Week 3 - Cells of the brain Flashcards
1
Q
What are the pathological changes that are prevalent in the brains of patients with Alzheimer’s disease?
A
- Amyloid plaques
- Neurofibrillary tangles
2
Q
What two types of cells can brain cells be broadly categorised as?
A
- Glial cells
- Neurons
3
Q
Roughly how many neurons are there in the brain?
A
86 billion
4
Q
Is the ratio of glial cells to neurons constant across the brain?
A
No, it varies from region to region
5
Q
Where are the cell bodies of motor neurons located?
A
Within the brain or spinal cord
6
Q
Where do the axons of motor neurons carry information from and to?
A
From the brain to the spinal cord and out to effector organs (eg muscles/glands)
7
Q
Where are granule cells found?
A
In the cerebellum and other brain regions
8
Q
Which type of cell is one of the most numerous cell types in the brain?
A
Granule cells
9
Q
Where are pyramidal cells mainly located?
A
- Cerebral cortex
- Hippocampus
- Amygdala
10
Q
What is the function of pyramidal cells?
A
They carry information long distances within and outside of the brain
11
Q
Which part of the brain are purkinje cells found in?
A
The outer layer of the cerebellum
12
Q
Where do purkinje cells transmit information to?
A
Deep within the cerebellum
13
Q
Which are among the largest cells within the brain?
A
Purkinje cells
14
Q
What is the function of purkinje cells?
A
They receive and transmit information from other brain areas
15
Q
What is the function of the dendrites of a neuron?
A
They receive information and pass it on to the cell body for processing
16
Q
What does the cell body of a neuron do?
A
It integrates information received from neighbouring neurons and processes it before passing it on to other neurons via the axon
17
Q
What is the myelin sheath?
A
The fatty substance which surrounds and insulates the axon
18
Q
What is the function of the myelin sheath?
A
It increases the speed that an action potential can travel along the axon
19
Q
What is a synapse?
A
The junction between neurons which enables information to be passed from one neuron to another
20
Q
What are the axon terminals?
A
The branches of the axon which form connections with neighbouring neurons
21
Q
What is the function of an axon?
A
It passes the information from the cell body to the axon terminal
22
Q
What is an action potential?
A
It is an electrical impulse that allows information to be passed from the cell body to the axon terminal
23
Q
How large are axons?
A
They can vary widely, some stretch from the foot all the way to the spinal cord, others travel just within one brain region
24
Q
What is the axon hillock?
A
The area of the neuron where the cell body and the axon form a junction
25
What is the function of the axon hillock?
It is where action potentials are initiated
26
What is the function of dendrites?
They are the main information receivers of the neuron
27
What are dendrites?
They are small branching extensions of the cell body of neurons and receive synaptic connections from other neurons
28
What is an action potential?
An electrical signal which travels along the axon and allows presynaptic neuron to communicate with postsynaptic neuron
29
How is an action potential often described as?
The language of the nervous system
30
What is a synapse?
The junction between the axon terminal of a presynaptic neuron and the dendrite of a postsynaptic neuron
31
Complete this:
information received at the ____________ is passed on to the ____________ for processing
- Dendrites
- Cell body
32
The information from the cell body is passed along which structure to the axon terminal?
The axon
33
In the form of what is information passed from the axon to the axon terminals?
An action potential
34
What feature of a neuron can increase the speed at which an action potential can travel along the neuron?
Myelin sheath
35
At the axon terminal, information is passed from one neron to the dendrites of the next neuron via what?
A synapse
36
Name the four main types of glial cell
- Astrocyte
- Ependymal cell
- Oligodendrocyte
- Microglial cell
37
Name a function of astrocytes
Any of the following:
- Form part of the blood-brain barrier
- Regulate concentration of ions and neurotransmitters around neurons
- Help regulate oxygen and nutrient supplies to neurons
- Play a protective and structural role
- Help regulate the immune and inflammatory responses
38
Which type of glial cell plays a part in regulating oxygen and nutrient supplies to neurons?
Astrocytes
39
Name a function of ependymal cells
Any of the following:
- Filter plasma from the blood to produce CSF
- Aid the circulation of CSF around the central nervous system
40
Which type of glial cell plays a part in the production of CSF?
