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anatomy > muscles > Flashcards

muscles Flashcards

1
Q

skeletal muscle tissues

A

striations; long, cylindrical cells called muscle fibers;
multinucleate cells

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2
Q

cardiac muscle tissues

A

striations; branching cells with intercalated discs;
uninucleate cells

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3
Q

smooth muscle tissue

A

No striations; spindle-shaped cells.
uninucleate cells

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4
Q

skeletal muscle as an organ consists of

A

-skeletal muscle tissue
- Connective tissue (CT) membrane
- blood vessels
-nerve endings

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5
Q

Each skeletal muscle fiber ( = skeletal muscle cell) is wrapped in..

A

a delicate CT membrane called ENDOMYSIUM

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6
Q

Fascicle

A

consists of a group of endomysium-covered muscle
fibers wrapped in a coarse CT membrane called PERIMYSIUM

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7
Q

Skeletal muscle (the organ)

A

consists of a group of fascicles
wrapped in a tough CT membrane called EPIMYSIUM
Skeletal muscles are attached to bones in the skeletal system

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8
Q

Patterns of arrangement of fascicles in skeletal muscles

A

Muscle fibers in a skeletal muscle form bundles called fascicles.
The muscle fibers in a single fascicle are parallel, but the
organization of fascicles in the skeletal muscle can vary, as can
the relationship between the fascicles and the associated tendon.
The different patterns of fascicle organization form parallel
muscles, convergent muscles, pennate muscles, circular muscles

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9
Q

The muscle fibers in a single fascicle are

A

parallel

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10
Q

parallel muscles

A

In a parallel muscle, the fascicles are parallel to the long axis of the muscle. Most of
the skeletal muscles in the body are parallel muscles. Example: Biceps brachii
muscle

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11
Q

convergent muscles

A

in a convergent muscle, the muscle fibers are spread over a broad area, but all the
fibers converge at one common attachment site.
Example: Pectoralis major

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12
Q

pennate muscles

A

In a pennate muscle, the fascicles form a common angle with the tendon.
Example: Deltoid

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13
Q

circular muscles

A

the fascicles are arranged in concentric rings; they surround external body openings.
Example: Orbicularis oris

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14
Q

direct attachments

A

the epimysium of the skeletal muscles is fused directly to the periosteum.
the CT fuses with the bone

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15
Q

indirect attachments

A

the connective tissue wrappings of the skeletal muscles extend as a tendon or an aponeurosis to anchor the muscle to bone, cartilage or facia.
outer CT forms a tendon that connects to the bone.
most skeletal muscles in human bod are attached indirectly.

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16
Q

the advantages of indirect attachment of skeletal muscles (1)

A

1.) tendons occupy smaller bone surface so that 650 SM can attach to 206 bones in the bod

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17
Q

the advantages of indirect attachment of skeletal muscles (2)

A

2.) several skeletal muscles binding to the same bone allows for interrelationships in the functions of skeletal muscles such as synergistic muscles and antagonistic muscles

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18
Q

the advantages of indirect attachment of skeletal muscles (3)

A

3.) protects skeletal muscles (flesh) from direct contact with the rough bone surface which can tear the skeletal muscles

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19
Q

the advantages of indirect attachment of skeletal muscles (4)

A

4.) allows for on bones to act a lever for movement when skeletal muscles coursing over joints contract

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20
Q

advantages of direct attachment of skeletal muscles

A

to provide physical protection to vital organs in the body cavities

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21
Q

myoglobin

A

a red pigment that binds and stores oxygen

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22
Q

myofibrils

A

rod-like structures that run the entire length of the muscle fiber;
80% of the volume of the muscle fiber is occupied by the myofibrils. Myofibrils
contain 2 myofilaments: thick filaments and thin filaments

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23
Q

inclusions

A

glycosomes contain glycogen

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24
Q

mitochondria

A

or aerobic respiration to produce energy

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25
Q

sarcoplasm

A

cytoplasm of the muscle fiber

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26
Q

sarcolemma

A

plasma membrane of muscle fiber

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27
Q

Sarcoplasmic reticulum(SR)

