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BIO 150 A&P I > Unit 4: Ch 11 (Muscular Tissue) > Flashcards

Unit 4: Ch 11 (Muscular Tissue) Flashcards

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1
Q

Contraction & relaxation (twitch) cycle

A
  1. Excitation
  2. Excitation-contraction coupling
  3. Contraction
  4. Relaxation
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2
Q

Contraction phase of a twitch

  • Description
  • Steps
A
  • 3rd step in the twitch cycle
    • Muscle fiber develops tension and may shorten
  • Steps:
    1. Hydrolysis of ATP to ADP + Pi; recovery stroke
    2. Formation of myosin-actin cross-bridge
    3. Power-stroke; sliding of thin filament over thick filament
    4. Binding of new ATP; breaking of cross-bridge
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3
Q

Contraction strength of twitches

A
  • Muscle twitch
    • Low stimulus frequency
  • Temporal summation & incomplete tetanus
    • Physiologically normal frequency
    • Doesn’t see full relaxation phase
  • Complete (fused) tetanus
    • Unnaturally high stimulus frequency
    • Sustained contraction without relaxation
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4
Q

Cross-bridge

A
  • The attachment of myosin with actin within the muscle cell
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5
Q

Electrical potential

A
  • The difference in voltage from one point to another
  • The voltage is the resting membrane potential (RMP) and is maintained by the sodium-potassium pump
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6
Q

Electrical potential process

A
  • Ion channels open
  • Na+ flows down the electrochemical gradient into the cell; the membrane becomes depolarized
  • Na+ channels close & K+ channels open; cell is repolarized
  • An action potential is created
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7
Q

Electrophysiology

A
  • The study of the electrical activity of cells
  • It is the key to understanding nerve activity, muscle contraction, the heartbeat and electrocardiogram, and other physiological phenomena
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8
Q

End-plate potential (EPP)

  • Description
  • Process
A
  • Description
    • Voltages that cause depolarization of skeletal muscle fibers
    • A result of neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction
  • Process
    • The RMP charge changes when the ACh binds to an ACh receptor
    • Allows for different ion channels to open to allow K & Na ions to move so an EPP can be created
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9
Q

Excitation phase of a twitch

  • Description
  • Steps
A
  • 1st step in a twitch cycle
    • Links action potentials in a nerve fiber to the generation of action potentials in the muscle fiber
  • Steps:
    1. Arrival of nerve signal
    2. ACh is released & binds to the receptor
    3. Ligand-regulated ion gate opens, creating end-plate potential
    4. Voltage-regulated ion gates open, creating an action potential
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10
Q

Excitation-contraction coupling phase of a twitch

  • Description
  • Steps
A
  • 2nd step in a twitch cycle
    • The link (transduction) between the action potential generated in the sarcolemma and the start of a muscle contraction
    • Converts an electrical stimulus to a mechanical response
  • Steps:
    1. Action potentials propagated down T tubules
    2. Ca released from terminal cisterns & binds to troponin
    3. Shifting of tropomyosin results in exposure of active sites on actin
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11
Q

Factors impacting muscular strength

A
  • Muscle size
  • Fascicle arrangement
  • Size of active motor units
  • Multiple unit summation
  • Temporal summation
  • The length-tension relationship
  • Fatigue
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12
Q

Fascicle

A
  • A bundle of muscle fibers within a muscle
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13
Q

Fast twitch

A
  • AKA fast glycolytic, white, type IIb fibers
  • Glycolysis and anaerobic respiration
  • Produce powerful movements
  • Large motor units
  • 2 subtypes
    • Type IIA: Relatively rare in humans except in some endurance-trained athletes
    • Type IIB: Combine fast-twitch responses with aerobic fatigue-resistant metabolism
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14
Q

Immediate energy

A
  • Myoglobin supplies oxygen for a limited amount of aerobic respiration
  • Muscle borrows ATP requirements from phosphate groups (Pi) and transfers them to ADP
  • 2 enzyme systems control these phosphate transfers
    1. Myokinase
    2. Creatine kinase
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15
Q

Latent period

A
  • The interval between the stimulus being applied and the contraction occurring
  • The force generated during this time is the internal tension
    • It isn’t visible on the myogram because it causes no shortening of the muscle
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16
Q

Length-tension relationship

A
  • Distance between the Z disc and the sarcomere
  • The tension generated by a muscle depends on how stretched or contracted it was at the outset
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17
Q

Main pathways of ATP synthesis

A
  • Aerobic respiration
    • Preferred method to make ATP in muscle cells
    • Requires O, mitochondria, & glucose
    • Final product is H2O & O
  • Anaerobic fermentation
    • Produces ATP without oxygen
    • ATP yield is limited and the process generates a toxic by-product, lactate (lactic acid), which must be removed from the muscle and disposed of by the liver
18
Q

Maximum oxygen uptake (Vo2max)

A
  • When the rate of oxygen consumption plateaus
    • Vo2max is proportional to body size
    • Peaks around age 20
    • usually greater in males than in females
19
Q

Motor units

  • Variables
  • Sizes & description
  • Motor unit recruitment
A
  • Variables
    • Power
    • Control (precision)
  • Sizes
    • Small motor units: 1 somatic neuron; strong in control & precision (ie fine motor skills; eye movement)
    • Large motor units: 1 somatic neuron providing to more cells; increased amount of force/lots of contractions (ie gross movements; walking)
  • Motor unit recruitment: recruits additional fibers so that movement can occur without damage
20
Q

