Brain Function Part 1 Flashcards
1
Q
How can a neuron be described?
A
Building block of the nervous system
2
Q
What are neurons?
A
Chemical and electrical information and communication cell
Variable size and structure throughout the nervous system
3
Q
What are the cellular constituents of neurons and their function?
A
Microtubules: transportation
Neurofibrils: structural support
Nissl substances: protein synthesis
4
Q
Will neurons continue to divide?
A
Some neurons, such as olfactory neurons, will continue to divide
However, others die if they are not needed
5
Q
What happens if a neuron cell dies?
A
Cannot be replaced
6
Q
What are the components of the neuron?
A
Cell body (soma)
Dendrites
Axons
7
Q
What are the key features of the cell body (soma)?
A
Located mainly in the CNS
Nuclei: densely packed cell bodies in the CNS (white matter contains nuclei)
Ganglia and plexuses: group of cell bodies in the PNS
8
Q
What are the key features of the dendrites?
A
Receptive portion of the neuron- sends impulses to the cell body
Dendritic zone: receptive portion of the neuron that receives a stimulus and continues further conduction
9
Q
What are the key features of the axons?
A
Carry nerve impulses away from cell body
Axon hillock: cone-shaped, organelle-free area where the axon leaves the cell body
10
Q
What is significant about the axon hillock?
A
First part of the axon hillock is the area of lowest threshold for stimulation; therefore, action potentials begin here
11
Q
Why is myelin important for the axon?
A
Segmented layer of lipid material
Insulating material
Myelin sheath (entire membrane) on axon
Formed and maintained by the Schwann cells
12
Q
Why are nodes of Ranvier important for axons?
A
Regular interruptions of the myelin sheath, speeds up transmission of impulses
13
Q
What is the neurilemma?
A
Schwann sheath
14
Q
How can neurons be structurally classified, and what are the names of the classifications?
A
Structurally classified on the basis of the number of processes extending from the cell body
Can be classified as:
Multipolar (most common)
Bipolar
Unipolar/Pseudounipolar
Anaxonic
15
Q
What are multipolar neurons and what is an example of one?
A
Neurons with one axon and two or more dendrites
Motor neurons
16
Q
What are bipolar neurons and what are examples of them?
A
Neurons with one axon and one dendrite
Comprise the sensory neurons of the retina, the olfactory epithelium and the inner ear
17
Q
What are unipolar/pseudounipolar neurons and what are examples of them?
A
Each have a single process that bifurcates close to the perikaryon, with the longer branch extending to a peripheral ending and the other toward the CNS
Includes all other sensory neurons that aren’t bipolar neurons
18
Q
What are anaxonic neurons and what are their functions?
A
Many dendrites but no true axon
Do not produce action potentials, but do regulate electrical charges of adjacent CNS neurons
19
Q
How do the motor pathway and sensory pathway interact?
A
Brain will act on stimuli from sensory pathway and send impulses via motor pathway
20
Q
What are the classifications of neurons based on function?
A
Sensory neurons
Associational or interneurons
Motor neurons
21
Q
What is the function of sensory neurons?
A
Transmit impulses from peripheral sensory receptors to the CNS
Are transmitted via an afferent pathway (Afferent=Arrive)
22
Q
What are common types of sensory neurons?
A
Associational or interneurons (transmit impulses from neuron to neuron/CNS)
23
Q
What is the function of motor neurons?
A
Transmit impulses from CNS to effector organs (i.e., skeletal muscle or organs)
24
Q
How are impulses transmitted via motor neurons?
A
Transmitted via an efferent pathway (Efferent= Exit)
25
How are motor neurons and neuromuscular junctions linked together?
In skeletal muscle the end processes of an axon form the specialised structure (neuromuscular junction)
26
Which information is correct regarding associational neurons?
Associational neurons
1. Carry impulses between two distinct processes arising from the cell body
2. Carry impulses from peripheral receptors to the CNS
3. Transmit impulses to an effector organ
4. Transmit impulses from neuron to neuron
ANSWER: 4
These interneurons are multipolar and are involved in cognitive function
1. Bipolar neurons have two distinct processes arising from the cell body and are found in the retina of the eye. These neurons connect the rods and cone cells of the retina.
2. Sensory neurons carry impulses from peripheral receptors to the CNS
3. Motor neurons transmit impulses to an effector organ
27
What does the term neuroglia mean?
Nerve glue
28
How many more times numerous are neuroglia compared to neurons?
5-10 times more numerous
29
What is the main function of the neuroglia?
Supports the neurons of the CNS
30
What are the neuroglia of the CNS and what are their function?
