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science for medicine benj > Nerves > Flashcards

Nerves Flashcards

1
Q

Name the depression & raised folds of brain matter?

A

Gyrus - Raised folds

Sulcus - Depression between folds

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2
Q

What makes up forebrain?

A

Cerebrum & diencephalon

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3
Q

What makes up the cerebrum?

A

Frontal Lobe
Parietal Love
Occipital Lobe
Temporal Lobe

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4
Q

What makes up the diencephalon?

A

Thalamus

Hypothalamus

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5
Q

What makes up the brainstem?

A

Midbrain
Pons
Medulla Oblongata

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6
Q

What other brain structure controls automatic motor function?

A

Cerebrum

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7
Q

How many pairs of spinal nerves are there? (split them up)

A

31 pairs:

  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
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8
Q

What matter contains the cell bodies & axons?

A

In spinal corD:

  • White matter contains axons
  • Grey matter contains cell bodies
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9
Q

Where in the neurone are things syntehsised?

A

The cell body

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10
Q

When in a neuron are signals recieved?

A

Dendrites (post-synaptic)

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11
Q

What is the axon hillock?

A

Section just after cell body where info for APs is gathered & theyre fired from

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12
Q

What do axon terminals do?

A

Convert an axon-potential to a chemical signal for synapse.

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13
Q

How much of the CNS is glia?

A

Around 90% of CNS cells are Glia

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14
Q

NAme the 3 types of GLia?

A

Astrocytes
Microglia
Oligodendrocytes

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15
Q

What do astrocytes do?

A

Astrocytes:

  • Maintain external enviroment for neurones
  • Surround blood vessels & produce the blood-brain barrier
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16
Q

What do oligodendrocytes do?

A
  • Dorm myelin sheafs around CNS fibres
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17
Q

What do microglia do?

A

Produce phagocytes

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18
Q

What is the value of the resting membrnae potential?

A

-70mV. Basically the inside is 70mV negative to the outside

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19
Q

How is the RMP produced?

A
  • K+ pumped in/Na+ pumped out

- Leaky potassium channels let K+ out

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20
Q

Why doesnt half the K+ move out the cell through the leaky channels to form a chemical equilibirum?

A
  • Because it creates an electrical gradient
  • This is eventually = & opposite ot hte chemical gradient
  • So the electrochemical gradient = 0
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21
Q

Define equilibirum potential?

A

The membrane potential at which electrical gradient is equal & opposite to the conc. gradient.

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22
Q

How does hyperkalemia cause ventricular fibrillation?

A
  • High K+ external conc.
  • Lower conc. gradient
  • Lower eectrical gradient maintained at equilibirum
  • Cell depolarised
  • Random APs fire
  • Ventricular fibirllation
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23
Q

Why doesnt the brain experience the effects of hyperkalemia?

A

Its protected by the blood brain barier

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24
Q

Why is the blood brain barrier protectivE?

A

Its capillaires are espeicially tight due to:
- Astrocytes
- Tight junctions
The astrocytes prevent ion movement into the brain ISF

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25
Q

What other ions have a small effect on the RMP?

A

Na+
Cl-
Both are small intracellular conc. & large extracellular concs.

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26
Q

If the potassium equilibirum potential would be -90mV. Why is the RMP closer to -70mV?

A
  • Electrogenic nature of the Na+/Cl- pump
  • Other leaky ion channels
  • Large intracellular -ve molecuels
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27
Q

Name the 4 types of graded potentials:

A
  • Generator (sensory receptors)
  • Postsynaptic
  • Endplate (NMJ)
  • Pacemaker
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28
Q

Other names for graded potentials?

A
  • Electrotonic potential
  • Decremental
  • Non-propagated
  • Local potential
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29
Q

What are the properties of a graded ptenital?

A
  • Decremental
  • Hyper- or Depolarising
  • Graded
  • Can Summate
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30
Q

Why are graded potentials decremental?

