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Biology (S2) > Neuroscience > Flashcards

Neuroscience Flashcards

1
Q

Learn the structure of a neuron

A

cell body
nucleus
dendrite
axon hillock
Myelin sheath
axon
node on ranvier
axon terminals

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2
Q

How many neurons does the brain contain?

A

About 86 billion

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3
Q

What is the average number of connections a neuron makes?

A

1000

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4
Q

What does the property ‘excitability’ of neuronal cells refer to?

A

The ability to respond to stimuli

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5
Q

What does the property ‘conductivity’ of neuronal cells refer to?

A

Ability to generate and propagate electrical signals known as action potentials

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6
Q

What does the property ‘secretion’ of neuronal cells refer to?

A

When chemical neurotransmitters are used to bridge gaps at synapses between neurons

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7
Q

What is the resting charge across a membrane?

A

Approximately -70mV
(maintained as a result of balance between chemical and electrical gradient)

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8
Q

What is the permeability like of a resting neuron membrane?

A

Membrane itself is relatively impermeable to ions

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9
Q

What do Na+/K+ ATPase membrane protein pumps do to maintain resting potential?

A

Pumps out 3 Na+ for every 2 K+ it brings in
Works continuously in presence of ATP

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10
Q

What are ion channels?

A

Proteins found in membranes that selectively control the permeability to cations (Na+, K+) and some anions (Cl-)

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11
Q

Describe the charge inside and out a membrane during resting potential?

A

The inside of the membrane has a negative charge with respect to the outside

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12
Q

What is the equilibrium potential of an ion?

A

The point at which there would be no net movement of the ion across the membrane

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13
Q

What is the resting equilibrium potential for Potassium (Ek)?

A

approximately -80mV

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14
Q

What is the resting equilibrium potential for Sodium (ENa)?

A

approximately +60mV

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15
Q

What is the membrane more permeable to at rest?

A

K+ (this is what gives membrane resting potential of -70mV in neurons)

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16
Q

What is the membrane state during rest?

A

membrane potential of -70mV
Votage gated Na and K channels closed
Intracellular - high [K+]
Extracellular - high [Na+]

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17
Q

What is local potential?

A

Where membrane potential rises - Eg in respond to a ligand gated ion channel

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18
Q

What happens to local potential if it doesn’t reach threshold?

A

Potential will diminish without causing action potential

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19
Q

What happens when membrane reaches threshold?

A

Depolarisation
Voltage gated Na open
K channels remain closed
Sodium moves into cell - membrane potential rises rapidly

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20
Q

What happens when membrane potential peaks at approximately 35mV?

A

Repolarisation
Voltage gated Na channels inactivated (not closed)
Voltage gated K channels open
K+ ions move out of cell
Membrane potential falls back towards resting

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21
Q

What is absolute refractory period?

A

When it is impossible to fire another action potential
Lasts about 1ms
K channels closing, Na channels inactivated
Potential drops below resting

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22
Q

What is relative refractory period?

A

When it is possible to fire an action potential but a larger stimulus is required
Lasts several milliseconds
Potassium channels closing, sodium channels de-inactivated
Sodium/potassium pump restores ion balance

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23
Q

What ae action potential generated in and what by?

A

In the trigger zone
By graded potentials of sufficient size (when a certain voltage threshold is reached)

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24
Q

Are action potentials graded?

A

No!
All or none response

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25
Q

Are action potentials decremental?

A

No
They do not decrease in size with distance from initial stimulus (non-decremental)

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26
Q

How do action potentials carry sensory or motor information?

A

They propagate along axons to the appropriate location

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27
Q

What is myelinination?

A

Where the neuron axon is insulated
This allows for more rapid conduction of the action potential

28
Q

Are all neurons myelinated?

A

No, different types of neurons may be myelinated or unmyelinated

29
Q

What is the progress along an unmyelinated axon called?

A

Continuous propagation

30
Q

What is the progress along a myelinated axon called?

A

Saltatory propagation

31
Q

What are areas without myelin called?

A

Nodes of Ranvier

32
Q

How do action potentials pass the nodes of Ranvier?

A

The action potential jumps along these nodes, allowing for much faster propagation

33
Q

How does axon diameter affect the speed of action potentials across it?

A

The greater the diameter, the faster the action potential can travel (max up to 120m/s)

34
Q

What myelinates the peripheral axons?

A

Schwann cells

35
Q

What myelinates CNS axons?

