Chapter 10: Muscular Tissue Flashcards
Summarize the major features of the types of muscular tissue
Both cardiac and skeletal muscle tissues are striated and smooth muscle is not, hence its name.
Skeletal muscle cells have more than one nucleus, are large and run parallel to each other.
Cardiac muscle cells usually have only one, sometimes two, centrally located nuclei and are branched. They also are connected to each other via gap junctions.
Smooth muscle cells are small but form thick layers of hollow organs. Stretchy!
Like cardiac muscle cells, some smooth muscle cells communicate via gap junctions. Skeletal muscle is voluntarily controlled while both cardiac and smooth muscle tissue are involuntary and autorhythmic.
explain the structural differences among the three types of muscular tissue.
The three types of muscular tissue are skeletal, cardiac, and smooth.
Skeletal muscle tissue is primarily attached to bones; it is striated and voluntary.
Cardiac muscle tissue forms the wall of the heart; it is striated and involuntary.
Smooth muscle tissue is located primarily in internal organs; it is nonstriated (smooth) and involuntary
compare the functions and special properties of the three types of muscular tissue.
Through contraction and relaxation, muscular tissue performs four important functions:
producing body movements;
stabilizing body positions;
moving substances within the body and regulating organ volume;
and producing heat.
Special properties of Muscular tissue:
(1) electrical excitability, the property of responding to stimuli by producing action potentials;
(2) contractility, the ability to generate tension to do work;
(3) extensibility, the ability to be extended (stretched); and
(4) elasticity, the ability to return to original shape after contraction or extension
Skeletal Muscles: Producing body movements, Stabilizing body positions, Moving substances within the body, producing heat
Cardiac Muscles: Moving blood and blood products through the body
Smooth Muscles: Moving substances within the body, regulates organ volume
explain the importance of connective tissue components, blood vessels, and nerves to skeletal muscles.
Connective Tissue:
Areolar Connective Tissue – Separates muscle from Skin provides pathway for nerves and blood vessels to enter and exit the skin
Adipose Tissue - Separates muscle from Skin provides pathway for nerves and blood vessels to enter and exit the skin, prevents heat loss protects from trauma
Fascia Dense Sheet or Broad Band (Irregular Connective Tissue) – Lines and supports body wall, limbs and organs, supports movements. Carries nerves blood vessels and lymph vessels, fills spaces between muscles
Epimysium – Outer layer encircles the entire muscle; dense irregular
Perimysium – Surrounds groups of 10 – 100 or more muscle fibers separating them into bundles called fascicles; dense irregular
Endomysium – Penetrates interior of each fascicle and separates individual muscle fibers from one another; mostly reticular fibers
Blood Vessels & Nerves: Artery and one or two veins accompany each nerve, Somatic motor neurons stimulate skeletal muscles to contract, threadlike axons extend from the brain or spinal cord and branch many times, each branch to a different muscle, Capillaries are plentiful, one or more bring oxygen and nutrients and remove heat and waste products in each muscle fiber
describe the microscopic anatomy of a skeletal muscle fiber.
Diameter can range from 10 – 100um, mature fibers range from 10cm -30cm, Comes from myoblasts in embryonic development, each mature fiber has a hundred or more nuclei, Once fusion occurs the fibers lose their ability to undergo cell division, Sarcolemma a muscle fiber plasma membrane surrounds the sarcoplasm, transverse tubules are found folded back on each other on the sarcolemma, contain hundreds of myofibrils (contractile element),
Sarcoplasmic Reticulum surrounds each myofibril, myofibril contains thin and thick filaments arranged in compartments called sarcomeres
distinguish thick filaments from thin filaments.
Thick - Consists primarily of myosin (protein) approximately 15nm in diameter and made of several hundred molecules of myosin shaped like a golf club with a tail formed of two inter twined chains and a double globular head projecting from itat an angle Zone of everlap, A band, H zone.
