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Neurology and Neuroscience (Bioregulatory Systems) > Lecture 1: Cells of the nervous system and neuromuscular junction > Flashcards

Lecture 1: Cells of the nervous system and neuromuscular junction Flashcards

1
Q

What are the highly convoluted surface of ridges on the brain called?

A

Gyri

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2
Q

What are the valleys in the brain called?

A

Sulci

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3
Q

What are the 4 functional regions of the brain?

A
  • frontal
  • parietal
  • temporal
  • occipital
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4
Q

What does the brainstem consist of?

A
  • midbrain
  • pons
  • medulla
    NOTE: descending disorder
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5
Q

What is the cerebellum?

A

Hindbrain structure attached to brainstem, important in motor coordination, fine movement, balance and posture

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6
Q

What is the function of the spinal cord?

A
  • conduit for neural transmission

- coordinates some reflex actions

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7
Q

Where does the spinal cord extend down from?

A

The medulla

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8
Q

What is a unipolar neuron?

A

1 axonal projection

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9
Q

What is a pseudo-unipolar neuron?

A

single axonal projection that divides into 2

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10
Q

What is a bipolar neuron?

A

2 projections from cell body but still only 1 axon

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11
Q

What is a multipolar neuron?

A

numerous projections from cell body but still only 1 axon

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12
Q

What are the different types of multipolar neurons?

A
  • pyramidal: ‘pyramid’ shaped cell body
  • purkinje cells: GABA neurons found in cerebellum
  • Golgi cells: GABA neurons found in cerebellum
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13
Q

What are the shared common features of neurons?

A
  • Soma (cell body, perikaryon)
  • Axon
  • Dendrites
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14
Q

What is the soma of a neuron?

A

Cell body that contains nucleus and ribosomes.

Neurofilaments for structure and support

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15
Q

What is the axon of a neuron?

A
  • long process (a.k.a nerve fibre) - originates from soma at axon hillock
  • can branch off into ‘collaterals’
  • usually covered in myelin
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16
Q

What is the dendrite of a neuron?

A
  • highly branched cell body, not covered in myelin

- branches receive signals from other neurons

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17
Q

What is the most abundant cell type within the CNS?

A

Astrocytes

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18
Q

What are astrocytes?

A
  • able to proliferate
  • structural cells: blood-brain barrier, keeping neurones in place
  • cell repair: synthesis of neurotrophic factors, growth + maintenance
  • homeostasis: neurotransmitter removal and reuptake
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19
Q

What are oligodendrocytes?

A
  • myelin-producing cells for CNS
  • numerous projections that form internodes of myelin
  • variable morphology and function
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20
Q

How many axons can one oligodendrocyte myelinate?

A

Many axons

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21
Q

What is a Schwann cell?

A
  • myelin-producing cell for peripheral nerves
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22
Q

How many axons can 1 Schwann cell myelinate?

A

1 cell myelinates one axon segment only

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23
Q

What are microglial cells?

A
  • specialised cell, similar to macrophages

- immune cells of CNS, perform immune functions

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24
Q

What are ependymal cells?

A
  • epithelial cells lining fluid-filled ventricles

- regulate production and movement of cerebrospinal fluid (CSF)

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25
Q

What are glial cells?

A

The glial cells surround neurons and provide support for and insulation between them

26
Q

What cells are included within glial cells?

A
  • astrocytes
  • oligodendrocytes
  • microglia
  • ependymal
27
Q

What are the 4 major physiological ions?

A
  • potassium (K+)
  • sodium (Na+)
  • chloride (Cl-)
  • calcium (Ca2+)
28
Q

How is transportation of important ions regulated?

A

By channels and pumps because cell membrane is impermeable to these ions

29
Q

Which ions have a high extracellular concentration?

A

Na+ and Cl-

30
Q

Which ion has a low extracellular but high intracellular concentration?

A

K+

31
Q

Which ion has a high concentration gradient across the cell membrane?

A

Ca2+

32
Q

What creates the potential difference across the cell membrane?

A

the difference in ion concentrations

33
Q

What charge do neuronal cells have inside?

