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Anatomy and Physiology I > Ch. 9 The Muscular System > Flashcards

Ch. 9 The Muscular System Flashcards

1
Q

Functions of muscle

A
  1. Movement
  2. Maintaining posture
  3. Stabilizing the joints
  4. Temperature homeostasis
  5. Regulate movement of substances between compartments
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2
Q

Characteristics of Muscle Tissue

A
  1. Excitability - receives and responds to stimulus
  2. Contractility - ability to shorten
  3. Extensibility - ability to be stretched beyond resting length
  4. Elasticity - ability to resume original length after stretching
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3
Q

Skeletal

Muscle type

A
  • attached to bones
  • voluntary control
  • striated
  • limited regeneration
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4
Q

Cardiac

Muscle type

A
  • in heart walls
  • involuntary
  • striated
  • no regeneration
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5
Q

Smooth

Muscle type

A
  • in the walls of the hollow organs
  • involuntary
  • not striated
  • fast regeneration
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6
Q

Epimysium

Skeletal Muscle

A
  • 1 of 3 connective tissue sheaths (all continuous with one another)
  • Dense conn. tissue
  • Surrounds whole muscle
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7
Q

Perimysium

Skeletal Muscle

A
  • 1 of 3 connective tissue sheaths (all continuous with one another)
  • Fibrous conn. tissue
  • Surrounds fascicles
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8
Q

Endomysium

Skeletal Muscle

A
  • 1 of 3 connective tissue sheaths (all continuous with one another)
  • Sheath of fine areolar conn. tissue with reticular fibers
  • Surrounds each muscle fiber (cell)
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9
Q

Origin

Attachment

A

attachment to bone that does not move during contraction

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10
Q

Insertion

Attachment

A

attachment to bone that moves during contraction

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11
Q

Direct

Attachment

A

epimysium of muscle fused to periosteum of bone or perichondrium of cartilage

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12
Q

Indirect

Attachment

A
  • muscles connective tissue wrappings extend beyond muscle as a ropelike tendon or aponeurosis
  • Indirect much more common due to durability & small size
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13
Q

General Anatomy of a skeletal muscle cell - fiber

A
  • Long (up to 30 cm) cylinder shaped cells
  • Cells are called “muscle fibers”
  • Several important modifications related to function
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14
Q

Triad

Muscle fiber anatomy

A
  • Formed where T-tubules and terminal cisterns meet
  • Allows messages from the cell membrane to be transferred into the cell
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15
Q

T-tubule

Muscle fiber anatomy

A
  • Invaginations from cell membrane
  • Passes message deep into cell quickly
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16
Q

Terminal cisterns

Muscle fiber anatomy

A
  • Flattened areas of the smER
  • Closely associated with the T-tubules
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17
Q

Sacroplasmic reticulum

Muscle fiber anatomy

A
  • Extensive smER
  • Needed for Ca2+ storage
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18
Q

Sarcolemma

Muscle fiber anatomy

A
  • Muscle cell membrane
  • Forms T-Tubules
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19
Q

Sacroplasm

Muscle fiber anatomy

A
  • Stores glycogen, myoglobin, and creatine phosphate
  • All are related to energy needs
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20
Q

Nucleus

Muscle fiber anatomy

A
  • Multinucleated because they originate from the fusion of several myoblast cells
  • Nuclei are pushed to side
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21
Q

Mitochondrian

Muscle fiber anatomy

A
  • Many large mitochondria
  • For energy production
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22
Q

Myofibril

Muscle fiber anatomy

A
  • Rod-like structures that fill the cell
  • Contain bundles of proteins that compose the contractile units
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23
Q

Thin filaments

Muscle fiber anatomy

A

The proteins of the myofibrils

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24
Q

Sacromere

Muscle fiber anatomy

A
  • The contractile units
  • Formed by the thick and thin filaments of the myofibril
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25
Q