A

specialized smooth endoplasmic
reticulum that stores/releases calcium into the sarcoplasm; the expanded ends of
SR are called TERMINAL CISTERNAE

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28
Q

triad

A
  • composed of a transverse tubule in between 2 terminals cisternae of two SR
    function is to release calcium ions into the sarcoplasm when the sarcolemma depolarizes.
29
Q

Myofilaments

A

each myofibril contains smaller structures called myofilaments, there are 2 types

30
Q

thick filaments

A

16nm in diameter; composed of the protein
MYOSIN . Each thick filament consists of 300 myosin molecules .
Thick filament is also known as an A band
Each myosin consists of a tail and 2 globular heads.
The myosin globular heads contain the enzyme ATPase; binding sites for
actin; binding sites for ATP

31
Q

thin filaments

A

8nm in diameter; anchored by the Z lines; Thin
filaments contain 3 different proteins:
- Actin
- Tropomyosin
- Troponin

32
Q

actin (thin filaments)

A

several actin proteins for the structural framework of the thin
filament. Actin molecules contain the binding sites for the myosin
globular heads

33
Q

tropomyosin (thin filaments)

A

a rod-shaped regulatory protein that spirals around the actin
and blocks myosin binding sites on actin in a relaxed skeletal muscle

34
Q

troponin (thin filaments)

A

a three-polypeptide complex namely (refer to slide #19)
TnC – binds calcium ions (ca2+)
TnT – binds to tropomyosin
TnI - inhibitory subunit that binds to actin
300 myosin

35
Q

sarcomeres

A

Sarcomeres are the Structural and Functional units of skeletal
muscles = sarcomeres are arranged end to end throughout a
myofibril

36
Q

Length of a sarcomere

A

A sarcomere is the distance between 2 successive Z discs in a
myofibril.

37
Q

Thick and thin filament

A
  • Thick filament: A band
    -Thin filaments alternating with “A” bands; the alternating
    pattern of the thick and thin filaments results in the characteristic
    striated appearance of skeletal muscle
38
Q

Z discs (zlines)

A

anchor the thin filaments in myofibril.

39
Q

H zone

A

middle region of the A band not overlapping with the thin filament.

40
Q

M line

A

line that bisects the H zone and anchors the A band.

41
Q

Transverse tubules(T-tubules)

A

involutions of the sarcolemma into the
sarcoplasm

42
Q

I bands

A

region of the thin filament not overlapping with the A band

43
Q

The sliding filament mechanism of muscle contraction

A

states that the sliding of the thin filaments in the sarcomeres into the H zone, toward the M results in muscle shortening= contraction. shorting of the sarcomere results in shortening of myofibrils which result in shorting of skeletal muscle fibers and thus, shortening (contraction) of the skeletal muscle.

44
Q

What happens to everybody when the muscles contract?

A

According to this mechanism when a muscle
contracts there is more overlap between the thin
filaments and the A bands:
- H zone decreases or disappears
- I bands decrease or disappear
- Sarcomere length shortens = Skeletal muscle
shortens ( contracts)
*** However, the length of the A bands
and the length of the thin filaments remain the
same – they do not shorten

45
Q

Wat stimulates skeletal muscles to contract.

A

When motor neurons that innervate skeletal muscles are activated

46
Q

How do motor neurons make contact with skeletal muscles fibers

A

Axon terminals

47
Q

each axon terminal innervates one skeletal muscle fiber in the skeletal muscle to form..

A

The neuromuscular junction

48
Q

Motor Unit

A

A motor neuron and all the skeletal muscle fibers it
innervates in a skeletal muscle via its axon terminals is
called a MOTOR UNIT
* Motor units come in different sizes based on
the number of skeletal muscle fibers
innervated by a motor neuron via its axon
terminals: small motor units; medium-sized
motor units; large motor units

49
Q

Motor unit size?

