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Clinical Physiology > Nervous System 2 - Membrane Potentials > Flashcards

Nervous System 2 - Membrane Potentials Flashcards

1
Q

What is resting membrane potential?

A

The voltage (charge) difference across a cell membrane at rest

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2
Q

What is variation of resting membrane potentials?

A

Resting membrane potential varies: -70mV - +5mV

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3
Q

What is the resting membrane potential of a neuronal membrane?

A

Neuronal membrane - Polarised with respect to charge
Extracellular fluid - Positive at rest
Intracellular fluid - Negative at rest

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4
Q

Size of resting membrane potential governed by 3 factors. What are they?

A

Unequal distribution of ions in intracellular & extracellular fluid
Inability of molecules to leave the cell
Relative permeability of neuronal membrane to different ions

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5
Q

In resting membrane potentials, what is the concentration in extracellular fluid?

A

High concentration of sodium & chloride ions

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6
Q

In resting membrane potentials, what is the concentration in intracellular fluid?

A

High concentration of potassium, phosphates & protein

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7
Q

Negatively charged proteins are too big to leave the cell. True or False?

A

True

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8
Q

What does the sodium potassium pump do?

A

Pumps more positive ions out of the cell membrane than it pumps in (Electrogenic)

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9
Q

Most ion channels are gated. What does that mean?

A

They are either open or closed

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10
Q

What factors control the gates ion channels?

A

Membrane potential (voltage)
Neurotransmitters (chemical)

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11
Q

What are the 4 types of channel?

A

Leakage channel
Ligand-gated channel
Mechanically gated channel
Voltage-gated channel

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12
Q

What are leakage channels?

A

Alternate between open & closed positions (randomly)
Found in all cells
Higher number of potassium leakage channels than sodium leakage channels in membrane

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13
Q

What are ligand-gates channels?

A

Open & close in response to chemical stimuli
Found on dendrites & motor neurons
Opened via various chemical stimuli – Neurotransmitters | Hormones | Ions
E.g. Acetylcholine permits inward flux of sodium & calcium which is paired with outward flux of potassium

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14
Q

What are mechanically gated channels?

A

Open & close in response to vibration (sound), pressure or stretching
Found on sensory neurons e.g. Touch receptors | Pressure receptors

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15
Q

What are voltage gated channels?

A

Open in response to a change in membrane potential (voltage)
Enabler of action potentials
Found on all neurons e.g. Potassium gated channel

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16
Q

Membrane is more permeable to Potassium. True or False?

A

True

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17
Q

Membrane relatively impermeable to Sodium. True or False?

A

True

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18
Q

K+ ions (i.e. positive charge) diffuses out of
neuron until K+ equilibrium potential is reached. True or false?

A

True

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19
Q

Changes in membrane potential occur due to the movement of ions across the membrane. True or False

A

True

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20
Q

What are the 4 terms used to describe the state of a membrane?

A

Local potential - Small changes in membrane
potential in response to stimulus

Action potential - Large & rapid depolarisation to nerve cells
causing the cell membrane potential to reverse

Inhibitory - Hyperpolarisation

Excitatory - Depolarisation

21
Q

Do local potentials travel short or long distances?

A

Short

22
Q

Can local action potentials add together?

A

Yes

23
Q

What are Inhibitory local potentials?

A

Opening of small number of K
+ or Cl- channels in membrane

24
Q

What are Excitatory local potentials?

A

Opening of small number of Na+ channels in membrane

25
Q

What are the 3 main phases of an action potential?

A

Phase 1 - Depolarisation
Phase 2 - Repolarisation
Phase 3 - Hyperpolarisation

26
Q

Nerve impulse travels the length of axon towards terminals. True or False?

A

True

27
Q

Resting membrane potential - Inside of neuron is negative
& outside is positive. True or false

A

True

28
Q

Threshold potential (-55mV) – Action potential takes
place due to a transient reversal in membrane polarity. True or False?

A

True

29
Q

Peak of action potential (+30mV) - Inside of neuron is
positive, outside negative. True or false?

A

True

30
Q

What are Hyperpolarisation?

A

Overshoot in membrane potential that makes the membrane more polar

31
Q

An action potential can be generated from what?

A

Electrical stimulation of neuron
Sensory receptors receiving stimulus
from other neurons

32
Q

The action potential threshold can also be called the All or Nothing Law. True or false?

A

True

33
Q

For action potentials to be generated, neuronal membrane must
depolarise to threshold potential (-55mV) True or false?

A

True

34
Q

What is subthreshold?

A

No action potential produced
(local potential will be produced)

35
Q

What is threshold?

A

Action potential produced

36
Q

What is supra-threshold?

A

Action potential produced (same size as threshold)

37
Q

What is the refractory period?

A

Neuron is less excitable during & immediately after generation of an action potential than it is at
rest

38
Q

What are the 2 phases the refractory period occurs in?

A

Absolute and Relative

39
Q

What is absolute refractory period?

A

Occurs from start of depolarisation to end of repolarisation
A second action potential cannot be generated
during absolute refractory periods
During depolarisation – All Na+ channels open
During initial repolarisation - Na+ gates are inactivated
(closed) and cannot be opened by another stimulus

40
Q

What is relative refractory period?

A

Occurs immediately after absolute refractory period
Possible to generate a 2nd action potential -
Only in response to a stronger stimulus
Some K+ channels remain open beyond repolarisation
phase (temporary hyperpolarisation)
It is ‘harder’ to depolarise the neuron but a stronger
stimulus is required

41
Q

What are the 2 types of axons?

A

Unmyelinated and Myelinated

42
Q

What is Continuous propagation?

A

Conduction in unmyelinated axons

43
Q

What is Conduction in unmyelinated axons called?

A

Resting state

44
Q

What are myelinated neurons covered by?

A

Myelin Sheath

45
Q

Local potentials travel short distances & can be excitatory or inhibitory. True or false?

A

True

46
Q

Action potentials travel long distances & are only generated following threshold potential. True or false?

A

True

47
Q

True or false? Local & action potentials are underpinned by the movement of Na+ & K+ across the membrane?

A

True

48
Q

Action potentials propagate more quickly along myelinated axons. True or false?

A

True

Clinical Physiology (12 decks)

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