Astrocytes: Fill the spaces between neurons and surround the blood vessels in the CNS
Oligodendroglia (oligodendrocytes): Deposit myelin within the CNS
Microglia: Remove debris in the CNS
Ependymal cells: Line the cerebrospinal fluid (CSF)–filled cavities of the CNS
31
What is the importance of astrocytes in the CNS?
Fill spaces between neurons and surrounds the blood vessels
Included in the formation and maintenance of the blood-brain barrier
32
What is the significance of the blood-brain barrier?
Acts selectively-regulates what passes in the brain and what doesn't
Need to think if nerve tissue is damaged due to blood-brain barrier breach
33
What is the importance of oligodendroglia (oligodendrocytes) in the CNS?
Wrap around CNS nerve fibres to form myelin
Deposit myelin within CNS
34
What is the importance of microglia (microglial cells) in the CNS?
Act like macrophages and remove debris from the CNS
35
What is the importance of cerebrospinal fluid (CSF)?
"Washes the brain"
36
What is the importance of ependymal cell in the CNS?
Line the CSF-filled cavities of the CNS
Form sheets
37
What is the brain protected by in the skull?
The brain is connected to the skull but is protected by the meninges
38
What are Schwann cells also known as and what are their function?
Also known as neurolemmocytes
Are glial cells that wrap around and cover axons in the PNS
Form and maintain the myelin sheath
39
What does the term myelinated mean?
Myelin layer is tightly wrapped many times around the axon, forming nodes of Ranvier
40
Why are nodes of Ranvier useful?
Increase the velocity of conduction
41
What types of motions does the autonomic nervous system control?
Involuntary, e.g., heart rate, blood pressure, etc.
42
What can the autonomic nervous system be split into?
The sympathetic nervous system, and the parasympathetic nervous system
43
What types of motion does the somatic nervous system control?
Voluntary, e.g., muscle movement
44
What does the central nervous system consist of?
Brain and the spinal cord
45
What does the peripheral nervous system consist of?
Everything outside of the CNS
Cranial nerves and spinal nerves
46
What are the pathways associated with the PNS?
Afferent (ascending; sensory to spinal column)
Efferent (descending; innervate effector organs)
47
What can the peripheral nervous system be split into and what are their functions?
Somatic nervous system:
Motor and sensory pathways regulate voluntary motor control of skeletal muscle
Autonomic nervous system (ANS)
Motor and sensory pathways regulate the body’s internal environment through the involuntary control of organ systems
48
What can the autonomic nervous system be divided into?
The sympathetic and parasympathetic nervous system
49
What is significant about all ANS divisions?
They all have acetylcholine --> different neurotransmitters
50
What type of movement are smooth muscles associated with?
Involuntary
51
What is the name one of the functions that the parasympathetic nervous system is responsible for?
Vasodilation
52
What is the significance of the sympathetic nervous system?
Stimulation of certain organs
53
Why is it important to know what organs the sympathetic nervous system stimulates, and what the parasympathetic, autonomic and somatic nervous systems do?
Important to know due to medication potentially causing side effects, and could lead to identification of under lying conditions
54
What are synapses?
Regions between adjacent neurons
55
How are impulses transmitted across synapses?
Via chemical and electrical conduction across protein channels
56
Why are synapses important?
Allow connections between pre-synaptic (towards) and post-synaptic (away) neurons
57
What are the different types of synapses and where are they located?
Axoaxonic synapses: between axons
Axosomatic synapses: axon to cell body
Axodendritic synapses: axon to dendrites
Dendrodentritic synapses: dendrite to dendrite
58
What is responsible for the transmission of impulses?
Neurotransmitters, e.g., dopamine, acetylcholine and serotonin
59
Where are neurotransmitters formed?
In neurons
60
How are neurotransmitters stored?
In synaptic boutons
61
How are nuerotransmitters able to become mobile?
Neurotransmitters are released across the synaptic cleft, which is the space between neurons
62
What are some of the common types of neurotransmitters?
Norepinephrine, acetylcholine, dopamine, histamine and serotonin
63
What are the possible effects of the neurotransmitters on the post-synaptic neurons?
Excited: Depolarized; excitatory postsynaptic potentials (EPSPs)
Inhibited: Hyperpolarized; inhibitory postsynaptic potentials (IPSPs)
64
Are neurotransmitters permanently on?
No, as they go through degradation and recovery
65
What happens to neurotransmitters during diffusion?
They move away from the synapse
66
What happens to the neurotransmitter during reuptake?
Neurotransmitter re-enters pre-synaptic axon terminal
67
What is an example of a neurotransmitter that undergoes the process of reuptake?
