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NSB! > 3. Physiology of Neurons :) > Flashcards

3. Physiology of Neurons :) Flashcards

1
Q

Which channels help a cell maintain its resting membrane potential?

  1. Na+ and Ca2+
  2. Na+ and K+
  3. Na+ and Cl-
  4. Na+ and Po
A
  1. Na+ & K+ leak channels (slow leaking)
  2. Na+ K+ pump
  • Na+ = 3 molecules leave the cell
  • K+ = 2 molecules enter the cell

SO PI

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2
Q

What is the function of the Na+/K+ pump?

A

Na+/K+ pump function:

  • transfer 3 Na+ out of the cell
  • transfer 2 K+ into the cell
  • requires ATP to maintain membrane potential
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3
Q

What is required for a voltage gated channel to open?

  1. ligand binding
  2. neurotransmitters recognised in synaptic cleft
  3. change in membrane potential
  4. GPCR to activate
A

voltage gated channel opens = change in membrane potential

  • Must be above a specific threshold (tissue dependent)
  • remain closed when membrane is at resting state
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4
Q

What is the equilibrium potential?

  1. voltage is the same across membranes due to fluid levels
  2. voltage is the same across membranes do to neurotransmitter concentration
  3. voltage is the same across membranes due to balance between ion concentration and voltage of electrical energy
A

voltage is the same across membranes due to balance between ion concentration and voltage of electrical energy

ion concentration = electrical potential energy are equal

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5
Q

What is the general concentration of Na+ inside & outside the nerve cell?

  1. inside = 10mM and outside = 145mM
  2. inside = 140mM and outside = 4mM
  3. inside = 140mM and outside = 145mM
  4. inside = 10mM and outside = 140mM
A

inside (intracellular) = 10mM

outside (extracellular) = 145mM

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6
Q

What is the general concentration of K+ inside & outside the nerve cell?

  1. inside = 10mM and outside = 145mM
  2. inside = 140mM and outside = 4mM
  3. inside = 140mM and outside = 145mM
  4. inside = 10mM and outside = 140mM
A

inside = 140mM

outside = 4mM

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7
Q

What are the 4 stages of the action potential graph in order?

  1. voltage rises above threshold, de-polarisation, re-depolarisation, hyper-polarisation
  2. de-polarisation, voltage rises above threshold, re-depolarisation, hyper-polarisation
  3. voltage rises above threshold, de-polarisation, hyper-polarisation, re-depolarisation
  4. hyper-polarisation, voltage rises above threshold, de-polarisation, re-depolarisation
A

voltage rises above threshold,

de-polarisation,

re-depolarisation,

hyper-polarisation

1 - voltage of cell increases & threshold is reached

2 - depolarisation occurs

3 - repolarisation occurs

4 - resting state (following hyperpolarisation)

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8
Q

In an action potential, what channels help maintain a membrane potential of around -70mV?

  1. Cl- and Na+
  2. Na+ and K+
  3. K+ and Cl-
  4. K+ and Ca2+
A

leaky Na+ & K+ channels

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9
Q

Once an action potential is received, what happens to generate an action potential and allow the cell to reach its membrane potential?

  1. Cl- channels open
  2. K+ channels open
  3. Ca+2 channels open
  4. Na+ channels open
A
  1. Na+ channels open
    • Na+ channels open and Na+ influx inside cell
    • membrane potential reaches threshold and we get depolarisation
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10
Q

Once the neuronal cell has received an action potential, Na+ has rushed inside the cell through Na+ voltage gated channels, depolarisation occurs. In addition to Na+ channels, what other main channel drives depolarisation?

  1. Cl- channels open
  2. K+ channels open
  3. Ca+2 channels open
  4. Na+ channels open
A
  1. K+ channels open
    • K+ voltage channels open & K+ leaves the cell
    • K+ rushes out of the cell
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11
Q

When a cell is undergoing hyperpolarisation, is the cell able to receive another action potential?

A
  • no
  • Na+ voltage pump cannot open during hyperpolarisation
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12
Q

What does propagation of an action potential mean?

  1. a Na+ channel opening then opens a K+ channel and continues
  2. a K+ channel opening then opens a Na+ channel and continues
  3. a Na+ channel opens which stimulates surrounding Na+ channels to open
  4. a Na+ channel closes then closes other Na+ channel and continues
A

3 - a Na+ channel opens which stimulates surrounding Na+ channels to open

  • one Na+ voltage channel opens stimulating surrounding channels
  • action potential spreads to surrounding Na+ channels
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13
Q

To facilitate saltatory conduction there is a specific channel that is densely populated at the nodes of Ranvier. Which channels are these?

  1. Na+ voltage gated channels
  2. K+ voltage gated channels
  3. Ca2+ voltage gated channels
  4. Cl- voltage gated channels
A

Na+ voltage gated channels = densely populated at the nodes of Ranvier.

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14
Q

What are the 2 different types of synapse?

A

1 - chemical (more common)

2 - electrical (physically connected)

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15
Q

What are graded potentials and their function?

  1. small temporary changes in membrane potential
  2. large static changes in membrane potential
  3. small permanent changes in membrane potential
  4. large permanent changes in membrane potential
A

graded potentials = small temporary changes in membrane potential

  • alone they are insufficient to reach threshold
  • lots of graded potential combined can facilitate depolarisation
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16
Q

What are the 2 types of graded potentials?

