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1.1.3 The Human Body > 3. Inside the Neuron > Flashcards

3. Inside the Neuron Flashcards

1
Q

Nerve Impulse/Action Potential

A

The electrical impulse that travels between neurons to share messages
A massive momentary reversal of a neuron’s membrane potential from about -70 mV to about +50 mV

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2
Q

Action Potential Process

A

Resting Potential
Depolarization
Repolarization
Hyperpolarization

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3
Q
  1. Resting Potential
A
  • High in tension, enables neuron to react quickly to stimulation
  • Begins at resting -70mV
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4
Q
  1. Depolarization
A
  • The charges flip, positive inside the neuron, negative outside (after threshold is reached)
  • When the right amount of stimulation is achieved (-55mV), the sodium ion channels open and Na+ ions flood the cell

Caused by the electrostatic pressure and and pressure from the concentration gradient

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5
Q
  1. Repolarization
A
  • At the peak of the sodium ion influx (+30), the sodium channels close while the potassium channels stay open (potassium ions leave)
  • Membrane potential decreases
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6
Q
  1. Hyperpolarization
A
  • As the ions are flooding out and moving around, the neuron becomes hyperpolarized
  • Further decrease in membrane potential
    • Opposites, sodium is inside, potassium is outside
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7
Q

Refractory period

A
  • After the action potential
  • Sodium channels need to close, potassium is flowing at a faster rate
  • Resists another action potential
  • Explains why the action potential can only go in one direction
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8
Q

Absolute refractory period

A

Membrane cannot produce an action potential

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9
Q

Relative refractory period

A

A very strong stimulus is required to generate another action potential

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10
Q

All-or-none Law

A

the action potential always has the same strength, despite any changes in strength of the stimulation

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11
Q

Rate law

A

stronger stimulation leads to more frequent action potential

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12
Q

Cause of action potential

A

The electrical impulse is caused by ions (which have an electrical charge) moving across the cell membrane

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13
Q

Membrane potential

A

difference in electrical charge inside and outside of the cell
- Caused by the unequal distributions of ions inside and outside
Sodium (Na+) and Potassium (K+) ions
- More sodium ions outside, more potassium inside (neuron is polarized)

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14
Q

Resting membrane potential

A

-70mV

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15
Q

3 causes of uneven ion distribution

A
  1. Sodium potassium pump
  2. Electrostatic pressure
  3. Pressure from concentration gradient
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16
Q

Sodium potassium pump

A
  1. Takes 3 Na+ ions out, lets 2 K+ ions in
  2. This active ion transport requires energy
  3. Working during resting potential stage - maintains membrane potential
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17
Q

Electrostatic pressure

A
  1. Inside of the neuron is negative, outside positive
  2. Na+ ions (outside) are drawn to the negative inside, opposites attract
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18
Q

Pressure from concentration gradient

A
  1. Pressure as a result of the concentration gradient
    1. ions don’t want to be so polarized, Na+ wants in, K+ wants out
    2. Concentration gradient - concentration of particles is very high in one area and not another. Particles try to restore equilibrium
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19
Q

Potassium ion channels

A
  • Mostly closed during resting stage, only a few can get through
  • Leave the cell
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20
Q

Sodium ion channels

A

Closed during resting stage

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21
Q

Domino effect

A
  • The action potential depolarizes nearby areas, causing more sodium channels to open
  • Each area is stimulated by the depolarization in the area near it
22
Q

Myelin sheaths

A
  • Increase the distance/reach of the action potential
    • Action potential only has to be generated at the ends of the Myelin sheaths, aka the nodes
23
Q

Nodes of Ranvier

A

Gaps between the myelin sheaths

24
Q

Saltatory conduction

A

action potential leaps between the gap
- More than 10x faster than normal conduction
- Less energy is required as fewer ions need to be transported through the membrane

25
Q

Neurotransmitters (by size)

