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Pathophysiology > Muscular System > Flashcards

Muscular System Flashcards

1
Q

skeletal muscles
functions
characteristics

A

Main Functions:
* Movement
* Heat production
* Posture

has crosswise stripes, or striations
Contractions can be voluntarily controlled

Characteristics of skeletal muscle
fibres:
* Excitability
* Contractility
* Extensibility

contract due to acetylcholine and relax because acetylcholine esterase breaks it down

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2
Q

Cardiac Muscle

A
  • Striated involuntary muscle
  • Only in the heart
  • Intercalated disks between fibres – forms continuous, electrically coupled mass (syncytium)
  • Single impulse across sarcolemma – coordinated pumping action
  • Self-exciting
  • Prolonged contractions
  • won’t produce tetanus
  • doesn’t fatigue (use up all the ATP available)
  • Sparse SR, forms diads with T-tubules
  • Mechanism of contraction and energy sources
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3
Q

Smooth Muscle

A

also called nonstriated, involuntary, or visceral muscle
Found in walls of hollow visceral structures such as digestive tract, blood vessels, and ureters
changing pupil diameter

two types of smooth muscle multiunit (if one fiber is stimulated then the others are as well ) and visceral
has autorhythmicity like cardiac muscle but used for peristalsis
aCH and norep

multiunit helps to move hormones

  • No T-tubules, loosely arranged SR
  • Ca++ comes from outside of cell, binds to calmodulin to trigger contraction
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4
Q

Overview of the Muscle Fibre
(Cell)

A

Sarcolemma – cell membrane
* Sarcoplasm – cytoplasm
* Lots of mitochondria, several nuclei

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5
Q

Sarcomeres

A

smallest functioning unit of muscle
* composed of actin (thin) and myosin (thick) protein myofilaments
* one sarcomere extends from “Z Line to Z line
causes striations

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6
Q

Myofibrils

A

“straw-like” structures extending length of cell (about 1-3 µm in diameter)
* composed of myofilaments

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7
Q

Myofilaments

A

Very fine filaments of 2 types: thick filaments and thin filaments
* Filaments are organized into sarcomeres

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8
Q

4 different kinds of protein molecules make up myofilaments -thin filments

A

Myosin
* Actin-2 helical strands of fibrous actin with binding sites (strung together like beads)
* Tropomyosin -Protein; wraps around within the groove formed by helix of actin
* Troponin -3 binding subunits binds to actin, tropmysosin, ca2

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9
Q

Thick Filaments

A

Myosin
* “thick” rods shaped like a golf club
Myosin Heads
* contain ATPase
* have binding site for actin myofilament

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10
Q

Mechanism of Contraction
Excitation of the Sarcolemma

A

Motor neurons connect to the sarcolemma and form a
neuromuscular junction
* Neurotransmitter acetylcholine (Ach) is released and initiates an electrical impulse

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11
Q

Mechanism of Contraction
Sliding Filament Theory

A

ATP binds to myosin head
ca released and binds to trop
troponin/tropmyosin binding complex is changed
actin binding sites unblock so myosin heads can bind
ATP realeased
ADP released and actin/myosin bond is broken
. If ATP and Ca2+ are available, more cross bridges are formed

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12
Q

Mechanism of Contraction
Relaxation

A
  • SR actively pumps Ca++ back into sacs
  • Tropomyosin moves back to cover actin active sites – myosin heads are blocked
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13
Q

Energy Sources for
Contraction

A

ATP
* Hydrolysis of ATP
* Muscle fibres must continuously resynthesize ATP
* Creatine phosphate (CP) can be used as backup energy
* ATP and CP resynthesized by cellular respiration

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14
Q

Glucose –

A

catabolized in sarcoplasm and mitochondria, energy
transferred to ATP and CP molecules
* glucose stored as glycogen (uninterrupted supply)
* glucose from blood stream

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15
Q

Oxygen as energy source

A

from blood –carried by hemoglobin, aerobic respiration
* Stored in cells attached to myoglobin

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16
Q

Anaerobic Respiration

A

pyruvic acid will be converted to lactic acid that accumalates in the cell
* diffuses out of the cell and taken to liver
* can be converted to glucose by liver or to pyruvic acid by cardiac muscle

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17
Q

Motor Unit**

A

is a nerve cell that transmits an impulse to a muscle, causing contraction

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18
Q

Twitch Contraction

A

quick, jerky responses to a stimulus— are
laboratory phenomena and do not play a significant role in
normal muscular activity

Latent period – impulse along sarcolemma and down T-tubules resulting in release of Ca++ ions
2. Contraction phase – binding of Ca++ to troponin and sliding of myofilaments
3. Relaxation phase – sliding ceases

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19
Q

“All Or None Principle”
of Muscle Contraction

A

when motor unit receives a stimulus strong enough to generate a response. The muscle fibres in the unit will all contract at the same time to the most possible extent

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20
Q

Muscles exhibit graded contractions (when stimuli is applied to a nerve) in two ways

A

Multiple Motor Unit (Spatial) Summation
* increasing the strength of stimulus increases the strength of contraction by recruiting more units

Wave Summation and Tetanization
* increasing frequency of stimulation to a muscle cell before it has relaxed from a previous stimulus building on the stimuli causes a wave pattern sustained contraction is called tetany or tetanus