A

1 - hyperpolarising graded potential

2 - depolarising graded potential

17
Q

Can graded potentials create an action potential alone?

A
  • No
  • but with lots of of them then YES, accumulate to cross the threshold
18
Q

Carbamazepine is a drug that is used to treat epilepsy, functioning as an anti convulsant (GABA agonist). What is its mechanism of use?

1 - bind and inhibit Na+ channels so no action potential and depolarisation
2 - bind and inhibit K+ channels so no action potential and depolarisation
3 - bind and inhibit Ca2+ channels so no action potential and depolarisation
4 - bind and inhibit Cl- channels so no action potential and depolarisation

A

binds and inhibits Na+ channels reducing depolarisation and action potential
- act as an agonist of GABA, allowing Cl- into cell and ensure less or no depolarisation occurs

19
Q

Carbamazepine is a drug that is used to treat epilepsy, functioning as an anti convulsant. It works by binding to and in inhibiting voltage gated Na+ channels, increases the threshold, so it is harder to reach an action potential. Does Carbamazepine work on everyone?

A
  • no
  • 30% of patients develop resistance related to genetics
20
Q

Lidocaine is a local anaesthetic (means only a small part of the body is treated and patient is generally awake) medication that is used to block pain sensations in a wide variety of superficial and invasive procedures. Lidocaine is able to inhibit action potentials, therefore reducing the sensation of pain in the CNS. What is the mechanism of action of Lidocaine?

1 - enters cell, ionised, binds with K+ channels and keeps them closed
2 - enters cell, ionised, binds with Ca2+ channels and keeps them closed
3 - enters cell, ionised, binds with Na+ channels and keeps them closed
4 - enters cell, ionised, binds with Po+4 channels and keeps them closed

A

Lidocaine enters cell, ionised, binds with Na+ channels and keeps them closed

  • able to pass into the cell
  • due to lower pH inside cell Lidocaine is ionised and cannot leave the cell
  • ionised lidocaine then binds with Na+ channels and keeps them closed
21
Q

Sodium Valproate is an anticonvulsant medication that is used primarily in the treatment of epilepsy and neuropathic pain. It have been shown to have a broad spectrum and reduce action potentials. What is its mechanism of action?

1 - binds and inhibits Na+ and Ca2+ channels reducing depolarisation and action potential
2 - binds and inhibits K+ and Na+ channels reducing depolarisation and action potential
3 - binds and inhibits Cl- and K+ channels reducing depolarisation and action potential
4 - binds and inhibits Mg+ and Ca2+ channels reducing depolarisation and action potential

A

1 - binds and inhibits Na+ & Ca2+ channels reducing depolarisation and action potential
- acts as an agonist on GABA receptors

22
Q

The ability to do work. In terms of neurons it refers to the separation of charge

A

Defines ‘potential’ in terms of neurons…

23
Q

At resting state which ion is in greater concentration on the inside of the cell K+ or Na+?

A

More K+ is on the inside (Remember SOPI)

24
Q

Proteins in neurons have a what charge?

A

Negative

25
Q

What is this diagram demonstrating?

A

At resting potential when there is a large concentration of positive ions on the outside of the cell the electrochemical gradient will be larger because the pull is stronger. However, if there are negative ions outside despite the concentration gradient the total electrochemical gradient will be reduced because the membrane potential on the inside is negative and therefore there is repulsion from the negative ions trying to flow into the cell.

26
Q

Ion channels that let through specific ions occasionally are called …. Their channel is restricted so there is no free flow of ions and therefore both K+ and Na+ are slowly transferred.

A

Leak channels

27
Q

In the cell membrane there is leak channels that slowly allow for K+ and Na+ (separate channels for each) to be transferred which allows for the creation of the membrane potential. However, despite this a Na+/K+ ATPase pump is also required, why?

A

Over time the membrane potential would degrade if there was only leak channels leading to an equilibrium. The pump prevents this from happening by letting more Na+ out (3) than K+ in (2).

28
Q

What is present inside voltage gated ion channels that allows them to respond to the membrane potential inside the neuron?

A

Voltage Sensing Elements (VSE). These elements are positively charged.

29
Q

Where are Leak ion channels found? Describe the passage?

A

Leak:

  • Randomly open/close (restricted passage)
  • All cells.
30
Q

Where are voltage gated ion channels found? In response to what do they open/close?

A

Voltage gated ion channel

  • In the axon of all neurons.
  • Open/close in response to membrane potential
31
Q

Where are ligand gated ion channels found ? When do they open?

A

Ligand gated ion channels:

  • Open after the binding of a specific ligand
  • Dendrites of some sensory neurons (e.g. pain), interneuron cell bodies and motor neurons.
32
Q

Where are mechanically gated channels found? In response to what do they open?

A
  • Dendrites of some sensory neurons (e.g. touch, pressure and pain receptors)
  • Open in response to a physical stimulus
33
Q

In neurons what is the approximate resting membrane potential?

A

-90mV

34
Q

What are the equilibrium potentials in neurons for:

1) Na+
2) K+
3) Ca+
4) Cl-

A

1) Na+ = +60
2) K+ = -90
3) Ca+ = +123
4) Cl- = -40

NSB! (53 decks)

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