A

They leak out the membrane.

Furhter from the initial site of depolarisation the weaker the current

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31
Q

How do graded potentials transmit stimulus intensity?

A

In their amplitude

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32
Q

Whats the process behind graded potentials being graded?

A
  • Stronger stimulus
  • More channels opened
  • Bigger current
  • Larger potential
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33
Q

Whats an EPSP?

A

Excitatory Post Synaptic Potential

Depolarises the membrane

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34
Q

Whats an IPSP?

A

Inhibitory Post Synaptic Ptential

Hyperpolarizes the cell

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35
Q

How does a fast IPSP occur?

A

Chlorine channels open and Cl- ions flood the cell

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36
Q

How does a slow IPSP occur?

A

Potassium channels open & K+ leaves cell

Slow because K+ channel is seperate the the receptor

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37
Q

What transmitter vauses both fast & slow IPSPs?

A

GABA

38
Q

How does a fast EPSP occur?

A

Non-specific monovalent cation channels open.
Some k+ leaves but lots of Na+ enters
Cell depolarises

39
Q

How does a slow EPSP occur?

A

Leaky potassium channels are closed

K+ builds up even higher in cell

40
Q

What kind of gated channels ar einolved in graded potentials?

A

Ligand-gated

41
Q

What gated channels are involved in APs?

A

Voltage gated

42
Q

What are the 2 types of summation (or integration)?

A

Temporal summation

Spatial summation

43
Q

What is temporal summation?

A

Triggering the same graded potential multiple times to build up.

44
Q

What is spatial summation?

A

Triggering different gradient potentials

45
Q

Whats differnet about postsynaptic potentials generated at differnet dendrites?

A

They are diffent distances from the axon hillock

Therfore they decay different amounts before summating

46
Q

What is usually the threshold for an AP to be triggered?

A

-55mV

47
Q

How far does an AP overshoot?

A

Usually around +30/40mV

48
Q

How does an AP occur?

A
  • voltage-gated Na+ channels open
  • cell flooded with Na+
  • Rapid depolarisation
49
Q

How is an AP resolved?

A
  • Na+ chanells close
  • Voltage-gated K+ open
  • K+ floods out
  • repolarisation
  • Na+/K+ pump slowly restores normal concs & RMP
50
Q

What is the period just after an AP called?

A

Refractory period

51
Q

Why is there a refractory period?

A

This time is needed for the Na+ channels to recover (they are blocked temporarily)

52
Q

What other things block Na+ channels & why?

A

Anaesthetics, Tetrodotoxin, Saxitoxin

To cause paralysis

53
Q

Where is tetrodotoxin found?

A

In puffer fish

54
Q

What are the properties of APs?

A
  • Voltage-gated chanell mediated
  • Threshold
  • All or nothing
  • Self-propagating
  • refractory period
55
Q

How do APs code stimulus intensity?

A

Firing frequency

56
Q

How do APs self-propagate?

A
  • First AP opens first Na+ channel
  • Depolairses membrane just enough to open the next Na+ channel
  • so on and on
57
Q

Why do APs only self-propagate in one direction?

A

When an Na+ channel causes the next one to open, it itself closes entering its refractory period till after the AP has moved on.

58
Q

What is the time consuming part of AP movement?

A

The opening of the voltage gated Na+ channels

59
Q

How do Large axons increase AP travel speed?

A
  • Larger axons = lower axial resitance
  • depolarisation travels further
  • Na+ channels spread further & less
  • Time reduced
60
Q

What is myelin?

A

The folds of the membrane from schwann cells or oligodendrocytes

61
Q

Where are oligodendrocytes & schwann cells?

A

Scwann cells form myelin in PNS

Olgiodendrocytes form myelin in CNS

62
Q

What does myelin do?

A

Decreases the leakage of the current allowing it to pass further

63
Q

How does myelin improve AP movement speed?

