Introduction to cellular neuroscience Flashcards
1
Q
What is the goal of cellular neuroscience
A
Understand how the nervous system works from a bottom up approach, starting from a knowledge of cellular structure and physiology , leading to knowledge of systems and how they work together to underpin cognitive functions
2
Q
What is the hardware of the nervous system
A
ie cells- constrain how the system mediates behaviour and function
3
Q
What does the nervous system do
A
Coordinates physiology and behavior through 3 principle processes- sensation, integration and action
4
Q
Nervous system principle processes- sensation
A
Gathering info about the internal (happy, hungry) and external environment (threat, surroundings)
5
Q
Nervous system principle processes-integration
A
Determining appropriate response based on multisensory info (different representatinos of internal/external environment) and past experience
6
Q
Nervous system principle processes-response
A
Conveying coordinated signals from CNS to the muscles and glands
7
Q
Why do multicellular organisms need a nervous system
A
For fast long-range communication
8
Q
What are nerves
A
Bundles of fibres emanating from the brain and central cord that branch repeatedly to innervate every body part,, and carry info from senses into CNS to effector organs to enact motor responses
9
Q
What does the nervous system include in vertebrates
A
The brain, spinal cord, nerves and sense organs
10
Q
What are the 2 defining features of neurons
A
Electrical excitability (can emit fast, electrical impulses), formation of synapses
11
Q
What cells in the body other than neurons can show excitability
A
Cells in the heart and muscles
12
Q
What do synapses do
A
Connect neurons, convert an electrical signal into a chemical signal to an electric signal, for fast intercellular communication
13
Q
What are the typical features of neurons
A
Dendritic arbours, soma, axon,
14
Q
What are dendrites
A
Provide the major site for convergent synaptic input from other neurons, and propagate the signal all the way down to the common branch
15
Q
How does the no of synaptic inputs received by each neuron differ
A
Varies from about 1-100,000
No of inputs a neuron receives is reflected in the complexity of its dendritic arbor
16
Q
What is the soma
A
Cell body- contains machinery for translating and transcribing proteins (nucleus, ER, ribosomes, Golgi), mitochondria for generating energy stores and other organelles essential for cellular function
Integrates dendritic inputs
17
Q
Where are dendritic inputs integrates
A
Soma
18
Q
What does the axon do
A
Generates and propagates fast electrical impulses to targets, can branch to contact multiple postsynaptic cells
Output cables of neurons
19
Q
How long can axons be
A
Can be up to several m in length to transfer info over long distances
20
Q
What is the nervous system defined by
A
The presence of neurons which form synaptic connections for high speed communication
21
Q
Examples of cells specialised for transduction of sensory stimuli
A
Hair cells in auditory and vestibular systems
Photoreceptors in the retina
Merkel cells in the skin
22
Q
What does the estimated ratio of glia to neurons in the nervous system vary from
A
100:1 to around 1:1
23
Q
What types of glia cells are in the CNS
A
Astrocytes, ependymal cells, oligodendrocytes, microglia
24
Q
What type of glia cells are in the PNS
A
Satellite cells, Schwann cells
25
What do glia play key roles in
Development, maintaining and supporting neural activity, pathogenesis of neurological disorders
26
Where are ependymal cells located
Line the ventricles and central canal of the spinal cord
27
What do ependymal cells do
Have beating cilia that direct movement of cerebral spinal fluid- cushions against shock to skull and spinal cord, washes away waste products, delivers metabolised ions
28
What is the result of issues with ependymal cell function
Disturbances in the flow of cerebral spinal fluid leads to hydroencephaly (build up of water in the brain, extra pressure can be very damaging)
29
What do astrocytes and satellite cells do
Regulate the external chemical and physical environment of neurons
Astrocytes fill most of the space between neurons
30
What functions do astrocytes carry out to regulate the external chemical and physical environment of neurons
Ionic homeostasis, neurovascular coupling, maintaining synaptic functioning
31
How do astrocytes control ionic homeostasis
Regulate the ionic concentration of extracellular sites around neurons via connections that allow molecules taken in by one astrocyte to diffuse to another
32
How do astrocytes control neurovascular coupling
Link between brain activity and blood flow to that region, can cause blood vessels to dilate to increase oxygen supply
33
How do astrocytes maintain synaptic function
End feet wrap around synaptic junctions that regulate what happens to the transmitters once they're released from the presynaptic neuron, restricting the extracellular space
34
What do oligodendrocytes and Schwann cells do
Generate and maintain the myelin sheath that surround and insulate axons to allow high speed conduction of action potentials
35
How do oligodendrocytes and Schwann cells differ
Oligodendrocytes- CNS, provide mylination for many axons
