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BIOL 319 > The Muscular System > Flashcards

The Muscular System Flashcards

1
Q

what control do we have over skeletal muscle

A

voluntary control

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2
Q

what skeletal muscles don’t all attach to the skeleton

A

many facial muscles

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3
Q

what are the functions of skeletal muscle

A
  • movement
  • posture
  • joint stability
  • thermogenesis
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4
Q

describe this muscle function: movement

A

muscles produce tension to move things by pulling or squeezing

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5
Q

how do cells produce tension

A

rapidly contracting

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6
Q

what type of muscle are sphincters made of

A
  • smooth muscle
  • skeletal muscle
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7
Q

what are example of skeletal sphincter muscles

A
  • sphincter at the anus
  • sphincter at the urethra
  • orbicularis oris
  • orbicularis oculi
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8
Q

describe this muscle function: posture

A
  • baseline tension exerted at all times
  • holds the body is a certain position against the force of gravity
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9
Q

when do muscles have posture control

A

when conscious

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10
Q

describe this muscle function: joint stability

A

constant tension holds joints together

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11
Q

define diarthrotic joints

A

freely moveable joints

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12
Q

where are most diarthrotic joints found

A

in the limbs

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13
Q

examples of diarthrotic joints

A
  • shoulder
  • hip
  • elbow
  • knee
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14
Q

what is the relationship between joint mobility and stability

A

inverse relationship

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15
Q

what are the 3 factors of joint stability

A
  • ligaments holding the joint together
  • snugness of fit of the bones comprising the joint
  • contribution from muscles crossing over the joint
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16
Q

what type of joint are both the shoulder and hip joint

A

ball and socket

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17
Q

describe the joint stability of the shoulder joint in comparison to the hip joint

A
  • shallower fit/less snugness of the humerus in the glenoid cavity
  • more mobile
  • less stable
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18
Q

describe the joint stability of the hip joint in comparison to the hip joint

A
  • deeper fit/more snugness of the femur in the acetabulum
  • less mobile
  • more stable
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19
Q

what joints are the easiest to dislocate

A
  • shoulder
  • mandible
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20
Q

when is the shoulder joint most vulnerable to dislocation

A

when extended laterally and posteriorly

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21
Q

what muscles help to stabilize the shoulder joint

A

rotator cuff muscles

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22
Q

define rotator cuff muscles

A
  • 4 muscles surrounding the shoulder joint
  • stabilize the humerus head in the glenoid cavity
  • insert onto a cuff-like tendon
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23
Q

what are the 4 rotator cuff muscles

A
  • subscapularis
  • supraspinatus
  • infraspinatus
  • teres minor
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24
Q

describe this muscle function: thermogenesis

A

skeletal muscles can be stimulated by impulses from the hypothalamus to shiver which warms you up

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25
Q

what is the difference between a muscle cell and a muscle fiber

A

nothing, they are synonymous

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26
Q

what are the 4 characteristics of muscle cells

A
  • excitable
  • contractile
  • extensible
  • elastic
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27
Q

describe this characteristic of muscle cells: excitable

A

respond to chemical and mechanical stimuli by generating organized wave-like movement of electrical charge across membranes

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28
Q

define resting membrane potential

A
  • voltage across the cell membrane under normal circumstances
  • all cells have resting membrane potential
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29
Q

what is a synonym for voltage

A

electrical potential

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30
Q

what type of cells can use resting membrane potential as a platform to create action potentials

A
  • excitable cells
  • ex: muscle cells
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31
Q

what is a synonym for action voltage

A

action potential

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32
Q

define muscle potential

A

action potentials in muscles

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33
Q

define action potential in muscle cells

A
  • muscle potential
  • the resting membrane potential can have a wave-like change in voltage to create action
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34
Q

what do muscle cells need to have before they can contract

A

action potential

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35
Q

contraction is ________ by a previous action potential

A

predicated

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36
Q

what comes first: contraction or action potential

A

action potential

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37
Q

describe this characteristic of muscle cells: contractile

A

muscle cells can shorten to produce force

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38
Q

describe this characteristic of muscle cells: extensible

A

muscle cells can tolerate stretching

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39
Q

what muscle type has the most extensibility

A
  • smooth muscle
  • can tolerate the most stretching
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40
Q

skeletal muscle is considered extensible and elastic when compared to ____________

A

other organs

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41
Q

describe this characteristic of muscle cells: elastic

A

muscle cells can snap back into position after they stretch

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42
Q

are ligaments extensible or elastic

A

no, neither extensible or elastic

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43
Q

how far can ligaments stretch

A

1-2% of their resting length

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44
Q

what happens if ligaments stretch

A
  • not elastic
  • won’t snap back into position
  • why one dislocation can cause it to be easier to dislocate that joint in the future
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45
Q

list the order of components of muscles from smallest to largest

A
  • myofilaments
  • myofibrils
  • muscle fibers
  • muscle fascicles
  • whole muscle
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46
Q

how long can each muscle fiber be

A
  • over 1cm
  • as long as the whole muscle
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47
Q

are muscle fibers thick enough to see

A

no

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48
Q

what is the longest muscle

A

sartorius

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49
Q

how wide can each muscle fiber be

A

up to 0.1millimeters (100 micrometers)

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50
Q

what are the strongest muscles in the body

A
  • hamstrings
  • quadriceps
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51
Q

what is the relationship between the cross sectional area of a muscle and the strength of the muscle

A

directly proportional (more area = more strength)

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52
Q

where are the thickest muscle fibers found

A

in the thickest muscles

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53
Q

how are muscle fibers formed

A

fusion of myoblasts in embryo

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54
Q

describe myoblasts

A
  • small cells with a single nucleus
  • fuse together to become muscle fibers in utero
  • myo=muscle; blast=building
  • muscle stem cells in a sense
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55
Q

when do we have all the skeletal muscle fibers that we will ever have

A

at birth

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56
Q

how to muscle cells grow

A

hypertrophy (NOT hyperplasia)

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57
Q

what hormones cause muscle cells to hypertrophy

A

anabolic hormones (growth hormone, testosterone)

