The Muscular System



Download 26.89 Kb.
Date05.05.2018
Size26.89 Kb.
The Muscular System

  • Three Types of Muscle Tissue

  1. ____________________________________:

    • Attached to bones and skin

    • Striated

    • Voluntary (i.e., conscious control)

  1. ____________________________________:

    • Only in the heart

    • Striated

    • Involuntary

  2. ____________________________________:

    • In the walls of hollow organs (e.g., stomach, urinary bladder, and airways)

    • Not striated

    • Involuntary

  • 5 Primary Functions of Skeletal Muscles

  1. ______________________________________________________

  2. ______________________________________________________

  3. ______________________________________________________

  4. ______________________________________________________

  5. ______________________________________________________

  • Skeletal Muscle

    • Connective tissue layers of skeletal muscle:

      • _______________: a layer of collagen fibers surrounding entire muscle

      • _______________: connective tissue fibers dividing skeletal muscle into compartments surrounding fascicles (_______________________________)

      • _______________: within the fascicle; surrounding each muscle fiber and ties adjacent muscle fibers together

    • 3 layers come together to form either a bundle known as a tendon (________________) or a broad sheet called a aponeurosis (_________________)

  • Skeletal Muscle Fiber

    • Multiple peripheral nuclei

    • Components of skeletal muscle

      • ____________________ (cell membrane)

      • __________________________________

      • __________________________________

      • __________________________________

      • __________________________________

  • T Tubules

    • Openings in the sarcolemma lead to the T tubules

    • Filled with extracellular fluid and form passageways through the muscle fiber

    • ________________________________________________________________________

  • Myofibrils

    • Cylindrical structures that are bundles of thick and thin myofilaments (protein filaments consisting primarily of proteins actin and myosin)

      • _____________________________________________

      • _____________________________________________

    • Responsible for muscle fiber contraction



  • Sarcoplasmic Reticulum (SR)

    • Network of smooth endoplasmic reticulum surrounding each myofibril between T tubule attachments

      • ____________________________________

    • Functions in the regulation of intracellular Ca2+ levels

      • _________________________________________________________________

  • Sarcomere

    • Thick and thin myofilaments are organized into repeating functional units called sarcomeres

    • _____________________________________________________________________

    • The arrangement of the sarcomeres produces a banded look (striated)

    • The region of a myofibril between two successive sarcomeres is called a Z line

  • Features of a Sarcomere

    • _______________________: run the entire length of an A band

    • _______________________: run the length of the I band and partway into the A band

    • _____________: sheet of proteins that anchors the thin filaments and connects myofibrils to one another

    • _____________: lighter midregion where filaments do not overlap

    • _____________: line of protein myomesin that holds adjacent thick filaments together

  • Ultrastructure of Thick and Thin Filaments

    • Thick

      • ________________________________________

        • Myosin tails

        • Myosin heads containing:

          • 2 small, light polypeptide chains that act as cross-bridges during contraction

          • Binding sites for actin of thin filaments

    • Thin

      • ________________________________________

      • Tropomyosin and troponin: regulatory proteins bound to actin

        • Change to allow myosin-actin binding when calcium ions are released form SR

  • Sliding Filament Theory of Contraction

    • In the relaxed state, thin and thick filaments overlap only slightly

    • _____________________________________________________________________ _____________________________________________________________________

    • As the H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens

    • _____________________________________________________________________

  • The Contraction Cycle

    • At rest, the thin filament-myosin head cross-bridge is bound to an ADP molecule and a phosphate group

      • This primes the cross-bridge for contraction

    • Steps in contraction

      1. __________________________________________________________________________________________________________________________________

      2. _________________________________________________________________

      3. __________________________________________________________________________________________________________________________________

      4. _________________________________________________________________

      5. __________________________________________________________________________________________________________________________________

    • Cycle ends when calcium levels return to normal

  • Tension

    • Individual muscle cells are surrounded and tied together by connective tissue. When muscle cells contract, they pull on collagen fibers, producing an active force called tension

    • _____________________________________________________________. But before movement can occur, the applied tension must overcome the objects resistance

    • In contrast, compression (a push applied to an object) forces the object away from the source of compression