A

negative compared to outside

34
Q

What is the range of the resting membrane potential?

A

-40 to -90mV

35
Q

Where are the positive and negative charges concentrated?

A

Around the membrane

36
Q

What is the state of the ion channels at RMP?

A

voltage-gated Na+ and voltage -gated K+ channels are closed

37
Q

What happens at membrane depolarisation?

A

voltage-gated sodium channels open which leads to an influx of Na+ and further depolarisation

38
Q

What happens at membrane repolarisation?

A

voltage-gated potassium channels open at a slower rate and cause efflux of K+ from cell

39
Q

What does an action potential leave?

A

a sodium and potassium imbalance

40
Q

How is the Na+ and K+ imbalance restored?

A

Using Na+-K+-ATPase pump to restore ion gradients

41
Q

What is the resting configuration of Na+-K+-ATPase?

A

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

42
Q

What is the active configuration of Na+-K+-ATPase?

A

Na+ removed from cell, K+ enters vestibule

43
Q

What happens when the pump returns to resting configuration?

A

K+ is transported back into the cell

44
Q

What is saltatory conduction?

A

action potential jumps between nodes of Ranvier to speed up transmission

45
Q

How does myelin prevent action potential from spreading?

A

It has high resistance and low capacitance

46
Q

What are the nodes of Ranvier?

A

small gaps of myelin intermittently along axon

47
Q

Outline how a synapse works. (4 steps)

A

1) Propagation of the action potential (AP) - Na+ influx, AP moves along neuron, K+ efflux for repolarisation
2) Neurotransmitter release - AP opens voltage-gated Ca2+ channels at presynaptic terminal, Ca2+ influx leads to vesicle exocytosis
3) Activation of postsynaptic receptors - NT binds to receptors on post-synaptic membrane, receptors modulate post-synaptic activity
4) Neurotransmitter reuptake - NT dissociates from receptor and can be metabolised by enzymes in synaptic cleft or recycled y transporter proteins

48
Q

What type of communication occurs between nerve cells?

A

Autocrine and paracrine via neurotransmitter release

49
Q

What is an axodendritic synapse?

A

connection between presynaptic terminal to neuronal dendrite

50
Q

What is an axosomatic synapse?

A

connection between presynaptic terminal to neuronal soma

51
Q

What is an axoaxonic synapse?

A

connection between presynaptic terminal to neuronal axon

52
Q

What is the neuromuscular junction?

A

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

53
Q

What type of communication occurs between nerve and effector cells?

A

paracrine via neurotransmitter release

54
Q

What 4 steps happen at the neuromuscular junction?

A

1) AP propagated along axon –> Ca2+ entry at presynaptic terminal
2) Ca2+ entry leads to acetylcholine (ACh) release into synapse
3) ACh binds to nicotinic ACh receptors (nAChR) on skeletal muscle –> change in end plate potential (EPP)
4) 1 ACh vesicle (quantal ACh release) results in mini EPP so need summation of lots of mini EPPS for transmission

55
Q

What is the sarcolemma?

A

skeletal muscle membrane with nAChR receptors which when activated lead to depolarisation and so an action potential

56
Q

What are the T-tubules?

A

tubes that are continuous with sarcolemma & closely connected to sarcoplasmic reticulum

57
Q

Where does the AP travel through in skeletal muscle?

A

T-tubules

58
Q

Where is the sarcoplasmic reticulum?

A

surrounds myofibrils - contractile units of muscle

59
Q

What is the function of the sarcoplasmic reticulum?

A

Ca2+ storage - Ca2+ is released following sarcolemma depolarisation

60
Q

What is the effect of Ca2+ in skeletal muscle?

A

causes myofibril contraction and muscle contraction

61
Q

What are some disorders of the neuromuscular junction?

A
  • botulism (botulinum toxin irreversibly disrupts stimulation-induced ACh release)
  • myasthenia gravis (MG): antibodies directed against ACh receptor, autoimmune
  • Lambert-eaton myastenic syndrome (LEMS): antibodies against VGCC, autoimmune

Neurology and Neuroscience (Bioregulatory Systems) (10 decks)

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