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58
Q

women produce __% of the amount of testosterone than men produce

A

5%

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59
Q

how are damaged muscles repaired by the body

A
  • myoblasts are maintained in each muscle fiber throughout life
  • myoblasts will fuse together to create new muscle cells if needed
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60
Q

what do sarco- and myo- mean

A

muscle

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61
Q

define myofilaments

A
  • protein filaments in muscle
  • slide past each other during contraction
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62
Q

what is the term for the cytoplasm in muscle cells

A

sarcoplasm

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63
Q

what is the term for the cell membrane in muscle cells

A

sarcolemma

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64
Q

what is the old term used for plasma membrane

A

plasmolemma

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65
Q

what is the term for the smooth endoplasmic reticulum in muscle cells

A

sarcoplasmic reticulum

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66
Q

define muscular fascia

A
  • surrounds individual muscles and groups of muscles
  • connects muscles to each other
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67
Q

define epimysium

A
  • surrounds each muscle
  • connective tissue
  • bundles fascicles together
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68
Q

define perimysium

A
  • surrounds each fascicle
  • connective tissue
  • bundles muscle fibers together
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69
Q

define endomysium

A
  • surrounds each muscle fiber
  • connective tissue
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70
Q

can muscle fibers be seen with the naked eye

A

no

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71
Q

what do the epimysium, perimysium, and endomysium converge to form

A

components of the tendon

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72
Q

define myofibrils

A
  • organelles in each muscle fiber
  • contain myofilaments
  • each muscle cell has many myofibrils
  • takes up most of the muscle cell volume -
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73
Q

describe what happens to the actin and myosin myofilaments during contraction

A
  • do NOT change length
  • actin myofilaments slide past the stationary myosin myofilaments
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74
Q

how many myofibrils are in a single muscle fibers

A

hundreds to thousands

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75
Q

what takes up most of the muscle cell volume

A

myofibrils

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76
Q

describe the position of the nuclei in a muscle fiber

A
  • pushed to the outer edge of the cell
  • makes the cell membrane (sarcolemma) pucker out
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77
Q

define triad in a muscle fiber

A
  • repeating structure composed of 3 elements
  • 2 terminal cisterns and 1 T tubule
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78
Q

what is the opening of the T tubule called

A

pore

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79
Q

what is the plural of cisterna/cistern

A

cisternae/cisterns

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80
Q

what is the full name of the T tubule

A

transverse tubule

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81
Q

describe why T tubules are called transverse tubules

A

the tubule extends across and into the muscle fiber

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82
Q

describe T tubules

A
  • follows the contours of myofibrils from one side of the muscle fiber to the other
  • extension of the sarcolemma that helps to communicate action potentials from the sarcolemma to the myofibrils
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83
Q

describe terminal cisterns

A

specialized portion of the sarcoplasmic reticulum

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84
Q

where are terminal cisterns located

A

on either side of the T tubule

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85
Q

what ion do terminal cisterns store in high concentrations

A

calcium

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86
Q

when do terminal cisterns release calcium

A

when the action potential travels down the T tubule

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87
Q

how much does calcium concentration spike within the cell once the terminal cisterns begin releasing it

A

10x increase in calcium

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88
Q

what is the chemical link between electrical action potentials and mechanical sliding of actin/thin filaments

A

calcium ions

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89
Q

describe the path of an action potential from an axon to a sarcomere

A
  • action potential moves from axon terminal to the sarcolemma
  • action potential moves down the sarcolemma
  • action potential splits in 2 as it hits a T tubule (moves further down the sarcolemma and down the T tubule towards the sarcomeres)
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90
Q

why is it necessary for capillaries to be attached to muscle fibers

A

muscle fibers need good blood supply to get nutrients needed to convert ATP during movement

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91
Q

what is the atomic unit of contraction

A

sarcomere

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92
Q

what is the smallest element that can contract in a skeletal muscle cell

A

sarcomere

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93
Q

list the contractile elements of muscle from smallest to alrgest

A
  • sarcomere
  • myofibrils
  • muscle fiber
  • muscle fascicles
  • muscle
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94
Q

how many axons connect to a single muscle fiber

A

one axon per muscle fiber

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95
Q

where do axons typically connect to the muscle fiber

A

near the middle of the muscle fiber

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96
Q

how much can sarcomeres contract

A

up to 2/3 their resting length

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97
Q

list all the steps of a muscle contraction

A
  • action potential moves down the axon which induces the fusion of vesicles containing acetylcholine
  • acetylcholine moves into the synaptic cleft through exocytosis
  • acetylcholine binds to protein receptors on the motor end plate
  • binding of acetylcholine leads to the opening of sodium protein channels
  • sodium begins moving from outside the muscle cell to inside causing depolarization of the sarcolemma which stimulates the action potential
  • more sodium channels begin to open up as the action potential moves across the sarcolemma
  • action potential moves down the T tubule and calcium is released from the terminal cisterns
  • calcium will bind to the troponin on actin filaments allowing for myosin binding and therefore contraction
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98
Q

define acetylcholine

A

neurotransmitter inducing muscle contraction

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99
Q

define synaptic cleft

A

area between the axon terminal and sarcolemma

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100
Q

define motor end plate

A

area of the sarcolemma that is opposite of the axon terminal

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101
Q

where is a sarcomere located

A

between Z discs

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102
Q

define I band

A
  • lighter area of the sarcomere
  • less dense
  • only contains thin filaments
  • 1/2 I band on either side of the Z disc
  • split by the sarcomere
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103
Q

define A band

A
  • darker area of the sarcomere
  • denser
  • contains both thick and thin filaments
  • also contains the H zone and the M line
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104
Q

define H zone

A
  • lighter region within the A band
  • still darker than the I band
  • contains only thick filaments
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105
Q

define M line

A
  • proteins attach thick filaments together
  • darker line than H zone
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106
Q

what is the significance of the M line

A

proteins attach thick filaments together so they can’t slide

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107
Q

describe the organization of thick and thin filaments in the lateral portion of the A band

A
  • thick filaments have hexagonal relationship with thin filaments
  • each thick filament associates with 6 thin filaments
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108
Q

describe the structure of each myosin filament

A

composed of 8 repeating structures of myosin each containing 2 globular heads

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109
Q

describe the structure of each myosin protein within a myosin filament

A
  • 2 myosin polypeptides coiled around each other
  • each polypeptide has 1 globular head
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110
Q

how many myosin proteins make up a thick filament

A

few hundred

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111
Q

what are thin filaments made of

A

2 chains of actin polymers wrapped around each other

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112
Q

describe a single actin protein that makes up thin filaments

A

each actin polypeptide is spherical and has its own active site for myosin heads to bind

