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Cell Biology > L8-11 Excitable Cells > Flashcards

L8-11 Excitable Cells Flashcards

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1
Q

The action potential in a neurone originates at the ? and moves towards the ? ⚡️

A

Axon hillock, axon terminal

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2
Q

An action potential is a rapid change in the..

A

Membrane potential

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3
Q

Resting membrane potential (RMP/ Em) is…

A

-70mV

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4
Q

Resting membrane potential is maintained by the action of (2)…

A
  • Potassium leak channel

* Sodium/Potassium ATPase pump

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5
Q

The Na+/K+ ATPase pump can be described as electrogenic because…

A

It creates an electrical gradient between the inside and outside of the membrane

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6
Q

The Nerst Equation calculates the point at which the concentration gradient and the electrical gradient balance out, a.k.a….

A

The equilibrium potential ⚖️

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7
Q

E ion =

A

( -RT /zF ) * ( ln [ion] in / [ion] out )

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8
Q

An action potential can be divided into 3 distinct phases…

A
  1. Depolarisation
  2. Repolarisation
  3. Hyperpolarisation
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9
Q

The voltage gated ion channels involved in action potentials are (2)…

A
  • Voltage gated Sodium channel

- Voltage gated Potassium channel

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10
Q

The refractory period can be divided into 2 phases…

A
  1. Absolute Refractory period

2. Relative Refractory period

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11
Q

The absolute refractory period is defined as the…

A

Period in which the membrane cannot generate another action potential, no matter how big the stimulus

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12
Q

The relative refractory period is defined as the…

A

Period in which the membrane can generate another action potential, but only if the stimulus is bigger than normal

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13
Q

Why is a greater stimulus required during the refractory period in order to generate an action potential?

A

Because the membrane is hyperpolarised, so the membrane potential is more negative than usual, thus further from the threshold

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14
Q

Action potentials travel down the axon via…

A

Current loops 🔁

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15
Q

Backwards movement of an action potential is prevented by…

A

The refractory period

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16
Q

Action potentials are caused by an influx of (A) and an efflux of (B) through voltage-dependent ion channels

A 
(A) = Sodium ions (IN)
(B) = Potassium ions (OUT)
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17
Q

During depolarisation, the membrane potential ( increases to 30mV / decreases to -70mV / stays the same )

A

Increases to 30mv

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18
Q

During depolarisation, the membrane potential decreases, because the voltage gated potassium channels are ( open / closed )

A

Open

19
Q

Voltage gated sodium channels open quickly, inactivate quickly and close ( quickly / slowly )

A

Slowly 🐢

20
Q

Voltage gated sodium channels are opened when the membrane potential exceeds the threshold voltage (-55mv). Inactivation and closure are ? dependent.

A

Time 🕐

21
Q

The voltage gated potassium channel is either open or closed. These phases are ( slow / fast ) and both voltage gated.

A

Slow 🐌

22
Q

The three factors affecting action potential velocity (V) are…

A
  1. Diameter (D) - more room for current loops
  2. Membrane resistance (Rm) - less current lost
  3. Distance between Modes of Ranvier - shorter distance = faster
23
Q

To increase membrane resistance (Rm), some axons are surrounded by a…

A

Myelin sheath

24
Q

The action potential ‘jumps’ from node to node. This is known as…

A

Saltatory conduction

25
Q

Myelination has ( no effect / a significant effect / a small effect ) on conduction velocity (V).

A

A significant effect

26
Q

NMJ stands for…

A

NeuroMuscular Junction

27
Q

The synaptic cleft is only ? across.

A

50nm

28
Q

In the NMJ, the post-synaptic membrane is known as the…

A

Muscle endplate

29
Q

The muscle endplate features invaginations known as…

A

Junctional folds

30
Q

An increase in ? concentration in the axon terminal causes vesicles to migrate and fuse with the pre-synaptic membrane.

A

Ca2+

31
Q

The Acetylcholine (Ach) receptors on the muscle endplate also function as…

A

Ligand-gated sodium channels (the ligand being Ach)

32
Q

The Ach receptor protein is also permeable to potassium ions, thus potassium ions move out from the (synaptic cleft / muscle endplate) via ion channel mediated facilitated diffusion.

A

Muscle endplate

33
Q

The endplate potential (EPP) is ? mV, which is between the equilibrium potentials of sodium and potassium

A

-15mV

34
Q

There is no action potential at the muscle endplate because…

A

There are no voltage gated sodium channels!

35
Q

Mini endplate potentials (mini EPPs) measure ? mV

A

0.5mV

36
Q

An mEPP represents the random fusion of a single ? with the membrane.

A

Vesicle

37
Q

One mEPP equates to one vesicle, which is known as…

A

One ‘quantum’

38
Q

Although 100 vesicles can generate sufficient change in membrane potential, 200-300 are generated as a…

A

Safety factor

39
Q

Acetylcholine is broken down by…

A

Acetylcholineesterase (Ach-ase)

40
Q

The EPP triggers an action potential via…

A

Nearby voltage gated sodium channels in the junction folds

41
Q

Curare is South American arrow poison, which blocks the Ach receptor. It is administered as a…

A

Muscle relaxant by anaesthetists

42
Q

Myasthenia Gravis is an autoimmune disorder which results in the…

A

Destruction of Ach receptors

43
Q

Myasthenia Gravis is treated by increasing the availability of Ach by using…

A

Ach-ase inhibitors (Anti-cholineesterase)

Cell Biology (21 decks)

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