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Flashcards in Excitation Contraction Coupling Deck (75)
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1

innervation of skeletal muscle

somatic motor neurons

ventral horn of spinal cord
-except cranial nerves

2

motor unit

motor neuron and all muscle fibers it innervates

3

synapse vs NMJ?

-two excitable cells
-chemical messengers
-change in membrane potential both graded potentials

differences:
-synapse is junction of two neurons, NMJ is not
-one-to-one transmission at NMJ, neuron requires summation of multiple EPSPs
-NMJ always excitatory, neuron NO
-inhibition can only occur in neurons (not NMJ)

4

active zone

dense spot over which synaptic vesicles are clustered
-fusion of vesicles and release of ACh occurs
-oriented directly over secondary postsynaptic clefts between adjacent postjunctional folds

5

postjunctional folds

where there are lots of receptors
-folds increase SURFACE AREA

6

type of receptor in skeletal muscle?

nicotinic acetylcholine receptors

high density expression at crests of postjunctional folds

7

acetylcholinesterase

high concentration associated with synaptic basal lamina (basement membrane)

terminates synaptic transmission**
hydrolyzes acetylcholine > choline + acetate

8

neurotransmitter at NMJ?

acetylcholine

9

acetylcholine

vesicles produced in cell body and fast axonal transport sends them to nerve terminal
-microtubule mediated

vesicles for ACh (and other non-peptides) travel down axon empty
-vesicle destined contain peptide neurotransmitters travel down axon with presynthesized peptide precursors inside

10

site of ACh synthesis and uptake?

nerve terminal

11

choline acetyltransferase

synthesizes ACh from choline and acetyl CoA

12

ACh-H+ exchanger

allow ACh uptake by synaptic vesicle
-antiport of ACh into cell and H+ out of cell

-driven by vesicular proton electrochemical gradient
-positive voltage and low pH inside

13

synaptobrevin

v-snare

essential for transmitter RELEASE
forms complex with SNAP-25 and syntaxin
-helps drive vesicular fusion

14

synaptotagmin

Calcium receptor of vesicle
-detects rises in calcium and triggers exocytosis of docked vesicles

15

syntaxin and snap 25

t-snares

16

vesicle fusion?

snap-25 and syntaxin on membrane coil around synaptobrevin on the vesicle to bring vesicle closer to presynaptic membrane

17

exocytosis of neurotransmitter?

synaptotagmin is calcium sensor

calcium triggers vesicle fusion and exocytosis

18

tetanus toxin

endoproteinase that digests synaptobrevin

19

botulinum B, D, F, G

endoproteinase that digests synaptobrevin

20

botulinum A, E

cleave SNAP-25

21

botulinum toxin C1

cleave syntaxin

22

acetylcholine receptor?

ionotropic, nicotinic AcHR channel

non-selective cation channel at muscle endplate

23

what happens when ACh binds receptor?

allows influx of multiple cations (non-specific)
-to raise Vm above threshold

24

threshold at membrane with ACh receptor?

-50mV

25

opening of AChR channel?

Na+ and K+ become equally permeable

increase normally low permeability of sodium relative to K+

Vm shifts to value between Ek and Ena
-80 > +50

26

end-plate potential

for action potential
-due to increased sodium permeability relative to potassium

type of graded potential

is an EPSP

27

will you run out of ACh?

no, there's a lot at the end of the neuron in vesicles

-can maintain high rate of AP transmission without significant loss of function

28

termination of neurotransmitter action

enzymatic destruction removes ACh from NMJ synaptic cleft

ACETYLCHOLINESTERASE
-two step reaction

29

MEPP

??

30

myofibril

contractile element
contain thick and thin filaments