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113
Q

what are the 2 proteins attached to thin filaments

A
  • tropomyosin
  • troponin
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114
Q

describe the structure of tropomyosin

A
  • composed of 2 thin protein threads wrapped around each other
  • each protein strand is not long, but they splice together to form a tropomyosin filament
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115
Q

how many tropomyosin filaments are there per thin filament

A

2, one for each actin strand

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116
Q

where is tropomyosin located when a muscle is relaxed

A

covering the active sites on actin so myosin heads can’t bind

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117
Q

describe the structure of troponin

A
  • made of 3 unidentical proteins, each with a different job
  • one end protein: spherical, attaches to actin
  • middle protein: where calcium binds
  • one end protein: oval-shaped, attached to tropomyosin
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118
Q

how often are troponin proteins located on actin

A

every 90 nm

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119
Q

which protein making up troponin causes troponin to contract

A

middle protein where calcium binds

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120
Q

describe what happens when calcium binds to troponin

A
  • troponin contracts
  • tropomyosin moved towards the end attached to myosin
  • myosin heads can bind to actin and pull the thin filaments
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121
Q

what is the “origin” and “insertion” points of troponin when calcium binds

A
  • origin: protein attached to actin, part that doesn’t move
  • insertion: protein attached to tropomyosin, part that does move
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122
Q

describe how thick filaments are indirectly attached to Z discs

A

attached via the protein titin

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123
Q

describe titin

A
  • spring-like protein
  • attaches thick filaments to Z discs
  • 1 polypeptide made of 30,000 amino acids (very long)
  • limits the compression of the sarcomere to 2/3 its resting length
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124
Q

where is titin located in a contracted sarcomere

A

between the Z disc and the A band

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125
Q

what happen to titin in the sarcomere after contraction

A

extends back to normal position

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126
Q

what protein makes muscles compressible and extensible compared to other oragns

A

titin

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127
Q

what happens to Z discs as a sarcomere contracts

A

move towards each other/towards the middle

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128
Q

what happens to the I band as a sarcomere contracts

A
  • I band collapses
  • still some I band left in areas where titin is compressed to full extent
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129
Q

what happens to the H zone as a sarcomere contracts

A
  • goes away completely
  • no region left without thin filaments
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130
Q

describe dystrophin proteins

A
  • located under the sarcolemma
  • keep the sarcolemma from breaking
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131
Q

the lack of what protein causes muscular dystrophy

A

dystrophin proteins

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132
Q

when are you no longer able to hold a muscle in a contracted position

A

once you feel fatigue

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133
Q

define complete tetanus

A

complete contraction of sarcomeres and therefore the muscle

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134
Q

define incomplete tetanus

A

any range of muscle contraction between completely relaxed and completely contracted

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135
Q

what happens when someone has the disease tetanus

A
  • all skeletal muscles are in complete uncontrolled tetanus
  • you cannot relax your muscles
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136
Q

how do people die from tetanus

A

breathing muscles cannot relax leading to respiratory failure and asphyxiation

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137
Q

what causes the disease tetanus

A

the bacteria clostridium tetani

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138
Q

how does clostridium tetani often enter the body

A

through a puncture wound

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139
Q

how does clostridium tetani cause the disease tetanus

A
  • releases a toxin that migrates up nerve axons to the spinal cord
  • toxin stops motor neurons from being able to be inhibited so motor neurons have uncontrolled activity
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140
Q

how long is the delay of symptoms for the disease tetanus

A

2-3 weeks

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141
Q

what predicates tension developed via filament sliding

A

an electrical impulse (action potential) that radiates from the neuromuscular junction

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142
Q

what is another term for voltage

A

potential

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143
Q

what happens to pressure and current as voltage increases

A
  • pressure increases
  • current increases
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144
Q

what helps to move a current from one place to another

A

electrical pressure

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145
Q

describe an electrical current

A
  • electrons flowing across a membrane
  • energy conversion across a membrane
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146
Q

do all cell membranes have a resting membrane potential

A

yes

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147
Q

what cell was used to first determine resting membrane potential

A

neurons in the loligo squid

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148
Q

why were neurons in the loligo squid used to first determine resting membrane potential

A
  • had a large axon that can be seen with the naked eye
  • excitable cell
  • similar on the molecular level to human neurons
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149
Q

what instrument was used to measure the resting membrane potential

A

oscilloscope

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150
Q

where are the microelectrodes placed to determine resting membrane potential

A
  • measurement electrode: inside cell membrane
  • reference electrode: outside cell membrane
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151
Q

which electrode on an oscilloscope is set to the baseline of 0

A

reference electrode placed outside the cell membrane

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152
Q

describe what it means that voltage is relative in terms of the resting membrane potential

A

the voltage of the inner surface of the cell membrane is measured with respect to the voltage of the outer surface of the cell membrane

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153
Q

what is the resting membrane potential neurons

A

-70 mv

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154
Q

what is the resting membrane potential for human skeletal muscle

A

-85 mv

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155
Q

what is the resting membrane potential for red blood cells

A

-10 mv

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156
Q

what is the sign of resting membrane potentials (+ or -)

A

always negative

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157
Q

how do excitable cells produce action potentials

A

using resting membrane potential

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158
Q

define leakage channels

A
  • protein channels in cell membranes that allow a specific substance to move through (selective)
  • open all the time, allowing substances to move across the membrane constantly
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159
Q

examples of two leakage channels in cell membranes

A
  • Na+
  • K+
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160
Q

which type of leakage channel is more abundant

A

100x more K+ channels than Na+ channels

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161
Q

what are the only substances than can move through Na+ leakage channels

A

Na+ ions

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162
Q

what are the only substances that can move through K+ leakage channels

163
Q

where is Na+ concentrated (inside or outside cell)

A

more Na+ outside the cell

164
Q

where is K+ concentrated (inside or outside cell)

A

more K+ inside the cell

165
Q

describe the concentration difference between Na+ and K+ inside and outside of the cell

