locomotor system

Question 1

what activates voltage gated sodium channels

Answer 1

when the threshold is reached

Question 2

what causes action potential

Answer 2

rapid activation and fluxes of ion currents

Question 3

what causes depolarisation

Answer 3

upstroke of action potential

Question 4

which ion triggers the contraction of myofilaments

Answer 4

calcium

Question 5

what introduces calcium into the sarcoplasmic reticulum

Answer 5

sarcoplasmic reticululm calcium ATPase (SERCA)

Question 6

what removes calcium from the cell

Answer 6

plasma membrane sodium calcium exchanger and the calcium ATPase

Question 7

what binds to troponin C

Answer 7

cytoplasmic calcium ions

Question 8

when is an action potential generated

Answer 8

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

Question 9

what does the action potential activate

Answer 9

voltage regulated l type calcium channel

Question 10

describe contraction in smooth muscle

Answer 10

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

Question 11

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

Answer 11

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

Question 12

what removes calcium from the cell to stimulate relaxation

Answer 12

SERCA
NCX
PMCA

Question 13

what is the resting membrane potential

Answer 13

-90mV

Question 14

location of action potential generation in the heart

Answer 14

sino atrial node propagation

Question 15

location of action potential generation in the voluntary skeletal muscle

Answer 15

motor unit, acetylcholine

Question 16

location of action potential generation in smooth muscle

Answer 16

neurotransmitters from enruon varicosities

Question 17

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

Answer 17

less than 0.1 to 1uM

Question 18

what do smooth muscle cells rely on for contraction

Answer 18

action potential
agonists

Question 19

what is myosin

Answer 19

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

Question 20

how large is the displacement from a power stroke

Answer 20

5-10 nanometers

Question 21

describe the process of excitation contraction coupling

Answer 21

• 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

Question 22

describe excitation coupling in smooth muscle

Answer 22

• 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

Question 23

describe the power stroke

Answer 23

• 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

Question 24

what is RyR

Answer 24

ryanodine receptor - skeletal muscle calcium release channel

Question 25

what does an abnormality in RyR lead to

Answer 25

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

Question 26

what is the consequence of abnormal RyR function

Answer 26

intracellular calcium and contraction is reduced leading to heart failure

Question 27

what is the main reason for reduced contractility in heart failure

Answer 27

reduced intracellular calcium amplitude

Question 28

what causes muscular dystrophy

Answer 28

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.

Question 29

what does reduced RyR stability lead to

Answer 29

muscle weakness with loss of skeletal muscle function and control

Question 30

what is the prognosis of duchenne muscular dystrophy

Answer 30

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

Question 31

impact of muscular dystrophy on oral health

Answer 31

- 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

Question 32

what may counteract deficiency in RyR

Answer 32

therapeutically increased SERCA

Question 33

what are pain receptors

Answer 33

nociceptors

Question 34

what are the types of nociceptors

Answer 34

a-delta and c fibres

Question 35

what are the nociceptors that produce sharp and localised pain

Answer 35

alpha delta fibres

Question 36

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

Answer 36

c fibres