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Anatomy and Physiology > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

Muscle Tissue

A

Nearly 1/2 the body’s mass
Function:
-Chemical energy to movement

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2
Q

Types of Muscle Tissue (3)

A

Skeletal
Cardiac
Smooth

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3
Q

Prefixes of Muscle Involvement (3)

A

Myo, Mys, Sarco

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4
Q

Skeletal Muscle Tissue

A
  • Organs attached to bones and skin
  • Muscle Fibers
  • Striated
  • Voluntary
  • Contract rapidly, tire easily, powerful
  • Require nervous system stimulation
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5
Q

Cardiac Muscle Tissue

A
  • Only in heart, bulk in heart walls
  • Striated
  • Can contract without nervous system stimulation
  • Involuntary
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6
Q

Smooth Muscle Tissue

A
  • In walls of hollow organs
  • No striations
  • Can contract without nervous system stimulation
  • Involuntary
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7
Q

Special Characteristics of Muscle Tissue

A

-Excitability (responsiveness)
-Contractility (contract)
-Extensibility (Stretchable)
Elasticity (Recoil)

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8
Q

Muscle Functions (8)

A

-Movement
-Posture
-Stabilization
-Heat
Can also
-Protect Organs
-Forms Valves
-Controls Pupil Size
-Causes “Goosebumps”

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9
Q

Skeletal Muscle

A

Each muscle served by one artery, one nerve, and one or more veins

  • Run together in connective tissue sheaths
  • Every skeletal muscle fiber supplied by nerve ending that controls its activity
  • Huge nutrient and oxygen need, generates large amount of waste
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10
Q

Connective Tissue Sheaths of Skeletal Muscle

A 
Supports cells, reinforce whole muscle
External to internal
-Epimysium
-Perimysium
-Endomysium
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11
Q

Epimysium

A

Dense irregular connective tissue surrounding entire muscle

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12
Q

Perimysium

A

Fibrous connective tissue surrounding fascicles

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13
Q

Endomysium

A

Fine areolar connective tissue surrounding each muscle fiber

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14
Q

Fascicles

A

Groups of muscle fibers

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15
Q

Skeletal Muscle Attachment

A

Two Places

  • Insertion
  • Origin
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16
Q

Insertion

A

Movable bone

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17
Q

Origin

A

Immovable/less movable bone

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18
Q

Microscopic Anatomy of Skeletal Muscle Fiber

A 
Long, cylindrical cell
-up to 30cm long
Sarcoplasm=cytoplasm
-Glycosomes for glycogen storage
-Myoglobin for oxygen storage
Modified structures: myofibrils, sacroplasmic reticulum, and T tubules
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19
Q

Myofibrils

A 
Densely packed, rodlike elements
-about 80% of cell volume
Contains sarcomeres contractile units
-Sarcomeres contain myofilaments
Exhibit striations- perfectly aligned repeating series of dark bands and light bands
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20
Q

Sarcomere

A
  • Smallest contractile unit
  • Align along myofibril like boxcars of train
  • Composed of thick and thin myofilaments made of contractile proteins
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21
Q

Myofibril Banding Pattern

A

Orderly arrangement of actin and myosin myofilaments within sacromere

  • Actin
  • Myosin
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22
Q

Actin Myofilaments

A

Thin Filaments

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23
Q

Myosin Filaments

A

Thick Filaments

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24
Q

Structure of Thick Filament

A

Composed of protein myosin
Each of 2 heavy and four light polypeptide chains
-Myosin tails contain 2 heavy polypeptide chains
-Myosin heads contain 2 light polypeptide chains
–Act as cross bridges during contraction
–Binding sites for actin of thin filaments
–Binding sites for ATP

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25
Q

Structure of Thin Filament

A

Double strand of fibrous protein
Bears active sites for myosin head attachment during contraction
Tropomyosin and Troponin- regulatory proteins bound to actin

