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(old)SK298 > Week 3 - Cells of the brain > Flashcards

Week 3 - Cells of the brain Flashcards

1
Q

In which century did studying individual brain cells start to become possible?

A

19th Century

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2
Q

Who was one of the pioneers of the study of individual brain cells?

A

Camilio Golgi (1843 - 1926)

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3
Q

Who first showed that the brain consists of billions of interconnected neurons?

A

Santiago Ramon y Cajal (1852 - 1934)

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4
Q

What is a neurofibrillary tangle?

A

Aggregates of a specific protein which is a primary biomarker of Alzheimer’s disease

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5
Q

What are amyloid plaques?

A

Extracellular deposits of the amyloid beta protein - large numbers of which are characteristic of Alzheimer’s disease

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6
Q

What does the new immunohistochemical technique called CLARITY enable?

A

Allows visualisation of brain cells in situ

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7
Q

What structural feature has CLARITY uncovered in the tissue sample of a 7-yo boy with autism?

A

‘Ladder-like’ structures in the frontal lobe, where single neurons formed connections back onto themselves and to other neurons

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8
Q

Roughly how many neurons are there in the brain?

A

86 billion

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9
Q

What is the ratio of glial cells to neurons thought to be?

A

Previously thought to be 50 : 1 but now thought to potentially be closer to 1 : 1

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10
Q

Is the ratio of glial cells to neurons consistent across the brain?

A

No - it differs between brain regions

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11
Q

What can cause neurons to differ in shape and size?

A
  • Their location in the nervous system
  • Their function
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12
Q

What are some traits of a motor neuron?

A
  • Roughly spherical cell body
  • Branches of dendrites merge to form several larger dendrites directly attached to the cell body
  • Their axons carry information to the spinal cord and out to effector organs such as muscles
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13
Q

What are some traits of a granule cell?

A
  • Found in cerebellum and other brain regions
  • Very small cell body
  • One of the most numerous cell types in the brain
  • Small number of dendrites
  • Axon travels a short distance then divides in two
  • Varied functions depending on location
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14
Q

What are some traits of Purkinje cells?

A
  • Found in the outer layer of the cerebellum
  • Send information to cells deeper within the cerebellum
  • Among the largest cells in the brain
  • Highly branched and numerous dendrites
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15
Q

What are some traits of pyramidal cells?

A
  • They are large
  • Found mainly in the cerebral cortex
  • Also found in hippocampus and amygdala
  • Carry information long distances within and outside of the brain
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16
Q

What is the function of dendrites?

A

To receive information and pass it to the cell body for processing

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17
Q

What is the purpose of the axon?

A

It passes on information from the cell body to the axon terminals in the form of an action potential

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18
Q

What are dendritic spines?

A

Small protrusions from dendrites that form the postsynaptic component of synaptic connections from other neurons

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19
Q

What are the main types of glial cells?

A
  • Astrocyte
  • Ependymal cell
  • Oligodendrocyte
  • Microglial cell
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20
Q

What are some features of astrocytes?

A
  • Form part of the blood-brain barrier
  • Regulate concentration of ions and neurotransmitters around neurons
  • Help regulate oxygen and nutrient supplies to neurons
  • Protective and structural role
  • Help regulate immune and inflammatory responses
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21
Q

What are some features of ependymal cells?

A
  • Filter plasma from the blood to produce CSF
  • Aid in circulation of CSF around the CNS
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22
Q

What are some features of oligodendrocytes?

A
  • Form myelin around axons of neurons in order to increase the speed of transmission of electrical information
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23
Q

What are some features of microglial cells?

A
  • Remove bacteria and debris from dead and dying cells
  • Involved in immunological response to pathogens
  • Provide growth factors for formation of blood vessels and glial cells
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24
Q

Why are astrocytes so important in the brain?

A
  • Form part of the neurovascular unit
  • Send projections to neurons and around blood vessels
  • Can detect increase in neuronal activity and signal blood vessels to dilate in order to increase bloody supply to active brain regions
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25
Q

What types of roles do astrocytes have?

A
  • Part of the neurovascular unit
  • Influence synaptic transmission
  • Mediate immune response and inflammatory response in the brain
  • Involved in generation of new synapses
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26
Q

What condition has been linked to a reduction in astrocyte numbers in certain brain regions?