Muscle fatigue

  • Description
  • Fatigue factors
A
  • The progressive weakness and loss of contractility that results from prolonged use of muscles
  • Factors:
    • High-intensity/short-duration exercise
      • Potassium accumulation
      • ADP/Pi accumulation
    • Low-intensity/long-duration exercise
      • Fuel depletion
      • Electrolyte loss
      • Central fatigue
21
Q

Muscle fiber classifications

A
  • Fast twitch
  • Slow twitch
22
Q

Muscle fiber structure

  • Muscle cells
  • Sarcoplemma
  • Sarcoplasm
A
  • Cells
    • Myoblasts: immature cell that will create a myocyte
    • Satellite cells: potential stem cells that are able to create new myocytes
  • Sarcolemma: Plasma membrane of the muscle fiber
  • Sarcoplasm: Cytoplasm of the muscle cell
    • Sarcoplasmic reticulum (SR)
      • Calcium reservoir
      • Terminal cisternae
      • T tubules
      • Note: Triad consists of 2 terminal cisternae & 1 T tubule
    • Mitochondria
    • Myoglobin: binds to O to keep O in the cell
    • Glycogen: polysaccharide that undergoes hydrolysis of glycogen which can be used with mitochondria and O to create ATP
    • Myofibrils: individual proteins
23
Q

Muscle types

A
  • Cardiac
  • Skeletal
  • Smooth
24
Q

Myofilaments

  • Description
  • Types
A
  • Filament proteins slide over each other to shorten each sarcomere
  • Types
    • Thin
    • Thick
25
Q

Myofilament physiology (proteins)

A
  • Contractile proteins
    • Myocin & actin
    • Creates a contraction; shortens the muscle fiber
  • Regulatory proteins
    • Tropomyosin & troponin
    • Acts like a switch to determine when a fiber can contract and when it cannot
  • Structural proteins
    • Ensures that thin & thick filaments are geographically located in the correct positions
26
Q

Myogram

A
  • Recording of muscle activity
27
Q

Neuromuscular Junction (NMJ)

A
  • A chemical synapse between a motor neuron and a muscle fiber
  • It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction
28
Q

Oxygen debt

aka Excess Postexercise Oxygen Consumption (EPOC)

A
  • Difference between the elevated rate of oxygen consumption at the end of an exercise and the normal rate at rest
  • Notes
    • Occurs in part because oxygen is needed to regenerate ATP aerobically and that ATP goes in part to regenerate ATP aerobically and that ATP goes in part to regenerate creatine phosphate
29
Q

Phosphagen system

A
  • A form of anaerobic metabolism
  • Uses creatine phosphate to generate ATP
  • It will support activity for only about 10 seconds
30
Q

Relaxation phase of a twitch

  • Description
  • Steps
A
  • Final step in a twitch cycle
  • When a muscle fiber relaxes and returns to its resting length
  • Steps:
    1. Nerve fiber stops stimulating the muscle
    2. Ca level in the cytoplasm falls, myosin releases the thin filaments and muscle tension declines
    3. Muscle fiber relaxes and returns to its resting length
31
Q

Sarcomere

  • Description
  • Lines
A
  • The repeating unit between two Z lines
  • Lines
    • A band: both thick and thin filaments
    • H band: thin myofilaments that surround the M line
    • I band: thin filaments only
    • M line: middle/median of the sarcomere
32
Q

Sarcoplasmic Reticulum (SR)

A
  • Contains a Ca reservoir that allows for muscle contractions to occur
33
Q

Sliding filament theory

A
  • The mechanism of contraction
  • Holds that the myofilaments don’t become any shorter during contraction; rather the thin filaments slide over the thick ones and pull the Z discs behind them, causing each sarcomere as a whole to shorten
34
Q

Slow twitch

A
  • Slow oxidative, red, type I fibers
    • More efficient at using oxygen to generate more ATP for continuous, extended muscle contractions over a long time
    • They fire more slowly than fast-twitch fibers and can go for a long time before they fatigue
    • Small motor units
    • Aerobic respiration
35
Q

Synaptic cleft

A
  • A space that separates two neurons
  • Forms a junction between 2+ neurons and helps nerve impulse pass from one neuron to the other
36
Q

Thick filaments

  • Protein composition
  • Binding sites
A
  • Composed of myosin; consists of a moving head and a stationary tail
  • Binding sites
    1. ATP binding site: determines if the head is flexed or extended
    2. Actin binding site (thin filaments): forms a cross-bridge
37
Q

Thin filaments

  • Protein composition
  • Binding site
A
  • Composed of actin, troponin, & tropomyosin
  • Myosin binding site
38
Q

Threshold

  • Description
  • Types
A
  • The pre-determined voltage required to generate an action potential in the muscle fiber
  • Types
    • Subthreshold
      • Does not reach pre-determined voltage
      • Does not create a contraction
    • Suprathreshold
      • A change in charge that exceeds the threshold
      • Creates a contraction
39
Q

Twitch strength factors

A
  • Stimulus frequency
  • Concentration of Ca+2
  • How stretched muscle was before it was stimulated
  • Muscle temperature
  • pH of sarcoplasm
  • State of hydration
  • Recruitment or multiple motor unit (MMU) summation
40
Q

Types of muscle contractions

A
  • Isometric
    • Contraction without a change in length
    • Muscle develops tension but does not shorten
  • Isotonic
    • Contraction with a change in length but no change in tension
    • Types
      • Concentric: Muscle shortens, tension remains constant
      • Eccentric: Muscle lengthens while maintaining tension
41
Q

Universal characteristics of muscle

A
  • Elasticity: ability to recoil
  • Excitability: responsiveness
  • Extensibility: ability to extend or stretch
  • Conductivity: stimulation of a muscle cell produces more than a local effect
  • Contractility: ability to generate a force to create a contraction

BIO 150 A&P I (25 decks)

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