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Neurophysiology > Introduction to cellular neuroscience > Flashcards

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

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2
Q

What is the hardware of the nervous system

A

ie cells- constrain how the system mediates behaviour and function

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3
Q

What does the nervous system do

A

Coordinates physiology and behavior through 3 principle processes- sensation, integration and action

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4
Q

Nervous system principle processes- sensation

A

Gathering info about the internal (happy, hungry) and external environment (threat, surroundings)

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5
Q

Nervous system principle processes-integration

A

Determining appropriate response based on multisensory info (different representatinos of internal/external environment) and past experience

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6
Q

Nervous system principle processes-response

A

Conveying coordinated signals from CNS to the muscles and glands

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7
Q

Why do multicellular organisms need a nervous system

A

For fast long-range communication

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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

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9
Q

What does the nervous system include in vertebrates

A

The brain, spinal cord, nerves and sense organs

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10
Q

What are the 2 defining features of neurons

A

Electrical excitability (can emit fast, electrical impulses), formation of synapses

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11
Q

What cells in the body other than neurons can show excitability

A

Cells in the heart and muscles

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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

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13
Q

What are the typical features of neurons

A

Dendritic arbours, soma, axon,

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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

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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

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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

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17
Q

Where are dendritic inputs integrates

A

Soma

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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

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19
Q

How long can axons be

A

Can be up to several m in length to transfer info over long distances

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20
Q

What is the nervous system defined by

A

The presence of neurons which form synaptic connections for high speed communication

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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

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22
Q

What does the estimated ratio of glia to neurons in the nervous system vary from

A

100:1 to around 1:1

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23
Q

What types of glia cells are in the CNS

A

Astrocytes, ependymal cells, oligodendrocytes, microglia

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24
Q

What type of glia cells are in the PNS

A

Satellite cells, Schwann cells

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25
Q

What do glia play key roles in

A

Development, maintaining and supporting neural activity, pathogenesis of neurological disorders

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26
Q

Where are ependymal cells located

A

Line the ventricles and central canal of the spinal cord

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27
Q

What do ependymal cells do

A

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

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28
Q

What is the result of issues with ependymal cell function

A

Disturbances in the flow of cerebral spinal fluid leads to hydroencephaly (build up of water in the brain, extra pressure can be very damaging)

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29
Q

What do astrocytes and satellite cells do

A

Regulate the external chemical and physical environment of neurons
Astrocytes fill most of the space between neurons

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30
Q

What functions do astrocytes carry out to regulate the external chemical and physical environment of neurons

A

Ionic homeostasis, neurovascular coupling, maintaining synaptic functioning

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31
Q

How do astrocytes control ionic homeostasis

A

Regulate the ionic concentration of extracellular sites around neurons via connections that allow molecules taken in by one astrocyte to diffuse to another

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32
Q

How do astrocytes control neurovascular coupling

A

Link between brain activity and blood flow to that region, can cause blood vessels to dilate to increase oxygen supply

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33
Q

How do astrocytes maintain synaptic function

A

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

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34
Q

What do oligodendrocytes and Schwann cells do

A

Generate and maintain the myelin sheath that surround and insulate axons to allow high speed conduction of action potentials

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35
Q

How do oligodendrocytes and Schwann cells differ

A

Oligodendrocytes- CNS, provide mylination for many axons

Schwann cells- PNS, only wrap around one axon

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36
Q

What are microglia

A

Immune effector phagocytic cells of the CNS- become active and destroy any invading agent
Clear away dead cells and remodel synapses during development

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37
Q

Why are microglia largely inactive under normal physiological conditions

A

CNS is very well protected by the blood brain barrier from invading agents

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38
Q

What directly underlies fast and adaptive behaviour

A

High speed communication in neuronal networks

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39
Q

What do glia do for the neurons they surround

A

Insulate, support and nourish them

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40
Q

What is Nissl stain

A

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

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41
Q

What is Golgi stain

A

Makes a small percentage of neurons entire;y darkly covered

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42
Q

What can axons and dendrites both be classified as types of

A

Neurites- thin tubes extending from the soma

43
Q

What is the neuron doctrine

A

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
Q

What is reticular theory

A

Golgi- the brain is an exception to cell theory, neurites of different cells are fused together to form a continuous reticulum

45
Q

When was the neuron doctrine vs reticular theory conflict solved

A

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
Q

What is the diameter of the soma

A

About 20um

47
Q

What is the cytoplasm

A

Refers to everything within the cell membrane including organelles excluding the nucleus

48
Q

How do the ribosomes on the RER gives neurons their information-processing abilitiies

A

They produce special membrane proteins

49
Q

What do different sections of the SER do

A

Some fold proteins that jut out from the RER, some regulate the internal concentration of substances like calcium

50
Q

What is the Golgi apparatus’ role

A

Sorting proteins for delivery to different parts of the neuron eg axon and dendrites

51
Q

What do mitochondria do

A

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
Q

How many ATP molecules are released for every model of pyruvic acid taken in by the mitochondria

A

17 ATP molecules

53
Q

How thick is the neuronal membrane

A

5nm thick

54
Q

How does the membrane’s protein composition vary across location

A

Varies depending on whether it is the soma, dendrites or axon

55
Q

What does the cytoskeleton consist of

A

Microtubules, microfilaments and neurofilaments

56
Q

What are the diameter of microtubules, microfilaments and neurofilaments

A

Microfilaments- 5nm
Neurofilamets- 10nm
Microtubules- 20nm

57
Q

What do microtubules do

A

Polymerisation/depolymerisation of microtubules and hence neuronal shape can be regulated by signals in the neuron

58
Q

What regulates the assembly and function of microtubules

A

Microtubule associated proteins (MAPS)

59
Q

What do microfilaments do

A

Involved in changing cell shape, especially numerous in the neurites

60
Q

What do neurofilaments do

A

Very mechanically strong, resemble the bones and ligaments of the skeleton

61
Q

What are the different segments of the axon called

A

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
Q

Rough ER in axon vs soma?