A

Depression

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27
Q

Roughly how many connections can one neuron have with others?

A

Up to 15000

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28
Q

What three things is a synapse a combination of?

A
  • Presynaptic endings
  • Synaptic cleft
  • Postsynaptic endings
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29
Q

What are synapses?

A

The connections between neurons

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30
Q

What is synaptic transmission?

A

The flow of information across a synapse from the presynaptic neuron to the postsynaptic neuron

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31
Q

What is an action potential?

A

The basic events which nerve cells use to transmit information from one place to another

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32
Q

What causes an action potential?

A

Depolarisation of the neuron membrane

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33
Q

When does an action potential occur?

A

When information is sent away from the neuron’s cell body

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34
Q

When an action potential reaches the axon terminal what determines what then happens?

A

If the synapse is either electrical or chemical

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35
Q

What happens when an action potential reaches an electrical synapse?

A

The electrical signal passes from one neuron to the next via gap junctions

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36
Q

What happens when an action potential reaches a chemical synapse?

A

It triggers the release of neurotransmitters which influence the postsynaptic neurons

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37
Q

Are electrical or chemical synpases more common within the CNS?

A

Chemical

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38
Q

What are the characteristics of an axon terminal?

A
  • The enlarged zone at the end of an axon that forms the synapse with the postsynaptic neuron
  • It releases neurotransmitters
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39
Q

What are the key neurotransmitters?

A
  • GABA and glutamate (GABA is inhibitory, glutamate almost always excitatory)
  • Catecholamines (e.g. dopamine, noradrenalin - important in mental health)
  • Serotonin (also important in mental health)
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40
Q

What is a synaptic cleft?

A
  • The small gap between the presynaptic and postsynaptic neuron
  • Where the neurotransmitter is released into by the presynaptic neuron
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41
Q

What are synaptic vesicles?

A

Small packages in the presynaptic axon terminal that contain many molecules of neurotransmitter ready to be released into the synapse

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42
Q

What is an axon terminal?

A

The region at the end of the axon where the neurotransmitter is released

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43
Q

What is a dendrite?

A

The area of the postsynaptic neuron that receives the signal from the presynaptic neuron

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44
Q

What are synaptic vesicles?

A

Packages containing neurotransmitter molecules ready for release at the synapse

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45
Q

What is a neurotransmitter?

A

A signalling molecule that communicates information between neurons via the synapse

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46
Q

What are postsynaptic receptors?

A

Proteins located on the dendrites of the postsynaptic neuron that bind neurotransmitters

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47
Q

What is the difference between a hormone and a neurotransmitter?

A
  • Hormones are generally released into the bloodstream and travel the body
  • Neurotransmitters are released from neurons and act on neighbouring neurons or other cells in close proximity
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48
Q

Where are neurotransmitters synthesised?

A

Either in the axon terminal or the cell bodies or neurons

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49
Q

What is a neuromodulator?

A

Something that potentiates or inhibits the transmission of a nerve impulse but is not the actual means of transmission

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50
Q

What are the key stages of synaptic transmission?

A
  • Synthesis and storage
  • Neurotransmitter release
  • Neurotransmitter postsynaptic receptors
  • Inactivation of neurotransmitters
51
Q

Where does chemical neurotransmission take place?

A

At the synapse between the axon terminal of a presynaptic neuron and the dendrites of a postsynaptic neuron

52
Q

What does an excitatory postsynaptic potential (EPSP) do?

A

Brings the postsynaptic neuron closer to the threshold for firing an action potential

53
Q

What does an inhibitory postsynaptic potential (IPSP) do?

A

Takes the postsynaptic neuron further from the threshold for firing an action potential

54
Q

If a neuron receives an excitatory stimulus, what will happen to its rate of firing action potentials?

A

It will increase in accordance with the level of the stimulus

55
Q

What is the order of events that take place at the synapse?

A
  • Action potential reaches axon terminal
  • Synaptic vesicles fuse wtih membrane of axon terminal
  • Neurotransmitter released into synaptic cleft
  • Neurotransmitter diffuses across cleft
  • Neurotransmitter binds to receptors on postsynaptic neuron
  • Binding creates change in excitability of postsynaptic neuron
  • If great enough excitation, action potential is initiated in postsynaptic neuron
56
Q

Do specific neurotransmitters always have the same effect?