NAT (a.k.a. NET): noradrenaline transporter
68
Where does enzymatic degradation occur?
Inside terminal cytosol or synaptic cleft
69
What is an example of enzymatic degradation?
AChE cleaves ACh to inactive state
70
What is ageing?
The gradual loss of neurons and neuroglia
71
What is the impact of ageing on the brain between the ages of 20-60?
Brain loses ~0.1% of neurons per year
72
How does ageing affect the brain by the age of 90?
Brain mass decreased by ~11% compared to a 50 year old
About 150g of neural tissue is lost
73
What is significant about ventricles in the brain?
Filled with cerebrospinal fluid (CSF)
74
How are ventricle affected by ageing?
Progressive loss of cells lining the ventricles
Volume increases ~2.9% per year
>70 years- volume increases ~4.25% per year
Cognitive impact is unclear
75
What happens to sulci as of ageing?
Sulci become deeper
76
What is also associated with ageing?
Increase in pigmentation
77
What is brown pigment and why is it significant?
Lipofuscin
Linked to plaques and neurofibrillary tangles
Low density in "normal" aged brain
Associated with oxidative stress, appears red
78
What is black pigment and why is it significant?
Neuromelanin
Protective role (mostly against toxicity)
Parkinson's disease is associated with the death of neuromelanin-rich dopaminergic and noradrenergic cells in the substantia nigra (SN) and the locus coeruleus (LC), respectively, resulting in motor and cognitive impairments
79
What is the hippocampus and how does ageing affect it?
Hippocampus is the part of the brain that is responsible for memory and skill acquisition
Ageing leads to reduced neurogenesis
80
Why is exercising important for ageing?
Exercise keeps the brain active and allows cells to re-divide, promoting neurogenesis
Reduces risk of Alzheimer's disease
81
What is the somatic cortex and how is it affected by ageing?
The somatic cortex is an important part of the cerebral cortex in the brain that processes sensory information from the body
35% of people >70 years old have gait problems
Age-related changes to muscles and joints
Middle age onwards neurons show signs of atrophy
82
What are gait problems?
Abnormal walking patterns
83
What is atrophy?
Atrophy- shrinkage/degradation
84
What is hypertrophy?
Increase in volume
85
What is the telencephalon of the brain and why is it important?
Cerebrum
Memory storage and processing unit
Conscious thought processes, intellectual functions
Conscious and subconscious regulation of skeletal muscle contractions
86
What is the metencephalon of the brain and why is it important?
Cerebellum
Co-ordinates complex somatic motor patterns
Adjusts output of other somatic motor centres in brain and spinal cord
87
How many parts of the diencephalon are there and what are they called?
Two parts
Thalamus and hypothalamus
88
What is the function of the thalamus?
Relay and processing centre for sensory information
89
What is the function of the hypothalamus?
Centres controlling emotions, autonomic functions, and hormone production
90
How many parts of the brain stem are there and what are their names?
Mesencephalon (Midbrain)
Metencephalon (Pons)
Medulla Oblongata (Myelencephalon)
91
What is the role of the midbrain (mesencephalon)?
Processing of visual and auditory data
Generation of reflexive somatic motor responses
Maintenance of consciousness
92
What is the role of the pons (metencephalon)?
Relays sensory information to the cerebellum and thalamus
Subconscious somatic and visceral motor centres
93
What is the role of the medulla oblongata (myelencephalon)?
Relay sensory information to the thalamus
Autonomic nervous centres for regulation of visceral functions such as cardiovascular, respiratory, and digestive activities
94
How does ageing affect the brain stem and autonomic function?
Brain stem loses fewer neurons than other regions
Autonomic function declines
95
What is an example of autonomic function decline?
Delayed baroreceptor responses
Postural hypertension (stand up and blood pressure drops)
Loss of bladder control (incontinence)
96
What are some examples of results due to the brain being impacted by the process of ageing?
Stem cell exhaustion, (metabolism)
Aberrant neuronal network activity, (metabolism)
(Cell senescence), (metabolism)
Impaired DNA repair, (metabolism)
Impaired molecular waste disposal, (dysregulated)
Mitochondrial dysfunction, (dysregulated)
Oxidative damage, (dysregulated)
Dysregulated neuronal calcium calcium homeostasis, (dysregulated)
Impaired adaptive stress response signaling, (energy)
(Telomere damage), (energy)
Glial cell activation and inflammation, (energy)
97
What occurs due to mitochondrial dysfunction?
ATP presence is reduced therefore different materials are descreted
98
What is a ROS and what are examples of it?
Reactive Oxygen Species
E.g., smoking, environment, etc.
