Chapter 10
Oxygen Debt
Refers to the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise
Compare the structure and function of the three types of skeletal muscle fibers
Slow oxidative fibers (SO) fast oxidative-glycolytic (FOG) fibers fast glycolytic fibers
Outline the steps involved in the sliding filament mechanism of muscle contraction
1.ATP hydrolysis- myosin heads hydrolyze ATP and become reoriented and energized 2.Attachment of myosin to actin to form cross-bridges - myosin heads bind to actin, forming cross-bridges 3.Power stroke- Myosin cross-bridges rotate toward center of sarcomere (power stroke) 4.Detachment of myosin from actin -As myosin head bind ATP, the cross-bridges detach from actin
In what order are the various types of skeletal muscle fibers recruited when you sprint to make it to the bus stop?
Slow oxidative, fast oxidative-glycolytic, fast glycolytic
Which type of muscular tissue has the highest capacity for regeneration?
Smooth muscle
Which structures develop from myotomes, dermatomes, and sclerotomes?
Somite
On a cellular level, what causes muscle hypertrophy?
The increase in size of thick and thin filaments
How are the structures of think and thick filaments different?
Thin filament-molecules strung together like beads to form two fibrous strands that twist around each other. Thick filament- shaped like golf clubs, with their long shafts bundled together to form a thick filament and their "heads" sticking out from the bundle.
Distinguish thick filaments from thin filaments
Thin filaments = action Thick filaments = myosin
What are differences between visceral and multiunit smooth muscle?
Visceral smooth muscle is found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach Multiunit smooth muscle consists of individual fibers, each with its own motor neuron terminals and with few gap junctions between neighboring fibers
Why are some skeletal muscle fibers classified as "slow" and others are said to be "fast"?
a fiber is categorized as either slow or fast depending on how rapidly the ATPase in its myosin heads hydrolyze ATP
Contractility
ability of muscular tissue to contrast forcefully when stimulated by an action potential (holding a book in a outstretched hand)
Extensibility
ability of muscular tissue to stretch, within limits, without being damaged ex. each time you fill your stomach with food, the smooth muscle in the wall is stretched.
Electrical excitability
ability to respond to certain stimuli by producing electrical signals
nerve action potentials
action potential in nerves
muscle action potentials
action potentials in muscles
Which sources provide ATP during a marathon race?
aerobic cellular respiration ( pyruvic acid, fatty acids and amino acids)
Which ATP- producing reactions are aerobic and which are anaerobic ?
aerobic- carbon dioxide, water, ATP, and heat anaerobic- glycolysis
Describe how frequency of stimulation affects muscle tension
affected by the amount of stretch before contraction
Distinguish between anaerobic and a aerobic cellular reaction
anaerobic cellular respiration -a series of ATP-producing reactions that don't require oxygen. provides enough energy for about 30 to 40 seconds of maximal muscle activity aerobic cellular respiration-series of ATP producing reactions that require oxygen. aerobic supplies enough ATP for prolonged activity provided sufficient oxygen and nutrients are available
How are the sizes of motor units related to the degree of muscular control they allow?
because all of the muscle fibers of a motor unit contract and relax together, the total strength of a contraction depends, in part, on the size of the motor units and the number that are activated at a given time
Before muscle fatigue, the feelings of tiredness and the desire to cease muscle activity; caused by changes in the nervous system
central fatigue
Define each of the following terms:
concentric isotonic contraction eccentric isotonic contraction isometric concentration
Explain the importance of connective tissue components, blood vessels, and nerves to skeletal muscles
connective tissue components -
Describe the functions of skeletal muscle proteins
contractile proteins proteins that generate force during muscle contractions. Regulatory proteins proteins that help switch muscle contraction process on/off Structural proteins proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to sarcolemma and extracellular matrix
The four properties of muscular tissue
electrical excitability contractility extendibility elasticity
Muscle cell stimuli
electrical signals (autorhythmic) chemical signals (neurotransmitter)
Action potentials (impulses)
electrical signals produced during electrical excitability
How is muscle tone produced
established by neurons in the brain and spinal cord that excite the muscle's motor neurons
Thermogenesis
heat produced during muscle contraction
Concentric isotonic contraction
if the tension generated is great enough to overcome the resistance of the object to be moved, the muscle shortens and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at a single joint
Describe the factors that contribute to muscle fatigue
inadequate release of calcium ions from the SR, resulting in a decline of CA2+ concentration depletion of creatine phosphate insufficient oxygen depletion of glycogen and other nutrient buildup of lactic acid and ADP failure of action potential in the motor neuron to release acetylcholine
Which factors contribute to muscle fatigue?
inadequate release of calcium ions from the SR, resulting in a decline of CA2+ concentration depletion of creatine phosphate insufficient oxygen depletion of glycogen and other nutrient buildup of lactic acid and ADP failure of action potential in the motor neuron to release acetylcholine
Hyperplasia
increase in the number of fibers
Shivering
increases the rate of heat production
Fast oxidative-glycolytic (FOG) fibers
intermediate in diameter between the other two types of fibers. FOG fibers generate considerable ATP by aerobic cellular respiration, which gives them a moderately high resistance to fatigue
Distinguish between isotonic and isometric contractions
isotonic contractions the tension remains constant while the muscle changes length; used for body movements and for moving objects (concentric and eccentric) isometric contractions the tension generated is not enough to exceed the resistance of the object to be moved, and the muscle does not change in length
Why is muscle tone important?