A
  • more Na+ outside the cell
  • more K inside the cell
166
Q

describe how ions move through leakage channels

A
  • facilitated diffusion
  • moving from an area of high concentration to low concentration
167
Q

why are leakage channels necessary

A
  • ions are hydrophilic while cell membranes are hydrophobic (on the inside)
  • ions need to move through specialized protein channels to be able to cross the cell membrane
168
Q

list the brief steps of establishing and maintaining the resting membrane potential

A
  1. sodium potassium pump moves Na+ out of the cell and K+ into the cell
  2. ions move down their concentration gradient
  3. an electrical gradient is produced
  4. gradients move into an equilibrium state
  5. resting membrane potential is created
169
Q

what is needed to establish the concentration gradient of Na+ and K+

A

sodium potassium pump

170
Q

what is another name for concentration gradient

A

chemical gradient

171
Q

what is another name for the sodium potassium pump

A

sodium potassium ATPase

172
Q

what type of movement occurs in the sodium potassium pump

A

active transport

173
Q

what does active transport in the sodium potassium pump require

A

energy, ATP

174
Q

how much ATP is needed for one pump of the sodium potassium pump

175
Q

what is pumped during one cycle of the sodium potassium pump

A
  • 3 Na+ pumped out of the cell
  • 2 K+ pumped into the cell
176
Q

which has a greater effect on the resting membrane potential: sodium potassium pump OR ions moving through leak channels

A

ions moving through leak channels

177
Q

describe how the sodium potassium pump helps to create an electrogenic effect (voltage across the cell membrane)

A
  • there is not an equal distribution of Na+ and K+ inside and outside of the cell
  • sodium potassium pump moves more Na+ outside of cell (3) than K+ inside the cell (2)
  • makes the outside of the cell more positive than inside the cell
178
Q

describe the movement of K+ in response to both the electrical gradient and concentration gradient

A
  • electrical gradient: K+ moving into the cell
  • concentration gradient: K+ moving out of the cell
179
Q

what is the overall charge of cytoplasm within the cell

180
Q

why is the inner surface of the cell near the cell membrane slightly negative in charge

A
  • negative anions are concentrated near the cell membrane
  • anions are not neutralized here because K+ moves out of the cell due to the concentration gradient
181
Q

describe what happens to K+ in terms of the electrical gradient

A
  • K+ move out of the cell following the concentration gradient
  • leaves anions inside the cell creating a negative environment (electrical gradient)
  • K+ begins to move back into the cell following the electrical gradient
182
Q

define equilibrium potetnail

A

electric potential needed to attract an ion into a cell to balance the ions moving out of the cell

183
Q

describe the equilibrium potential for potassium

A
  • when the K+ moving into the cell due to the electrical gradient is equal to the K+ moving out of the cell due to the concentration gradient
  • -90 mv
184
Q

describe how Na+ moves across the cell membrane

A

moves down the concentration gradient into the cel

185
Q

what is the equilibrium potential for sodium

186
Q

what is the resting membrane potential for a skeletal muscle cell based on the equilibrium potentials of sodium and potassium

A
  • EP K+ = -90 mv
  • EP Na+ = +65 mv
  • RMP = -85 mv
187
Q

how is the resting membrane potential of a membrane determined

A

based on the equilibrium potentials of all ions moving across the cell membrane

188
Q

define voltage gated channels

A
  • not always open
  • opens when a change in voltage moves through it (such as an action potential)
  • quickly open and close
189
Q

define ligand gated channels

A

capable of binding smaller molecules that change the large channel protein, allowing it to open

190
Q

define acetylcholine

A
  • neurotransmitter
  • small molecule
  • acetate (2 carbons) covalently linked to choline
191
Q

how does the diameter of an axon relate to the speed of an action potential

A
  • directly related
  • larger axon diameter = faster movement of action potential
192
Q

define motor end plate

A

portion of the sarcolemma where the axon terminal connects at the neuromuscular junction

193
Q

what happens when an action potential moves down the axon to the axon terminal

A
  • causes depolarization of the axon membrane
  • leads to the opening of voltage gated calcium channels on the axon terminal
  • calcium will enter the axon terminal
194
Q

describe the movement of calcium when an action potential moves down an axon

A
  • calcium moves through voltage gated channels down its concentration gradient
  • higher concentration of calcium outside of the axon, so calcium will move into the axon
  • spike of calcium levels inside the axon terminal
195
Q

what does calcium do in the axon terminal

A

begins the exocytosis of acetylcholine vesicles into the synaptic cleft

196
Q

what does acetylcholine do in the synaptic cleft

A

binds to ligand gated sodium channel proteins on the motor end plate to open them

197
Q

how many acetylcholine bind to one ligan gated sodium channel for the channel to open

198
Q

what happens as sodium moves into the muscle cell through ligand gated channels on the motor end plate

A

depolarization of the motor end plate

199
Q

define end plate potential

A

the depolarization of the motor end plate as sodium enters the cell

200
Q

describe how the end plate potential moves to generate an action potential

A
  • end plate potential spreads to the sarcolemma from both sides of the motor end plate
  • generates an action potential
201
Q

define acetylcholinesterase

A
  • enzyme that breaks down (hydrolyzes) acetylcholine in the synaptic cleft after it has binded to sodium channels
  • off switch that stops overstimulation of cell
202
Q

what does acetylcholinesterase hydrolyze acetylcholine into

A
  • acetic acid
  • choline
203
Q

what is acetylcholinesterase in terms of acetylcholine

A

inhibitor of acetylcholine

204
Q

define toxins

A
  • blocks physiological pathways necessary for life
  • often understood to be bad
205
Q

how are toxins and medicines related

A

toxins can be used in some circumstances as a treatment for a condition

206
Q

define acetylcholinesterase inhibitors

A
  • toxins
  • inhibit acetylcholinesterase; stimulate acetylcholine
  • many different types with different potencies
207
Q

what acetylcholinesterase inhibitor is considered extremely strong

208
Q

define sarin

A
  • strong acetylcholinesterase inhibitor
  • toxin
  • aka nerve gas
209
Q

what is sarin often used for illegally

A
  • weapon of war
  • poison gas
210
Q

what recent war was sarin used against civilians in

A

syrian war

211
Q

what happens when someone inhales sarin

A
  • acetylcholinesterase in inhibited
  • acetylcholine levels rise dramatically
  • causes uncontrolled contractions, leading to respiratory failure and death
212
Q

