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Muscular System
Stucy Stack for Quiz
| Term | Definition |
|---|---|
| skeletal Muscle | • Attached to the bones • Striated • Voluntary actions |
| cardiac Muscle | Walls of the heart • Striated with the presence of intercalated discs • Involuntary actions |
| Smooth Muscle | Hollow organs • No striations • Involuntary actions |
| 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 |
| Structural Levels | Sarcolemma Myofibrils Sarcomere Myofilaments Thick filaments Thin filaments |
| Sarcolemma | many oval nuclei, specialized plasma membrane |
| Myofibrils | long organelles inside muscle cell |
| Sarcomere | contractile unit of a muscle fiber |
| Myofilaments | produce banding (striped) pattern |
| Thick filaments | myosin filaments |
| Thin filaments | actin filaments (contractile protein) |
| Myofibril or fibril | complex organelles composed of bundles of myofilaments |
| Sarcoplasmic reticulum (SR) | Specialized smooth endoplasmic reticulum • Surrounds the myofibril • Stores and releases calcium |
| Special functional properties of skeletal muscles | Irritability Contractility Extensibility Elasticity |
| Irritability | (also called responsiveness) ability to receive and respond to a stimulus |
| Contractility | ability to forcibly 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 |
| motor neuron (nerve cell) | Skeletal muscles must be stimulated by a (blank) to contract = nerve impulses |
| Neuromuscular junction | Association site of axon terminal of the motor neuron and sarcolemma of a muscle |
| Neurotransmitter | Chemical released by nerve upon arrival of nerve impulse in the axon terminal |
| Acetylcholine (ACh) | is the neurotransmitter that stimulates skeletal muscle |
| Synaptic cleft | Gap between nerve and muscle filled with interstitial fluid Although very close, the nerve and muscle do not make contact |
| Acetylcholinesterase (AChE) breaks down acetylcholine into acetic | acid and choline |
| AChE | ends muscle contraction |
| (AChE) breaks down acetylcholine into acetic acid and choline | Acetylcholinesterase |
| Calcium ions (Ca2+) bind regulatory proteins on thin filaments and expose myosin-binding sites, allowing the myosin heads on the thick filaments to attach | What causes filaments to slide? |
| Each cross bridge pivots, causing the thin filaments to slide toward the center of the sarcomere | What causes filaments to slide? |
| Contraction occurs, and the cell shortens During a contraction, a cross bridge attaches and detaches several times ATP provides the energy for the sliding process, which continues as long as calcium ions are present | What causes filaments to slide? |
| Graded Responses | Different degrees of skeletal muscle shortening can be produced in two ways • By changing the frequency of muscle stimulation • By changing the number of muscle cells being stimulated at one time |
| Adenosine Triphosphate (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 |
| Direct phosphorylation of ADP by creatine phosphate Aerobic pathway Anaerobic glycolysis and lactic acid formation | 3 pathways to regenerate ATP |
| Muscle Fatigue | Ion imbalances (Ca2+, K+) • Oxygen deficit and lactic acid accumulation • Decrease in energy (ATP) supply |
| Isotonic contractions | Myofilaments are able to slide past each other during contractions • The muscle shortens, and movement occurs |
| Isometric contractions | Muscle filaments are trying to slide, but the muscle is pitted against an immovable object • Tension increases, but muscles do not shorten |
| Functional Groups | Prime mover (agonist) Antagonist Synergist Fixator |
| Prime mover (agonist) | Major responsibility for producing specific movement |
| Antagonist | • Opposes or reverses particular movement |
| Synergist | • helps prime movers • Adds extra force to same movement |
| Fixator | • Synergist that immobilizes bone or muscle’s origin • Gives prime mover stable base on which to act |
| Muscle location Muscle size Direction of muscle fibers or fascicles Combined Muscle shape Number of origins Muscle action Location of attachments | NAMING SKELETAL MUSCLES |
| Frontalis | - covers the frontal bone; allows you to raise your eyebrows and to wrinkle your forehead |
| Occipitalis | - covers the posterior aspect of the skull and pulls the scalp posteriorly |
| Orbicularis Oculi | - run in circles around the eyes; allows you to close your eyes, squint, blink, and wink |
| ▪ Orbicularis Oris | - circular muscle of the lips; “kissing” muscle |
| Buccinator | - flattens the cheek; chewing muscle |
| Zygomaticus | - extends from the corner of the mouth to the cheekbone; “smiling” muscle |
| Masseter | - covers the angle of the lower jaw as it runs from the zygomatic process of the temporal bone to the mandible; closes the jaw by elevating the mandible |
| Temporalis | - fan-shaped muscle overlying the temporal bone. It inserts into the mandible and acts as a synergist of the masseter in closing the jaw |
