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FB1 Endterm - Anatomy > 21 - Classifications of Skeletal Muscle > Flashcards

21 - Classifications of Skeletal Muscle Flashcards

1
Q

How do we classify muscles?

A

By the way fascicles are organized + relationship of fascicles with tendons

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2
Q

What are the four patterns of fascicle organization? Describe them

A
  1. Parallel: muscles are parallel to long axis of muscle
  2. Convergent: fascicles converge toward a single insertion tendon
  3. Pennate: fascicles are obliquely attached to central tendon
  4. Circular: fascicles are arranged in concentric rings around opening/recess
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3
Q

What fascicle organization is the most common?

A

Parallel

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4
Q

Which fascicle organization is the strongest? Be specific

A

Pennate muscles with the highest concentration of fibers, they shorten a little

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5
Q

What are the types of parallel fascicles? Provide examples

A
  1. Straplike with aponeurosis/broad attachment → sartorius or sternohyoid
  2. Straplike with tendinous intersections → rectus abdominis
  3. Fusiform: spindle shaped with expanded belly → biceps brachii
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6
Q

What happens when pennate muscles contract?

A

They shorten

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7
Q

What’s an example of a convergent muscle?

A

Pectoralis major

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8
Q

What are the types of pennate muscles? Describe them and provide examples

A
  1. Unipennate, fascicles insert into one side of tendon
    o Extensor digitorum longus
  2. Bipennate, fascicles insert into both sides of tendon
    o Rectus femoris
  3. Multipennate, fascicles branch
    o Deltoid and subscapularis
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9
Q

Where are circular muscles found and what happens when they contract?

A

They’re found in external body openings, the diameter of the opening decreases as they contract

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10
Q

What are circular muscles called?

A

Sphincters

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11
Q

What’s an example of a circular muscle?

A

Orbicularis oris muscles

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12
Q

How do we classify muscles based on functional groups?

A

Prime movers (agonist), antagonists, synergists, and fixators

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13
Q

What is a prime mover?

A

Muscle that provides the major force for producing a movement

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14
Q

What is an antagonist?

A
  • Muscle that opposes a prime mover, regulating its action

* When a prime mover is active, antagonists are stretched or are in a relaxed state

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15
Q

What is a synergist?

A

Muscle that aids prime mover in movement and helps prevent rotation

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16
Q

What do synergists do in two joint muscles? Such as hinge or bone & socket joints?

A

They stabilize the joint

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17
Q

What is a fixator?

A

A synergist that immobilizes a muscle’s origin, it stabilizes the bone that the prime mover acts on

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18
Q

During elbow flexion, classify each muscle and its function + joint

A
  1. Prime mover: biceps brachii
  2. Antagonist: triceps
  3. Synergist: brachialis
  4. Fixator: serratus anterior → holds scapula against thorax
  5. Joint: hinge joint
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19
Q

What about elbow extension, what’s the prime mover & antagonist?

A

Prime mover is triceps & antagonist is biceps brachii

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20
Q

How do we name skeletal muscles?

A

Direction of muscle fibers + location + size + number of origins + shape + origin & insertion + action

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21
Q

How do we name skeletal muscles based on their relative position?

A
  1. Externus (superficialis) – visible at body surface
  2. Internus – deep
  3. Extrinsic – outside an organ
  4. Intrinsic – inside an organ
22
Q

How do we name skeletal muscles based on the direction of their muscle fibers? Provide examples

A
  1. Rectus – parallel to midline → rectus abdominis
  2. Transverse – perpendicular to midline → transverse abdominis
  3. Oblique – diagonal to midline → external oblique
23
Q

How do we name skeletal muscles based on their location?

A
  1. Frontalis – near frontal bone
  2. Occipitalis – near occipital bone
  3. Brachialis –arm
  4. Gluteus – buttocks
  5. Oris – mouth/oral
  6. Oculi – eye/ocular
  7. Scapulae – shoulder/scapula
  8. Femoris – thigh/femur
24
Q

How do we name skeletal muscles based on their size? Provide examples

A
  1. Maximus – largest → gluteus maximus
  2. Medius – middle → gluteus medius
  3. Minimus – smallest → gluteus minimus
  4. Longus – longest → fibularis longus
  5. Brevis – short → fibularis brevis
  6. Tertius – shortest → fibularis tertius
25
Q

How do we name skeletal muscles based on their number of origins? Provide examples

A
  1. Biceps = two → biceps brachii or biceps femoris
  2. Triceps = three → triceps brachii
  3. Quadriceps = four → quadriceps femoris
26
Q

How do we name skeletal muscles based on their shape?