| Schwann cells- PNS, only wrap around one axon
36
What are microglia
Immune effector phagocytic cells of the CNS- become active and destroy any invading agent
Clear away dead cells and remodel synapses during development
37
Why are microglia largely inactive under normal physiological conditions
CNS is very well protected by the blood brain barrier from invading agents
38
What directly underlies fast and adaptive behaviour
High speed communication in neuronal networks
39
What do glia do for the neurons they surround
Insulate, support and nourish them
40
What is Nissl stain
Stains clumps of material surrounding neuron nuclei called Nissl bodies, useful distinguishing neurons and glia (neurons have more RER), allow study of the neuronal arrangement in the brain
41
What is Golgi stain
Makes a small percentage of neurons entire;y darkly covered
42
What can axons and dendrites both be classified as types of
Neurites- thin tubes extending from the soma
43
What is the neuron doctrine
Cajal- follows cell theory that the individual cell is the elementary functional unit of all animal tissues, neurites are not continuous but communicate by contact
44
What is reticular theory
Golgi- the brain is an exception to cell theory, neurites of different cells are fused together to form a continuous reticulum
45
When was the neuron doctrine vs reticular theory conflict solved
The increased resolving power of the electron microscope in the 1950s revealed the neuron doctrine was correct- neurites are within 0.02um of each other
46
What is the diameter of the soma
About 20um
47
What is the cytoplasm
Refers to everything within the cell membrane including organelles excluding the nucleus
48
How do the ribosomes on the RER gives neurons their information-processing abilitiies
They produce special membrane proteins
49
What do different sections of the SER do
Some fold proteins that jut out from the RER, some regulate the internal concentration of substances like calcium
50
What is the Golgi apparatus' role
Sorting proteins for delivery to different parts of the neuron eg axon and dendrites
51
What do mitochondria do
Pull inside pyruvic acid and oxygen from the cytosol, Krebs cycle produces energy that via the electron transport chain along the cristae results in ADP + P -> ATP
52
How many ATP molecules are released for every model of pyruvic acid taken in by the mitochondria
17 ATP molecules
53
How thick is the neuronal membrane
5nm thick
54
How does the membrane's protein composition vary across location
Varies depending on whether it is the soma, dendrites or axon
55
What does the cytoskeleton consist of
Microtubules, microfilaments and neurofilaments
56
What are the diameter of microtubules, microfilaments and neurofilaments
Microfilaments- 5nm
Neurofilamets- 10nm
Microtubules- 20nm
57
What do microtubules do
Polymerisation/depolymerisation of microtubules and hence neuronal shape can be regulated by signals in the neuron
58
What regulates the assembly and function of microtubules
Microtubule associated proteins (MAPS)
59
What do microfilaments do
Involved in changing cell shape, especially numerous in the neurites
60
What do neurofilaments do
Very mechanically strong, resemble the bones and ligaments of the skeleton
61
What are the different segments of the axon called
Axon hillock forms initial segment of axon branching off from the soma, middle section is axon proper, end of axon is the axon terminal
62
Rough ER in axon vs soma?
No rough ER extends into the axon, so all axon proteins produced by protein synthesis originate in the soma- axons cannot be sustained without the cell body providing proteins
63
Ribosomes in axon vs soma
Mature axons contain few free ribosomes, so no protein synthesis and all axon proteins are made in the soma
64
Why does protein composition of the axon membrane differ from the soma membrane
Allows the axon to act as a wire sending info over long distances
65
What are axon collaterals
Axon branches that return to communicate with the same cell they branched
66
What are recurrent collaterals
Axon branches that return to communicate with dendrites of neighbouring cells
67
What does the axon terminal do
Branches out to other synapses to form the terminal arbor
Can also form synapses at boutons en passant than terminate elsewhere
Forms synapses with other cells to provide innervation
68
How does the axon terminal cytoplasm differ from axon cytoplasm
Microtubules don't extend into terminal
Contains synaptic vesicles, small bubbles of membrane
Inside surface of the terminal membrane facing the synapse has a dense covering of proteins
Numerous mitochondria indicating high energy demand
69
What is the synaptic cleft
The space between the presynaptic and postsynaptic membrane
70
What does a synapse consist of
Presynaptic and postsynaptic membrane, synaptic cleft
71
What is axoplasmic transport
Flow of materials from the soma to the axon terminal
72
Who demonstrated slow axoplasmic transport
Weiss in 1940s- tying off an axon led to material building up on the soma side of the knot, when untied material moved down the axon at 1-10mm a day
73
How was fast axoplasmic transport shown
Seen in 1960s- by tracking the movement of radioactive amino acids injected into neuron somata as they were assembled into radioactive proteins and travelled to the axon terminal, rate of transport found to be 200-400mm a day
