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Functional Anatomy & Embryology > Anatomy and Embryology of Skeletal Muscle > Flashcards

Anatomy and Embryology of Skeletal Muscle Flashcards

1
Q

List 3 types of muscle

A
  1. Skeletal
  2. Cardiac
  3. Smooth
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2
Q

Describe characteristics of skeletal muscle

A
  • Striated
  • voluntary,
  • controlled by somatic nervous system,
  • cells multinucleated,
  • un-branched.
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3
Q

Describe characteristics of cardiac muscle

A
  • Striated
  • involuntary
  • controlled by autonomic nervous system
  • single (branched) cells joined by intercalated disk
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4
Q

Describe characteristics of smooth muscle

A
  • Non-striated
  • involuntary
  • controlled by autonomic nervous system,
  • spindle-shaped single cells
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5
Q

List the three separate layers of connective tissue that hold muscle fibres in position in skeletal muscle

A
  1. Epimysium
  2. Perimysium
  3. Endomysium
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6
Q

What is epimysium?

A

tough outermost layer surrounds the entire muscle (epi = upon)

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7
Q

What is perimysium?

A

surrounds bundles of muscle fibres to create a fascicle (peri = around)

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8
Q

What is endomysium?

A

surrounds each muscle fibre within the fasciculus (endo = within) – between fibres

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9
Q

What is also embedded in CT in skeletal muscle?

A

Blood vessels and nerves

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10
Q

List the diff muscle shapes with e.g.s

A
  1. Digastric e.g. omohyoid
  2. Multipennate e.g. deltoid
  3. Convergent e.g. pectoralis major
  4. Quadrate e.g. rectus abdominis
  5. Thin parallel e.g. Sartorius
  6. Unipennate e.g. extensor digitorium longus
  7. Bipennate e.g. rectus femoris
  8. Flat parallel with aponeurosis e.g. EO
  9. Fusiform e.g. biceps
  10. Circular e.g. Orbicularis occuli
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11
Q

How do muscles gen force?

A
  • only by contracting
  • only pull (not push),
  • only move in 1 direction
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12
Q

What are antagonistic muscles?

A
  • work in pairs
  • if muscle doing 1 action, need another to bring back to original pos
  • muscle that bends the joint (dec the joint angle) = flexor muscle
  • muscle that straightens the joint (inc the joint angle) = extensor muscle
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13
Q

List 2 types of muscle contraction

A
  1. Isotonic

2. Isometric

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14
Q

What is isotonic contraction and list 2 types

A

= cause the muscle to change length as it contracts

  1. Concentric
  2. Eccentric
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15
Q

What is concentric contraction and give e.g.?

A

muscle shortens during force production

lifting a heavy weight,

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16
Q

What is eccentric contraction and give e.g?

A
  • Muscle produces force but length increases

- controlled lowering of the heavy weight raised

17
Q

What is isometric contraction?

A

Muscle exerts force without changing length – no movement of muscle

18
Q

Give e.g.s of isometric contraction

A
  • Pulling against immovable object
  • pushing against a wall.
  • grip
  • maintain posture.
  • holding a heavy weight steady, neither raising nor lowering it.
19
Q

Using deltoid as an e.g. describe the diff muscle contractions

A
  • isometric - holding arm out straight - deltoid in steady pos
  • concentric - raise arm up using force - deltoid shortens
  • eccentric - lower arm down using gravity - deltoid lengthens
20
Q

Give e.g. of antagonistic muscles

A
  • flexors = biceps (concentric - raise forearm)

- extensor = triceps (eccentric - bring forearm back down)

21
Q

List diff types of muscle in movement

A
  1. Agonist/Prime mover
  2. Antagonist
  3. Synergist
  4. Fixator
22
Q

What is the agonist?

A
  • muscle(s) that provides the major force to complete the movement.
  • Because of this aka ‘prime movers’
  • not always the muscle that is shortening (contracting concentrically).
  • e.g. In a bicep curl the bicep is the agonist on the way up when it contracts concentrically, and on the way down when it contracts eccentrically - prime mover in both cases.
23
Q

What is antagonist?

A
  • muscles that oppose agonist.
  • During elbow flexion, bicep = agonist, tricep = antagonist.
  • While agonist contracts - causing the movement, antagonist typically relaxes so as not to impede agonist
  • another function can be to slow down/stop a movement. e.g. if weight in bicep curl was v. heavy, when being lowered from top position, antagonist tricep would produce a sufficient amount of tension to help control the movement as weight lowers to prevent damage to elbow joint
24
Q

What is the synergist?

A
  • muscle(s) that stabilises a joint around which movement is occurring, which in turn helps agonist function effectively.
  • also help to create the movement.
  • In bicep curl, synergists = brachioradialis + brachialis which assist biceps to create the movement + stabilise elbow joint.
25
Q

What is a fixator?

A
  • muscle(s) that stabilises the origin of agonist through isometric contraction + the joint that the origin spans (moves over) in order to help agonist function most effectively.
  • In bicep curl = rotator cuff muscles, the ‘guardians of the shoulder joint’.
  • majority of fixator muscles are found working around hip + shoulder joints.
26
Q

Do muscles perfom just one type of moevemt?

A

No - The same muscle can act as prime mover, antagonist synergist/fixator under diff cond/actions

27
Q

What can also act as prime mover?

A
  • Gravity can be a prime over pushing arm down

– upper arm adduction muscles to antagonise that action

28
Q

What are striations and what causes them?

A

= alternating light and dark bands that appear across the length of the fibre
- Organisation of thick and thin filaments + division into sarcomeres causes skeletal muscle to have this striated appearance

29
Q

List 2 major filament types of myofibrils

A
  1. thick filaments composed of myosin

2. thin filaments composed of actin

30
Q

How are myofibrils div?

A

Into sarcomeres - contractile units

31
Q

What is diff between myofibre and myofibril?

A

A myofibre is filled with many myofibrils

32
Q

Describe sarcomere org

A
  • Z line, 1/2 I band, A band (contains M line + H zone), 1/2 I band + Z line
  • Each sarcomere has a complete A-band and two half I bands
33
Q

What is the A band?

A

Thick myosin filaments (but also contains actin)

34
Q

What is I band?

A

Only actin filaments

35
Q

What is H zone?

A

In the centre of the sarcomere, portion of the myosin filament with no overlap of the actin

36
Q

What is M line?

A
  • attachment site for the thick filaments.

- in the center of the A band and, thus, in the center of the sarcomere.

37
Q

What are Z lines?

A

div each sarcomere

Functional Anatomy & Embryology (8 decks)

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