Inside the mitochondria
99
How is an aged neuron and ROS linked together?
Altered synaptic neurotransmission--> Injury of synapses--> Synapses are susceptible to being altered and to degenerate
This leads to a decrease in axons, decrease in conduction, but an increase in myelin sheath disorganisation (and decreased NAD+)
Increased ROS production--> Reduced antioxidant defenses--> Perturbed Ca2+ regulation--> Reduced glucose consumption--> BDNF- NGF reduction--> Proinflammatory cytokines accumulate--> Altered signal transduction pathways
Degenerating dendritic tree--> N+ dendritic shafts decrease--> Less branches--> Shorter branches
100
How does ROS affect peroxisomes?
Leads to increased proxisomal dysfunction
101
How are ROS and mitochondria linked together?
Leads to mitochondria producing more ROS as of decreased antioxidant enzymes, decreased OXPHOS, and increased mtDNA mutations
102
How does ROS affect endoplasmic reticulum?
Increased reticulum stress
Increased unfolded protein responses
Increased misfolded proteins
103
How does ROS affect proteins neurotoxis aggregation?
AD: misfolded tau and amyloid beta
PD: alpha synuclein (Lewy body)
HD: alpha synuclein and mutant Huntington protein
104
How does ROS affect metabolism and neurotrophins in a degenerating neuron?
Compromised Ca 2+ signalling
GLUT1 and GLUT3 levels reduction (AD)
Altered insulin and IGF pathway (AD)
Pro-BDNF expression increased (AD, PD)
Pro-NGF expression increased (AD)
105
How does ROS affect the endoplasmic reticulum in a degenerating neuron?
Increased misfolded protein accumulation
Increased changes in organelle dynamics
PD: misfolded parkin accumulation
106
How does ROS affect the mitochondria in a degenerating neuron?
Decreased ATP production
Increased ROS
Increased apoptosis
AD: reduced motility and density in axons (altered trafficking)
PD: functional alterations of mitochondrial complex l
HD: lower mitochondrial membrane potential
107
How does ROS affect the peroxisomes in a degenerating neuron?
Increased peroxisomal dysfunction
108
Why can mutations lead to detrimental impacts?
The mutation may lead to altered proteins, which will therefore cause a different change in structure
109
What does NMJ stand for, where is it located and what happens if it is negatively impacted?
Neuromuscular Junction
Gap between muscle and neuron
If the NMJ is affected then the muscular activity is also affected
110
What are the primary causes of NMJ dysfunction?
Inflammation
Mitochondrial dysfunction and oxidative stress
Neurodegeneration
111
How does inflammation occur?
Impaired amino acid utilisation and protein anabolism
Increased levels of inflammatory markers (IL-6, IL-1, TNFa (alpha), CRP...)
Chronic and systematic inflammation
112
How does mitochondrial dysfunction and oxidative stress occur?
Changes in mitochondria morphology
Downregulation mitochondrial metabolism genes
Decreased ATP production
Impaired calcium buffering
Decreased enzimatic activity
Increased ROS
113
How does neurodegeneration occur?
Excitation-contraction uncoupling
Fiber type transformation
Decreased alpha motoneuron excitation
Decreased motor units size
Increased dispersion of Achr
Increased fragmentation Schwann cells
114
What changes are present in ageing neuromuscular junction?
Structural changes and functional (mechanical properties) changes
115
What are the key structural changes of an ageing NMJ?
Remodelling endplate morphology
Decreased: nerve terminal, post-synaptic folds, synaptic vesicles, neurotransmitters, mitochondria in the plaque region, satellite cell proliferation
Increased: fusion events in mitochondria, quantal content
116
What are the key functional changes (mechanical properties) of an ageing NMJ?
Excitation-contraction uncoupling (less efficient contractions)
Impairment activation of muscle agonists
Uncoupling of RyRs to the voltage -sensing DHRPrs
Decreased:
Repair capacity by Schwann cells
Capacity motoneuron to re-innervate
Motor neuron sprouting capacity
Calcium released
AChr dispersion
117
What are key features of the mitochondria?
20% of cell volume
Crucial role in metabolism
Controls other activities (e.g., Ca2+ and Fe3+ buffering, haem biosynthesis, programmed cell death)
Own DNA- own replication complex and diverse within cell
118
What is programmed cell death and what is it useful to prevent?
Apoptosis
Useful to prevent cancer formation from faulty cells an tumour formation from uncontrolled cell mitosis
119
How does ageing affect mitochondria?
Mitochondrial mass decreases during ageing
Reduced mitochondriogenesis
Incomplete depolarisation