Ependymal cells
41
What is the function of oligodendrocytes?
They form myelin around axons, which increases the speed of transmission of electrical information
42
Which type of glial cell is repsonsible for the production of myelin?
Oligodendrocytes
43
Name a function of microglial cells
Any of the following:
- Remove bacteria and debris from dead and dying brain cells
- Involved in immunological response to foreign invaders
- Provide growth factors for formation of blood vessels and glial cells
44
Which type of glial cell is involved in the immunological response to foreign invaders?
Microglial cells
45
Which type of glial cell is involved in providing growth factors for the formation of blood vessels and glial cells?
Microglial cells
46
Why are astrocytes important in the brain?
Any of the following:
- Form part of the neurovascular unit
- Influence synaptic transmission
- Mediate immune and inflammatory response
- Involved in the generation of new synapses
- Cause dilation of blood vessels in active brain regions in order to increase blood supply
47
Which type of glial cell has the most diverse role?
Astrocytes
48
Brains of some patients with major depressive disorder were found to have a reduction in which type of glial cell?
Astrocytes
49
How many other neurons can one neuron form connections with?
Up to 15000
50
What does the term presynaptic refer to?
The neuron that is sending out the information
51
What does the term postsynaptic refer to?
The neuron which receives information
52
What is meant by the term synaptic transmission?
The flow of information across a synapse from the presynaptic neuron to the postsynaptic neuron
53
When an action potential reaches the axon terminal, what are the two potential things it could do (depending on the nature of the synapse)?
- Pass from one neuron to the next via gap junctions
- Trigger the release of neurotransmitter that influences the postsynaptic neurons
54
What is a synaptic cleft?
The very small space between the presynaptic and postsynaptic neuron
55
Neurotransmitter is released into the synaptic cleft from what?
The presynaptic neuron
56
What is a synaptic vesicle?
The small vesicles at presynaptic terminals which store neurotransmitters
57
Neurotransmitter is released into the synapse from where?
Synaptic vesicle
58
What is the enlarged region at the end of an axon where neurotransmitter is released?
Axon terminal
59
Which area of the postsynaptic neuron receives a signal from the presynaptic neuron?
Dendrite
60
What is the name for the packages which contain neurotransmitter ready for release at the synapse?
Synaptic vesicles
61
What is neurotransmitter?
The signalling molecule that communicates information between neurons via the synapse
62
What are the proteins that are located on the dendrites of the postsynaptic neuron that bind neurotransmitters?
Postsynaptic receptors
63
What is the difference between a hormone and a neurotransmitter?
A hormone is generally released into the bloodstream and travels round the body to work on organs whereas a neurotransmitter is released from a neuron and acts on neighbouring neurons or other cells in close proximity
64
Where are neurotransmitters synthesised?
Either in the axon terminal or in the cell bodies of neurons
65
After being synthesised in either the axon terminal or the cell bodies of neurons, where are neurotransmitters then transported to?
The axon terminal
66
After being transported to the axon terminal, why are neurotransmitters then packaged into synaptic vessels?
So they can be released in response to an action potential
67
The neurotransmitter dopamine is synthesised from which molecule in the axon terminal?
Tyrosine
68
What are neuromodulators?
Chemicals which are found in the synaptic cleft which can influence synaptic transmission
69
As well as influencing synaptic transmission, what else can neuromodulators influence?
The responsiveness of postsynaptic neurons
70
What are some of the key neurotransmitters?
Any of the following:
- GABA
- Glutamate
- Catecholamines such as dopamine and noradrenaline
- Serotonin
71
The neurotransmitter GABA has which type of effect, inhibitory or excitatory?
Inhibitory
72
The neurotransmitter glutamate has which type of effect, inhibitory or excitatory?
Excitatory
73
What is excitatory postsynaptic potenial (EPSP)?
An electrical charge in a postsynaptic neuron which brings it closer to the threshold for firing an action potential
74
What is inhibitory postsynaptic potential?