      • _______________________________________________________________

  • Muscle Twitch

    • Response of a muscle to a single, brief threshold stimulus

    • __________________ – graph of tension development in a muscle during a twitch

    • Three phases of a twitch:

      1. Latent period: ___________________________________________________ _______________________________________________________________

      2. Period of contraction: _____________________________________________

      3. Period of relaxation: ______________________________________________

    • ______________________ – the addition of 1 twitch to another

    • ______________________ – a muscle producing almost peak tension during rapid cycles of contraction and relaxation

    • ______________________ – occurs when the rate of stimulation is increased until the relaxation phase is completely eliminated, producing maximum tension

  • Motor Units and Muscle Tone

    • _________________________ – all muscle fibers controlled by a single motor neuron

    • Muscle tone

      • Motor units are always active, even when not contracting

      • ___________________________________________________________________________________________________________. This is called muscle tone

  • Isotonic and Isometric Contractions

    • _____________________________

      • Muscle changes in length and tension rises

      • Tension remains constant until relaxation occurs

    • _____________________________

      • Muscle as a whole does not change length and tension never exceeds resistance

  • Muscle Metabolism: Energy for Contraction

    • _____________________________________________________________________

    • At rest, extra ATP is produced. Under these conditions, ATP transfers energy to creatine. This transfer creates creatine phosphate (CP):

      • ATP + creatine ADP + creatine phosphate

    • During contraction, ATP is broken down and creatine phosphate is used to “recharge” the ADP back into ATP

      • ADP + creatine phosphate ATP + creatine

    • _____________________________________________________________________



  • Aerobic Metabolism and Glycolysis

    • Aerobic Metabolism

      • Produces 95% of ATP during rest and light to moderate exercise

      • ____________________________________________________

      • Basic steps:

        • Mitochondria absorb oxygen, ADP, phosphate ions, and small organic substrate molecules from the surrounding cytoplasm

        • These substrates enter the TCA cycle and are broken down

        • Large amounts of energy are released during the cycle and used to make ATP

    • Glycolysis

      • The breakdown of glucose to pyruvic acid in the cytoplasm in the cell

      • Lower ATP yield; however, ____________________________________ __________________________________________________________

  • Muscle Fatigue

    • _________________________________________________________________

    • Occurs when:

      • Energy reserves are used up

      • There is a buildup of lactic acid

    • Recovery

      • Conditions within the muscle are returned to normal preexertion levels

      • 2 types:

        • ________________________

          • When oxygen is available, lactic acid can be recycled by converting it back to pyruvic acid

        • ________________________

          • When skeletal muscles are contracting at peak levels, body temperature begins to climb

          • In response, blood flow to the skin increases, promoting heat loss

  • Skeletal Muscle Fiber Types

    • Fast fibers

      • Can contract in 0.01 second or less following stimulation

      • ________________________________________________________________

      • Fatigue rapidly

    • Slow fibers

      • ________________________________________________________________

      • 3 specializations related to the availability and use of oxygen make this possible:

        • _____________________ – more capillaries that allow for more oxygen to be supplied

        • _____________________ – contain myoglobin to store oxygen

        • _____________________ – contain a larger number of mitochondria

  • Origins, Insertions, and Actions

    • Each muscle begins at an origin, ends at an insertion, and contracts to produce a specific action

      • _________________________________________________________________

    • Muscles can be described by their primary actions:

      • ____________________ – a muscle whose contraction is chiefly responsible for producing a particular movement

      • ___________________ – muscles whose actions oppose the movement produced by another muscle. Functional opposite of agonist

      • ___________________ – is a muscle that helps a prime mover work efficiently

        • __________________ – synergists that stabilize the origin of a prime mover by preventing movement to another joint

  • Axial Muscles

    • _________________________________________________

      • Includes the muscles responsible for facial expressions, chewing, and swallowing

    • _________________________________________________

      • Includes flexors and extensors of the head, neck, and spinal column

    • _________________________________________________

      • The oblique and rectus muscles form the muscular walls of the thoracic and abdominopelvic cavities

    • _________________________________________________

      • Extend between the sacrum and pelvic girdle and form the muscular perineum, which closes the pelvic outlet

  • Muscles of the Head

    • The muscles of the face originate on the surface of the skull and insert into the dermis of the skin

