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Normal Physiology > Skeletal Muscles > Flashcards

Skeletal Muscles Flashcards

1
Q

Structure of the skeletal muscle

A

Muscle fibers, myofibril, myofilament (actin and myosin)

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2
Q

Muscle fibers consist of

A

Myofibrils

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3
Q

Sacromere is?

A

It’s in myofibrils and it’s the junction between two z-lines

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4
Q

Which are thin filaments and which are thick filaments?

A

Thin filaments are actin filaments
Thick filaments are myosin filaments
Both form sacromere

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5
Q

How do muscle contract?

A

By the sliding of thick filament (myosin) and the thin filaments (actin) along each other

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6
Q

Sacroplasmatic reticulum

A

The main storage of Ca ions

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7
Q

What is a traid?

A

Two terminal cisternae and one T-tubule

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8
Q

Innervation of skeletal muscle

A

It’s innervated by A alfa nerve fibers. This fiber makes neuromuscular synapse where ACH is the NT and N-choline is the receptor

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9
Q

Neuromuscular synapse is only?

A

Excitatory

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10
Q

Motor unit is

A

One motor neurone + muscle fiber it innervates

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11
Q

Function of skeletal muscle

A
  1. Contraction and posture control
  2. Receptive
    Heat production
  3. Protection
  4. Facilitate venous return
  5. Breath, speech, drinking…
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12
Q

What are the two properties of skeletal muscle?

A

Active properties

  1. Excitability
  2. Conduct ability
  3. Contract ability

passive properties

  1. Ability to stretch
  2. Elasticity
  3. Plasticity
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13
Q

Tittin filaments

A

Are non-contractile filaments that attach myosin to actin filaments
Hold the myosin to z-lines

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14
Q

Inhibitory proteins

A

Tropomyosin

Trponin

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15
Q

Ca ions role in skeletal muscle

A

Ca ions releases from SPR and bind to Troponin c-part which removes Tropomyosin from active site on actin filaments allows myosin head to bind to active site

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16
Q

What do use ATP for ?

A

For contraction and relaxation

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17
Q

Receptors in Ca release from SPR

A

dihydropiridine receptors : located on T-tuble, sensing the AP traveling along
Ryanodine receptors: located on SPR, change conformation

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18
Q

How strength of the stimuli affect muscle contraction?

A

A single motor unite contract according to all or non principle so it means,
Subthreshold stimulus is weak and doesn’t cause any response.
Threshold stimuli, only motor unites with highest excitability respond, but since the HE motor unites are few so force of contraction is not maximum.
Suprathreshold stimuli, the strength of the stimuli increases so force of contraction increases

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19
Q

Single contraction

A

Its one type of the frequency that affect muscle contraction, and it’s produced with single electrical stimuli or low frequency impulses
Slow muscle fibers less than 5 Hz
Fast muscle fibers up to 15 Hz

20
Q

Phases of single contraction

A

Latent phase
Contraction phase
Relaxation phase

21
Q

Tetanic contraction

A

Caused by electrical rythmatic stimuli, and high frequency impulses

22
Q

Does tetanic contraction go through all 3 single contraction phases?

A

No, because the high frequency impulses causes the muscle inability to go through all the phases

23
Q

Incomplete tetanic

A

The stimuli is produced during relaxation phase of the previous contraction

24
Q

Complete tetanic

A

The stimuli is produced during contraction phase of the previous contraction

25
Q

In epilepsy disease what phases can we see?

A

All types of contraction. It goes from complete tetanic, to incomplete tetanic, the to single contraction

26
Q

A person that had seizures, what type of contraction has?

A

We can observe tetanic contraction

27
Q

Ca+ accumulation

A

Happens in summation of contraction, when we have multiple stimulation, causes ca ions release, while the Ca pump didn’t pump out all the Ca and causes greater ca+ ions concentration

28
Q

Change in muscle length but not tension

A

Isometric contraction

29
Q

Change in tension but no length change

A

Isotonic contraction

30
Q

Both length and tension changes

A

Autotonic contraction

31
Q

Sacromere length on muscle contraction

A
  1. Before stretching the muscle, sacromere length is shorten (1,2nm)
  2. When sacromere is stretched it goes to optimal resting length 2.1-2.2 nm
  3. If sacromere is stretched more than optimal resting length before contraction, force of contraction decreases
32
Q

How to break down the cross bridge cycle?

A

Myosin hydrolysis of ATP to ADP and P , myosin head bind to actin filament, AP travels and Ca+ is released, it undergoes conformational change, mysoin releases ADP and P and we get a power stroke
ATP bind to myosin causing cross bridge to detach

33
Q

What is power stroke?

A

The cross bridge moves pulling the actin along

34
Q

Fastest to lowest energy sources are:

A
  1. ATP stored in muscle fibers (1-3 seconds)
  2. Phosphocreatine (5-8 seconds)
  3. Anaerobic glycolysis (40sec-1 min)
  4. Aerobic glycolysis (oxidative) (the slowest ATP production)
35
Q

How much energy do muscles use?

A

Only 25-30% of the energy to preform work where the rest 70% us used for heat

36
Q

Types of the skeletal muscle fibers

A

I : slow- oxidative fibers
II a: fast oxidative - glycolytic fibers
II b: fast glycolytic fibers

37
Q

Which skeletal muscle type has more myoglobin?

A

I : slow oxidative fibers

38
Q

Why I group is fatigue resistant?

A

Because we use oxidative pathway which leads to Co2 and H2o

Meaning they can work for long time

39
Q

Why II b reach fatigue very fast?

A

Because it uses anaerobic glycolysis which lead to build up lactate which decreases ph and stop energy production

40
Q

Compare marathon runners and sprint runners

A

Sprint runners have more than 80% fast fibers
Marathon runners have more 80% slow fibers
Marathon runners have higher amount of mitochondria
More capillaries

41
Q

Motor unit

A

One motor neuron + the muscle fibers it innervates

42
Q

Small motor neuron

A

It provide a presized movement and contain several to several tens of muscle fibers which are innervated by single motor neuron

43
Q

Explain slow and fast motor units

A

Slow (I slow oxidative fibers) small in size, high excitability
Fast ( IIa, IIb fast fibers) large in size, low excitability

44
Q

Motor unit recruitment

A

The activation of additional motor units to accomplish an increase in contractile strength in muscle

45
Q

Factors that affect force of muscle contraction

A 
Physiological cross section area
Number of activated motor units
Functional state of bones and joints
Frequency of impulses 
Length of sacromeres
Blood supply 
Fatigue

Normal Physiology (2 decks)

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