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NSB > Physiology of Neurons: Electrochemical Properties and Communication > Flashcards

Physiology of Neurons: Electrochemical Properties and Communication Flashcards

1
Q

Membrane potential

A

voltage (difference in charge (more negative inside membrane, more positive outside) across neuron cell membrane

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2
Q

Membrane potential is the result of

A

the distribution of ions across the cell membrane and the permeability of the membrane

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3
Q

Deploarisation

A

membrane potential > resting potential

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4
Q

Hyperpolarisation

A

membrane potential < resting potential

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5
Q

Equilibrium Potential:

A

the voltage across the membrane that precisely balances the concentration gradient. If you had only one ion then the equillibrium potential would be the same as the resting membrane potential

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6
Q

Na+ Equilibrium Potential:

A

+60mV (outside to inside is positive potential)

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7
Q

K+ Equilibrium Potential:

A

-90mV

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8
Q

Ca2+ Equilibrium Potential:

A

+123

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9
Q

Cl- Equilibrium Potential:

A

-40mV

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10
Q

How do Na+ and K+ leak channels allow the generation of the membrane potential?

A
  • each channel is selective and restricted (no free flow of ions)
  • hence there is a slow transfer of Na+ into and K+ out of)
  • the membrane has more K+ leak protein channels and hence is more permeable
  • when K+ crosses the membrane, the cytoplasm becomes more negative
  • the positive charge increases on the exterior side of the membrane
  • which repels more K+ and the negatively charged interior is more attractive
  • net movement of K+ becomes zero as less K+ crosses

Na: tries to establish a positive Ek
K: tries to establish a negative Ek

because more permeable to K+, the final resting potential is negative

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11
Q

Na+/K+ pump:

A
  • 3 Na+ out
  • 2K+ in
  • against concentration grad
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12
Q

Voltage Gated Ion Channels:

A
  • ion channel responds to the membrane potential/voltage in the neuron
  • when the neuron is resting at -70mV, Na+ and K+ channels are closed
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13
Q

Ion Channel Summary:

A
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14
Q

Action Potential General Overview:

A
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15
Q

K+/Na+ Permeability graph:

A
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16
Q

Propogation of the action potential:

A
  • membrane in resting state (outside +, inside -)
  • depolarisation and outside becomes more negative
  • the outside becomes more negative when threshold is achieved
  • channels open, more influx of Na+/efflux of K+
  • hence action potential spreads
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17
Q

Saltatory Conduction:

A

Nodes of Ranvier is where ion exchange occurs
hence when myelinated only depolarisation at those points so impulse seems to jump
hence unidirectional transmission of action potential

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18
Q

Detailed action potential generation (include channels open/responsible):

A
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19
Q

Saltatory Conduction:

A
20
Q

Graded Potentials:

A

1) action potentials are the direct result of a defined stimulus eg received signal at the dendrite
2) graded potentials are a deviation (usually small) from the resting potential)
3) found mainly in dendrites and somas

Small change due to some neurotransmitter binding but threshold is not achieved

21
Q

Graded potentials:

A
21
Q

Graded potential vs action potential:

A
  • graded potential: small amplitude, long wave
  • lasts 10ms vs action potential is 1ms
22
Q

How can graded potentials result in action potentials?

A
  • amplitude of graded potential is directly proportional to the signal
  • the signal will weaken in a process known as decremental conduction
  • high amplitude graded potential can accumulate more ion channels open and result in threshold and hence action potential firing

*signal summation

22
Q

What is shown below?

A
22
Q

Graded Potential are the result of

A

generally ligand/mechanical gated ion channels

23
Q

Graded Potentials travel to adjacent locations on the membrane passively.

True or False?

A

True

24
Q

The amplitude of a graded potential increases with travel.

True or False?

A

False
reduces with travel

25
Q

Graded potentials have no refractory period because

A

the change in potential is small

26
Q

Graded Potentials can travel long distances.

True or False?

A

False
short distances

27
Q

Core Drug: Carbamazepine:

A
  • anticonvulsant for epilepsy
  • Inhibits Nav
  • binds within the core of Na+ voltage
    gated channel in the INACTIVE
    formation
  • raises the threshold required for
    action potential, resulting in
    dampening of stimuli/signals

*30% develop resistance

28
Q

Core Drug: Lidocaine:

A
  • local anaesthetic
  • binds to and inhibits Na+ voltage
    gated ion channels
  • inhibits generation of local action
    potentials
  • raises the threshold required for an
    action potential
  • blocks signalling from local pain
    receptors
29
Q

Sodium Valproate:

A
  • sodium salt of valproic acid
  • converted into valproate ion in blood
  • increases the conc of GABA
  • via the inhibition of catabolic GABA
    enzymes, hence increases the conc
    of GABA
  • hence causes hyperpolarisation, so
    inhibitory

May indirectly interact with K+ voltage gated channels

30
Q

Post-Synaptic Receptors:

A

ionotropic = fast
open and allow passage of ions upon activation but activated by the binding of a ligand

31
Q

Ionotropic Receptors:

A
32
Q

General Receptor Characteristics (6):

  • ion permeability
  • ion conductance
  • dynamics & conductance
  • ligand affinity
  • agonist
  • antagonist
A
33
Q

Most synapses contain receptor types that can be activated by

A

various neurotransmitters

34
Q

Fast and Slow Transmission:

A
35
Q

Metabotropic Receptors:

A
  • as opposed to direct ion channel
    binding, the neurotransmitter binds
    to a G-protein coupled receptor
  • binding to GPCR causes a
    conformational change
  • GPCR forms
  • heteromic g protein is released
  • initiates a biochemical cascade
36
Q

Metabotropic Receptors:

A
37
Q

GPCR

A
38
Q

GPCR:

A
39
Q

Second Messengers:

A
40
Q

What is the secondary messenger when Gs coupled receptor is activated?

A
  • effectory protein = adenylate cyclase
  • second messenger = cyclic AMP
41
Q

What is the second messenger when Gq coupled protein is activated?

A
  • effector protein = phospholipase C (PLC), which converts PIP2 into IP3 and DAG
  • secondary messenger = PIP2
41
Q

Gs & GI

A
41
Q

Gq

A
41
Q

G-proteins can be inhibitory (?), stimulatory (Gs) or Gq …..

A
  • inhibitory = Gi
  • stimulatory = Gs
  • Gq = activated PLC

NSB (50 decks)

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