Skeletal musle

1st level of muscle organization

A
  • surrounded by epimysium
  • contains muscle fascicles
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26
Q

Muscle fascicle

2nd level of muscle organization

A
  • Surrounded by perimysium
  • contains muscle fibers
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27
Q

Muscle fiber

3rd level of muscle organization

A
  • surrounded by endomysium
  • contains myofibrils
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28
Q

Myofibrils

4th level of muscle organization

A
  • surrounded by sacroplamsic reticulum
  • consists of sacromeres (Z line to Z line)
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29
Q

Sacromere

5th level of muscle organization

A

contains thick and thin filaments

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30
Q

I band

Sacromere Anatomy

A
  • thin actin filaments ONLY
  • light region where Z disk is
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31
Q

H Zone

Sacromere Anatomy

A
  • thick myosin filaments ONLY
  • light region where M line is
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32
Q

M line

Sacromere Anatomy

A

thick myosin filaments linked by accesory proteins

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33
Q

A band

Sacromere Anatomy

A
  • thick myosin and thin acitin filaments overlap
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34
Q

Thick filaments

A
  • made out of myosin
  • Each thick filament contains –> 300 myosin molecules
  • Protein shaped like a double headed golf club
  • Head “cross bridge”
    Head contains:
  • ATPase (enzyme to split ATP)
  • actin binding site
  • ATP binding site
35
Q

Thin filaments

A
  • Made of Actin
  • 2 thin strands of protein that wind around each other
    Thin flaments contains:
    1. myosin binding sites (that the myosin heads attach to)
    2. troponin
    3. tropomyosin
36
Q

Troponin

Thin filament anatomy

A
  • Has calcium binding sites
  • Moves the tropomyosin off the myosin binding sites so that contraction can occur
37
Q

Tropomyosin

Thin filament anatomy

A
  • Reinforces the structure and covers the myosin binding sites when the cell is resting
38
Q

Ion Channels

Muscle Physiology

A

Allow ions to diffuse across the cell membrane

39
Q

Gated Channels

Muscle Physiology

A

These open and close, when closed do not allow any diffusion of ions

40
Q

Voltage-Gated Channels

Type of gated channel

A

open when membrane
potential changes

41
Q

Ligand-Gated Channels

Type of gated channel

A

open when chemicals (such as neurotransmitters) attach to them

42
Q

Muscle contraction - relaxation steps

A

4 steps:
– Excitation
– Excitation-contraction coupling
– Contraction
– Relaxation

43
Q

Nerve stimulation to the Skeletal Muscle (Excitation)

A
  • Each muscle cell is stimulated by a nerve impulse
  • Neuron cell body is in CNS, but sends axons out to muscles
  • Axons branch so that each cell is in contact with a neuron
44
Q

Excitation – change in Resting Membrane Potential

A
  • Pumps move ions across the membrane against their concentration gradient (requires ATP)
  • The Na/K pump creates and maintains a resting membrane potential (a voltage difference across the membrane)
  • Muscle cells typically have a -90mV resting membrane potentia
45
Q

Structure of the Neuromotor Junction

A
  • Neuron’s axon end bulb filled with vesicles of acetylcholine (ACh)
  • Synaptic cleft
  • Muscle cell’s motor end plate with receptors for ACh
46
Q
  1. Excitation

Muscle contraction - relaxation

A

Nerve impulse reaches axon end bulb
↓
ACh is released into cleft
↓
ACh attaches to receptors (ligand gated ion channels
↓
Na+ floods more quickly than K+ into the cell and the sarcolemma depolarizes
↓
Action Potential

47
Q

Action Potential

A
  1. Membrane potential (Vm ) reaches threshold (-55mV)
  2. Fast Na+ channels open and Na+ rushes in causing the Vm to depolarize to +30mV.
  3. The depolarization stops when the Na+ channels become inactivated.
    1. Slow K+ channels have opened & K+ efflux occurs. This returns Vm back to its resting level. This is repolarization.
48
Q
  1. Excitation – Contraction Coupling