A

Amino acids
Monoamines
Neuropeptides

26
Q

Amino acids

A

GABA - inhibitory
Glutamate - excitatory

27
Q

Monoamines

A

Dopamine
Serotonin
Norepinephrine

28
Q

Neuropeptides

A

Endorphin

29
Q

Additional neurotransmitter

A

Acetylcholine

30
Q

Production & Release (amino acids & monoamines)

A

Amino acids & monoamines are produced at the presynaptic terminal
- Both are stored in vesicles
- These vesicles can then move freely

31
Q

Production & Release (neuropeptides)

A

Also stored in vesicles but have to be transported to the site of release

32
Q

Synthesis

A

Production of chemical compounds through reactions with simpler materials

33
Q

Ionotropic receptors

A
  • Similar to ion channels - neurotransmitter binds, ion-channel opens and lets ions into the cell
    On the side of an ion channel
  • Changes postsynaptic potential very fast
  • Used for fast events
34
Q

Excitatory Postsynaptic Potentials (EPSPs)

A

A stimulating, excitatory change
Increases the chance that an action potential will occur

35
Q

Inhibitory Postsynaptic Potentials (IPSPs)

A

An inhibitory change
Decreases the chance that an action potential will occur

36
Q

Metabotropic Receptors

A

aka G-protein receptor
Neurotransmitters bind, metabolic reactions are activated
- Uses a G-protein & second messenger system
Slower than ionotropic receptors

37
Q

G-protein

A
  • Activates a ‘second messenger’ which can
    • alter a metabolic pathway
    • change gene expression
    • open or close an ion channel
    • increase production of a certain protein
38
Q

Endogenous chemicals

A

Originate outside the body e.g. neurotransmitters

39
Q

Exogenous chemicals

A

Originate outside the body but can influence neurotransmitters once inside e.g. psychoactive drugs

40
Q

Reflex arcs

A

stimulus - sensory neuron - muscle

Goes through the spinal cord, not the brain

41
Q

Sherrington’s 3 Properties of Reflexes

A
  1. A reflex isn’t as fast as a message travelling along an axon
  2. Several weak stimuli close together in position or time produce a stronger effect than one stimulus
  3. One set of muscles will relax when another is excited
42
Q

Summation

A

Spacial or temporal

Determines the start of an action potential

43
Q

Temporal summation

A

EPSPs combine in one location (or stimulate several times) to exceed the threshold and kickstart another action potential

44
Q

Spacial summation

A

EPSPs in different locations (e.g. different dendrites) combine to exceed the threshold and kickstart another action potential

45
Q

Synapse

A

The gap between one neuron & the next

46
Q

Receptors

A
  • Located in the cell membrane of the neuron
  • Neurotransmitters can bind here
  • Each receptor is ‘sensitive’ to specific neurotransmitters
    • Key-lock principle
    • Sub-types of receptors for each neurotransmitter
47
Q

Presynaptic

A

Sends information from the end of the neuron’s axon

48
Q

Postsynaptic

A

Receives information form dendrites

49
Q

Synaptic transmission

A
  1. Neurotransmitters are held in vesicles at the axon terminal, waiting for stimulation to be released
  2. Action potential causes the release of the neurotransmitters into the synapse (exocytosis)
  3. Neurotransmitters bind to receptor sites, causing a change in potential
  4. Reuptake - after binding and changing potential, the neurotransmitter is reabsorbed into the first neuron through uptake pumps
50
Q

Exocytosis

A

Bursts of releases of neurotransmitters (or anything else in the body) from the presynaptic neuron

Vesicles fuse with the membrane after releasing the neurotransmitters
More vesicles are created again from the membrane (pinched off)

51
Q

Reuptake

A
  • Feedback mechanism
    • Autoreceptors on the presynaptic neuron monitor the release of neurotransmitters
    • Neurotransmitters bind to the autoreceptors on their original neuron as part of reuptake & a signal is released to send less of the neurotransmitter into the synaptic gap

1.1.3 The Human Body (8 decks)

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