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YEAR 2: Skeletal Muscle in Health and Disease (MGEM2017 UNUK) (SPR1 23-24) > intro to Skeletal Muscle Structure, Function & Metabolism > Flashcards

intro to Skeletal Muscle Structure, Function & Metabolism Flashcards

1
Q

what are the three types of muscle tissue

A
  • skeletal
  • cardiac
  • smooth
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2
Q

what are 4 features of skeletal muscle

##

think:
- locomotion,
- body weight,
- multinucleate cells and what they have
- willingness of contraction

A
  • attach to and move skeleton
  • 40% of body weight
  • there are multinucleate cells with ovbious striations
  • contraction of this musle is voluntary
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3
Q

what are 2 features of cardiac muscle other than being only found in the heart

Think about visibility of the cells and willingness of contraction

A
  • cells are striated
  • contractions are involuntary
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4
Q

what are 2 features of smooth muscles other than them being in the walls of hollow organs

A
  • lack striations
  • contractions are involuntary
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5
Q

skeletal muscle tissue

what are the 3 functions of skeletal muscle

Think shivering, storage and mobility

A
  • heat generation (shivering and involuntary contractions)
  • nitrogen store/metabolism (CHO/PRO)
  • locomotion/external movement
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6
Q

skeletal muscle

what attaches skeletal muscle to the skeleton

A

tendons

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7
Q

skeletal muscle

what is the site at which skeletal muscle is attached to an immobile bone at one end called?

A

the origin

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8
Q

skeeletal muscle

what is the site at which skeletal muscle attaches to a bone and moves it called?

A

the insertion

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9
Q

what needs to occur before tension at the muscle attachement sites occur?

A

stretch of the elastic/non-contractile parts of the muscle

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10
Q

skeletal muscle ultrastructure

what are 2 features of myofibres (muscle cells)

A
  • elongated cells
  • arranged parallel to one another and bundled by connnective tissue into fascicles
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11
Q

skeletal muscle ultrastructure

what is the sarcolemma

A

muscle cells’ cell membrane

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12
Q

SKM connective tissue

what is:

  • superficial fascia
  • deep fascia
A

superficial fascia:
- loose connective tissue underlying skin

Deep fascia:
- dense connective tissue around muscle

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13
Q

SKM connective tissue

what are the 3 components of connective tissue and where are they found

A

Epimysium: surrounds whole muscle

Perimysium: surrounds bundles (fascicles) of muscle cells

Endomysium: separates individual muscle cells

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14
Q

myofibrils

what are myofibrils

A

long bundles of protein made up of thick and thin filaments

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15
Q

myofibrils

how are myofilaments arranged

A
  • arranged in sarcomeres from one Z-disc to the next
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16
Q

the proteins of muscle

what 3 types of protein make up myofibrils and give 2 examples of each

A
  1. contractile proteins:
  • myosin and actin
  1. Regulatory proteins that turn contraction on and off
  • troponin and tropomyosin
  1. structural proteins which provide proper alignment, elasticty and extensibility:
  • titin, myomesin, nebulin and dystrophin
17
Q

Protein in muscles - Myosin

what are the thick filaments of myofibrils composed of

A

myosin

18
Q

what do M line proteins do?

A

hold myosin filaments in place

19
Q

proteins of the muscles - actin

what 3 things are the thin filaments of myofibrils made out of

A
  • actin
  • troponin
  • tropomyosin
20
Q

what holds thin filaments together

A

Z-lines

21
Q

Does the length of filaments change?

A

No

22
Q

nerve muscle anatomy

what specialized nerve cells are associated with muscles

A

motor neurons

23
Q

excitation-contraction coupling

outline excitation contraction coupling

A
  1. action potential propagates down sarcolemma
  2. Transverse tubules conduct AP to cell’s interior
  3. Ca2+ release channels open in Sarcoplasmic reticulum, allowing for Ca2+ to enter the sarcoplasm
24
Q

activation of muscle contraction by action potentials: OUTLINE the 3 steps

A
  1. action potenital induce release of Ca2+ into sarcoplasm
  2. Ca2+ binds to troponin on thin filament, changing the troponin
  3. this shifts tropomyosin off myosin binding sites, enabling myosin to bind to actin
25
Q

outline the 7 steps of cross-bridge cycling

this occurs after excitation-contraction coupling

A
  1. myosin head binds to actin forming cross bridge
  2. Pi is released from myosin head, causing conformational change in myosin
  3. power stroke occurs, where myosin head bends towards centre of sarcomere, sliding thin filaments towards the centre too.
  4. ADP is released
  5. New ATP molecule binds to myosin head, allowing for the head to release from actin
  6. ATP is hydrolysed, causing the myosin head to return to its original orientation
  7. this repeats, however the sarcomere’s length has shortened
26
Q

contractile properties

what is “Twitch”

A
  • single contraction and relaxation of a muscle in response to a single brief stimulus
27
Q

contractile properties

what is henneman’s size principle

A

motor units are generally recruited in order of smallest to largest (or Fewest to most fibres) as contraction increases

28
Q

what is the importance of normal resting length for skeletal muscles?

A
  • it is the optimal resting length for generation of max tension
29
Q

Sarcomere length at muscle’s optimal resting length?

A

~2.0 µm

30
Q

if length of skeletal muscle is increased, why is tension reduced

A
  • because overlap between thick and thin filaments decreases
31
Q

if skeletal muscle length decreases, why does tension decrease?

A

because fluid pressure builds and thin filaments from either end of the sacromere collide.

32
Q

types of mucles contraction

what is summation

A

when a muscle is stimulated multiple times in rapid succession so strength of contraction increases

33
Q

types of muscle contraction

what is incomplete tetanus

A

muscles stimulated at high enough rate so that muscle does not fully relax between contractions

34
Q

types of muscle contraction

what is complete tetanus

A

muscle stimulated at high frequency so that NO relaxation occurs (steady state of tension)

35
Q

types of muscle contraction

give 1 in vitro example of complete tetanus and 1 in vivo example

A

In vitro:
- high rate of stimulation prevents muscle fibres from relaxing

In vivo:
- different motor units acitvated in rapid succession to generate sustained contraction

YEAR 2: Skeletal Muscle in Health and Disease (MGEM2017 UNUK) (SPR1 23-24) (18 decks)

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