Muscle contraction - relaxation

A

Neighboring voltage gated Na+ channels open and depolarization sweeps across sarcolemma and into T-Tubules
↓
Causes Ca2+ to be released from terminal
cisternae into cytoplasm
↓
Ca2+ attaches to troponin
↓
Troponin changes shape and pulls the tropomyosin off the myosin binding sites on
the actin
↓
Myosin heads bind to the exposed binding sites

49
Q

Muscle Contraction - Power Stroke

A

When the cell is resting, Ca2+ levels in the cell are low and myosin binding sites on actin are physically blocked by Tropomyosin
1. When terminal Cisterns releases Ca2+ into cytoplasm
2. Calcium attaches to Troponin
3. Troponin/Tropomyosin complex moves which opens the Myosin binding sites on the Actin
4. Power Stokes occur

50
Q

ATP hydrolysis

Contraction Cycle (sliding filament theory)

A
  • The ATP binding site on myosin head contains ATPases
    – ATP ADP + P (which are attached to myosin head)
    – This energizes myosin head
51
Q

Attachment of myosin to actin to form crossbridges

Contraction Cycle (sliding filament theory)

A

Energized myosin head attaches to myosin binding site on actin and releases P

52
Q

Power Stroke

Contraction Cycle (sliding filament theory)

A
  • Spot where ADP is bound on myosin head opens causing the head to rotate and release ADP
  • Force is generated as the head moves near sarcomere center (actin filament slides past the myosin filament towards M line)
53
Q

Detachment of Myosin from Actin

A
  • Myosin head stays attached to actin until ATP binds to it at ATP binding site
  • Myosin head detaches from actin
  • Steps are repeated until contraction is complete
  • tropomyosin blockage restored; contraction ends
54
Q

For attachment of myosin to actin

Contraction Cycle (sliding filament theory)

A

P then ADP are released

55
Q

For release of myosin from actin

Contraction Cycle (sliding filament theory)

A

ATP must reattach to myosin head

56
Q

Muscle Contraction

A
  • Contraction is the result of sarcomeres shortening
  • When relaxed the thin and thick filaments overlap slightly
  • During contraction myosin heads act as little ratchets to pull the thin filaments to the center of the sarcomere
  • As a result thin and thick filaments overlap extensively - H zone disappears and Z lines are closer to each other
57
Q

Contraction - Relaxation

A
  1. Cycle repeats to shorten Sarcomeres
    (muscle contracts)
  2. Cycle is broken when calcium is reabsorbed into Terminal Cisterns
  3. Tropinin/Tropomyosin move back to cover Myosin binding sites on Actin
  4. Sarcomeres return to original length (muscle relaxes)
58
Q

Smooth Muscle

A

Gross Anatomy:
- Arranged in layers in walls of hollow organs
- Cells in adjacent layers have opposite orientation
(alternating contractions and relaxation causes peristalsis

59
Q

Microscopic smooth muscle anatomy

A
  • Small, spindle–shaped cells
  • 1 nucleus
  • Smooth ER extends to surface
  • No T-tubules
  • Gap junctions
  • Few mitochondria
  • Surrounded by thin endomysium
60
Q

Myofibrils

A
  • Uses Actin & Myosin
  • No sarcomeres
  • Intermediate filaments attach actin to plasma membrane
  • Tropomyosin present
  • No tropinin
  • Calmodulin present
  • Light chain kinases (LCK)
61
Q

Physiology of Smooth Muscle Contraction

A

Stimulation for contraction may be:
- Autonomic innervation
- Hormonal
- Local conditions

62
Q

Diffuse Junction

Physiology of Smooth Muscle Contraction

A

Varicosity = large bulb-like swelling in the neuron
 Neurotransmitter is released into a wide cleft
 Neurotransmitter attaches to many cells

