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neuroanatomy 2021 > Lecture 9: The Cellular Structure of the Brain > Flashcards

Lecture 9: The Cellular Structure of the Brain Flashcards

1
Q

the nervous system is the

A

control system of the body

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2
Q

principal function of the nervous system is to

A

produce behaviour

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3
Q

nervous system functions

A

Major controlling, regulatory and communicating system in the body

Centre of all mental activity

Responsible for regulating and maintaining
homeostasis (body temperature, blood pressure etc)

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4
Q

Principal cell types of the nervous system

A

neurons (nerve cells, fundamental units of the NS)
Neuroglia (glia)
Cells from the vascular system

all of these cells are interconnected

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5
Q

The cells of the nervous system - number of neurons

A

86 billion (vast)

long lived (majority stay till death, must live without cell division) and looked after by glial cells

can communicate via electrical impulses

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6
Q

The cells of the nervous system - number of synapses

A

1500000000000000 synapses

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7
Q

Cells of the nervous system connections

A

wired together in a network via synapses to do their function

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8
Q

Number of glia relative to neurons

A

glia outnumber neurons by as much as 50 to one

glial cells can divide therefore can be maintained easier

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9
Q

Structure of a neuron list

A 
Dendrites 
cell body 
nucleus 
cell membrane 
axon hillock 
axon 
nodes of ranvier 
myelin sheath 
Schwann cells 
axon terminal
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10
Q

Dendrites

A

Receive signals from other cells

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11
Q

Cell body

A

Organises and keeps the cell functional

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12
Q

Nucleus

A

Controls the entire neuron

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13
Q

Cell membrane

A

Protects the cell and also maintains membrane potential

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14
Q

Axon hillock

A

Generates impulse in the neuron

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15
Q

Axon

A

Transfers signals to other cells and organs

can be myelinated or not

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16
Q

Node of Ranvier

A

allow diffusion of ions

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17
Q

Myelin Sheath

A

increases the speed of the signal

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18
Q

Schwann Cell

A

produces the myelin sheath (PNS)

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19
Q

Axon terminal

A

Forms junctions with other cells

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20
Q

Action potential

A

An action potential is the electrical signal that travels through the axon of a neuron to send a message.

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21
Q

Neuronal communication steps

A

1 - Input (chemical) : dendrites, allows ions to flow therefore chemical to electrical
2- summation (electrical) : axon hillock, change overall charge and could be enough to trigger an action potential
3- conduction (electrical): axon, nodes are important for saltatory conduction
4 - output (chemical) : at the synapse

information travels from the dendrite to the axon terminals

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22
Q

The synapse

A

allows for communication between neurons

electrical - chemical (neurotransmitter release) - electrical

axon terminal is the presynaptic element, post synapse dendrite which has receptors for the neurotransmitters

synaptic cleft is where neurotransmitters are released from presynaptic element

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23
Q

Neurotransmitters are stored in

A

vesicles

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24
Q

Dendritic spines

A

Dendritic spines are small protrusions from the dendrite membrane, where contact with neighbouring axons is formed in order to receive synaptic input