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26
Q

Sacroplasmic Reticulum

A

Network of smooth endoplasmic reticulum surrounding each myofibril
-Run longitudinally
Pairs of terminal cisterns form perpendicular cross channels
Functions in regulation of intracellular Ca2 levels
-Stores and releases Ca2

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27
Q

Sliding Filament Model of Contraction

A

Generation of force

Does not necessarily cause shortening of fiber

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28
Q

Sliding Filament Model of Contraction

A

In relaxed state, thin and thick filaments overlap only at ends of A band
Sliding filament model of contraction
-During contraction, thin filaments slide past thick filaments > Actin and myosin overlap more
-Occurs when myosin heads bind to actin > cross bridges

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29
Q

Sliding Filament Model of Contraction

A

Myosin heads bind to actin, sliding begins
Cross bridges form and break several times, ratcheting thin filaments toward center of sacromere
-Causes shortening of muscle fiber
-Pulls Z discs toward M line

30
Q

Skeletal Muscle to Contract

A

Activation (at neuromuscular junction)
-Nervous system stimulation
-Must generate action potential in sarcolemma
Excitation-Contraction Coupling
-Action potential propagated along sarcolemma
-Intracellular Ca2+ levels must rise briefly

31
Q

Nerve Stimulus and Events at Neuromuscular Junction

A
  • Skeletal muscles stimulated by somatic motor neurons
  • Axons of motor neurons travel from central nervous system via nerves to skeletal muscle
  • Each axon forms several branches as it enters muscle
  • Each axon ending forms neuromuscular junction with single muscle fiber
  • -Usually only one per muscle fiber
32
Q

Neuromuscular Junction (NMJ)

A
  • Stimulated midway along length of muscle fiber
  • Axon terminal and muscle fiber separated by gel-filled space called synaptic cleft
  • NMJ includes
  • -Axon Terminals
  • -Synaptic Cleft
  • -Junctional Folds
33
Q

Events at Neuromuscular Junction

A
  • Nerve impulse arrives at axon terminal
  • ACh released into synaptic cleft
  • ACh diffuses across cleft and binds with receptors on sarcolemma
  • Electrical events
  • Generation of action potential
34
Q

Destruction of Acetylcholine

A

ACh effects quickly terminated by enzyme acetylcholinesterase in synaptic cleft

  • Breaks down ACh to acetic acid and choline
  • Prevents continued muscle fiber contraction in absence of additional stimulation
35
Q

Generation of an Action Potential

A

Resting Sarcolemma polarized
-Voltage across membrane
Action potential caused by changes in electrical charges

36
Q

Action Potential by changes in Electrical Charges (3 Steps)

A

End Plate Potential
Depolarization
Repolarization

37
Q

End Plate Potential

A
  • ACh binding opens ion channels
  • Simultaneous diffusion Na+ inward and K+ outward
  • More Na+ diffuses in, so interior of sarcolemma becomes less negative
  • Local depolarization = end plate potential
38
Q

Depolarization

A

Generation and propagation of an action potential (AP)

  • End plate potential spreads to adjacent membrane areas
  • Na+ channels open
  • Na+ influx decreases membrane voltage toward critical voltage called threshold
  • If threshold is reached, AP initiated
  • Once initiated, is unstoppable- muscle fiber contraction
39
Q

Events in Generation of an Action Potential

A

AP spreads across sarcolemma

Voltage-gated Na+ channels open in adjacent patch, causing it to depolarize to threshold

40
Q

Repolarization

A

Restoring electrical conditions of RMP

  • Na+ channels close and voltage-gated K+ channels open
  • K+ efflux rapidly restores resting polarity
  • Fiber cannot be stimulated- in refractory period until repolarization complete
  • Ionic conditions of resting state restored by Na+ -K+ pump
41
Q