63
Q

Contraction of Smooth Muscle

A

Contractions are slow, synchronized because of gap junctions, cells are resistant to fatigue, and use little energy

64
Q

Botulism

A

blocks release of Ach

65
Q

Rigor Mortis

A
  • 3 h after death, full rigor about 12 h
    – After 12 h rigor slowly ceases, around 72 h rigor disappears.
  • some cells within their tissues continue to survive.
    – After the circulation of blood ceases, surviving muscle cells resort to anaerobic glycolysis but eventually they become unable to make any more ATP.
  • no more ATP production after death so heads can not unattach
  • Ca 2+ leaks into cytoplasm & myosin heads attach to actin – rigor sets in
  • tissues decompose: proteolytic enzymes in the lysosomes of the muscle cells escape and begin to dissolve the myofilaments –> rigor disappears
66
Q

Motor unit

A
  • a motor neuron and all the cells it innervates
  • As small as 1 neuron – 4 muscle cells
  • As large as 1 neuron – several hundred muscle cells
  • Average is 150 muscle cells
  • The cells in the motor unit are spread throughout the muscle – stimulation of 1 motor unit causes a weak muscle contraction
67
Q

The smaller the motor unit __

A

the finer and more delicate the movements

68
Q

Extraocular muscles

A

typically have small motor units while the large postural muscles have large motor units

69
Q

When this neuron is stimulated ___

A

all the muscle fibers it synapses upon will be stimulated and will contract as a unit

70
Q

Cells have All-or-None contraction

A

when a muscle cell is stimulated to contract it contracts to its full extent

71
Q

Muscle tissue

A
  • has a graded response to stimulus
  • Force, velocity, and duration of contraction is variable
  • Depends on how many motor units are stimulated and the frequency of stimulation
72
Q

Muscle Twitch

A
  • stimulated isolated muscle
  • response of motor unit to single action potential (this is not how we typically use our muscles)
73
Q

Latent period

A

Excitation-Contraction
Coupling (muscle not changed shape)

74
Q

Period of contraction

A

Power strokes are shortening the muscle

75
Q

Period of relaxation

A

Calcium is returning to SR and muscle is relaxing

76
Q

Myogram

A
  • graphic record of muscle contraction
  • Strength of contraction
  • Altered by recruiting more motor units
  • Small motor units in a muscle stimulated first and larger motor units later
77
Q

Isotonic

A
  • Muscle length changes, load moves
    – Concentric: muscle shortens ex picking up book
    – Eccentric: muscle lengthens ex walking uphill
78
Q

Isometric

A
  • tension builds to peak but no change in muscle length
  • Ex: lifting a piano
79
Q

ATP

A
  • Molecule that directly attaches to cross bridges to them provide energy
  • energy for muscle contraction
  • Muscles only store enough ATP for 4-6 seconds –> must have mechanisms to regenerate it quickly
80
Q

Three Mechanisms of energy for contraction

A
  1. Creatine-Phosphate
    2.Anaerobic respiration (glycolysis)
    3 Aerobic respiration
81
Q

Creatine-Phosphate

Energy for Contraction

A

Provides enough ATP for an additional 15 seconds

82
Q

Anaerobic respiration

Energy for contraction

A
  • Makes ATP very quickly
  • Only makes 2 ATP
  • Makes Lactic acid (toxic)
  • Can fuel muscles for up to 45 sec
83
Q

Aerobic respiration

Energy for contraction

A
  • Requires O2
  • 2 sources Myoglobin and hemoglobin
  • Makes CO2 (lungs remove)
  • Makes a lot of ATP
  • Can fuel muscles for hours
84
Q

Muscle Fatigue

A
  • Muscle fatigue: inability to contract, even when stimulated to do so
    May be several factors:
  • Low ATP
  • build up of lactic acid
  • excess free phosphate binding calcium ions
  • Na+/K+ imbalances

Anatomy and Physiology I (15 decks)

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