can get bigger or smaller

3 main shapes - thin, mushroom, stubby

thin and stubby likely part of development stage

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25
Dendritic spines and shape
Actin creates shape in the spine which can respond to the learning that we are doing Lots of potassium/sodium ATPases under the plasma membrane (abundant proteins)
26
Spine numbers in a life span and their profile in different neurological conditions
Spine elimination in normal people happens during adolescence and is known as synaptic pruning where the ones we do not really need are removed ASD - pruning doesn't work to its best ability, more disorder in spines could be related to the behavioural problems AD, PD, HD - steeper spine decline in aging which results in their symptoms in beginning of all pretty normal in that spine numbers increase between prenatal, birth and childhood (spine formation, spine development, spine maturation)
27
Concussion
Traumatic brain injury can be forwards, lateral etc shock waves can also give you a concussion because of the impact CSF and meninges are the brains protection but when you hit a hard object etc then it can cause injury forward motion can cause brain damage when you hit forwards and also as you are coming back it can also damage the posterior part of the brain Common symptoms is becoming unconscious as a results or sometimes can just be out of it 80% of people are able to recover from a concussion
28
Concussion has significant effects on neurons summary
Forward motion impact is giving you a biomechanics injury to the neurons (physical injury to the nruons) which leads to mechanoporation neurometabolic cascade results in a chemical injury ionic flux - potassium out, sodium and calcium in, uncontrollable glutamate release
29
Concussions effect on neurons
Disruption to the cell membrane/axon stretching as a result of mechanical trauma can cause holes in the membrane which causes potassium to lead out (over excitation) and sodium and calcium to rush in which causes depolarisation K+ rushing out and sodium and calcium rushing in which causes depolarisation which may cause uncontrolled glutamate release and all of this can lead to excitotoxicity which can kill the neuron bit it can be fixed
30
How to fix concussions effect on neurons
... excitotoxicity which can kill the neuron but it can be fixed, need energy for the membranes proton pumps to maintain ionic homeostasis in the neurons and what we now know is that we need this energy that we would normally use for activity in our brains to actually pump out and actually reset the standard ionic balance across the membrane, so if the patients rest and relax and avoid stimulation then this energy can be redirected to the brain to repair it really quickly hence dark room eyes closed is a treatment redirect all energy to reset and look after the neurons rest, energy used for repaid and function returns to normal
31
1 pixel (3x3x3mm) of brain activity on an fMRI is actually
7000 cells
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when wanting to look at cellular resolution use
TEM
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TEM stands for
transmission electron microscopy
34
Why use the TEM?
Higher resolution - organelles, nanoparticles etc good for internal structure (compared to the scanning microscope which is just surface features) cons as long as electrons can pass through has to be dead - complex process to stabilise the sample very expensive
35
TEM process in depth
Have an illumination source at the top which provides the illumination which in this case is electrons that come down from the electron generator and forms a small cloud of electrons about 50 micrometers in diameter, condenser lens convert the 50 micrometers of electrons to 1 micrometer spot which strikes the sample, electrons are passed through the sample and some are deflected and some pass right through and this produces the image and this is focused by the objective lens which is underneath the sample itself
36
Function of TEM
Lets users look at very thin cross sections of an object such as a cell
37
Maximum magnification of TEM
approximately 5 million times
38
TEM is best for
Looking at internal structure of objects. Looking at objects at very high resolution. Looking at relationships between structures at high resolution.
39
Disadvantages fo TEM
Can’t be used to look at living things (samples need to be prepared extensively before visualising). Costly to run
40
Why do neurons have their shape?
to establish a network that allows a pathway for transmission of information variable shape, quite plastic i.e. dendritic spine, high energy requirement (20% of the body energy is utilised by the brain ), polarised, transmission
41
How do neurons have their shape?
the cytoskeleton
42
neurons features
``` shape polarised extra and intracellular energy supply transmission ```
43
Is there a typical neuron?
many different types determined by input (dendrites) and output (axons) as well as what kind of information they are transmitting have their shape to make specific connections
44
Purkinje neurons
central role in motor function
45
what turns into neurons (and glial cells)
epithelial cells of the neural plate neurons begins its life as a columnar epithelial cell and then develops to become a neuron
46
How does a neuron differ from an epithelial cell?
structure and function (not that different, it is just how they are arranged)
47
Differences between neurons and epithelial cells
neuron same organelles in the cell body, plasma membrane and cytoskeleton - just arranged differently synapse - chemical junction epithelial cells plasma membrane - lipid bilayer with proteins, surface extensions and microtubules organelles - nucleus, m/c, RER, SER, Golgi, lysosomes cytoskeletons - microtubules, intermediate filaments, microfilaments
48
3 structures that make up the neuronal cytoskeleton
microtubules intermediate filaments/neurofilament actin filaments/ microfilament
49
microtubules made up of
tubulin molecules
50
intermediate filaments/neurofilaments made up of
intermediate filament
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actin filaments/microfilaments made up of
f-actin - filamentous | g-actin - monomeric
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biggest neuronal cytoskeleton element
microtubule
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smallest neuronal cytoskeleton element
microfilament
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order of neuronal cytoskeleton elements from biggest to smallest
microtubule (20-28nm) - neurofilament (10nm) - microfilament (5nm)
55
Microtubule diameter
20-28nm | biggest cytoskeletal element
56
Microtubule structure
Hollow tube of protein tubulin (13) ``` Made of dimers –⍺/ß tubulin soluble tubulin (⍺/ß) in cell (cytoplasm) - because they are being built ``` Polarized molecule, +/– end add tubulin dimers at + end to elongate (axon) Labile – de- or re-polymerize as needed
57
MAPs
Microtubule Associated Proteins (MAPs) Important in arranging microtubules into networks unique -> identification MAP-2 in soma and dendrite ((specific) - very unique so can use to identify the dendrites as well Tau in dendrite and axon, inc. distal axon
58
what end of the microtubule is added to
only the positive end has tubulin dimers added to it
59
the two different microtubule associated proteins that I need to know
MAP-2 | Tau
60
microtubules are involved in
axonal transport - transport molecules down the axon to where they are needed
61
microtubule features that relate to its function of axonal transport
oriented lengths held in place positive end to axon end

neuroanatomy 2021 (32 decks)

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