what acetylcholinesterase inhibitor is considered mild

A

neostigmine

213
Q

define neostigmine

A
  • mild acetylcholinesterase inhibitor
  • toxin
  • soluble compound
214
Q

what condition is neostigmine often used as a treatment

A

myasthenia gravis

215
Q

define myasthenia gravis

A
  • autoimmune disease
  • body attacks protein channels in the synaptic cleft of skeletal muscle cells
  • because acetylcholine cannot bind to protein channels, the body has a hard time activating muscles leading to muscle weakness
216
Q

what are treatments for myasthenia gravis

A
  • cortisol
  • neostigmine
217
Q

describe how cortisol is a treatment for myasthenia gravis

A
  • cortisol suppresses the immune system
  • myasthenia gravis is caused by an overactive immune system
218
Q

what is the oral form of cortisol

A

prednisone

219
Q

describe how neostigmine is a treatment for myasthenia gravis

A
  • neostigmine inhibits acetylcholinesterase so there is more acetylcholine in the synaptic cleft
  • has more opportunities for acetylcholine to find protein channels that are healthy and stimulate them
220
Q

what toxins stimulate muscle contraction

A

acetylcholinesterase inhibitors

221
Q

what toxins are paralytics to muscles

A
  • botulinum toxin
  • curare
222
Q

what produces botulinum toxin

A

bacterium clostridium botulinum

223
Q

what is one of the most toxic compounds on earth

A

botulinum toxin

224
Q

how much botulinum toxin will kill someone

A

2 nanograms

225
Q

what does botulinum toxin do

A
  • interrupts the fusion of acetylcholine filled vesicles with the axon terminal membrane
  • no exocytosis of acetylcholine into the synaptic cleft
  • leads to weak muscles, paralysis, respiratory failure, and death
226
Q

how do people end up ingesting botulinum toxin

A

through poor canning sanitation processes

227
Q

what are the medical benefits of botulinum toxin

A
  • can treat spastic paralysis
  • can be used to smooth out wrinkles
228
Q

define spastic paralysis

A
  • motor neurons in the spinal cord are not well regulated
  • often caused by a stroke
  • person has no control over a particular muscle
229
Q

how does botulinum toxin treat spastic paralysis

A
  • can be injected into the muscle that has spastic paralysis
  • will inhibit the contraction of that muscle
230
Q

what is the name for botulinum toxin when it is being used to smooth out wrinkles

231
Q

how does botulinum toxin treat wrinkles

A
  • lightly paralyzes muscles of the face
  • smooths out the face but also lessens control of facial muscles
232
Q

define curare

A
  • plant neurotoxin
  • causes muscle weakness
233
Q

how was curare first used

A

hunting in old tribes to paralyze animals before killing them

234
Q

does curare have an effect on humans when taken orally

235
Q

how was curare first used in medicine

A
  • gateway drug for anesthesiology
  • relaxes muscles to allow for surgery, specifically relaxing tracheal muscles to allow for intubation
236
Q

what type of toxin is curare

A

antagonist

237
Q

describe what curare does

A
  • almost identical structure to acetylcholine
  • can bind to protein channels in the synaptic cleft but cannot open them; blocks acetylcholine from binding
  • muscles won’t react to action potentials causing muscle weakness
238
Q

what are the two voltage gated ion channels in the sarcolemma that propagate action potentials

239
Q

which voltage gated ion channels open first following an action potential

240
Q

describe what happens as Na+ voltage gated channels open in the sarcolemma

A
  • open immediately after action potential arrives
  • depolarization of sarcolemma as Na+ moves into the cell
  • polarity flips from -85 mv to slightly positive
  • channels close after 1/2 millisecond
241
Q

what part of the action potential wave is created when Na+ voltage gated channels open

A

first half

242
Q

describe what happens as K+ voltage gated channels open in the sarcolemma

A
  • open 1/2 millisecond after action potential arrives (happens to be right when Na+ channels close)
  • repolarization of sarcolemma as K+ moves out of the cell
243
Q

what part of the action potential wave is created when K+ voltage gated channels open

244
Q

define threshold potential

A
  • the potential needed for voltage gated Na+ channels to open
  • -55 mv
245
Q

how long are voltage gated Na+ channels open after detecting an action potential

A

1/2 millisecond

246
Q

at what polarity do voltage gated K+ channels open

247
Q

define after hyperpolarization

A

following the closing of voltage gated K+ channels after an action potential, the sarcolemma gets too negative (lower than -85 mv)

248
Q

how is after hyperpolarization addressed

A

sodium potassium pump re-establishes the RMP

249
Q

describe what it means that an action potential is a self-reinforcing chain reaction

A

uses positive feedback to move the action potential down the sarcolemma

250
Q

when does the self-reinforcing chain reaction of an action potential end

A

when it reaches the end of the sarcolemma

251
Q

what would happen if voltage gated Na+ and K+ channels opened at the same time after an action potential

A
  • nothing
  • depolarization and repolarization at the same time would cancel out
252
Q

what happens to the thick and thin filaments during muscle contraction

A

thin filaments are pulled and slide past the stationary thick filaments

253
Q

what are the 2 positions of the myosin head

A
  • high energy
  • lower energy
254
Q

describe the high energy position of the myosin head

A
  • energy in stored
  • myosin head is holding ADP or ADP+P
255
Q

describe the low energy position of the myosin head

A
  • no energy is stored
  • myosin head is holding nothing or ATP
256
Q

list the steps of cross bridge cycling

A
  • exposure of active sites
  • cross bridge formation
  • power stroke
  • cross bridge release
  • hydrolysis of ATP
  • recovery stroke
257
Q

describe this step of cross bridge cycling: 1. exposure of active sites

A
  • calcium levels must increase intracellularly
  • calcium binds to troponin
  • tropomyosin moves to expose the active sites on actin
258
Q

describe this step of cross bridge cycling: 2. cross bridge formation

A
  • myosin head binds to active site
  • phosphate detaches from the myosin head
259
Q

describe this step of cross bridge cycling: 3. power stroke

A
  • movement of the myosin head
  • actin filaments pulled past stationary myosin filament
  • ADP detaches from the myosin head
260
Q

describe this step of cross bridge cycling: 4. cross bridge release

A
  • ATP binds to the myosin head
  • myosin head detaches from the active site
261
Q

describe this step of cross bridge cycling: 5. hydrolysis of ATP

A

ATP is broken down into ADP and P

262
Q

describe this step of cross bridge cycling: 6. recovery stroke

A
  • breakdown of ATP supplies energy for recovery stroke
  • myosin head returns to high energy position
  • myosin head rebinds to an active site farther down on the actin filament
263
Q

what factors are necessary for cross bridge cycling

A
  • calcium (formation)
  • ATP (release)
264
Q

how many action potentials will generally run down the muscle cell compared to the number of action potentials that run down the neuron

