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AA > 2.1 Neuron Properties > Flashcards

2.1 Neuron Properties Flashcards

1
Q

Dendrites

A

Receive synaptic INPUTS from neuronal axons

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2
Q

Cell Body (neuron)

A

Same organelles as any other cell

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3
Q

Trigger zone

A

Action potentials are started here, axon runs with them

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4
Q

Axons

A

Fire rapid impulses (APs) to synaptic terminals

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5
Q

Pre-synaptic terminal

A

Releases output signal to “post,” releases neurotransmitters at synapse

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6
Q

Multipolar neurons are found in…

A

Brain, spine, motor

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7
Q

Bipolar neurons are found in…

A

Retina, ear, nose

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8
Q

Unipolar neurons are…

A

Sensory receptor neurons

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9
Q

3 things necessary for cellular membrane potentials

A

1) Ions can be pumped through ion carriers embedded in cell membrane
2) Ions are maintained at different concentrations on either side of cell membrane (concentration gradient)
3) The ion (thus the potentials) can change by flowing through ion channels

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10
Q

Major ions that are pumped in neurons

A

Na+, K+, Cl-, Ca2+

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11
Q

What happens if there is not a constant source of energy for ion pumps?

A

Gradients erode very quickly, if you die from running out of energy it is probably because these pumps stopped working

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12
Q

Passive / Leakage (nongated channels)

A

Open randomly, important in maintaining the baseline neuronal membrane potential ; ion flow sensitive to concentration gradients
POTASSIUM

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13
Q

Ligand-gated channels

A

Open in response to binding of a ligand (neurotransmitters, hormones, etc)

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14
Q

Voltage-gated channels

A

Respond to changes in transmembrane potential (when it deviates from ‘normal’ resting membrane potential”

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15
Q

Mechanically gated ion channels

A

Respond to mechanical vibration; pressure

Activated by physical stretching of plasma membrane

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16
Q

Resting membrane potential

A

Baseline, status quo, where neuron sits most of the time, -70mV

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17
Q

Depolarization

A

Reduces the potential difference, brings it closer to zero.. Describes the state of flux when going more positive

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18
Q

Repolarizing

A

Potential is fluxing, getting more negative and returning to the reference point

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19
Q

Hyperpolarization

A

Increasing the potential difference; making it more negative (further away from 0) goes beyond -70mV

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20
Q

What does an RMP of -70 mV mean?

A

It’s more negative inside the neuron’s plasma membrane

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21
Q

Three compartments that matter to the RMP

A

1) Aqueous extracellular fluid (ECF) (aka interstitial fluid)
2) Non-conducting lipid barrier
3) Aqueous cytoplasm

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22
Q

What causes the potential difference?

A

1) Ion differences between ECF and cytoplasm
2) Ion pumps
3) Selective ion leakage

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23
Q

Ion differences

A

Phosphates and proteins are anions at physiological pH, they stay trapped in the cell
THEIR (-) CHARGES DOMINATE OVER THE IONS (Na/Cl/K)
-Primary reason the cytoplasm stays more negative

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24
Q

Are anions more concentrated inside or outside cell?

A

Inside

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25
Q

Is K+ more concentrated inside or outside cell?

A

Inside

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26
Q

Is Cl- more concentrated inside or outside cell?

A

Outside

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27
Q

Is Na+ more concentrated inside or outside cell?

A

Outside

28
Q

Intracellular ions create…

A

An electrostatic force field (both attracts and repels more mobile ions)

29
Q

Sodium-potassium pump

A

-3 Na+ ions out
-2 K+ ions in
ATP -> ADP +Pi
*Cl- also gets pumped out

30
Q

What ion as many leak channels?

A

K+, the membrane is very permeable to K+

31
Q

Inward forces on K+

A

1) Pumps push K+ into the cell (against gradient)
2) K+ tends to follow the anions into the cell (attracted to negative charge)
3) High Na+ in the ECF repels K+

32
Q

Outward Force on K+

A

1) Leak channels (moving down the concentration gradient)

33
Q

Result of forces on K+

A

K+ going inside offsets anions slightly, pushes RMP towards (+)
(RMP is at -70 rather than -80 b/c of potassium)

34
Q

Movers of Na+

A

Sodium potassium pumps

Very, very slow leak channels

35
Q

Hyperkalemia

A

Increase in bloodstream (ECM) potassium

  • Decreases gradient
  • K+ doesn’t diffuse out of cells as rapidly
  • Membrane DEPOLARIZATION
36
Q

Hypokalemia

A

Decrease in extracellular K+

  • Increase in concentration gradient
  • More diffusion of K+ out of the cell
  • Membrane hyperpolarization
37
Q

What keeps neurons at a resting membrane potential of -70 mV?

