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Flashcards in Nerves Deck (92):
1

Name the depression & raised folds of brain matter?

Gyrus - Raised folds
Sulcus - Depression between folds

2

What makes up forebrain?

Cerebrum & diencephalon

3

What makes up the cerebrum?

Frontal Lobe
Parietal Love
Occipital Lobe
Temporal Lobe

4

What makes up the diencephalon?

Thalamus
Hypothalamus

5

What makes up the brainstem?

Midbrain
Pons
Medulla Oblongata

6

What other brain structure controls automatic motor function?

Cerebrum

7

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

31 pairs:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal

8

What matter contains the cell bodies & axons?

In spinal corD:
- White matter contains axons
- Grey matter contains cell bodies

9

Where in the neurone are things syntehsised?

The cell body

10

When in a neuron are signals recieved?

Dendrites (post-synaptic)

11

What is the axon hillock?

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

12

What do axon terminals do?

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

13

How much of the CNS is glia?

Around 90% of CNS cells are Glia

14

NAme the 3 types of GLia?

Astrocytes
Microglia
Oligodendrocytes

15

What do astrocytes do?

Astrocytes:
- Maintain external enviroment for neurones
- Surround blood vessels & produce the blood-brain barrier

16

What do oligodendrocytes do?

- Dorm myelin sheafs around CNS fibres

17

What do microglia do?

Produce phagocytes

18

What is the value of the resting membrnae potential?

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

19

How is the RMP produced?

- K+ pumped in/Na+ pumped out
- Leaky potassium channels let K+ out

20

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

- Because it creates an electrical gradient
- This is eventually = & opposite ot hte chemical gradient
- So the electrochemical gradient = 0

21

Define equilibirum potential?

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

22

How does hyperkalemia cause ventricular fibrillation?

- High K+ external conc.
- Lower conc. gradient
- Lower eectrical gradient maintained at equilibirum
- Cell depolarised
- Random APs fire
- Ventricular fibirllation

23

Why doesnt the brain experience the effects of hyperkalemia?

Its protected by the blood brain barier

24

Why is the blood brain barrier protectivE?

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

25

What other ions have a small effect on the RMP?

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

26

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

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

27

Name the 4 types of graded potentials:

- Generator (sensory receptors)
- Postsynaptic
- Endplate (NMJ)
- Pacemaker

28

Other names for graded potentials?

- Electrotonic potential
- Decremental
- Non-propagated
- Local potential

29

What are the properties of a graded ptenital?

- Decremental
- Hyper- or Depolarising
- Graded
- Can Summate

30

Why are graded potentials decremental?

They leak out the membrane.
Furhter from the initial site of depolarisation the weaker the current

31

How do graded potentials transmit stimulus intensity?

In their amplitude

32

Whats the process behind graded potentials being graded?

- Stronger stimulus
- More channels opened
- Bigger current
- Larger potential

33

Whats an EPSP?

Excitatory Post Synaptic Potential
Depolarises the membrane

34

Whats an IPSP?

Inhibitory Post Synaptic Ptential
Hyperpolarizes the cell

35

How does a fast IPSP occur?

Chlorine channels open and Cl- ions flood the cell

36

How does a slow IPSP occur?

Potassium channels open & K+ leaves cell
Slow because K+ channel is seperate the the receptor

37

What transmitter vauses both fast & slow IPSPs?

GABA

38

How does a fast EPSP occur?

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

39

How does a slow EPSP occur?

Leaky potassium channels are closed
K+ builds up even higher in cell

40

What kind of gated channels ar einolved in graded potentials?

Ligand-gated

41

What gated channels are involved in APs?

Voltage gated

42

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

Temporal summation
Spatial summation

43

What is temporal summation?

Triggering the same graded potential multiple times to build up.

44

What is spatial summation?

Triggering different gradient potentials

45

Whats differnet about postsynaptic potentials generated at differnet dendrites?

They are diffent distances from the axon hillock
Therfore they decay different amounts before summating

46

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

-55mV

47

How far does an AP overshoot?