A

Oligodendrocytes

36
Q

What is axoplasm?

A

cytoplasm of axon

37
Q

What is axolemma?

A

cell membrane of an axon

38
Q

What is neurilemma?

A

Sheath surrounding nerve axon, including the myelin sheath

39
Q

What is multiple sclerosis (MS)?

A

Autoimmune disorder when myelination of central nerves is targeted

40
Q

What is Guillain-Barre syndrome?

A

An autoimmune disorder when myelination of peripheral nerves is targeted

41
Q

Where do neurons communicate with one another?

A

At synapses

42
Q

What are the 2 types of synaptic transmission?

A

Electrical and Chemical

43
Q

Which type of synapse is rare in the adult brain?

A

Electrical synapse

44
Q

What is the synaptic cleft?

A

A gap at a chemical synapse between the pre and post synaptic elements

45
Q

What is the first step in synaptic transmission?

A

An action potential opens voltage-gated Ca2+ channels in presynaptic membrane
Entry of Ca2+ triggers release of ACh from vesicles
The ACh diffuses across synaptic cleft

46
Q

What is step 2 in synaptic transmission after ACh diffuses across synaptic cleft?

A

ACh interacts with ACh receptors (Na+ channels) which trigger an influx of Na+ ions

47
Q

What produces an excitatory postsynaptic potential?

A

Influx of Na+

48
Q

When is an action potential triggered in the postsynaptic neuron?

A

When the excitatory postsynaptic potential reaches -55mV

49
Q

What is reffered to as the language of the nervous system?

A

Neurotransmitters along with electrical signals (means of communication between neurons)

50
Q

Name 3 additional neurotransmitters

A
  1. Acetylcholine (ACh)
  2. Adrenaline
  3. Noradrenaline
51
Q

3 amino acid neurotransmitter examples

A
  1. glutamate
  2. GABA
  3. glycine
52
Q

What ere monoamine neurotransmitters derived from? Example?

A

Derived from amino acids
Eg. Serotonin

53
Q

3 catecholamine neurotransmitter exaples

A
  • Dopamine
  • Epinephrine
  • Norepinephrine
    (Also monoamines)
54
Q

2 Peptide neurotransmitters examples

A

Substance P
Endorphins

55
Q

Slide 32

A

Neurotransmitter examples

56
Q

What are the 5 important processes in regulating different transmitter systems?

A
  1. Synthesis
  2. Storage
  3. Release
  4. Receptor binding
  5. Inactivation/Reuptake
57
Q

Synthesis of acetylcholine

A

Choline acetyltransferase is not saturated. The substrate’s (choline’s) availability is the rate determining step
Supplementing/restricting choline can increase/decrease acetylcholine production

58
Q

Synthesis of dopamine

A

L-Tyrosine—>L-Dopa (catalysed by tyrosine hydroxylase) - rate determining step as normally saturated by substrate.
L-Dopa—>Dopamine (catalysed by dopa decarboxylase DDC) - enzyme has high activity and is non-specific

59
Q

Give an example of a treatment targeting synthesis

A

L-Dopa for Parkinson’s Disease
Provides additional substrate for substrate production

60
Q

Storage: what is glutamate?

A

Glutamate is a neurotransmitter packaged in vesicles in the presynaptic terminal

61
Q

How are transmitter systems relaeased?

A
  • Action potential reaches the presynaptic terminal
  • Voltage gated Ca2+ ion channels open
  • Influx of calcium ions
  • This causes vesicle to bind with presynaptic membrane
  • Contents of vesicle is released into synaptic cleft by exocytosis
62
Q

What is a receptor?

A

Protein target which initiates a cellular response when activated

63
Q

What are the 2 main categories of receptors?

A
  1. Inotropic (eg. nicotinic Ach receptor and NMDA receptor)
  2. Metabotropic (eg.muscarinic Ach receptor and mGluR)
64
Q

Where can receptors be located?

A

On both the presynaptic and postsynaptic membrane

65
Q

What are excitatory postsynaptic potentials (EPSPs) caused by?

A

Excitatory neurotransmitter receptors to transmitters. These include:
-glutamate
-acetylcholine
-noradrenaline

66
Q

What are inhibitatory post synaptic potentials (IPSPs) caused by?

A

Inhibitatory neurotransmitters such as:
-GABA
-Glycine
-Noradrenaline

67
Q

See slide 43 onwards

A

Biology (S2) (7 decks)

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