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PHSL 231 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

sarcomere

A

individual contractile units of skeletal muscle

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2
Q

thin filament

A

actin which gets pulled during contraction

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3
Q

thick filament

A

myosin which pulls the muscle fibre to initiate contraction

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4
Q

Neuromuscular Junction

A

the junction where the nerve is meeting the muscle between the actual presynaptic terminal and muscle fibers

  • not an actual synapse
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5
Q

what is the other name for NMJ?

A

motor end plate

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6
Q

Myelin sheath

A

coats the nerves as it helps with the conductance of electrical signals

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7
Q

schwann cells

A

a type of glial cells which sorrounds a neuron (forms a myelin sheath), and is mostly responsible in the metabolic processes

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8
Q

Junctional folds

A

increases the surface membrane of the sarcolemma and for the of acetylcholine (the area is densely pack with acetylcholine and ach receptors)

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9
Q

agonist

A

a drug or substance (nicotine) that will stimulate more functions

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10
Q

antagonist

A

a substance that is able to block functions of another substance

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11
Q

Myasthenia Gravis

A

a chronic immune diseases, a neuromuscular diseases which cause weakness in the skeletal muscle

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12
Q

Occupancy

A

how much acetylcholine has been released and is bound to the receptor itself

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13
Q

Sarcoplasmic Reticulum

A
  • encloses all the individual myofibrils which also contains connections to itself
  • Calcium storage
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14
Q

Why does the sarcomere have striped pattern?

A

it contains intercalated thin and thick filaments which are contractile proteins

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15
Q

What does the body mass mostly contained?

A

skeletal muscles

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16
Q

Sarcolemma

A

an outer membrane which encapsulates the myofibril

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17
Q

When does a triad occurs?

A

occurs when we have the terminal cristernae of an Sr and a T-tubule

  • triad is important for regulation of excitation-contraction coupling
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18
Q

What is the function of a serca pump?

A

it uses ATP to move calcium from the cytoplasmic space up to the SR itself

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19
Q

myosin complex

A

part of thick filament (long arms and flexible heads)

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20
Q

actin helix

A

thin filament (made up of globular proteins)

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21
Q

Tropomyosin

A

wraps around the actin filament which acts as a stabiliser

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22
Q

What is rigor mortis?

A

the stiffening of the body muscles due to the chemical changes in the myofibrils (this occurs due to the lack of ATP)

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23
Q

Fast fibres

A
  • are big in diameter and have a large cross sectional area
  • they produce lots of energy and stores them (energy ready for used) because they are slow at producing energy
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24
Q

slow fibres

A

are smaller in diameter and cross sectional area
- they produce energy faster as their function is to support, therefore flow is steady and slow and that is why they have lots of capillaries beds for bloods supply and to produce more energy

25
Q

Motor unit

A

motor neuron and the recruitment of a muscle fibres

26
Q

Active zone

A

docking sites of vesicles

27
Q

What effects does having action potential in the motor neuron

A

Action potential in the motor neuron leads to depolarization of muscle fibers via Acetylcholine (Ach)

  • depolarization is caused by having a negative membrane potential going into a positive membrane potential due to sodium channels opening
28
Q

Synthesise Acetylcholine

A
  • Acetyl coA + choline gets synthesise through an enzyme called acetyltransferase (ChAT)
  • we can then break this down to have acetylcholine as an input
  • Ach, we then use acetylcholinesterase (AchE) to break it down into acetic acid + choline
29
Q

What is the function of the NMJ?

A

this is the area where we get a transferal of action potential or electrical signal from an actual nerve to translating it into an action potential into the muscle itself

  • this action potential tells the muscle it is time to contract
30
Q

Importance of the NMJ structure?

A
  • important for linking the signal from the nerve and the brain to the muscle
  • the structure of NMJ allows the muscle to be under involuntary control
31
Q

Features of a muscle fibres

A
  • contain lots of mitochondria which is located between myofibrils
  • nuclei are dotted in regular interval throughout the outer membrane (sarcolemma of the cell

-multinucleated

32
Q

Why are slow fibres more efficient than fast fibres?

