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Neurology > Structure of Neurons > Flashcards

Structure of Neurons Flashcards

1
Q

What are the different regions of neurons?

A

Dendrites, soma (cell body), axon hillock and initial segment, axon, synapse

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2
Q

What is the function of dendrites?

A

Receive inputs from other neurons and convey graded electrical signals passively to the soma

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3
Q

What is the function of the soma?

A

Integrates electrical signals that are incoming via passive conduction to the axon hillock

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4
Q

What are some features of the soma?

A

Synthetic and metabolic centre

Contains nucleus, ribosomes, mitochondria and ER

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5
Q

What is the purpose of the axon hillock and initial segment?

A

Site of initiation of the all or nothing AP

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6
Q

What is the function of the axon?

A

Conducts output signals as APs to presynaptic terminal

Mediates transport of materials between soma and presynaptic terminal (anterograde direction) and vice versa

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7
Q

What is the function of the synapse?

A

Point of chemical communication between neurons or to other cells

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8
Q

What are the different classes of neurons?

A 
Unipolar = one neurite, found in PNS
Pseuodunipolar = one neurite that splits 
Bipolar = two neurites 
Multipolar = three or more neurites
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9
Q

What are the different functional regions of neurons?

A

Input region = electrical signals enter
Integrative region = all signals are assimilated
Conductile region = signal conducted away from soma
Output region = signal leaves neuron

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10
Q

Do all neurons have all of the functional units?

A

Yes, all four regions are present irrespective of function

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11
Q

When is an all or nothing AP generated?

A

Once threshold is reached

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12
Q

What is the overshoot period during AP generation?

A

Very brief period when polarity is reversed to inside positive

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13
Q

What do APs allow electrical signals to do?

A

Allows electrical signals to be conducted over large distances without degrading

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14
Q

What is the difference between passive signals and APs?

A

Passive signals diminish as they spread but APs have constant amplitude

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15
Q

What is the impact caused by the nerve cell membrane being leaky?

A

Passive signals don’t spread far due to current loss across the membrane accompanied by a reduced change in potential

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16
Q

What does the distance across which current spreads depend on?

A

Membrane resistance and axial resistance of axoplasm

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17
Q

What is passive conduction a factor in?

A

Propagation of the AP

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18
Q

What effect does increasing the length constant have on the local current spread?

A

It increases the local current spread = this in turn increases AP conduction velocity

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19
Q

How can you improve the spread of passive conduction?

A

Decrease axial resistance by increasing axon diameter

Increase membrane resistance by adding insulating material

20
Q

How does insulation impact conduction?

A

Conduction in myelinated axons is much faster than in unmyelinated axons of the same diameter

21
Q

What is salatory conduction?

A

AP jumps from one node of Ranvier to the next = occurs in myelinated axons

22
Q

What are the steps in synaptic transmission?

A 
Uptake of precursor 
Synthesis and storage of precursor
Depolarisation by AP and Ca2+ influx
Ca2+ induced release of transmitter 
Receptor activation 
Enzyme mediated inactivation or reuptake of transmitter
23
Q

What separates pre and post synaptic membranes?

A

A narrow synaptic cleft

24
Q

What does the synaptic cleft contain?

A

Matrix of fibrous extracellular protein that holds the membranes together

25
Q

Where is neurotransmitter stored that is used for synaptic transmission?

A

In vesicles within the presynaptic terminal

26
Q

What are the different structural classes of synapses?

A 
Axodendritic = very common
Axosomatic = common
Axoaxonic = uncommon
27
Q

How are synpases classified?

A

By the location of the presynaptic terminal upon the postsynaptic cell

28
Q

Can all of the different structural classes of synapse be present on the one axon?

A

Yes

29
Q

What are the different physiological classes of synapses?

A

Excitatory and inhibitory

30
Q

What are some features of an excitatory synapse?

A

Most frequently glutamate
Cation selective postsynaptic receptor
Depolarising response

31
Q

What are some features of inhibitory synapses?

A

Most often GABA or glycine
Activates postsynaptic anion selective receptor
Hyperpolarising response

32
Q

Can an inhibitory postsynaptic potential initiate and AP?

A

No

33
Q

What does EPSP stand for?

A

Excitatory postsynaptic potential

34
Q

What occurs in spatial summation?

A

Many inputs converge upon neuron to determine its output

35
Q

What occurs in temporal summation?

A

Single input may modulate output by variation in AP frequency of that input

36
Q

Are temporal and spatial summation complementary processes?

A

Yes

37
Q

How is direct gating carried out?

A

By inotrophic receptors = receptor is integral component of molecule that forms channel it controls

38
Q

What mediated indirect gating?

A

By activation of metabotropic receptors = receptor and channel it controls are distinct

39
Q

Is direct or indirect gating faster?

A

Direct gating is faster

40
Q

What type of transmission displays both direct and indirect gating?

A

Cholinergic synaptic transmission in autonomic ganglia

41
Q

How does cholinergic synaptic transmission display direct gating?

A

Fast epsp due to activation of nicotinic ACh receptors = channels conduct Na+ and K+

42
Q

How does cholinergic synaptic transmission display indirect gating?

A

Slow epsp follows activation of muscarinic ACh receptors = ACh closes K+ channels

43
Q

What are the features of non-NMDA glutamate receptors?

A

Bind agonists kainate or AMPA controlling a channel permeable to Na+ and K+

44
Q

What are the features of NMDA glutamate receptors?

A

Controls a channel permeable to Na+, Ca2+ and K+

45
Q

What is the difference between non-NMDA and NMDA glutamate receptors?

A

Non-NMDA receptors mediate fast excitatory synpatic transmission in CNS, whereas NMDA receptors contributes a slow component to the excitatory synaptic potential

46
Q

Why do NMDA glutamate receptors promote neurotoxicity?

A

Have high permeability to Ca2+

47
Q

How do metabotropic receptors exert an effect since they don’t have a integral ion channel?

A

By activation of second messenger cascade

Neurology (48 decks)

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