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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
How do we name skeletal muscles based on their number of origins? Provide examples
1. Biceps = two → biceps brachii or biceps femoris 2. Triceps = three → triceps brachii 3. Quadriceps = four → quadriceps femoris
26
How do we name skeletal muscles based on their shape?
* Deltoid – triangular △ * Trapezius – trapezoid (diamond) ♢ * Serratus – saw-toothed ♒ * Rhomboideus – rhomboid ⏥ * Teres – round ○
27
What are the different muscle attachments?
1. Origin: point of muscle attachment that doesn’t move during contraction 2. Insertion: muscle attachment that moves the most
28
What happens to muscle attachments during contraction?
The insertion moves towards the origin
29
What are flexor and extensor muscles? Provide examples
* Flexor: decreases angle at joint → flexor carpi radialis | * Extensor: increases angle at joint → extensor carpi ulnaris
30
What are abductor and adductor muscles? Provide examples
* Abductor: moves bone away from midline → abductor pollicis longus * Adductor: moves bone towards midline → adductor longus
31
What are levator and depressor muscles? Provide examples
* Levator: produce upper movement → levator scapulae | * Depressor: produce downward movement → depressor labii inferioris
32
What are supinator and pronator muscles? Provide examples
* Supinator: turns palm upward/anterior → supinator | * Pronator: turns palm downwards/posterior → pronator teres
33
What are muscle spindles? What’s their function?
* 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
Motor fibers make up ___% of a nerve to skeletal muscle while sensory fibers make up ___%
* Motor: 60% | * Sensory: 40%
35
What are motor fibers compromised of? What does each component supply?
* 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
Where do motor axons innervate skeletal muscle fibers?
At junctions called neuromuscular junctions or motor end plates
37
How many neuromusculars are associated with a single muscle fiber?
Just one
38
What separates the axon terminals from the plasma membrane (sarcolemma)?
Synaptic cleft
39
Describe the way the axon terminals lie
Each axon terminal lies in a trough-like depression of the sarcolemma, showing groove-like invaginations
40
What’s the difference between neuromuscular junctions and neural synapses?
The invaginations and the synaptic cleft in neuromuscular junctions contain a basal lamina that does not appear in synapses between neurons
41
What do the axon terminals release when a nerve impulse reaches the terminals?
A neurotransmitter
42
What neurotransmitter signals for the contraction of a muscle?
Acetylcholine
43
How does the neurotransmitter conduct its action?
It diffuses across the synaptic cleft and binds to receptor molecules on the sarcolemma, inducing an impulse
44
What enzyme does the basal lamina contain? For what function?
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
Describe sensory fibers
Myelinated fibers distributed to muscle spindles for proprioception, also to tendons
46
How many fibers does each spindle contain? What are the types?
* 6 to 15 intrafusal muscle fibers * Larger muscle bag fibers * Smaller muscle chain fibers
47
What nerves are spindles innervated by?
Both motor and sensory nerves
48
What are the types of sensory endings?
1. Primary sensory endings – around central nuclear region of intrafusal fibers 2. Secondary sensory endings – beyond nuclear region
49
What are the motor nerves of the spindle derived from?
Gamma motor neurons of spinal cord
50
What do muscle spindles act as?
Sensory receptors
51
How do muscle spindles regulate contraction?
By influencing alpha neurons

FB1 Endterm - Anatomy (2 decks)

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