    • The largest group of facial muscles is associated with the mouth

      • ______________________ – constricts the opening of the mouth

      • ______________________ – compresses the cheeks (pursing the lips, whistling)

      • ______________________ – produces the chewing motions

    • The epicranium (scalp) consists of 3 separate muscles: the frontalis, the occipitalis, and a tendinous sheet called the eipcranial aponeurosis

  • Muscles of the Neck

    • ____________________ – ventral surface of the neck; extends from the base of the neck to the mandible and the corners of the mouth

    • ____________________ – opens the mouth and depresses the mandible

    • ____________________ – muscular floor of the mouth and supports tongue

    • Stylohyoid – muscular connection between the hyoid & the styloid process of the skull

    • Sternocleidomastoid – rotates the head or flexes the neck

    • Orbicularis oculi – ___________________________________

  • Muscles of the Spine

    • Splenius capitis and semispinalis capitis – _____________________________________ _______________________________________________________________________

      • Splenius capitis also acts to rotate the head

    • Erector spinae – _________________________________________________________

      • Moving laterally from the spine, the muscles can be subdivided into spinalis, longissimus, and iliosostalis

  • Muscles of the Trunk

    • ________________ – compress underlying structures or rotate the spinal column

    • ________________ – important flexors of the spinal column; oppose the erector spinae

    • External intercostals—more superficial muscles that _____________________________

    • Internal intercostals—deeper muscles that _____________________________

    • Diaphragm

      • Partition between thoracic and abdominal cavities

      • _____________________________________________________________

      • Contraction expands thoracic cavity and compresses abdominopelvic cavity

  • Muscles of the Pelvic Floor

    • __________________________

      • Broad sheet of muscles connecting the sacrum & coccyx to the ischium & pubis

      • Supports the organs of the pelvic cavity, flexes the coccyx, and controls the movement of materials through the urethra and anus

    • _____________________________________ – stabilizes central tendon of perineum

    • _____________________________________ – closes urethra

    • _____________________________________ – closes anal opening

  • Appendicular Muscles

    • The muscles of the shoulders and upper limbs

    • The muscles of the pelvic girdle and the lower limbs

  • Muscles of the Shoulders and Upper Limbs

    • Muscles that position the pectoral girdle

      • ______________ – varied actions

      • ______________ – adducts the scapula, pulling it toward the center of the back

      • ____________________ – elevates the scapula (shrugging)

      • ____________________ – pulls the shoulder anteriorly

    • Muscles that move the arm

      • Deltoid – _________________________________________________________

      • Subscapularis/teres major/teres minor/infraspinatus – ____________________

      • Produce adduction and rotation of the humerus :

        • Pectoralis major – produces flexion at the shoulder joint

        • Latissimus dorsi – produces extension

  • Muscles of the Shoulders and Upper Limbs

    • Muscles that move the forearm and wrist

      • Triceps brachii – extends the elbow (__________________)

      • Biceps brachii – ____________________________________________________

      • Flexor carpi ulnaris/flexor carpi radialis/palmaris longus – __________________

      • Pronators and supinators – ___________________________________________

    • Muscles that move the hand and fingers

      • _____________________________ – extension at finger joints and wrist

      • _____________________________ – flexion at finger joints and wrist

  • Muscles of the Pelvis and Lower Limbs

    • Muscles that move the thigh

      • __________________________ – extension, rotation, and abduction at the hip

      • __________________________ – adductor magnus, adductor brevis, adductor longus, pectineus, and gracilis

    • Muscles that move the leg

      • _______________________ – _________________ (biceps femoris, semimembranosus, and semitendinosus) and sartorius

      • _______________________ – quadriceps femoris, vastus (3), and rectus femoris

    • Muscles that move the foot and toes

      • Gastrocnemius and soleus – _________________________________________

      • Fibularis – ________________________________________________________

      • Tibialis – _________________________________________________________

  • The Effect of Aging on Muscles

  1. Skeletal muscle fibers become smaller in diameter

  2. Skeletal muscles become less elastic

  3. Tolerance for exercise decreases

  4. The ability to recover from muscular injuries decreases



Share with your friends:


The database is protected by copyright ©dentisty.org 2019
send message

    Main page