Usually around +30/40mV

48

How does an AP occur?

- voltage-gated Na+ channels open
- cell flooded with Na+
- Rapid depolarisation

49

How is an AP resolved?

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

50

What is the period just after an AP called?

Refractory period

51

Why is there a refractory period?

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

52

What other things block Na+ channels & why?

Anaesthetics, Tetrodotoxin, Saxitoxin
To cause paralysis

53

Where is tetrodotoxin found?

In puffer fish

54

What are the properties of APs?

- Voltage-gated chanell mediated
- Threshold
- All or nothing
- Self-propagating
- refractory period

55

How do APs code stimulus intensity?

Firing frequency

56

How do APs self-propagate?

- First AP opens first Na+ channel
- Depolairses membrane just enough to open the next Na+ channel
- so on and on

57

Why do APs only self-propagate in one direction?

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

What is the time consuming part of AP movement?

The opening of the voltage gated Na+ channels

59

How do Large axons increase AP travel speed?

- Larger axons = lower axial resitance
- depolarisation travels further
- Na+ channels spread further & less
- Time reduced

60

What is myelin?

The folds of the membrane from schwann cells or oligodendrocytes

61

Where are oligodendrocytes & schwann cells?

Scwann cells form myelin in PNS
Olgiodendrocytes form myelin in CNS

62

What does myelin do?

Decreases the leakage of the current allowing it to pass further

63

How does myelin improve AP movement speed?

- Reduces decrementation
- Na+ channels can be spread further
- faster travel

64

What are the Gaps between myelin sheafs called?

Nodes of Ranvier
Where Na+ channels are found

65

Name some de-myelinating diseases:

- Guillan-Barre
- Multiple Sclerosis

66

What is the compound action potential?

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

How are action potentials classifed?

alphabetically from fastest to slowest

68

Why fibres are most sensitive to presssure? (Anoxia)

The largest ones (As)

69

Which fibres are most senstitive to local anaesthetics?

The smallest ones (Cs)

70

What do Aalpha fibres do?

70-120ms
Proprioception/Motorneurones

71

Abeta fibre speed/function?

30-70ms
Touch, pressure

72

Agamma fibre speed/function?

15-30ms
muscle spindle motorneurones

73

Adelta fibre speed/function?

12-30ms
Touch, cold, fast pain

74

B fibre speed/function?

3-15ms
Preganglionic Autonomic fibres

75

C fibre speed/function?

0.5-2ms
Heat, slow pain

76

What are the steps of an endplate potential?

- 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

How is Ach removed after the enplate potential is trigerd?

Its broken down by acetylcholinesterase
Then the products taken up by the sarcolemma & cell

78

What does Ca2+ trigger at the NMJ?

Vesicle Fusion

79

How does Tetrodotoxin affect NMJ?

Blocks Na+ channels
So blokcs APs

80

How does Joro Spider toxin affect NMJ?

Blocks Ca2+ channels
Stops transmitter release

81

How does botulinum toxin affect NMJ?

Disrupts vesicle fusion
Prevents Ach release

82

How do Curare affect NMJ?

Blocks Ach receptors
So prevents Endplate potential

83

How do anticholinesterases affect NMJ?

Block Ach breakdown
So increases NMJ transmission

84

In what ways are CNS synapses more complex than NMJ?

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

85

Name some neurotransmistters used in the CNS?

Acetylcholine
Norepinephrine
Serotonin (5hydroxytryptamine)
GABA
ATP
Peptides
NO

86

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

EPSPs & IPSPs
Fast & slow

87

What are the types of anatomical arrangement of synapses?

- Axo-dendritic
- Axo-Somatic
- Axo-axonal
- Gating

88

What does axo-dendritic mean?

Synapse between axon & dendrites

89

What does Axo-somtic mean?

Synapse between Axon & cell bdy

90

What does Axo-axonal mean?

Synapses between axon & axon

91

What is Axonal gating?

One neuron gates the synapse between two others

92

What are the types of synaptic connectivity?

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