An electrical charge in a postsynaptic neuron which takes it further from the threshold for firing an action potential
75
Which type of postsynaptic potential takes the postsynaptic neuron further away from firing an action potential?
Inhibitory postsynaptic potential
76
Which type of postsynaptic potential brings a postsynaptic neuron closer to the threshold for firing an action potential?
Excitatory postsynaptic potential
77
How is the frequency of action potential firing defined as?
The number of action potentials produced in a given time period
78
What is the frequency of action potential firing used as a measure for?
The level of activity in a neuron
79
Does the size of an action potential ever change?
No
80
Rather than the size of an action potential changing, what else does instead?
- The frequency of action potentials
- The number of action potentials produced in a given time
81
What is the order of events which take place at the synapse?
- Action potential reaches the axon terminal
- Synaptic vesicles fuse with the membrane of the axon terminal, releasing neurotransmitter into the synaptic cleft
- Neurotransmitter diffuses across the synaptic cleft and binds on the postsynaptic neuron
- Neurotransmitter is bound to receptors which results in a change in the excitability of the postsynaptic neuron
- If the excitation is great enough, an action potential is initiated in the postsynaptic neuron
82
Does dopamine have an inhibitory or excitatory effect?
It can be either
83
What is the background firing rate?
The low frequency level at which a neuron fires action potentials in the absence of any stimulation
84
What is the effect of making the presynaptic inhibitory neuron more active?
The frequency of action potentials in the postsynaptic neuron decreases
85
Along with neurotransmitters influencing the postsynaptic neuron, what else can they influence and how?
The presynaptic neuron, by binding to autoreceptors
86
What are autoreceptors?
Receptors which are found on the axon terminal of presynaptic neurons which can regulate the release of neurotransmitter
87
What can autoreceptors regulate?
The release of neurotransmitter
88
Where are autoreceptors found?
On the axon terminals
89
Binding of neurotransmitters to autoreceptors decreases what?
The amount of neurotransmitter which is released
90
Can neurotransmitters regulate their own release?
Yes
91
How many different ways can neurotransmitters be removed from synapses?
Three
92
What is synaptic reuptake?
One process by which neurotransmitter can be removed from synapses
93
What are the three mechanisms in which neurotransmitters can be removed from synapses?
- Synaptic reuptake
- Enzymatic degradation
- Diffusing away from the synapse, being taken up into astrocytes and metabolised into their constituent molecules
94
What is enzymatic degradation?
The process by which enzymes present in the synaptic cleft break down neurotransmitters
95
Excessive levels of neurotransmitter can ______________ to neurons?
Be toxic
96
What happens if a drug that blocks the reuptake of a neurotransmitter is introduced into the synapse?
The neurotransmitter remains in the synaptic cleft for longer and can therefore have a prologned effect on the postsynaptic neuron
97
What does the term synaptic reuptake mean?
The process which helps terminate the action of neurotransmitter
98
How does the process of synaptic reuptake terminate the action of neurotrasmitter?
It removes it from the synaptic cleft via specialist channels in the axon terminal
99
How does the process of enzymatic degradation remove neurotransmitter from synapses?
Enzymes in the synaptic cleft break down neurotransmitter
100
Neurons which utilise acetylcholine as the principal neurotransmitter are known as what type of neurons?
Cholinergic neurons
101
Reduced activity in the cholinergic pathway which originates in the pons and projects towards the hippocampus results in what?
Impairment of hippocampal functioning
102
Reduced hippocampal functioning is often a feature of which disease?
Alzheimer’s disease
103
How many principal dopaminergic pathways are there in the brain?
3
104
What is the dopaminergic pathway which runs from the substantia negra to the caudate nucleus and the putamen important for?
The production of movement
105
What is the route of the nigrostriatal pathway?
From the substantia nigra in the midbrain to the caudate nucleus and the putamen in the striatum
106
Loss of activity in the nigrostriatial pathway underlies which disease?
Parkinson’s disease
107
Where does the mesolimbic pathway run?
From the ventral tegmental area of the midbrain to the nucleus accumbens in the ventral striatum
108
What is the name of the dopaminergic pathway which runs from the ventral tegmental area of the midbrain to the nucleus accumbens in the ventral striatum?