A
  • Deltoid – triangular △
  • Trapezius – trapezoid (diamond) ♢
  • Serratus – saw-toothed ♒
  • Rhomboideus – rhomboid ⏥
  • Teres – round ○
27
Q

What are the different muscle attachments?

A
  1. Origin: point of muscle attachment that doesn’t move during contraction
  2. Insertion: muscle attachment that moves the most
28
Q

What happens to muscle attachments during contraction?

A

The insertion moves towards the origin

29
Q

What are flexor and extensor muscles? Provide examples

A
  • Flexor: decreases angle at joint → flexor carpi radialis

* Extensor: increases angle at joint → extensor carpi ulnaris

30
Q

What are abductor and adductor muscles? Provide examples

A
  • Abductor: moves bone away from midline → abductor pollicis longus
  • Adductor: moves bone towards midline → adductor longus
31
Q

What are levator and depressor muscles? Provide examples

A
  • Levator: produce upper movement → levator scapulae

* Depressor: produce downward movement → depressor labii inferioris

32
Q

What are supinator and pronator muscles? Provide examples

A
  • Supinator: turns palm upward/anterior → supinator

* Pronator: turns palm downwards/posterior → pronator teres

33
Q

What are muscle spindles? What’s their function?

A
  • Stretch receptors within the body of a skeletal muscle
  • They primarily detect changes in the length of the muscle & the speed of stretching, allowing the CNS to compute the position & movement of our extremities
34
Q

Motor fibers make up ___% of a nerve to skeletal muscle while sensory fibers make up ___%

A
  • Motor: 60%

* Sensory: 40%

35
Q

What are motor fibers compromised of? What does each component supply?

A
  • Large myelinated alpha efferents → supply extrafusal muscle fibers
  • Smaller myelinated gamma efferents → supply the intrafusal muscle fibers of the muscle spindles which refine and control muscle action
  • Fine non-myelinated autonomic efferents → supply the smooth muscle cell fibers of the blood vessels
36
Q

Where do motor axons innervate skeletal muscle fibers?

A

At junctions called neuromuscular junctions or motor end plates

37
Q

How many neuromusculars are associated with a single muscle fiber?

A

Just one

38
Q

What separates the axon terminals from the plasma membrane (sarcolemma)?

A

Synaptic cleft

39
Q

Describe the way the axon terminals lie

A

Each axon terminal lies in a trough-like depression of the sarcolemma, showing groove-like invaginations

40
Q

What’s the difference between neuromuscular junctions and neural synapses?

A

The invaginations and the synaptic cleft in neuromuscular junctions contain a basal lamina that does not appear in synapses between neurons

41
Q

What do the axon terminals release when a nerve impulse reaches the terminals?

A

A neurotransmitter

42
Q

What neurotransmitter signals for the contraction of a muscle?

A

Acetylcholine

43
Q

How does the neurotransmitter conduct its action?

A

It diffuses across the synaptic cleft and binds to receptor molecules on the sarcolemma, inducing an impulse

44
Q

What enzyme does the basal lamina contain? For what function?

A

Acetylcholinesterase → breaks down acetylcholine after it signals for a single contraction to prevent undesirable additional twitches that’ll occur if acetylcholine remains in the synaptic cleft

45
Q

Describe sensory fibers

A

Myelinated fibers distributed to muscle spindles for proprioception, also to tendons

46
Q

How many fibers does each spindle contain? What are the types?

A
  • 6 to 15 intrafusal muscle fibers
  • Larger muscle bag fibers
  • Smaller muscle chain fibers
47
Q

What nerves are spindles innervated by?

A

Both motor and sensory nerves

48
Q

What are the types of sensory endings?

A
  1. Primary sensory endings – around central nuclear region of intrafusal fibers
  2. Secondary sensory endings – beyond nuclear region
49
Q

What are the motor nerves of the spindle derived from?

A

Gamma motor neurons of spinal cord

50
Q

What do muscle spindles act as?

A

Sensory receptors

51
Q

How do muscle spindles regulate contraction?

A

By influencing alpha neurons

FB1 Endterm - Anatomy (2 decks)

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