A
  • same number
  • muscle cell action potentials generally mirror the number of action potentials in the neuron
265
Q

describe how calcium is released for the formation of cross bridges

A
  • action potential runs down sarcolemma and T tubule
  • depolarization opens voltage-gated calcium channels
  • calcium is released from the terminal cisterns
266
Q

define calcium pump proteins in the terminal cisterns

A
  • pump calcium back into the terminal cisterns
  • rely on ATP to function
  • always running to keep calcium levels high in concentration within the terminal cisterns
267
Q

what causes calcium levels to drop following the recovery stroke in cross bridge cycling

A

calcium pump proteins in the terminal cisterns pump calcium back into the terminal cisterns

268
Q

what is the “off switch” for cross bridge cycling

A
  • calcium pump proteins in the terminal cisterns
  • pump calcium back into the terminal cisterns, calcium will no longer bind to troponin, tropomyosin will cover active sites
269
Q

describe what happens in 1 cross bridge cycle compared to multiple cycles

A
  • 1 cycle: Z discs will move towards the M line slightly before titin pushes them back to the resting position
  • multiple: Z discs will move incrementally with each cycle towards the M line until the sarcomere is at full tetanus (or the action potentials stop arriving)
270
Q

what are the two requirements to maintain muscle contraction

A
  • high sarcoplasmic calcium levels
  • constant supply of ATP
271
Q

describe why muscles contractions stop when there is no ATP available

A
  • ATP is used to detach myosin heads from actin filaments
  • if there is no ATP, myosin heads cannot detach and the filaments will stay fused together, making the muscle stiff
272
Q

do skeletal muscle fibers store ATP

273
Q

describe how skeletal muscle fibers get ATP

A

adjust the synthesis of ATP based on the need for ATP

274
Q

what does skeletal muscle store and why is it important

A
  • glucose and oxygen
  • needed to make ATP when ATP is needed for muscle contraction
275
Q

do muscles usually run out of ATP

276
Q

what happens is a muscle runs out of ATP

A
  • physiological contracture: muscles seize up as myosin heads can’t detach from thin filaments
  • damages the muscle
277
Q

what usually happens before a muscle runs out of ATP

A
  • the muscle fiber will lose the ability to keep calcium levels high
  • stops the muscle from contracting, forcing relaxation
  • does not damage the muscle
278
Q

describe muscle fatigue and damage to muscle with the analogy of a car running out of gas and oil

A
  • running out of gas: muscle losing ability to keep calcium levels high; doesn’t damage muscle/car; needs to rest/refill
  • running out of oil: muscle running out of ATP; damages the muscle/car
279
Q

define rigor mortis

A

the body becoming stiff up to 12-16 hours after death

280
Q

how long after death does the body loosen up and decay

A

after 24 hours

281
Q

describe how/why rigor mortis occurs

A
  • muscle cells die so the calcium pumps in the terminal cisterns stop working causing calcium levels to rise slowly within the cell
  • there is some ATP still left within the cell
  • muscle contractions in flexing and extending muscles will occur as calcium levels rise
  • myosin heads will fuse to the thin filaments once the ATP runs out
282
Q

describe how the concept of rigor mortis is used in forensic science

A
  • can determine time of death based on level of rigor mortis if the temperature is known and a muscle sample is taken
  • only useful within 24 hours of death (before body becomes limp)
283
Q

what does the rate of rigor mortis depend on

A

temperature

284
Q

what does each action potential in a muscle fiber result in

A

muscle twitch

285
Q

what does myogram translate to

A

muscle chart

286
Q

how is tension produced in a single twitch measured

A

force-tension myogram

287
Q

what are the three phases of a muscle twitch

A
  • latent phase
  • contraction phase
  • relaxation phase
288
Q

how long is the latent phase of a muscle twitch

A

0-5 milliseconds

289
Q

describe what is happening at a gross anatomical level during the latent phase of a muscle twitch

A
  • nothing
  • no apparent physical response
290
Q

what triggers the start of the latent phase of a muscle twitch

A

action potential moving down the sarcolemma

291
Q

what is happening at a microanatomical level during the latent phase of a muscle twitch

A

excitation-contraction coupling

292
Q

describe excitation-contraction coupling

A
  • action potential moving down the sarcolemma and T tubules
  • voltage gated calcium channels in the terminal cisterns open and calcium diffuses into the muscle fiber
  • calcium binds to troponin causing tropomyosin to reveal active sites on actin
  • myosin heads bind to active sites on actin
293
Q

how long is the contraction phase of a muscle twitch

A

20-100 milliseconds

294
Q

describe what is happening during the contraction phase of a muscle twitch

A

power stroke: myosin filaments pulling actin filaments; sarcomere shortening

295
Q

how long is the relaxation phase of a muscle twitch

A

20-100 milliseconds

296
Q

describe what is happening during the relaxation phase of a muscle twitch

A
  • myosin heads detach from the actin filaments
  • sarcomere returns to a relaxed state
297
Q

how long is the total time of a muscle twitch

A

40-200 milliseconds

298
Q

define digital event

A

it either happens or it doesn’t, no in between

299
Q

define analog reponse

A

varying degrees or gradient of an event

300
Q

is a muscle twitch a digital event or analog reponse

A
  • digital event
  • it either happens or it doesn’t
301
Q

is most muscle activity a digital event or analog reponse

A
  • analog response
  • muscle activity requires graded contractions with variations in time and force
302
Q

what makes the analog response of a muscle movement possible

A
  • the controlling neuron
  • can send different frequencies of action potentials to change muscle contraction time and force
303
Q

what happens to muscle tension as the frequency of action potentials increases

A

muscle tension increases

304
Q

what frequency level will produce separate muscle twitches

A
  • low frequency
  • action potentials fired over 200 milliseconds apart
305
Q

how long does it take an action potential to reach the muscle fiber to begin a muscle contraction

