locomotor system Flashcards

1
Q

what activates voltage gated sodium channels

A

when the threshold is reached

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2
Q

what causes action potential

A

rapid activation and fluxes of ion currents

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3
Q

what causes depolarisation

A

upstroke of action potential

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4
Q

which ion triggers the contraction of myofilaments

A

calcium

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5
Q

what introduces calcium into the sarcoplasmic reticulum

A

sarcoplasmic reticululm calcium ATPase (SERCA)

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6
Q

what removes calcium from the cell

A

plasma membrane sodium calcium exchanger and the calcium ATPase

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7
Q

what binds to troponin C

A

cytoplasmic calcium ions

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8
Q

when is an action potential generated

A

if the depolarising ion, sodium, current of the plasma membrane is large enough

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9
Q

what does the action potential activate

A

voltage regulated l type calcium channel

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10
Q

describe contraction in smooth muscle

A

both voltage and receptor mediated influx of calcium may induce contraction
- calcium binds to calmoduin, and this activates myosin light chain kinase that phosphorylates myosin which leads to myosin binding to actin with subsequent induction of the power stroke

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11
Q

what is the difference between the contraction mechanisms of smooth and skeletal muscle

A

smooth - myosin light chain kinase
skeletal - troponin/tropomyosin complex

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12
Q

what removes calcium from the cell to stimulate relaxation

A

SERCA
NCX
PMCA

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13
Q

what is the resting membrane potential

A

-90mV

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14
Q

location of action potential generation in the heart

A

sino atrial node propagation

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15
Q

location of action potential generation in the voluntary skeletal muscle

A

motor unit, acetylcholine

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16
Q

location of action potential generation in smooth muscle

A

neurotransmitters from enruon varicosities

17
Q

what is the change in calcium concentration inside the cell in contraction

A

less than 0.1 to 1uM

18
Q

what do smooth muscle cells rely on for contraction

A

action potential
agonists

19
Q

what is myosin

A

a hexamer, 2 myosin heavy chains and 4 myosin light chains. the myosin head retains all the motor functions of myosin, ie the ability to produce movement and force
myosin is a molecular motor

20
Q

how large is the displacement from a power stroke

A

5-10 nanometers

21
Q

describe the process of excitation contraction coupling

A
  • calcium concentration in cytoplasm
  • calcium binds to troponin
  • conformational change in troponin
  • tropomyosin moves away from binding sites on actin filaments
  • myosin head groups bind to actin
  • cross bridge cycle begins
22
Q

describe excitation coupling in smooth muscle

A
  • increase in calcium concentration in the cytoplasm
  • calcium binds to calmodulin
  • calcium calmodulin complex activates myosin kinase
  • activated myosin kinase phosphorylates myosin head groups
  • phosphorylates myosin head groups bind to actin
  • cross bridge cycle begins
23
Q

describe the power stroke

A
  • myosin head cocks back in high energy form
  • binds to actin
  • inorganic phosphate released
  • power stroke
  • actin pulled toward middle of sarcomere
  • ADP released
  • rigor is when myosin is in low energy form
  • new ATP binds to myosin head
  • unbinding of myosin and actin
24
Q

what is RyR

A

ryanodine receptor - skeletal muscle calcium release channel

25
Q

what does an abnormality in RyR lead to

A

calcium sparks, abnormal acitivty of calcium release events from a single RyR cluster leading to loss of sarcoplasmic reticulum calcium

26
Q

what is the consequence of abnormal RyR function

A

intracellular calcium and contraction is reduced leading to heart failure

27
Q

what is the main reason for reduced contractility in heart failure

A

reduced intracellular calcium amplitude

28
Q

what causes muscular dystrophy

A

reduced calcium and contraction due to mutations in the dystrophin-glycoprotein macromolecular complex coupled to excitation countrating coupling leads to RyR abnormalities, this loss of stability then leads to RyR leak.

29
Q

what does reduced RyR stability lead to

A

muscle weakness with loss of skeletal muscle function and control

30
Q

what is the prognosis of duchenne muscular dystrophy

A

muscle degeneration
loss of skeletal muscle function
loss of movement
paralysis including muscles for life support

31
Q

impact of muscular dystrophy on oral health

A
  • masticatory pattern is distorted but the muscle wasting is less than on other skeletal muscles
  • patients need more time for mastication due to reduced function
  • malocclusion
  • poor muscle control leads to difficulty with oral hygiene
32
Q

what may counteract deficiency in RyR

A

therapeutically increased SERCA

33
Q

what are pain receptors

A

nociceptors

34
Q

what are the types of nociceptors

A

a-delta and c fibres

35
Q

what are the nociceptors that produce sharp and localised pain

A

alpha delta fibres

36
Q

what are the nociceptors that produce dull, burning or throbbing pain

A

c fibres