A

Motor units come in different
sizes based on the number of
skeletal muscle fibers
innervated by a motor units via
their axon terminals small motor
units; medium-sized motor
units; large motor units

50
Q

The neuromuscular junction

A

forms between an axon
terminal of a motor neuron and the motor end plate at the sarcolemma of a skeletal muscle
fiber. Each skeletal muscle fiber forms only one neuromuscular junction with an axon
terminal; each skeletal muscle fiber is a member of a single motor unit

51
Q

motor end plate

A

The highly folded region of the
sarcolemma of the muscle fiber at the
neuromuscular junction is called the
Motor End Plate – expresses
acetylcholine receptors

52
Q

factors that affect the strength/force of skeletal muscles contraction

A
  • size of motor units activated
  • number of motor units activated
  • frequency of skeletal muscles activation
    the length of the sarcomere prior to contraction
53
Q

size of motor units activated

A

larger motor units generate more force in a
skeletal muscle than smaller motor units

54
Q

number of motor units activated

A

force by a contracting skeletal muscle
increases as the number of motor units activated increases
Recruitment refers the order in which motor units are activated in a skeletal
muscle - smaller motor units are activated first followed by medium-sized motor
units and then the large motor units

55
Q

frequency of skeletal muscles activation

A

force generatedbythe skeletal muscle
increases as the rate of skeletal muscle stimulation increases

56
Q

the length of the sarcomeres prior to contraction

A

sarcomeres at the
optimum length generate the maximum force; sarcomere length below the
optimum length ( shortened sarcomeres) results in decreased force; sarcomere
length greater than the optimum length ( stretched sarcomeres) results in
decreased force of contraction

57
Q

Isometric contraction

A

force(tension) generated by the muscle is
increasing at a constant muscle length (
“isometric” = same length); occurs when the
weight exceeds the force generated by the
muscle

58
Q

isotonic contraction

A

muscle length changes at a relatively constant
force
( isotonic = same force)

59
Q

Resistance exercise or isometric exercises (weightlifting, isometric exercises where muscles are pitted against immovable objects)

A

changes that occur in the skeletal muscles:
Increase in the size of skeletal muscles = hypertrophy of skeletal muscles
occur due to increase in the number of myofibril within each muscle fiber
Increase in glycogen content
Overall, bulky muscles generate more force = increase in muscle strength

60
Q

Aerobic or endurance exercise (jogging, biking, swimming)

A

changes that occur in the skeletal muscles:
increase in capillaries
increase in mitochondria
increase in myoglobin content
Overall, endurance improved = increase in stamina

61
Q

2 types of smooth muscle

A

based on smooth muscle fiber arrangement, innervation and responsiveness to stimuli

62
Q

single unit smooth muscle

A

Composed of circular and longitudinal smooth muscle layers in the walls of
organs
– Innervated by autonomic nerve fibers
– Electrically-coupled by gap junctions hence, single-unit smooth muscle
all the cells contract at the same time– functional syncytium
– Stimulated to contract by chemicals
– **Exhibit pacemaker activity

63
Q

multiunit smooth muscle

A

Composed of individual smooth muscle fibers
– Lacks gap junctions – smooth muscle cells contract independently, not
together as a unit
– Innervated by the autonomic nerve fibers
– Stimulated to contract by chemicals
– No pacemaker activity

64
Q

concentric contraction

A

Force generated by
skeletal muscle exceeds the weight so the
skeletal muscle shortens, and work is done,
such as lifting the weight.

65
Q

eccentric contraction

A

force/tension develops as
the skeletal muscle lengthens

66
Q

3 major types of skeletal muscles fiber types based on 2 criteria

A
  • speed of contraction
  • major pathway for ATP production
67
Q

speed of contraction

A

due to the speed at which Myosin ATPase
hydrolyzes ATP to activate the myosin globular heads- 2 types:
- slow ATPase in slow fibers
- fast ATPase in fast fibers

68
Q

3 skeletal types

A

Slow Oxidative Fibers (also known as red fibers)
ii) Fast Oxidative Fibers (also known as intermediate fibers)
iii) Fast Glycolytic fibers (also known as white fibers)

anatomy (8 decks)

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