A
  • Reduces decrementation
  • Na+ channels can be spread further
  • faster travel
64
Q

What are the Gaps between myelin sheafs called?

A

Nodes of Ranvier

Where Na+ channels are found

65
Q

Name some de-myelinating diseases:

A
  • Guillan-Barre

- Multiple Sclerosis

66
Q

What is the compound action potential?

A

A summation of various almost (but not quite) simultaneous APs.
They arnt simultaneous because due to some fibres being differnet sizes/myelinated the various APs travel at differnt speeds

67
Q

How are action potentials classifed?

A

alphabetically from fastest to slowest

68
Q

Why fibres are most sensitive to presssure? (Anoxia)

A

The largest ones (As)

69
Q

Which fibres are most senstitive to local anaesthetics?

A

The smallest ones (Cs)

70
Q

What do Aalpha fibres do?

A

70-120ms

Proprioception/Motorneurones

71
Q

Abeta fibre speed/function?

A

30-70ms

Touch, pressure

72
Q

Agamma fibre speed/function?

A

15-30ms

muscle spindle motorneurones

73
Q

Adelta fibre speed/function?

A

12-30ms

Touch, cold, fast pain

74
Q

B fibre speed/function?

A

3-15ms

Preganglionic Autonomic fibres

75
Q

C fibre speed/function?

A

0.5-2ms

Heat, slow pain

76
Q

What are the steps of an endplate potential?

A
  • Motor neuron AP arrives
  • Triggers Ca2+ voltage-gated channels
  • Calcium triggers vesicle fusion
  • Ach released & crosses synaptic cleft
  • Ach acts on receptors in sarcolemma
  • Opens ligand gated Na+/K+ channels
  • Evokes end palte potential
  • Opens voltage gated Na+ channels evoking new AP
77
Q

How is Ach removed after the enplate potential is trigerd?

A

Its broken down by acetylcholinesterase

Then the products taken up by the sarcolemma & cell

78
Q

What does Ca2+ trigger at the NMJ?

A

Vesicle Fusion

79
Q

How does Tetrodotoxin affect NMJ?

A

Blocks Na+ channels

So blokcs APs

80
Q

How does Joro Spider toxin affect NMJ?

A

Blocks Ca2+ channels

Stops transmitter release

81
Q

How does botulinum toxin affect NMJ?

A

Disrupts vesicle fusion

Prevents Ach release

82
Q

How do Curare affect NMJ?

A

Blocks Ach receptors

So prevents Endplate potential

83
Q

How do anticholinesterases affect NMJ?

A

Block Ach breakdown

So increases NMJ transmission

84
Q

In what ways are CNS synapses more complex than NMJ?

A
  • Multiple neurotransmitters & receptors
  • Range of Post-synaptic potentials
  • Anatomical arrnagemtn of the synapses
  • Synapse connectivity
  • Inhibitory synapses
85
Q

Name some neurotransmistters used in the CNS?

A 
Acetylcholine
Norepinephrine
Serotonin (5hydroxytryptamine)
GABA
ATP
Peptides
NO
86
Q

What kind of post synaptic potentials are there in the CNs?

A

EPSPs & IPSPs

Fast & slow

87
Q

What are the types of anatomical arrangement of synapses?

A
  • Axo-dendritic
  • Axo-Somatic
  • Axo-axonal
  • Gating
88
Q

What does axo-dendritic mean?

A

Synapse between axon & dendrites

89
Q

What does Axo-somtic mean?

A

Synapse between Axon & cell bdy

90
Q

What does Axo-axonal mean?

A

Synapses between axon & axon

91
Q

What is Axonal gating?

A

One neuron gates the synapse between two others

92
Q

What are the types of synaptic connectivity?

A

Convergence (many neurons synapse to one)
Divergence (one neuron with multipl axons synapses to many neurons)
Feedback inhibition (Every AP this neuron fires also inhibits itself from sending anymore)
MonovsPolysynaptic pathway

science for medicine benj (35 decks)

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