| Platysma | - covers the anterolateral neck; originates from the connective tissue covering of the chest muscles and inserts into the area around the mouth; “sad clown” face muscle as it pulls the corners of the mouth inferiorly |
| Sternocleidomastoid | - two- headed muscles, one found on each side of the neck- one arises from the sternum, and the other arises from the clavicle; they flex your neck |
| Pectoralis Major | - covers the upper part of the chest; forms the anterior wall of the axilla (armpit) and acts to adduct and flex the arm |
| Intercostal Muscles | - deep muscles found between the ribs; external intercostals- help to raise the rib cage when you inhale; internal intercostals- depress the rib cage, helping to move air out of the lungs when you exhale forcibly |
| Rectus abdominis | - most superficial muscles of the abdomen; flex the vertebral column, compress the abdominal contents during defecation and childbirth, and are involved in forced breathing |
| External oblique | - make up the lateral walls of the abdomen; they flex the vertebral column, but they also rotate the trunk and bend it laterally. |
| Internal oblique | - paired muscles deep to the external obliques; same functions as the external obliques |
| Transversus abdominis | deepest muscle of the abdominal wall,; compresses the abdominal contents |
| Trapezius | - the most superficial muscles of the posterior neck and upper trunk; extend the head and can elevate, depress, adduct, and stabilize the scapula. |
| Latissimus dorsi | - two large, flat muscles that cover the lower back; extends and adducts the humerus. |
| Deltoid | - form the rounded shape of your shoulders; favorite injection site when relatively small amounts of medication (less than 5 ml) must be given intramuscularly (into muscle); prime movers of arm abduction. |
| Erector spinae | - deep muscles of the back. Each erector spinae is a composite muscle consisting of three muscle columns |
| Quadratus Lumborum | - form part of the posterior abdominal wall; each muscle of the pair flexes the spine laterally. Acting together, they extend the lumbar spine. |
| Biceps brachii | - bulges when you flex your elbow; powerful prime mover for flexion of the forearm and acts to supinate the forearm |
| Brachialis | - lies deep to the biceps brachii and is a prime mover in elbow flexion. The brachialis lifts the ulna as the biceps lifts the radius |
| Triceps Brachii | - straightens the arm; prime mover for elbow extension |
| Brachioradialis | - fairly weak muscle that arises on the humerus and inserts into the distal forearm. Hence, it resides mainly in the forearm. |
| Gluteus maximus | - superficial muscle of the hip that forms most of the flesh of the buttock, brings the thigh in a straight line with the pelvis, and is the most important muscle for extending the hip when power is needed. |
| Gluteus medius | - hip abductor and is important in steadying the pelvis during walking; important site for giving intramuscular injections |
| Iliopsoas | - fused muscle composed of 2 musclesiliacus and psoas major; acts to keep the upper body from falling backward when we are standing erect. |
| Adductor Muscles | - muscle mass at the medial side of each thigh; they adduct, or press, the thighs together; tend to become flabby very easily. |
| Hamstring Group | - muscle mass of the posterior thigh; consists of 3 muscles— the biceps femoris, semimembranosus, and semitendinosus; prime movers of thigh extension and knee flexion. |
| Sartorius | - the most superficial muscle of the thigh; “tailor’s” muscle because it acts as a synergist to help tailors sit with both legs crossed in front of them. |
| Quadriceps Group | - consists of 4 muscles— rectus femoris and 3 vastus muscles—that flesh out the anterior thigh; acts to extend the knee powerfully; can also help to flex the hip. |
| Tibialis anterior | - superficial muscle on the anterior leg; acts to dorsiflex and invert the foot. |
| Extensor Digitorum Longus | - arises from the lateral tibial condyle and proximal three-quarters of the fibula and inserts into the phalanges of toes 2 to 5. It is a prime mover of toe extension |
| Fibularis Muscles | - 3 fibularis muscles— longus, brevis, and tertius—are found on the lateral part of the leg; plantar flexes and everts the foot, which is antagonistic to the tibialis anterior. |
| Gastrocnemius | - forms the curved calf of the posterior leg; prime mover for plantar flexion of the foot- “toe dancer’s” muscle. |
| Soleus | - Deep to the gastrocnemius is the fleshy soleus muscle; it does not affect knee movement, but like the gastrocnemius, it inserts into the calcaneal tendon and is a strong plantar flexor of the foot. |
| Mobility Stability Posture Urination Childbirth Vision Digestion Organ Protection Temperature Regulation | Functions of the Muscular System |
Created by:
Markinadoo