keeps skeletal muscles firm also in smooth muscle tissues, such as those found in the gastrointestinal tract
Explain the phases of a twitch contraction
latent period (delay 2msec) the muscle action potential sweeps over the sarcolemma and the calcium ions are released from the SR contraction period( 10-100msec) Ca2+ binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form relaxation period(10-100msec) CA2+ is actively transported back into the SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases
Smooth Muscle
located in G.I. tract, uterus, eye, blood vessels; involuntary
Cardiac Muscle
located in the heart; involuntary
Skeletal Muscle
located in the skeleton; voluntary
What features distinguish the three types of muscular tissue?
location, function, appearance and control
Describe the structure and function of a motor unit
made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals;motor units often work together to coordinate the contractions of a single muscle
Producing body movements
movements of the entire body rely on the functions of the skeletal muscles, bones and joints
Describe the development of muscles
muscles derive from mesoderm
Generating heat
muscular tissue contracts and heat is produced (thermogenesis)
Sphincters
prevent outflow of the contents of a hollow organ
Define motor unit recruitment
process in which the number of active motor units increases
List the general functions of muscular tissue
producing body movements stabilizing body positions storing and moving substances within the body generating heat
Explain the structural differences between the three types of muscular tissue
skeletal - striated; parallel fibers cardiac- striated; branched fibers smooth- non striated
Stabilizing body positions
skeletal muscle contractions stabilize joints and help maintain body positions, such as standing or sitting
Compare the special properties of the three muscular tissue
skeletal- maintain your posture or stabilize your body positions cardiac-autorhythmicity smooth-
Compare the functions of the three muscular tissue
skeletal- movement, heat, posture cardiac-pump blood continuously smooth - peristalsis, blood pressure, pupil size and erects hairs
Slow oxidative fibers (SO)
smallest in diameter and are the least powerful; SO fibers generate ATP mainly by aerobic cellular respiration, which is why they are called oxidative fibers
Storing and moving substances within the body
storage is accomplished by sustained contractions of ring like bands of smooth muscles (sphincters)
Elasticity
the ability of muscular tissue to return to its original length and shape after contraction or extension
Fast glycolytic fibers
the largest in diameter and contain the most myofibrils. FG can generate the most powerful contractions
Describe the main structural and functional characteristics of cardiac muscle tissue
the principal tissue in the heart wall; the contractile cells of the heart, are sheets of connective tissue that contain blood vessels, nerves, and the conduction system of the heart
How is the motor end plate different from other parts of the sarcolemma?
the region of the sarcolemma opposite of the synaptic end bulbs. the muscle fiber part at the end of the NMJ
Describe how muscle action potentials arise at the neuromuscular junction
the synapse between a somatic motor neuron and a skeletal muscle fiber
Describe the main structural and functional characteristics of smooth muscle tissue
usually activated involuntarily; found in the skin and in tubular arrangements that form part of the walls of small arteries and veins
Eccentric isotonic contraction
when the length of a muscle increases during contraction
Isometric concentration
when the tension generated is not enough to exceed the resistance of the object to be moved, and the muscle does not change its legnth
Describe the reactions by which muscle fibers produce ATP
Creatine phosphate- When creatin phosphate transfers its high energy phosphate group to ADP, ATP is produced anaerobic cellular respiration -a series of ATP-producing reactions that don't require oxygen aerobic cellular respiration-series of ATP producing reactions that require oxygen
What types of fascia cover skeletal muscles?
Deep fascia
Why is the term recovery oxygen uptake more accurate than oxygen debt?
First: the elevated body temperatures after strenuous exercise increases the rate of chemical reactions throughout the body Second: the heart and muscles used in breathing are still working harder than they were at rest, they consume more ATP Third: tissue repair processes are occurring at an increased pace
Why is a rich blood supply important for muscle contraction?
For muscles to contract there needs to be an adequate supply of ATP within the cell. ATP is generated in part by a supply of glucose and oxidative phosphorylation. An inadequate supply of blood will not provide enough oxygen to keep up with the energy demands of contraction.
Demonstrate an isotonic contraction. How does it feel?
In an isotonic contraction, tension remains constant as muscle length decreases and increases;
During muscle contraction by the sliding filament mechanism, thin filaments are pulled towards the ?
M Line
Describe the microscopic anatomy of a skeletal muscle fiber
M-y S-on S-aw S-omeThing M-ean and S-trange M-oving and G-oing M-oo Mitrochondria - produces ATP for muscle Sacroplasm - cytoplasm of muscle fiber Sarcolemma - plasma membrane of muscle fiber Sarcoplamic reticulum - SER of muscle fiber full of Ca+ ions Transverse Tubules - extension of SER that signal when SR should release Ca+ Myofibrils - long bundles of myofilament that allow for muscle contraction Myofilaments - protein microfilaments composes of actin or myosin that help with muscle contraction Sarcomere - contractile mechanism of muscle fiber Glycogen - inclusion that provides energy during exercise Myoglobin - inclusion that stores oxygen
How does sarcomere length influence the maximum tension that is possible during muscle contraction?
Maximum tension during contraction occurs when the resting sarcomere length is 2.0-2.4 a muscle fiber develops its greatest tension when there is an optional zone of overlap between thick and thin filaments
The inability of a muscle to maintain force of contraction after prolonged activity
Muscle Fatigue
Describe the effects of exercise on different types skeletal muscle fibers
Total number of muscle fibers do not increase with exercise, changes can be induced Swimming, running: gradual change from fast glycolytic into fast oxidative glycolytic fibers, increases in diameter, number of mitochondria, blood supply, strength; endurance exercises cause cardiovascular and respiratory changes to receive better supplies of oxygen and nutrients but do not increase in muscle mass Great strength for short periods: increase in size from synthesis of thick and thin filaments and strength of fast glycolytic fibers, muscle enlargement from hypertrophy
