Excitation-Contraction Coupling

Question 1

Amyotrophic lateral sclerosis

Answer 1

motor neuron death in the spinal cord; reduced excitation

weakness, spasticity, muscle atrophy

Question 2

injury

Answer 2

axonal damage; reduced excitation

variable: paralysis, weakness, often some recovery

Question 3

Demyelination Guillan-Barre

Answer 3

nerve disease; autoimmune response against myelin; reduced excitation

ascending paralysis, weakness

Question 4

Myasthenia-Gravis

Answer 4

neuromuscular junction disease; autoimmune response against Acetylcholine receptor; reduced excitation

muscle weakness, sometimes paralysis

Question 5

Muscular Dystrophy

Answer 5

muscle disease; reduced attachment of muscle to ensheathing membrane; reduced contraction

muscle weakness and atrophy

Question 6

Malignant Hyperthermia

Answer 6

sarcomere disesae; mutation in Ryr1 causing excessive calcium release in muscle. triggered by inhaled anesthetics; reduced contraction

blood CO2 buildup, hyperthermia, circulatory collapse

Question 7

calsequestrin

Answer 7

binds to calcium in the SR

Question 8

triad junction

Answer 8

sarcoplasmic reticulum cisterna, transverse tubule, sarcoplasmic reticulum cisterna

Question 9

ryanodine

Answer 9

plant alkaloid that binds to and opens SR calcium release channels (ryanodine receptors) at nanamolar concentration. Higher concentrations (micromolar) closes ryanodine receptors.

Question 10

calcium induced calcium release (CICR)

Answer 10

small amount of calcium released into the cytoplasm by ryanodine receptors (at the tried) triggers adjacent ryanodine receptors (away from triad) to open and release calcium which in turn triggers the opening of additional ryanodine receptors

Question 11

Sarcoplasmic reticulum calcium ATPase (SERCA)

Answer 11

uses energy of ATP hydrolysis to pump calcium back into the SR where it can be bound by calcium binding proteins Calreticulin and Calsequestrin

Question 12

Sodium Calcium eXchanger (NCX)

Answer 12

NCX lets 3 sodium ions into cell to remove 1 calcium ion from the cell

Question 13

summation

Answer 13

increase in muscle tension from successive action potentials

Question 14

tetanus

Answer 14

maintained contraction in response to repetitive stimulation

Question 15

fused vs unfused tetanus

Answer 15

fused tenatus is tetanus without oscillations

Question 16

twitch

Answer 16

single action potential

Question 17

strength of contraction of skeletal muscle determined by

Answer 17

frequency of stimulation (rate coding) and recruitment of additional motor units

Question 18

treppe

Answer 18

steady increase in tension in successive twitches. different than summation. results in an increase in calcium concentration

Question 19

motor unit

Answer 19

somatic motor neuron and all the muscle fibers (myofibers) it innervates

Question 20

size principle

Answer 20

how motor units are recruited. smaller motor units are recruit first before large motor units.

Question 21

force generated when skeletal muscle is stimulated is related to

Answer 21

size of the motor units stimulated, number of motor units activated, frequency of stimulation of the muscle fibers

Question 22

muscle pain (burn)

Answer 22

is produced by lactic build up that accumulates in the muscle fiber

Question 23

delayed onset muscle soreness (DOMS)

Answer 23

occurs in the days following intense muscle use, not correlated with lactic acid levels

Question 24

muscle fatigue

Answer 24

decline in muscle tension as a result of previous contractile activity. decreased shortening velocity and slower rate of relaxation

Question 25

high frequency fatigue

Answer 25

accompanies high intensity short duration exercise; failure in the conduction of action potential in the T tubule

Question 26

low frequency fatigue

Answer 26

seen with low intensity, long duration exercise; due to buildup of lactic acid and phosphates