A

slow muscle fibres uses oxygen to generate more adenosine triphosphate for continuous muscle contraction over a long period of time

  • they fire AP more slowly which means than they can go longer before experiencing fatigue
33
Q

Type I: slow oxidative fibres

A

slower form of serca
- slower increase of tension produced

  • slow muscle twitch fibres
  • smaller and pinker fibres
  • slow contractors
  • slow at utilizing ATP
34
Q

Type II: Glycolytic Fibres

A

faster form of serca
- rapid increase to tension produce and very rapid relaxation phase which is due to having a fast form of myosin

  • fast twitch fibres
  • fast contractions
  • fast relaxation (super fatigable)
35
Q

Feature of Nicotinic acetylcholine receptor

A
  • has five subunit and four transmembrane domain
  • have pore gated: gate normally closed (at rest)
36
Q

Transmembrane domain

A
  • organised in a way that we have a subunit with a central pore
  • purpose of the central pore is to to use as transporter though passive diffusion
37
Q

Nicotinic AchR

A
  • chemically gated (opens when two Ach binds)
  • Non-slective; permeable to both Na+ and K+
  • opening results in depolarisation due to entry of sodium ions
38
Q

Concentration Gradient

A

Outside cell:
-High Na+
-Low K+

Inside cell:
- High K+
-Low K+

39
Q

Local depolarisation

A
  • having sodium ions in a negative space
40
Q

muscarinic acetylcholine receptor

A
  • not located in neuromuscular juncton, mostlyfound in smooth muscle
  • not chemically gated
41
Q

Nicotine recptors

A

-nicotine comes into the system via smoking or vaping, thesewill then affect more of the central located nicotinic receptors not the one in the neuromuscular junction

  • more effect in the CNS than the PNS
42
Q

Agonist

A

stimulate more function of the drugs

43
Q

Antagonist

A

able to block the function of how drugs or chemical works

44
Q

Effects of reduce number of Ach receptors?

A

Reducing the number of Ach recptors and we damage them, this results in impaired response of acetylcholine so there is a reduce in the neuromuscular junction function. This means that it is not getting enough nerve signal to muscle and will cause weakness

e.g. Myasthenia Gravis

45
Q

Fasciculi

A

individual bundle of muscle fibres in skeletal muscle

46
Q

skeletal muscle features

A
  • heavily multinucleated cells (formed from the fusion of embryonic myoblast)
  • large diameter in fast twitch fibre compare to the slow twitch fibre
47
Q

Type IIA: Intermediate fibres

A
  • fast form of myosin ATPase
  • mix of oxidative and glycolytic enzymes
  • intermediate speed / fatigue
48
Q

Slow oxidative fibres

A

useful for endurance events

49
Q

fast-oxidative fibres and fast-glycolytic fibres

A

useful for power and sprint events

50
Q

Recruitment

A

The process of activating more fibres to make force

  • the number of fibres activated is regulated by how many neurons are activated at one time
  • small number of active neurons tends to produce low force from the muscle
51
Q

Size principle of motor units

A

small units are recruited first, so more tonically active (results in fine graded control of small forces e.g. fingertips)

  • bigger units are autimatically recruited as required force increases
52
Q

Isometric

A

length of the muscle remains constant during contraction

  • no external force is being generated by the muscle
53
Q

concentric

A

muscle shortening during contraction

  • shortening against fixed load, speed dependent on M.ATPase activity and load
54
Q

eccentric

A

muscle lengthens during contraction

  • most likely to cause muscle injury
55
Q

voltage sensor (EC-Coupling)

A

senses any changes across the membrane potential of the actual sarcolemma itself of the skeletal muscle fibre

56
Q

Ryanodine receptor

A

a calcium release channel that sits on the terminal cisternae
- contain lots of calcium

57
Q

Voltage sensor is not a g-coupled protein

A

It does not have a secondary messenger system

  • but can mechanically activate the ryanodine receptor (calcium release channel) on the terminal cisternae of the sarcoplasmic reticulum
58
Q

Difference between EEG and EMG?

A
  • Electroencephalogram (EEG) is a non-invasive brain imaging technique that uses scalp electrodes to measure the voltage fluctuations induced by the mass electrical activity of neurons

whereas,

  • Electromyography (EMG) technique is usually used to record the electrical activity produced by skeletal muscles

PHSL 231 (7 decks)

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