A

1 millisecond

306
Q

which is faster: the electrical or mechanical event of muscle contraction

A

electrical event (action potential reaching muscle fiber)

307
Q

what frequency level will produce incomplete tetanus

A
  • intermediate frequencies
  • action potential fired before muscle has completely relaxed
308
Q

describe what happens to muscle tension during incomplete tetanus

A
  • increases with each action potential sent
  • the muscle doesn’t have time to fully relax before another action potential is fired leading to a more intense contraction
309
Q

are most muscle movements twitches, incomplete tetanus, or complete tetanus

A

incomplete tetanus

310
Q

what frequency level will produce complete tetanus

A
  • high frequency
  • neuron firing at maximal frequency
311
Q

describe the sarcomere during complete tetanus

A

maximally shortened

312
Q

what does an electromyogram measure

A

compound muscle potentials from multiple motor units

313
Q

what is the x-axis of both force-tension myograms and electromyograms

A

time (milliseconds)

314
Q

how are force-tension myograms and electromyograms different

A
  • force-tension myograms: measure tension directly
  • electromyograms: measure compound muscle potentials (excitation as a product of force, not force directly)
315
Q

what is a small motor unit

A

innervates 10-20 muscle fibers

316
Q

what is an intermediate motor unit

A

innervates 20-100 muscle fibers

317
Q

what is a large motor unit

A

innervates 1000s of muscle fibers

318
Q

what happens to the electromyogram spike as larger motor units are recruited

A

increasing the amplitude

319
Q

define Henneman’s size recruitment prinicple

A
  • small motor units will be recruited before larger motor units
  • controls the gradient of force to make muscle contractions smooth
320
Q

describe why we use electromyograms instead of force-tension myogrmas in clinical practice

A
  • electromyograms are painless, give good data, and can be done noninvasively
  • myograms must be done with a portion of the muscle taken out of the patient
321
Q

what are the four metabolic pathways that can generate ATP for muscle contraction

A
  • adenylate kinase
  • creatine kinase
  • anaerobic pathway
  • aerobic pathway
322
Q

what level of contraction are most daily muscle movements

A

minimal to moderate levels of contraction

323
Q

what happens when ATP goes down

A

ADP goes up

324
Q

what is the first metabolic pathway used for ATP generation for muscle contraction

A

adenylate kinase

325
Q

define kinase

A

an enzyme that transfers a phosphate from one molecule to another

326
Q

what does adenylate kinase do

A
  • transfers a phosphate from one ADP to another ADP
  • creates AMP (1 phosphate) and ATP (3 phosphates)
327
Q

how long can adenylate kinase create ATP for muscle contraction

A

2-3 seconds

328
Q

what is the second metabolic pathway used for ATP generation for muscle contraction

A

creatine kinase

329
Q

what does creatine kinase do when your muscle is at rest

A
  • transfers a phosphate group from ATP to creatine to make ADP and creatine phosphate
  • done because the muscle cell can store creatine phosphate but not ATP
330
Q

what does creatine kinase do when your muscle is contracting

A

transfers phosphate from creatine phosphate to ADP to make ATP

331
Q

what is the fastest metabolic reaction for generating ATP for muscle contraction

A

creatine kinase

332
Q

how long can creatine kinase create ATP for muscle contraction

A

5-7 seconds

333
Q

how long can adenylate kinase and creatine kinase create ATP for muscle contraction

A

10 seconds

334
Q

about how long does it take the aerobic pathway to be primed to create ATP

A

10-20 seconds

335
Q

what is the purpose of adenylate kinase and creatine kinase pathways

A
  • give muscle ATP while the aerobic or anaerobic pathway is getting ready to create ATP
336
Q

what are the two pathways that could follow after adenylate kinase and creatine kinase

A
  • aerobic pathway
  • anaerobic pathway
337
Q

when would the muscle use the aerobic pathway for ATP generation

A
  • if adequate oxygen is available
  • during mild to moderate muscle contraction
338
Q

when would the muscle use the anaerobic pathway for ATP generation

A
  • if adequate oxygen is not available
  • during extreme movement and muscle contraction
339
Q

what is the preferred metabolic pathway of ATP generation for muscle contraction

A

aerobic pathway

340
Q

what is the general equation for the aerobic pathway of ATP generation for muscle contraction

A

glucose + oxygen = 36 ATP + carbon dioxide + water

341
Q

list the general steps of the aerobic pathway of ATP generation

A
  • glycolysis
  • citric acid cycle
  • electron transport chain and oxidative phosphorylation
342
Q

where does glycolysis take place

A

in the cytoplasm

343
Q

how many steps are in glycolysis

344
Q

what is the general equation of glycolysis

A

glucose = 2 pyruvate + 2 ATP

345
Q

where does the citric acid cycle take place

A

mitochondria

346
Q

how many steps are in the citric acid cycle

347
Q

how much ATP does the citric acid cycle produce

348
Q

where does the electron transport chain and oxidative phosphorylation take place

A

mitochondria

349
Q

how much ATP does the electron transport chain and oxidative phosphorylation produce

350
Q

how much ATP does the aerobic pathway produce in total

351
Q

what is the main downside to the aerobic pathway of ATP production

A

it’s a very slow process because there are many steps that take place in different parts of the cell

352
Q

how long can the aerobic pathway create ATP for muscle contraction

353
Q

describe the process of the anaerobic pathway of ATP production

A

glycolysis (and lactate formation)

354
Q

how is glycolysis different in the anaerobic pathway of ATP production compared to the aerobic pathway

A
  • glycolysis has an extra step in the anaerobic pathway
  • pyruvate is converted to lactate
355
Q

how many ATP are produced in the anaerobic pathway of ATP production

356
Q

what is the upside to the anaerobic pathway of ATP production

A
  • very fast process
  • almost as fast at creatine kinase reactions
357
Q

what is the downside to the anaerobic pathway of ATP production

A
  • only makes 2 ATP
  • not sustainable, cannot continue extreme contractions for long
  • lactic acid formation lowers cell and blood pH
358
Q

how long can the anaerobic pathway create ATP for muscle contraction

A

30-40 seconds

359
Q

what happens to the pH of the cell and the blood during the anaerobic pathway of ATP production and why