Channels Involved in Initiating Muscle Contraction

Review of Muscle Contraction

A
  • Nerve impulse reaches axon terminal
  • Voltage-gated calcium channels open
  • ACh is released to synaptic cleft
  • ACh binds to its receptors on sarcolemma
  • Opens ligand-gated Na+ and K+ channels
  • End Plate Potential
  • Opens voltage-gated Na+ channels
  • AP propagation
  • Voltage-sensitive proteins in T tubules change shape
  • SR releases Ca2+ to cytosol
42
Q

Role Calcium in Muscle Contraction

A

Low Calcium= relaxed muscle

High Calcium= contractions start

43
Q

Cross Bridge Cycle

A

Continues as long as Ca2+ signal and adequate ATP present

Cross bridge formation- high-energy myosin head attaches to thin filament

44
Q

Rigor Mortis

A

Cross bridge detachment requires ATP
3-4 hours after death muscles begin to stiffen with weak rigidity at 12 hours post mortem
-Dying cells take in calcium- cross bridge formation
-No ATP generated to break cross bridges

45
Q

Muscle Tension

A

Force exerted on load or object to be moved

46
Q

Iso

A

Same as

47
Q

Metric

A

Length

48
Q

Tonic

A

Amount of contraction shorten or lengthen

49
Q

Isometric Contraction

A

No shortening, muscle tension increases but does not exceed load

50
Q

Isotonic Contraction

A

Muscle shortens because muscle tension exceeds load

51
Q

Motor Unit

A

Motor Neuron and all muscle fibers it supplies
Each muscle is served by at least one motor nerve
Muscle fibers from motor unit spread throughout muscle so single motor unit causes weak contraction of entire muscle
Motor units in muscle usually contract asynshronously

52
Q

Motor Nerve

A

Contains axons of up to hundreds of motor neurons

53
Q

Asynchronously

A

Take turns, not all at the same time

54
Q

Muscle Twitch

A 
3 Phases
-Latent Period
-Period of Contraction
-Period of Relaxation
Contracts faster than it relaxes
55
Q

Latent Period

A

Events of excitation-contraction coupling, no muscle tension

56
Q

Period of Contraction

A

Cross bridge formation, tension increases

57
Q

Period of Relaxation

A

Calcium leaves cells

58
Q

Muscle Twitch Comparisons

A

Different strength and duration of twitches due to variations in metabolic properties and enzymes between muscles
-Normal muscle contractions are smooth

59
Q

Graded Muscle Response

A

Varying Strength of contraction for different demands
Required for control of skeletal movement
Responses graded by
-Changing frequency of stimulation
-Changing strength of stimulation

60
Q

Stimulus results

A

Single stimulus results in single contractile response- muscle twitch

61
Q

Response to Change in Stimulus Frequency

A

If stimuli are given quickly enough, muscle reaches maximal tension- fused complete, tetany results

  • Smooth sustained contraction
  • No muscle relaxation- muscle fatigue
  • -Muscle cannot contract; zero tension
62
Q

Recruitment

A

Controls force of contraction

63
Q

Subthreshold

A

Not much muscle contraction

64
Q

Threshold

A

Muscle contraction as much as needed

65
Q

Maximal Stimulus

A

All the strength activates everything

66
Q

Recruitment and size principle

A
  • Motor units with smallest muscle fibers recruited first
  • Motor units with larger fibers recruited as stimulus intensity increases
  • Largest motor units activated only for most powerful contractions
67
Q

Isotonic Contractions

A

Concentric- shortens

Eccentric- lengthens

68
Q

Isometric Contractions

A

Tension increases to muscle’s capacity but muscle neither shortens nor lengthens

69
Q

Muscle Tone

A

Constant, slightly contracted state of all muscles

Keeps muscles firm, healthy, and ready to respond

70
Q

Anaerobic

A

No air, lots of lactic acid waste

  • Glycolysis- does not require oxygen
  • Lactic acid diffuses into bloodstream
71
Q

Aerobic

A

Uses air

Anatomy and Physiology (27 decks)

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