A

No - some can be either inhibitory OR excitatory

57
Q

What is synaptic integration?

A

A process which describes how neurons integrate the received signals from postsynaptic neurons before the generation of a nerve impulse

58
Q

What are autoreceptors?

A

Receptors found on the axon terminal of presynaptic neurons that can regulate the release of neurotransmitter

59
Q

What is an axon?

A

Part of the neuron that extends from the cell body out to the axon terminal where synapses with adjacent neurons are formed

60
Q

What type of feedback loop does binding of neurotransmitter to autoreceptor create?

A

Negative

61
Q

Where are autoreceptors located?

A

On axon terminals

62
Q

What is synaptic reuptake?

A

A process which helps terminate the action of a neurotransmitter by removing it from the synaptic cleft

63
Q

Where in the brain does synaptic reuptake occur?

A

Specialist reuptake channels in the axon terminal

64
Q

What are the ways neurotransmitter can be removed from synapses?

A
  • Synaptic reuptake
  • Enzymatic degradation
  • Diffusing away from the synapse and being taken up into astrocytes
65
Q

What problem may occur if levels of neurotransmitter are too high?

A

Neuronal toxicity

66
Q

What will happen if a drug that blocks reuptake of a neurotransmitter is introduced to the synapse?

A

The neurotransmitter will remain in the synaptic cleft for longer and thus its effect on the postsynaptic neuron will be prolonged

67
Q

What is a synapse?

A

The junction between the axon terminal of a presynaptic neuron and the dendrite of a postsynaptic neuron

68
Q

What function does a synapse perform?

A

It is where information is passed from the presynaptic to the postsynaptic neuron

69
Q

What initiates synaptic transmission?

A

The arrival of an action potential at the axon terminal of a neuron

70
Q

Synaptic transmisison triggers what process?

A

The release of neurotransmitter into the synaptic cleft

71
Q

What does neurotransmitter do?

A

Diffuses across the synaptic cleft and binds to receptors on the dendrite of the postsynaptic neuron

72
Q

Which part of the postsynaptic neuron does neurotransmitter bind to?

A

The dendrite

73
Q

Is GABA classed as an inhibitory or excitatory neurotransmitter?

A

Inhibitory

74
Q

Is glutamate classed as an inhibitory or excitatory neurotransmitter?

A

Excitatory

75
Q

As well as the dendrite of the postsynaptic neuron, what else can neurotransmitter also bind to?

A

Autoreceptors on the presynaptic axon terminal

76
Q

What happens if neurotransmitter binds to autoreceptors on the presynaptic axon terminal?

A

It can affect the amount of neurotransmitter that is released

77
Q

What are cholinergic neurons?

A

Neurons which utilise acetylcholine as the principle neurotransmitter

78
Q

Where do the two cholinergic pathways originate?

A
  • The pons
  • Basal forebrain
79
Q

Where do the cholinergic neuronal pathways which originate in the pons project to?

A
  • Down towards the spinal cord
  • Up through the brain
  • Hippocampus
80
Q

A reduction in hippocampal functioning is associated with which condition?

A

Alzheimer’s

81
Q

If there is reduced activity in the cholinergic pathway which starts in the pons and ends in the hippocampus, what effect is observed?

A

Loss of spatial memory, associated with Alzheimer’s

82
Q

Where do the cholinergic pathways which originate in the basal forebrain project to?

A
  • The hippocampus
  • The cortex
  • Other brain regions such as prefrontal cortex
83
Q

What are the four neurotransmitter pathways?

A
  • Acetylcholine pathway
  • Dopamine pathway
  • Noradrenaline pathway
  • Serotonin pathway
84
Q

How many principle dopamine pathways are in the brain?

A

Three

85
Q

What are the names of the three dopamine pathways?

A
  • Nigrostriatal pathway
  • Mesolimbic pathway
  • Mesocortical pathway
86
Q

Where does the nigrostriatal pathway run from and to?

A

From the substantia nigra in the midbrain to the caudate nucleus and putamen in the striatum

87
Q

What is the nigrostriatal pathway important for?

A

The production of movement

88
Q

Loss of the nigrostriatal pathway underlies which disease?

A

Parkinson’s disease

89
Q

Where does the mesolimbic pathway extend from and to?