74
What is anterograde transport
Movement of material from the soma to the terminal by kinesin
75
What is retrograde transport
Movement of material up the axon from terminal to soma using dynein
76
How is anterograde transport carried out
Vesicles carrying material 'walk down' the axon's microtubules to the terminal, using kinesin 'legs' fuelled by ATP
77
How is retrograde transport carried out
Material is moved up the axon from the terminal to the soma using dynein 'legs'
78
What is thought to be the goal of retrograde transport
Thought to provide signals to the soma about changes in the axon terminal's metabolic needs
79
What study shows the need for axons to be provided proteins by their soma
Wallerian degeneration- the degeneration of axons when they are cut, shown by Waller in mid-19th century
80
What are dendritic spines
Some dendrites have dendritic spines on them that receive synaptic input- thought to isolate various chemical reactions triggered by some types of synaptic activation, their structure thought to be sensitive to the type/amount of synaptic activity
81
Study showing the importance of dendritic spines
Padilla et al (1974)- intellectually disabled children had fewer dendritic spines, or unusually long and thin dendritic spines, with extent of change correlated with degree of intellectual disability
82
Classification of neurons by number of neurites
Unipolar, bipolar, multipolar (most neurons in the brain)
83
Classification of neurons by dendrites
Dendritic arbors vary widely across different types of neurons eg cerebral cortex contains 2 broad classes (stellate and pyramidal cells), spiny vs aspinous
84
Classification of neurons by connections
Primary sensory neurons- have neurites in sensory surfaces
Motor neurons-form synapses with muscles
Interneurons- form connections with other neurons only (most of nervous system)
85
Classification of neurons by axon length
Golgi type I/projection neurons extend beyond brain areas via long axons, Golgi type II/local circuit neurons have short axons that don't extend beyond the cell body vicinity
86
What are most differences between neurons explainable by
Explainable at the genetic level eg different gene expression -> different shapes of pyrimidal and stellate cells
87
How can transgenic mice allow investigation of neurons in a genetic class
eg green fluorescent protein (GFP) is commonly used as allows visualisation of the neuron it is expressed in when illuminated with the appropriate wavelength
88
What leads to differences in the neurotransmitter used by a neuron
Differences in the expression of proteins involved in transmitter synthesis, storage and use
89
Classification of neurons based on neurotransmitters
eg motor neurons used in voluntary movemet release acetylcholine so are cholinergic (express the genes that enable use of this particular neurotransmitter)
90
What is the resting membrane potential of astrocytes
Negative
91
What is in astrocytic membranes
Neurotransmitter receptors that can trigger electric and biochemical events inside the cell
92
What are the nodes of Ranvier
Short exposed sections of the axonal membrane where there are periodic gaps in the myelin sheath
93
What is vasculature in the brain
Arteries/veins/capillaries that deliver essential minerals and oxygen to neurons via the blood
94
What are the 3 main groups of transmitters
Amino acids, amines, peptides
95
What does the brain turn into what
Turns patterns of stimulation (S) into patterns of response (R)
96
How are patterns of stimulation turned into patterns of response in the brain
A pattern of of energy at one neuronal level is transformed into a different pattern in the next, meaning S is modified as it is transmitted across the levels, until it becomes a completely different pattern as R
97
What does each neuron on each neuronal level in the brain only respond to
A particular pattern of activity aong the neurons on the level immediately above it
98
What is the blood brain barrier
The tight junctions (no pores) held between astrocytes that separate neurons from cerebral capillaries, a highly selective border lining blood vessels
99
What is the plasma membrane of the axon called
The axolemma
100
What is the difference in location of boutons on motor neurons vs sensory neurons
Sensory neurons have few presynaptic boutons on its cell body or axons, whereas motor neurons have 95% of their boutons on their dendrtitic branches
101
How is the myelin sheath arranged
Arranged in concentric layers of membrane, with lipid layers interspersed with protein layers
70% lipid, 30% protein
102
What are genes in Schwann cells vs oligodendrocytes
| that encode myelin turned on by
Schwann cell- presence of axons
| Oligodendrocytes- presence of astrocytes
103
How does MS demonstrate the importance of myelin
MS is a demyelinating disease, involves problems with sensation and movement because the transmission of nerve signals is slowed causing problems with sensory perception and proper motor coordination
104
Mice demonstration of the importance of myelin
Mice with the shiverer (shi) mutatino have greatly deficient myelination in the CNS, leading to tremors, convulsions and early death