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21
Q

isometric**
Types of Contractions

A
  • muscle contractions that do not produce movement;
  • e.g. Postural muscles maintain same length
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22
Q

Isotonic
Types of Contractions

A
  • Contraction of a muscle that produces movement at a joint
  • e.g. Most arm and finger movements
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23
Q

Types of Smooth Muscle
Visceral (single unit) Muscle

A
  • Large sheets, gap junctions between individual fibres
  • Muscular layer in walls of hollow structures
  • Autorhythmicity
  • Example of movement: peristalis
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24
Q

Multiunit Muscle
Types of Smooth Muscle

A

Made up of many independent single-cell units
* Responds to nervous system input
* Can be found as sheets, bundles, or single fibres

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25
Q

: Strain

A
  • Stretched or torn muscle or tendon:
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26
Q

Sprain

A

Stretched or torn ligament:

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27
Q

: Myositis

A

Muscle inflammation:

28
Q

Fibromyositis

A
  • Tendon & muscle inflammation:
29
Q

Contusion

A
  • Muscle bruise:
30
Q
  • Crush Injury
A

severe trauma to skeletal muscle
* Releases muscle contents
* Can be fatal – myoglobinuria (acute renal failure)

31
Q
  • Tetanus
A
  • CNS infection with Clostridium tetani
  • Toxin overactivates nervous system
  • Painful muscle spasms
32
Q

Poliomyelitis

A
  • Virus infects nerves controlling sketelal muscle
  • Can lead to paralysis and death
33
Q

Duchenne muscular dystrophy

A
  • Progressive muscle weakness
    Defect of dystrophin - muscle protein essential for membrane integrity
    atrophy of skeletal muscle
    most common type of MD
    braces are used to treat it
34
Q

Myasthenia Gravis

A
  • Autoimmune disorder
  • Receptor sites for Ach are destroyed
  • Can cause severe motor weakness
35
Q

Serum creatine kinase (CK)

A

Marker for muscle pathologies
* Increases in myocardial infarction, rhabdomyolysis (muscle breakdown), muscular dystrophies, crush injuries

  • Additional enzymes that may be elevated:
  • lactate dehydrogenase (LD)
  • aspartate aminotransferase (AST)
  • alanine aminotransferase (ALT)
36
Q

types of movement of skeletal muscle

A

a. Prime mover— muscle responsible for most of the movement of the involved joint
b. Synergist— muscle that help prime mover by stabilizing joints
c. Antagonist— muscle that produces a movement opposite to that of the prime mover

37
Q

Tetanic contractions

A

sustained and steady muscular
contractions caused by a series of stimuli bombarding a muscle in rapid succession

38
Q

Individual muscle cells are surrounded by

A

endomysium

39
Q

what divides muscles into sections called fascicles

A

The perimysium is a sheath of connective tissue that surrounds a fascicle, or group of muscle fibers

40
Q

what does Fascia do

A

helps support and hold together muscles and other structures, such as blood vessels, bones, and nerves

41
Q

what is aponeurosis

A

fibrous connective tissue that attaches muscles to other muscles

42
Q

what is an origin

A

attachment site to the less movable bone when a muscle contracts it does not move when a muscle contracts

43
Q

what is an insertion

A

An attachment site to the more moveable bone that moves when a muscle contracts

44
Q

Gluteus medius

A

moves the thigh

45
Q

temporalis muscle

A

moves the jaw.

46
Q

trapezius muscle

A

moves the shoulder

47
Q

. Gastrocnemius

A

flexes the foot and is commonly called the calf muscle

48
Q

external oblique

A

muscle moves the abdominal wall.

49
Q

. sternocleidomastoid

A

muscle moves the head

50
Q

Muscle fatigue occurs when

A

when lactic acid levels are high, which causes pH levels to decrease.

51
Q

Perimysium

A

Perimysium surrounds a fascicle.

52
Q

Muscle cells are called

A

myocytes; myofibrils are the long structures within the sarcoplasm of a myocyte.

53
Q

What is the role of myoglobin in muscle contraction

A

Oxygen carrier in muscle

54
Q

a sign that oxygen debt is occurring

A

Heavy breathing

55
Q

The biceps brachii and triceps brachii are

A

antagonistic

56
Q

orbicularis oris

A

used in forming a kiss

57
Q

zygomaticus major

A

used to smile.

58
Q

. trapezius

A

trapezius adducts, depresses, and rotates the scapulae and helps extend the neck.

59
Q

aid in the process of inhalation

A

diaphragm and external intercostals

60
Q

rectus abdominis

A

flexes the trunk

61
Q

deltoid muscle

A

abducts the arm

62
Q

pectoralis major

A

flexes, adducts, and medially rotates the arm

63
Q

extensor digitorum muscle

A

extends the phalanges.

64
Q

biceps femoris

A

flexes the knee.

65
Q

iliopsoas muscle

A

extends and laterally rotates the thigh and also flexes the trunk.

66
Q

The tibialis anterior muscle

A

dorsiflexes and inverts the foot

67
Q

gastrocnemius muscle

A

allows you to stand on your tiptoes

Pathophysiology (6 decks)

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