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BRS - neuro > Cells of the Nervous System and the Neuromuscular Junction > Flashcards

Cells of the Nervous System and the Neuromuscular Junction Flashcards

1
Q

Unipolar neuron

A

1 axonal projection

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2
Q

Pseudo-unipolar

A

Single axonal projection that divides into two

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3
Q

Bipolar

A

2 projections from cell body

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4
Q

Multiplar

A

Numerous projections from cell body

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5
Q

Purkinje and Golgi cells

A

Multipolar GABA neurons found in the cerebellum

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6
Q

Pyramidal cell

A

Tripolar ‘pyramid’ shaped cell body

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7
Q

Neurons

A

Excitable cells of CNS
Heterogeneous morphology
Non-dividing cells

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8
Q

Soma (cell body, perikaryon)

A

Contains nucleus and ribosomes

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9
Q

Neurofilaments

A

Structure and transport

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10
Q

Axon

A

Long process (aka nerve fibre)
Sends information out from neural cell

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11
Q

What do axons branch off into

A

collaterals

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12
Q

Where do axons originate from

A

Soma at axon hillock

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13
Q

What are axons usually covered in

A

Myelin

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14
Q

Dendrites

A

Highly branched cell body - NOT covered in myelin
Receive signals from other neurons

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15
Q

What are neurons

A

Excitable cells of CNS responsible for electrical transmission

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16
Q

What are oligodendrocytes

A

Glial cells that produce myelin
Provides a substance for the axon to be more efficient

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17
Q

Astrocytes

A

Most abundant cell type in CNS
- Supportive function

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18
Q

What are microglia?

A

Neuronal macrophages

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19
Q

What are ependyma?

A

Epithelial cells lining the ventricles

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20
Q

What are the 4 major physiological ions involved in the resting membrane potential (RMP)?

A

Potassium
Sodium
Chloride
Calcium

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21
Q

How do these ions get around?

A

Cell membranes are impermeable to these ions hence transportation regulated by channels and pumps

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22
Q

What causes an uneven ion distribution?

A

Regulation by channels and pumps due to cell membrane impermeability

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23
Q

Which ions have a high extracellular concentration?

A

Sodium
Chloride

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24
Q

Which ion has a low extracellular concentration

A

Potassium

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25
Q

Which ion has the highest concentration gradient?

A

Calcium

26
Q

What creates a potential difference across the membrane?

A

Difference in ion concentration

27
Q

Describe the charge of neuronal cells

A

Negative charge inside compared to outside
RMP of between -40 to -90mV

28
Q

Where are the charges concentrated?

A

Positive and negative charges concentrated around the membrane

29
Q

Which ions play an important role in generation of AP?

A

Sodium and potassium ions

30
Q

Which channels are closed at resting membrane potential?

A

Voltage-gated Na+ channels (VGSCs)
Voltage-gated K+ channels (VGKCs)

31
Q

Describe what happens during membrane depolarisation

A

Opening of VGSC leads to Na+ influx causing further depolarisation

32
Q

Describe what happens during membrane repolarisation

A

VGKCs opens at a slower rate and causes efflux of K+ from cell leading to membrane repolarisation

33
Q

What restores the ion gradients after an action potential?

A

Na+K+ ATPase (pump) restores the ion gradients

34
Q

What happens during resting configuration?

A

Na+ enters vestibule and upon phosphorylation ions are transported through the protein

35
Q

What happens during active configuration?

A

Na+ removed from cell and K+ enters the vestibule

36
Q

How does the pump return to resting configuration?

A

K+ is transported back into the cell

37
Q

How does the AP spread along the axon

A

By ‘cable transmission’

38
Q

What is saltatory conduction?

A

when the action potential ‘jumps’ between nodes

39
Q

Nodes of Ranvier

A

small gaps of myelin intermittently along axon

40
Q

What does myelin do the AP and how?

A

Prevents AP spreading because it has high resistance and low capacitance

41
Q

Where is the AP unable to ‘jump’?

A

Unable to ‘jump’ across the gap at the axon terminal

42
Q

Summarise neurotransmission across the synapse

A
  1. Propagation of AP
  2. Neurotransmitter release from vesicles
  3. Activation of postsynaptic receptors
  4. Neurotransmitter reuptake
43
Q

What happens during propagation of the action potential?

A

AP propagated by VGSCs opening
Sodium ion influx leads to membrane depolarisation and AP ‘moves along’ neurone
VGKC opens leading to K+ efflux -> repolarisation

44
Q

How are neurotransmitters released from vesicles?

A

AP opens voltage-gated Ca2+ channels at pre-synaptic terminal
Calcium ion influx leads to vesicle exocytosis

45
Q

How do the postsynaptic receptors get activated?

A

Neurotransmitter binds to receptors on post-synaptic membrane
Receptors modulate post-synaptic activity

46
Q

Describe the reuptake of neurotransmitters

A

NT dissociates from receptor and can either be
metabolised by enzymes in synaptic cleft or recycled by transporter proteins

47
Q

Describe the mode of communication between nerve cells (post-synaptic cell)

A

Autocrine and paracrine : neurotransmitter release

48
Q

Synaptic organisation consists of what 3 things?

A

Axodendritic synapse
Axosomatic synapse
Axoaxonic synapse

49
Q

Axodendritic synapse

A

Connection between presynaptic terminal to neuronal dendrite

50
Q

Axosomatic synapse

A

Connection between presynaptic terminal to neuronal soma

51
Q

Axoaxonic synapse

A

Connection between presynaptic terminal to neuronal axon

52
Q

What is the neuromuscular junction?

A

Specialised structure incorporating axon terminal & muscle membrane allowing unidirectional chemical communication between peripheral nerve and muscle

53
Q

What kind of communication is there between nerve and effector cells?

A

Paracrine : neurotransmitter release

54
Q

Describe what happens at the neuromuscular

A
  1. Action potential propagated along axon (Na+ and K+) -> Ca2+ entry at presynaptic terminal
  2. Ca2+ entry -> acetylcholine (ACh) release into synapse
  3. ACh binds to nicotinic ACh receptors (nAChR) on skeletal muscle leading to achange in end-plate potential (EPP)
  4. Miniature EPP : quantal ACh release
55
Q

Excitation-contraction coupling in the sarcolemma

A

Skeletal muscle membrane : nAChR activation leading to depolarisation -> action potential
AP travels through T-tubules

56
Q

Where are the T-tubules?

A

Continuous with sarcolemma and closely connected to sarcoplasmic reticulum

57
Q

Where is the sarcoplasmic reticulum?

A

Surrounds myofibrils

58
Q

What are myofibrils

A

contractile units of muscle

59
Q

Function of sarcoplasmic reticulum

A

Ca2+ storage -> Ca2+ release following sarcoplasmic reticulum depolarisation

Causes myofibril contraction and muscle contraction

60
Q

What is botulism

A

Disorder of the neuromuscular junction

Botulinum toxin (BTx) irreversibly disrupts stimulation-induced ACh release from presynaptic nerve terminal

61
Q

What is Myasthenia Gravis (MG)

A

Disorder of the neuromuscular junction

Autoimmune disorder in which antibodies directed against ACh receptor

Causes fatigable weakness (becomes more pronounced with repetitive use)

62
Q

Lambert-Eaton myasthenic syndrome (LEMS)

A

Disorder of the neuromuscular junction

Autoimmune disorder : antibodies directed against VGCC

BRS - neuro (1 decks)

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