A
  • pH lowers (more acidic)
  • lactic acid is created during this pathway which lowers pH
360
Q

describe how someone could run a 4 minute mile

A
  • combining aerobic and anaerobic pathways of ATP production
  • must have high aerobic capacity to continue aerobic respiration for a longer time during extreme movement
361
Q

who was Robert Banister

A
  • physician
  • first person to break the 4 minute mile
362
Q

what are the 3 types of fibers in muscles

A
  • slow-twitch oxidative (SO) fibers (type I)
  • fast-twitch oxidative glycolytic (FOG) fibers (type IIa)
  • fast-twitch glycolytic (FG) fibers (type IIb)
363
Q

describe what muscle fiber types are in every muscle and how they compare in proportions

A
  • all muscles have all fiber types
  • muscles differ in the proportion of each fiber type that is in them
364
Q

describe slow-twitch oxidative fibers

A
  • SO fibers
  • type I
  • use aerobic pathway
365
Q

describe fast-twitch oxidative glycolytic fibers

A
  • FOG fibers
  • type IIa
  • can use both aerobic and anaerobic pathways
366
Q

describe fast-twitch glycolytic fibers

A
  • FG fibers
  • type IIb
  • use anaerobic pathway
367
Q

define myoglobin

A
  • produced by muscle cells
  • stores oxygen in muscle cells until it is needed for ATP production
368
Q

describe the myoglobin content of slow-twitch oxidative (SO) fibers (type I)

A
  • high
  • need lots of oxygen for aerobic respiration
369
Q

describe the mitochondria number of slow-twitch oxidative (SO) fibers (type I)

A
  • many
  • aerobic respiration takes place in mitochondria
370
Q

describe the capillary number of slow-twitch oxidative (SO) fibers (type I)

A
  • many
  • needed to receive oxygen for aerobic respiration
371
Q

describe the metabolism of slow-twitch oxidative (SO) fibers (type I)

A
  • high aerobic capacity
  • low anaerobic capacity
372
Q

what is the relationship between power/speed and endurance

A
  • inverse relationship
  • high power/speed = low endurance
  • low power/speed = high endurance
373
Q

describe the endurance of slow-twitch oxidative (SO) fibers (type I)

A
  • high
  • slow and efficient so they can work for long periods of time
  • low power/speed = high endurance
374
Q

what are the two types of myosin ATPases in muscle fibers

375
Q

what does myosin ATPase do

A

enzyme that performs hydrolysis on ATP during cross bridge cycling

376
Q

describe the myosin ATPase activity of slow-twitch oxidative (SO) fibers (type I)

A
  • slow
  • slower cross bridge cycling because it takes longer for myosin ATPase to hydrolyze ATP
377
Q

describe the glycogen concentration of slow-twitch oxidative (SO) fibers (type I)

A
  • low
  • less needed for aerobic respiration
378
Q

what muscles are slow-twitch oxidative (SO) fibers (type I) most abundant in

A
  • postural muscles -> muscles holding the head up
  • core muscles in torso
  • more in lower limbs than upper limbs
379
Q

how much does the head weight

380
Q

describe the functions of slow-twitch oxidative (SO) fibers (type I)

A
  • maintenance of posture
  • performance of endurance activities
381
Q

describe the myoglobin content of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • high
  • need lots of oxygen for aerobic respiration
382
Q

describe the mitochondria number of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • many
  • aerobic respiration takes place in the mitochondria
383
Q

describe the capillary number of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • many
  • needed to receive oxygen for aerobic respiration
384
Q

describe the metabolism of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • intermediate aerobic capacity
  • high anaerobic capacity
385
Q

describe the endurance of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A

intermediate

386
Q

describe the myosin ATPase activity of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • fast
  • faster cross bridge cycling because it takes less time for myosin ATPase to hydrolyze ATP
387
Q

describe the glycogen concentration of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A
  • high
  • need glucose for the anaerobic pathway (glycolysis)
388
Q

what muscles are fast-twitch oxidative glycolytic (FOG) fibers (type IIa) most abundant in

A

lower limbs

389
Q

describe the functions of fast-twitch oxidative glycolytic (FOG) fibers (type IIa)

A

endurance activities in endurance-trained muscles

390
Q

describe the myoglobin content of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • low
  • anaerobic pathway doesn’t require oxygen
391
Q

describe the mitochondria number of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • few
  • anaerobic pathways do not enter the mitochondria
392
Q

describe the capillary content of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • few
  • oxygen from capillaries is not needed in the anaerobic pathway
393
Q

describe the metabolism of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • low aerobic capacity
  • highest anaerobic capacity
394
Q

describe the endurance of fast-twitch glycolytic (FG) fibers (type IIb)

395
Q

describe the myosin ATPase activity of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • fast
  • faster cross bridge cycling because it takes less time for myosin ATPase to hydrolyze ATP
396
Q

describe the glycogen concentration of fast-twitch glycolytic (FG) fibers (type IIb)

A
  • high
  • need glucose for the anaerobic pathway (glycolysis)
397
Q

what muscles are fast-twitch glycolytic (FG) fibers (type IIb) most abundant in

A

upper limbs

398
Q

describe the functions of fast-twitch glycolytic (FG) fibers (type IIb)

A

rapid and intense movements of short duration

399
Q

what type of muscle fiber is in high concentration in the soleus muscle and why

A
  • high concentration of slow oxidative fibers
  • soleus is an endurance muscle needed for walking
  • needs less power/speed and more endurance
400
Q

what type of muscle fiber is in high concentration in the gastrocnemius muscle and why

A
  • high concentration of fast glycolytic fibers
  • gastrocnemius is used for higher intensity movement such as running
  • needs more power/speed and less endurance
401
Q

do everyone’s muscles have the same proportions of muscle fiber types

A
  • no, there are variations in proportions between people
  • why some people are better at power athletics and some are better at endurance
402
Q

describe how exercise effects fast glycolytic fibers

A
  • makes them hypertrophy
  • get stronger through the hypertrophy
403
Q

describe how exercise effects slow oxidative fibers

A
  • won’t hypertrophy
  • get stronger by recruiting more mitochondria, myoglobin, and capillaries (more oxygen capacity)

BIOL 319 (15 decks)

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