A

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
Q

Ribosomes in axon vs soma

A

Mature axons contain few free ribosomes, so no protein synthesis and all axon proteins are made in the soma

64
Q

Why does protein composition of the axon membrane differ from the soma membrane

A

Allows the axon to act as a wire sending info over long distances

65
Q

What are axon collaterals

A

Axon branches that return to communicate with the same cell they branched

66
Q

What are recurrent collaterals

A

Axon branches that return to communicate with dendrites of neighbouring cells

67
Q

What does the axon terminal do

A

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
Q

How does the axon terminal cytoplasm differ from axon cytoplasm

A

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
Q

What is the synaptic cleft

A

The space between the presynaptic and postsynaptic membrane

70
Q

What does a synapse consist of

A

Presynaptic and postsynaptic membrane, synaptic cleft

71
Q

What is axoplasmic transport

A

Flow of materials from the soma to the axon terminal

72
Q

Who demonstrated slow axoplasmic transport

A

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
Q

How was fast axoplasmic transport shown

A

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
Q

What is anterograde transport

A

Movement of material from the soma to the terminal by kinesin

75
Q

What is retrograde transport

A

Movement of material up the axon from terminal to soma using dynein

76
Q

How is anterograde transport carried out

A

Vesicles carrying material ‘walk down’ the axon’s microtubules to the terminal, using kinesin ‘legs’ fuelled by ATP

77
Q

How is retrograde transport carried out

A

Material is moved up the axon from the terminal to the soma using dynein ‘legs’

78
Q

What is thought to be the goal of retrograde transport

A

Thought to provide signals to the soma about changes in the axon terminal’s metabolic needs

79
Q

What study shows the need for axons to be provided proteins by their soma

A

Wallerian degeneration- the degeneration of axons when they are cut, shown by Waller in mid-19th century

80
Q

What are dendritic spines

A

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
Q

Study showing the importance of dendritic spines

A

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
Q

Classification of neurons by number of neurites

A

Unipolar, bipolar, multipolar (most neurons in the brain)

83
Q

Classification of neurons by dendrites

A

Dendritic arbors vary widely across different types of neurons eg cerebral cortex contains 2 broad classes (stellate and pyramidal cells), spiny vs aspinous

84
Q

Classification of neurons by connections

A

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
Q

Classification of neurons by axon length

A

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
Q

What are most differences between neurons explainable by

A

Explainable at the genetic level eg different gene expression -> different shapes of pyrimidal and stellate cells

87
Q

How can transgenic mice allow investigation of neurons in a genetic class

A

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
Q

What leads to differences in the neurotransmitter used by a neuron

A

Differences in the expression of proteins involved in transmitter synthesis, storage and use

89
Q

Classification of neurons based on neurotransmitters

A

eg motor neurons used in voluntary movemet release acetylcholine so are cholinergic (express the genes that enable use of this particular neurotransmitter)

90
Q

What is the resting membrane potential of astrocytes

A

Negative

91
Q

What is in astrocytic membranes

A

Neurotransmitter receptors that can trigger electric and biochemical events inside the cell

92
Q

What are the nodes of Ranvier

A

Short exposed sections of the axonal membrane where there are periodic gaps in the myelin sheath

93
Q

What is vasculature in the brain

A

Arteries/veins/capillaries that deliver essential minerals and oxygen to neurons via the blood

94
Q

What are the 3 main groups of transmitters

A

Amino acids, amines, peptides

95
Q

What does the brain turn into what

A

Turns patterns of stimulation (S) into patterns of response (R)

96
Q

How are patterns of stimulation turned into patterns of response in the brain

A

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
Q

What does each neuron on each neuronal level in the brain only respond to

A

A particular pattern of activity aong the neurons on the level immediately above it

98
Q

What is the blood brain barrier

A

The tight junctions (no pores) held between astrocytes that separate neurons from cerebral capillaries, a highly selective border lining blood vessels

99
Q

What is the plasma membrane of the axon called

A

The axolemma

100
Q

What is the difference in location of boutons on motor neurons vs sensory neurons

A

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
Q

How is the myelin sheath arranged

A

Arranged in concentric layers of membrane, with lipid layers interspersed with protein layers
70% lipid, 30% protein

102
Q

What are genes in Schwann cells vs oligodendrocytes

that encode myelin turned on by

A

Schwann cell- presence of axons

Oligodendrocytes- presence of astrocytes

103
Q

How does MS demonstrate the importance of myelin

A

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
Q

Mice demonstration of the importance of myelin

A

Mice with the shiverer (shi) mutatino have greatly deficient myelination in the CNS, leading to tremors, convulsions and early death

Neurophysiology (23 decks)

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