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Medneuro- M2-2- NT systems > Channelopathy - Plested > Flashcards

Channelopathy - Plested Flashcards

1
Q

what is the intracellular and extracellular concentration of Na+, K+, Ca2+ and Cl-?

A

Na+- intracellular: 12 uM, extracellular: 145 uM
K+- intracellular: 155 uM, extracellular: 4 uM
Ca2+ - intracellular: 100 nM, extracellular: 1.5 uM
Cl- - intracellular: 4 uM, extracellular: 12.3 uM

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2
Q

in the neuron, there is a specific localisation for each ion channel….(which statement is WRONG?)

a. K+ are located at the node of ranvier, at the soma and at the dendrites
b. Na+ are located at the node of ranvier, at the soma and at the dendrites
c. Cl- are located mainly at the soma
d. Ca2+ are mainly at axon terminals
e. K+ are located at the node of ranvier, at the axon terminals and a few at the soma & dendrites

A

a

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3
Q

how are receptors being delivered to their designated location?

A
  • channels are delivered to the membrane from intracellular organelles
  • they are grabbed by membrane scaffold proteins at a specific site of the membrane
  • receptors are recycled through endoscope and can be relocalised to a different spot
  • ion channels are synthesised in the dendrites –> delivered by SV to the soma and ER and matured in Golgi apparatus –> then delivered via SV to different membrane sites.
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4
Q

in sustained threshold recording…(which statements are correct?)

a. there is a rhythmic firing –> periodic generation of AP
b. high current injection leads to slow rhythmic firing
c. low current injection leads to slow rhythmic firing
d. high current injection leads to fast rhythmic firing
e. low current injection leads to fast rhythmic firing

A

a, c, d

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5
Q

what us the definition of channelopathy?

A

a defect in an ion channel that leads to a disease

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6
Q

long Qt syndrome…

a. is caused by channelopathy
b. does not have phenotypical expression
c. caused by neuronal degeneration
d. causes prolonged extremities (mainly legs)
e. causes enlargement of the heart

A

a

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7
Q

mutations in SCN1a channel…(which statements are correct?)

a. is found in patients with epilepsy
b. is easy to detect
c. is caused only by dominant mutations
d. is hard to detect because many mutations lead to similar problems which can be everywhere in the brain
e. show linear allele combination

A

a, d

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8
Q

what equation is used to assess mechanisms channel function/dysfunction? what is the relationship between the parameters?

A

I = N * P * i
with N= number of channels; P= open probability of 1 channel; i= unitary conductance of 1 channel

–> Each one can affect the function of channels- e.g. if 2 channel types have the same number of channels (N) but one type doesn’t open as ofter (P1

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9
Q

what changes in channel functions can be caused by mutations?

A
  • mutations can change selectivity of a channel
  • mutations can introduce leak currents
  • over expression of channels (number of channels is too high)
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10
Q

what are the characteristics of Hypokalemic periodic paralysis (HypoPP) and what is it caused by?

A
  • HypoPP is characterised by episodes of muscle weakness or paralysis associated with reduced serum potassium levels
  • Cause: The resting membrane potential of muscle fibers from patients with HypoPP is excessively depolarized, leading to inactivation of voltage-gated sodium channels, inexcitability, and paralysis of the muscle
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11
Q

what can a channelopathy in the K-ATP channel result in?

A
  • KATP channels are K+ channels that are controlled by ATP.
  • plays a role in insulin secretion
  • mutation in the KATP channel can lead to type 2 diabetes
  • KATP also plays a role in the CNS –> result: disrupted KATP in muscle - channel was not sensitive to ATP –> motor deficits
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12
Q

how can changes in channel function cause epilepsy? which channels are affected?

A

epilepsy can result from:

  • increased activity of excitatory neurons - gain of Na+ channel function and loss of K+ channel function
  • decreased activity of inhibitory neurons- gain of K+ channel function and loss of Na+ channel function
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13
Q

Timothy syndrome is caused by a problem in…

a. regulation of K+ channel (hyperactivity)
b. regulation of K+ channel (low activity)
c. regulation of Na+ channel (hyperactivity)
d. regulation of Na+ channel (low activity)

A

b

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14
Q

FHM2…

a. is a mutation in a single allele in ATPase leading to pump dysfunction
b. is a mutation in a two alleles in ATPase leading to pump dysfunction
c. is a mutation in Na+ channel

A

a

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15
Q

Charcot Marie Tooth (CMT)…(which answer is WRONG?)

a. is a very common genetic channelopathy
b. is an autosomal dominant mutation linked to TRPV channel
c. is an autosomal recessive mutation linked to TRPV channel
d. is a mutation in a scaffold protein anchoring TRPV channel which lead to over excitation and cell death

A

c

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16
Q

What is startle disease (hyperekplexia) and what channelopathy causes it?

A
  • impaired acoustic startle response
  • extremely rare
  • point mutation in glycine receptor and transporter
  • can be caused by many mutations: mutations in alpha and beta SV of the receptor
  • mutation in alpha4 glycine receptor (stop codon added to gene leading to channelopathy)
  • gating defect of alpha glycine receptor
17
Q

what types of epileptic seizures are there?

A
  • simple partial seizures- small disturbances in one hemisphere
  • complex partial seizures- large disturbances in one hemisphere
  • partial seizures with secondary generalisation- seizure starts in one hemisphere and spreads to the other
  • generalised seizures- seizure in both hemispheres
18
Q

what happens in in the brain during long wave synchronisation (for example in slow sleep oscillation)?

A
  • in the cortex- periodic long up and downstates
  • -> in interneurons- short upstate and long downstates
  • -> TC neurons
  • the activity in one area leads to different synchronised activities in other areas
19
Q

what happens when gamma oscillations are hypersynchronised?

A
  • under physiological conditions, there is a recurrent inhibition of theta and gamma network.
  • if the frequent inhibition through CCK interneurons is lost, the activity of fast spiking is increased and the overall synchronous activity if the recurrent inhibition of theta is lost.
  • -> incuces epilepsy
20
Q

what is the result of mutations in SCN1A and SCN1B?

A

SCN1A mutation:

  • impair channel inactivation – direct gain of function
  • this permits prolonged AP firing, prolongation of Na+ influx.

SCN1B mutation:
- gain of function of Na+ channel because the B SU normally accelerates kinetics of Na+ current

Medneuro- M2-2- NT systems (11 decks)

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