The mesolimbic pathway
109
What is the route of the mesocortical pathway?
It starts in the ventral tegmental area of the midbrain and projects to the prefrontal cortex
110
Together, what are the mesolimbic and mesocortical pathways known as?
The reward pathways
111
The reward pathways are involved in which type of behaviour?
Addictive behaviour
112
Where do the noradrenergic pathways originate in the brain?
A region of the brain stem known as the locus coeruleus
113
Where do the noradrenergic pathways project?
From the locus coeruleus in the brain stem down the spinal cord and upwards through many regions of the brain
114
What are the descending noradrenergic pathways involved in the control of?
Responses of the autonomic nervous system
115
Descending noradrenergic pathways are important in which type of response?
Stress response
116
Where do the ascending noradrenergic pathways project?
To the hypothalamus, amygdala, thalamus and widely throughout the cortex
117
The projection of the noradrenergic pathway to the prefrontal cortex is of particular importance in the context of what?
Mood disorders
118
Where in the brain do the serotinergic pathways originate?
In the raphe nuclei of the brain stem
119
Which regions of the brain do serotinergic pathways project to?
- Cerebellum
- Hippocampus
- Prefrontal cortex
- Widely through the cortex
120
What are some of the roles that serotonergic pathways are involved in?
- Sleep/wake cycle
- Emotions
- Mood
121
Selective serotonin reuptake inhibitor drugs act how?
By preventing the reuptake of serotonin, so that it remains active in the synapse for longer and continues to exert its effects
122
If more receptors are occupied by serotonin, what happens to the EPSP generated?
It increases
123
Increased EPSP due to serotonin reuptake inhibitors has what effect on the action potential firing rate in the postsynaptic neuron?
It increases
124
How does the type of drug known as an antagonist exert its effect?
It binds to the receptor on the postsynaptic neuron, which can prevent neurotransmitter from binding, meaning that the neurotransmitter cannot exert its effect
125
What are antagonists?
Chemical substances which bind to receptors and prevent binding of the neurotransmitter
126
Too much activity in certain pathways might be treated with which type of drug?
Antagonists
127
If a dopamine antagonist is present, what happens to the action potential firing rate in the postsynaptic neuron?
It is lower
128
If there is a deficit of activity in a certain pathway, which type of drug would be helpful?
Agonist
129
Which aspects of synaptic transmission could potentially be altered by drugs?
- Drugs which bind to postsynaptic receptors and autoreceptors
- Drugs that interfere with the processes which terminate the activity of a neurotransmitter
130
What is meant by the term neuroplasticity?
Changes that occur in the brain as a result of:
- Development and ageing
- Learning and experiences
- Disease processes
- Recovery from brain injury
131
What is synaptogenesis?
The formation of new synapses between neurons
132
What is the name of the process which removes dendrites from neurons during adolescence and into early adulthood?
Denritic pruning
133
What is dendritic pruning?
The process by which dendritic spines are removed from dendrites, thus reshaping the connectivity between neurons
134
During which period of life does dendritic pruning peak?
Adolescence and into early adulthood
135
What is Hebbian plasticity?
A type of neuroplasticity which occurs from prolonged or intense activity in one neuron, which leads to increased responsiveness of the next neuron in the pathway
136
What is the friendly explanation of Hebbian plasticity?
“Neurons that fire together, wire together”
137
Which brain imaging technique allows activity across the brain to be measured?
fMRI - functional magnetic resonance imaging
138
How do we measure brain activity directly?
Electoencephalography (EEG)
139
What is electroencephalography?
Recording of electrical activity from the cortex of the brain using an array of sensors applied to the scalp
140
What three things have made the study of consciousness scientifically possible?
- A better definition of consciousness
- The discovery that consciousness can be experimentally manipulated
- A new respect for subjective phenomena
141
Correlational studies are used for what purpose?
To evaluate relationships between two observations
142
What are some of the techniques that can be used to visualise brain structures?
- Microscopy
- Brain imaging
- Electrophysiology
143
What is the name for the process in which a chemical neurotransmitter communicates activity from one neuron to another?
Synaptic transmission