A

Electrostatic forces, Ion concentration gradients, Leakage channels and Pumps

38
Q

What can cause a flux or change in the RMP of a neuron?

A

Physical stimuli or input from other neurons

39
Q

Do all parts of the cell experience flux in RMP?

A

No, only regions near the plasma membrane

40
Q

Graded Potentials

A

Have an amplitude (height)

-Results from a variable degree of divergence (big, med, small) from the RMP

41
Q

Why does RMP change? (graded potentials)

A

It is changes in local ion permealbility

  • Na+ going in will make the neuron RMP more positive (stimulatory)
  • Cl- going in will make the RMP more negative (inhibitory)
42
Q

What’s the stimulus that elicits the Graded Potential?

A
  • Ligands (neurotransmitters, hormones) bind ligand gated ion channels
  • Mechanical stimulation
  • Temperature change, etc
43
Q

Summation

A

An additive effect on the amplitude when two or more stimuli occur at the same membrane locale at nearly the same time

44
Q

Spatial summation

A

Many / multiple synapses release stimulus or inhibitory signal in the same locale on the target neuron

45
Q

Temporal Summation

A

A single synapse may fire rapidly at a single point on the neuron

46
Q

This is the consequence to RMP of a graded potential that causes the opening of Cl- channels

A

Hyperpolarization

47
Q

Where are graded potentials in the neurons?

A

Dendrites, where summation and propagation of GPs to the trigger zone

48
Q

Trigger zone

A

Decision point.. If the GPs are pushing to threshold (~50 mV) then ACTION POTENTIAL

49
Q

Action potentials

A

Rapid, local reversals of the membrane potential

-All-or none (always same shape and amplitude)

50
Q

What is the main mechanism for rapid communication along nerve axons?

A

Action potentials!

51
Q

Why are action potentials triggered?

A

Because voltage-gated ion channels activated by crossing threshold in trigger zone

52
Q

Sequence of AP

A
  1. Stimulus (often graded potentials
  2. Depolarizing phase
  3. Repolarizing phase
  4. Hyperpolarizing phase
53
Q

What first happens when graded potentials cross threshold?

A

Voltage gated ion channels open, causes sharp depolarization

54
Q

What happens after sodium channels are opened?

A

(+30mV) Na+ channels close and voltage gated K+ channels open

55
Q

What happens when voltage gated K+ channels are opened?

A

Repolarization!

56
Q

Why does hyper polarization occur?

A

Goes too far on downstroke, close K+ channels, returns to -70mV, prevents immediate location from having another action potential

57
Q

Action potentials propagate…

A

UNIDIRECTIONALLY

58
Q

Action potentials cannot go backwards due to…

A

Refractory period, membrane can’t immediately fire an action potential due to channels being wide open & ion gradients exhausted

59
Q

Saltatory conduction

A

Voltage gated ion channels are only located at nodes (between myelin sheath), action potential jumps from node to node

60
Q

Information is encoded (strength of stimulus) in…

A

The FREQUENCY of action potentials

61
Q

What is the final output of a neuron

A

Release of a neurotransmitter at synapse (NOT action potentials)

62
Q

First step of synaptic transmission

A

AP triggers V-gated Ca2+ channels to open

63
Q

Calcium influx into presynaptic neuron causes… (synaptic transmission)

A

Exocytosis of secretory vesicles carrying neurotransmitters

64
Q

Are neurotransmitters stimulatory or inhibitory?

A

Both! (Could be either)

65
Q

Once neurotransmitters are released into the synaptic cleft…

A

They commonly bind to ion channels on the post-synaptic neuron

66
Q

What happens in an Excitatory Post-synaptic potential (EPSP)?

A

Postsynaptic neuron experiences depolarizing graded potential
ex: neurotransmitter (glutamate) opens Na+ channels

67
Q

What happens in Inhibitory Postsynaptic Potential (IPSP)?

A

Hyper-polarizing graded potential

ex: Neurotransmitter GABA opens Cl- channels (Cl- rushes into post-synaptic cell)

AA (21 decks)

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