Thin - 7nm in diameter, consists primarily of actin (protein) specifically fibrous actin.
Each tropomyosin molecule has a smaller calcium-binding protein call troponin bound to it. All thin filaments are attached to the Z-line, both A band and I band contain thin filaments
describe the functions of skeletal muscle proteins.
Myofibrils are composed of three types of proteins: contractile, regulatory, and structural.
The contractile proteins are myosin (thick filament) and actin (thin filament).
Regulatory proteins are tropomyosin and troponin, both of which are part of the thin filament.
Structural proteins include titin (links Z disc to M line and stabilizes thick filament), myomesin (forms M line), nebulin (anchors thin filaments to Z discs and regulates length of thin filaments during development), and dystrophin (links thin filaments to sarcolemma)
outline the steps involved in the sliding filament mechanism of muscle contraction.
Sliding Filament Mechanism of muscular contraction
The contraction cycle is the repeating sequence of events that causes sliding of the filaments: (1) Myosin ATPase hydrolyzes ATP and becomes energized; (2) the myosin head attaches to actin, forming a cross-bridge; (3) the cross-bridge generates force as it rotates toward the center of the sarcomere (power stroke); and (4) binding of ATP to the myosin head detaches it from actin. The myosin head again hydrolyzes the ATP, returns to its original position, and binds to a new site on actin as the cycle continues
An increase in Ca2+ concentration in the cytosol starts filament sliding; a decrease turns off the sliding process
describe the reactions by which muscle fibers produce ATP.
Lots of ATP needed in contraction. Produced by:
1) Creatine Phosphate (1st source of energy) 15 seconds
Creatine kinase catalyzes transfer of high energy phosphate group from creatinephosphate to ADP to form new ATP molecules
2) Anaerobic Glycolysis:
Glucose converted to pyruvic acid in the reactions of glycolysis, which yield to ATP’s without using oxygen, Anaerobic glycosides can provide enough energy for 2 minutes
3) Aerobic Respiration
Occurs over a prolonged time, mitochondrial reactions require oxygen to produce ATP, the process by which organisms use oxygen to turn fuel such as fats and sugars into energy
distinguish between anaerobic glycolysis and aerobic respiration.
AG - Glucose is broke down for ATP
AR - uses oxygen to breakdown sugars and fats for ATP (long time)
describe the factors that contribute to muscle fatigue.
Changes within muscle fibers, Central fatigue results from feeling tired, caused by changes in the CNS, Inadequate release of Ca ions from SR resulting in a decrease of Ca concentration in sarcoplasm, Depletion of creatine phosphate, insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, failure of action potential to release enough Ach
describe the structure and function of a motor unit and define motor unit recruitment.
Structure – Motor neuron and a group of 2 -3000 muscle fibers Function – Work together to coordinate contractions of a single muscleRecruitment – Process of increasing the number of active motor units to increase contractile strength in a muscle
explain the phases of a twitch contraction.
Latent Period – Short delay from when the action potential reaches the muscle until tension can be observed in the muscle, time when the action potential reaches the muscle until it can be observed
Contraction Phase – Muscle is generating tension, associated with cycling of cross bridges
Relaxation Phase – Time for the muscle to return to its normal length
describe how frequency of stimulation affects muscle tension, and how muscle tone is produced.
Repeated stimuli can produce unfused (incomplete) tetanus, a sustained musclecontraction with partial relaxation between stimuli. More rapidly repeating stimuli produce fused (complete) tetanus, a sustained contraction without
partial relaxation between stimuli.
Muscle tone -Continuous involuntary activation of a small number of motor units produces muscle tone, which is essential for maintain posture
distinguish between isotonic and isometric contractions.
Isotonic : Concentric isotonic contraction the muscle shorted to produce movement and to reduce the angle at the joint. During an eccentric isotonic contraction, the muscle lengthens
Isometric: Isometric contractions, in which tension is generated without muscle changing its length, are important because they stabilize some joints as others are moved.