A

The vental tegmental area of the midbrain to the nucleus accumbens in the ventral striatium

90
Q

Where does the mesocortical pathway extend from and to?

A

From the ventral tegmental area of the midbrain to the prefrontal cortex

91
Q

What are the mesolimbic and mesocortical pathways together known as?

A

The reward pathways

92
Q

What behaviours are the mesolimbic and mesocortical pathways involved with?

A

Addictive behaviour - activity in these pathways results in ‘feelgood’ sensations

93
Q

Where do noradrenergic pathways originate?

A

The locus coeruleus, in the brain stem

94
Q

Where do noradrenergic pathways project to?

A
  • Hypothalamus
  • Amygdala
  • Thalamus
  • Through the cortex
95
Q

What are noradrenergic pathways involved with?

A

Control of the responses of the CNS - e.g. altering heart rate in response to a threat

96
Q

Why is the projection of the noradrenergic pathway to the prefrontal cortex thought to be important?

A

It is believed to be the target of some drugs which treat depression

97
Q

Where do serotonergic pathways in the brain originate?

A

The raphe nuclei in the brain stem

98
Q

What areas do serotonergic pathways project to?

A
  • Cerebellum
  • Hippocampus
  • Prefrontal cortex
99
Q

What are some of the functions that serotonergic pathways have roles in?

A
  • Sleep/wake cycle
  • Emotions
  • Mood
100
Q

Disruptions in serotonergic pathways are of importance with regards to which condition?

A

Depression

101
Q

What are cholinergic pathways important for?

A

Understanding dementia

102
Q

In what ways might drugs which interfere with synaptic transmission?

A
  • Binding with postsynaptic receptors and autoreceptors thus interfering with the action of neurotransmitters
  • Processes which terminate the activity of a neurotransmitter
103
Q

What is an antagonist?

A

A drug which binds to a receptor and has no effect on a neuron but which prevents binding of the neurotransmitter

104
Q

What is an agonist?

A

Molecules that bind to a receptor and have a similar effect on the neuron to the neurotransmitter that usually binds to that receptor

105
Q

In which set of circumstances would an agonist be useful?

A

If there is a deficiency in a particular neurotransmitter pathway

106
Q

If a dopamine agonist is present, what happens to the action potenial firing rate in the neuron?

A

It increases

107
Q

What is an excellent example of neuroplasticity?

A

The changes which occur in the brains of London taxi drivers who have undertaken “The Knowledge”

108
Q

What part of the brain is notably different in London taxi drivers?

A

The hippocampus

109
Q

What are the main reasons that changes take place in the brain?

A
  • Development / ageing
  • Learning & experiences
  • Disease processes
  • Recovery from brain injury
110
Q

What is synaptogenisis?

A

The growth of new synapses between neurons

111
Q

What is dendritic pruning?

A

A process which underpins neuroplasticity

112
Q

What occurs as a result of dendritic pruning?

A

Dendritic spines are removed from dendrites, which reshapes the connectivity between neurons

113
Q

When does dendritic pruning peak?

A

During adolescence and into early adulthood

114
Q

What can occur if there is prolonged or intense activity in one neuron?

A

The next neuron in the pathway may become increasingly responsive

115
Q

What is the paraphrased definition of “Hebbian plasticity”?

A

“Neurons that fire together, wire together”

116
Q

Roughly how many branches do dendrites have at a time?

A

Four to five

117
Q

What is electrophysiology?

A

A technique used to record from individual brain cells in animals

118
Q

Which brain imaging technique allows activity across the brain to be measured?

A

Electroencephalography (EEG)

119
Q

What are the different types of brain waves?

A
  • Gamma waves (role unclear)
  • Beta waves (active concentration)
  • Alpha waves (drowsy/meditative state)
  • Theta waves (as above)
  • Delta waves (deep sleep)
120
Q

What are the main changes in the brain associated with Alzheimer’s?

A
  • Enlarged ventricles
  • Reduced grey matter
  • Appearance of protein deposits
121
Q

Deficits in memory are linked to which part of the brain?

A
  • Medial temporal lobe
122
Q

What are some of the conditions which are linked to the default mode network?

A
  • ADHD
  • Autism
  • Depression
123
Q

Dopamine agonists can be helpful in treating which condition?

A

Psychosis

(old)SK298 (7 decks)

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