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Medical Physiology > Neuron And Action Potential > Flashcards

Neuron And Action Potential Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the two parts of the Nervous system and their functions?

A

Central Nervous System:

  • Integrates signals
  • Sends signals to PNS

Peripheral Nervous system:

  • Senses input
  • Relays input to muscles
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2
Q

What are the two types of synapses in neurons?

A
  1. Electrical synapse/Gap junction

2. Chemical synapse

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3
Q

What is syncytium?

A

When an AP is elicited anywhere within a muscle mass, it generally travels in all directions in the muscle

Aka all cell act in synch

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4
Q

Which the cells are responsible for creating the myelin sheath?

A

CNS: Oligodenrocytes

PNS: Shwann cells

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5
Q

What are the roles of supporting cells of the CNS?

A

Ependymal cells: assist in producing and circulating CSF

Astrocytes: Maintain BBB

Oligodendrocytes: Increase conduction via myelin sheath

Microglia: Remveal of debris and waste via phagocytosis

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6
Q

Describe graded potential vs action potential.

A

In Graded Potential, there are a variable amounts of changes in charge; Cell body,dendrite

In action potential, Changes in charge are always identical; Axons

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7
Q

What is the resting potential of most neurons?

A

-80 to -60 mV

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8
Q

Differentiate Absolute Refractory period vs Relative Refractory period.

A

ARP: AP cannot be generated regardless of stimulus intensity. Due to closure of Na+ channel inactivation gate

RRP: Due to inactivated conformation of the voltage gated Na channels; Conductance of K+ is higher than the resting potential, so the membrane potential becomes more negative

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9
Q

Describe the pathology and symptoms of Multiple Sclerosis.

A
  • Autoimmune disorder where immune cells attack myelin sheath
  • Reduced conductance of neurons
  • Loss of sheath leads to leakage of K+
  • Partial loss of vision and problems with speech, balance,m and motor coordination
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10
Q

What are the types of propagation and where are they located?

A

Continuous -> Unmyelinated

Saltatory -> Myelinated

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11
Q

How are NTs transported down the axon?

A

In vesicles don microtubules via dynein and kinesin

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12
Q

What are the 3 types of ion channels on neurons?

A
  • Stretch-gated
  • Ligand gated
  • Voltage gated
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13
Q

What determines Nt release?

A
  • INC calcium into the presynaptic axon causes exocytosis of vesicle contents into synapse
  • Concentration of Ca++ determines concentration of NT released
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14
Q

Describe Lambert-Eaton syndrome.

A
  • Autoimmune
  • Antibodies attack voltage-gated calcium channels on presynaptic axon terminal
  • Impairs NT release
  • Characterized by general muscle weakness
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15
Q

Describe Gillian-Barre Syndrome.

A
  • Severe autoimmune disorder
  • Immunologic destruction of Schwann cells, nerve roots, and ganglia
  • Manifests as ascending weakness/paralysis
  • Rapidly travels upward, and result in fatal respiratory paralysis
  • prompt care to decrease inflammation can help recover normal function and demyelination of nerves
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16
Q

How does lidocaine work?

A
  • Inhibits local Voltage-gated Na+ channels
17
Q

What type of nerve fiber is the Dorsal root ganglia? What type of information do they send? Diameter?

A

Type C Fibers: Pain, Temperature; 0.4 - 1.2 micrometers

18
Q

Which type of receptors are most sensitive to local anesthetic?

A

Unlyelinated Type C Fibres (Nociceptive)

19
Q

How are ions distributed in terms of number between inside and outside of membrane At resting potential?

A

Total number of charged molecules and ions are distributed evenly

20
Q

What would be the result of an inhibited Na/K ATPase?

A

Inhibition of NA/K ATPase —> INC Na+ —> DEC Na+ Gradient —> Inhibiting Na/Ca exchanger —> INC Intracellular Ca

INC Intracellular —> Inhibits SGLUT

21
Q

What is the resting potential of a cardiac myocyte?

A
  • 90 mV
22
Q

What channels have the most significant impact on resting membrane potential?

A

Potassium and Chloride leak channels

23
Q

What are the four gated ion channels?

A
  • Voltage-gated
  • Ligand-gated
  • Messenger-activated
  • Stretch-activated channels
24
Q

How do Na voltage gated channels and K++ Chanel’s differ? (Besides ion duh)

A

1) The Na+ voltage-gated channels have two gates: an activation gate and a
deactivation gate.

2) The K+ channels only have one gate.

25
Q

During Ach binding and channel opening, how much does the potential depolarize?

A

Halfway between the Na+ and K+ potentials

26
Q

What are the L-type Calcium Channels?

A

L-type:

  • Long lasting
  • night voltage activated
  • plateau of cardiomyocytes; action potential pacemaker cells
  • Blocked by calcium channel antagonists
27
Q

What are the T-type Calcium channels?

A

T-type

  • Transcient, low voltage-activated
  • present in cardiomyocytes
  • Regulate vascular tone, signal conduction, and cardiac peacemaking
  • blocked by T-type calcium channel antagonist
28
Q

What are the N-type Calcium channels?

A
  • Neuron
  • High voltage-activated
  • Plasma membrane of presynaptic nerve terminal
29
Q

What are the P/Q-type calcium channels?

A
  • Purkinje fibers
  • High voltage-activated
  • Plasma membrane of Purkinje fibers and cerebellum granule cells
30
Q

What are the R-type calcium channels?

A
  • High voltage activated

- Plasma membrane of cerebellum granule cells

31
Q

What are Ca activated potassium channels, and what are the types?

A

Channels activated by changes in membrane electrical potential or increased concentration of intracellular Ca2+

BK (Big) - Regulate smooth muscle tone and mneuronal excitability

SK Channel - Synaptic plasticity

IK Channel - Peripheral tissue (Hematopoeitic, colon, placenta, lung, pancreas)

32
Q

What are the three states of voltage gated Na channels?

A
  1. Deactivated
  2. Activated
  3. Inactivated
33
Q

How do the actions of scorpion toxin and tetrodotoxin differ on Na channels?

A

ScTX interfere with gates closing

TTXX blacks channel

34
Q

How does Ca concentration affect Na channels?

A

Hypercalcemia —> Decreases the opening of channels

Hypocalcemia —> Increases openingof channel

35
Q

What pathology is associated with hypocalcemia and increased neurotransmission?

A

Tetany

36
Q

What are toxins which block Na passage through voltage gated channels?

A
  • TDT (puffer fish)
  • Saxitoxin (dinoflagellate)
  • i-conotoxin (cone snails)
37
Q

What are toxins which causer voltage gated Na channels to remain open

A
  • Batrachotoxin
  • Veratridine
  • Pyrethrins
  • Brevatoxins
38
Q

What are the different types of conotoxins?

A

α-conotoxin inhibits nicotinic acetylcholine receptors at nerves and muscles

δ-conotoxin inhibits the inactivation of voltage-dependent sodium channels

κ-conotoxin inhibits potassium channels

μ-conotoxin inhibits voltage-dependent sodium channels in skeletal muscle, not cardiac muscle or neurons

ω-conotoxin inhibits N-type voltage-
dependent calcium channels

Medical Physiology (43 decks)

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