmental Aspects of the Muscular System ▪ Increasing muscular control reflects the maturation of the nervous system ▪ Muscle control is achieved in a superior/inferior and proximal/distal direction ▪ To remain healthy, muscles must be exercised regularly ▪ Without exercise, muscles atrophy ▪ With extremely vigorous exercise, muscles hypertrophy ▪ As we age, muscle mass decreases, and muscles become more sinewy ▪ Exercise helps retain muscle mass and strength © 2018 Pearson Education, Inc. Figure 6.16a Superficial muscles of the head and neck. Figure 6.16b Superficial muscles of the head and neck. Cranial Frontalis aponeurosis Temporalis Orbicularis oculi Occipitalis Zygomaticus Buccinator Masseter Orbicularis oris Sternocleidomastoid Trapezius Platysma Posterior muscles of the neck. Figure 6.17a Clavicle Muscles of the anterior trunk, shoulder, and Deltoid arm. Sternum Pectoralis major Biceps brachii Brachialis Brachio- radialis Figure 6.19 The fleshy deltoid muscle is a favored site for administering intramuscular injections. Deltoid muscle Humerus © 2018 Pearson Education, Inc. Figure 6.17b Muscles of the anterior trunk, shoulder, and arm. Pectoralis Serratus major anterior Rectus abdominis Transversus abdominis Internal oblique External oblique Aponeurosis  Occipital bone Figure 6.18a Sternocleidomastoid Muscles of Spine of scapula Trapezius the posterior Deltoid (cut) neck, trunk, Deltoid and arm. Triceps brachii Latissimus dorsi Humerus Olecranon process of (a) ulna (deep to tendon)  Occipital bone Figure Sternocleidomastoid 6.18a Spine of scapula Muscles of Trapezius Deltoid (cut) the Deltoid posterior neck, trunk, and arm. Triceps brachii Latissimus dorsi Humerus Olecranon process of ulna (deep to tendon)  12th Figure 6.20c Pelvic, 12th rib thoracic vertebra hip, and thigh muscles of the right Iliac crest side of the body. Iliopsoas Psoas major Iliacus 5th lumbar vertebra Anterior superior iliac spine Tensor Fasciae Latae Sartorius Adductor group Rectus femoris Quadriceps* Vastus lateralis Vastus medialis Patella Patellar ligament (c) © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 6.20d Pelvic, hip, and thigh muscles of the right side of the body. Inguinal ligament Adductor muscles Sartorius Vastus lateralis (d) © 2018 Pearson Education, Inc. Figure 6.21a Superficial muscles of the right leg. Fibularis longus Tibia Fibularis brevis Soleus Tibialis anterior Extensor digitorum longus Fibularis tertius (a) © 2018 Pearson Education, Inc.  Figure 6.20 Pelvic, hip, and thigh muscles of Posterior superior iliac spine the right side of the body. Iliac crest Gluteus medius Gluteus maximus Safe area in gluteus medius Gluteus maximus Adductor magnus Sciatic nerve Iliotibial tract (b) Biceps femoris Semitendinosus Hamstring group Semimembranosus Gastrocnemius (a) © 2018 Pearson Education, Inc. Muscles of the Lower Leg Superficial Muscles: Anterior Superficial Muscles: Posterior Figure 6.22  Facial Major superficial Facial Frontalis Orbicularis oculi muscles of the Temporalis Masseter Zygomaticus Orbicularis oris anterior surface of the Shoulder Trapezius Neck Platysma Sternocleidomastoid body. Deltoid Thorax Pectoralis minor Pectoralis major Arm Serratus anterior Triceps brachii Biceps brachii Intercostals Brachialis Abdomen Rectus abdominis Forearm External oblique Brachioradialis Internal oblique Flexor carpi radialis Transversus abdominis Pelvis/thigh Iliopsoas Thigh Sartorius Adductor muscles Thigh (Quadriceps) Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius (not shown, deep to rectus femoris) Leg Fibularis longus Extensor digitorum longus Leg Gastrocnemius Tibialis anterior Soleus © 2018 Pearson Education, Inc. Major superficial Neck Occipitalis muscles of the Sternocleidomastoid Trapezius posterior surface of Shoulder/Back Deltoid the body. Arm Triceps brachii Brachialis Forearm Latissimus dorsi Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Hip Extensor carpi ulnaris Gluteus medius Extensor digitorum Gluteus maximus Thigh Iliotibial tract Adductor muscle Hamstrings: Biceps femoris Semitendinosus Semimembranosus Leg Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon © 2018 Pearson Education, Inc.