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Stage 1 > Neurobiology Theme 2 > Flashcards

Neurobiology Theme 2 Flashcards

1
Q

what is the average number of neurones in a human

A

100 billion

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2
Q

what id the rate of proliferation during foetal devlepment

A

250,000 neurones/minute

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3
Q

what is the diameter of a neurone cell body

A

4 to 100 microns

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4
Q

what is the length of the longest axon

A

5m

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5
Q

what is the length of all the neurones in the body

A

600 miles long

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6
Q

what is the function of dendrites

A

receive and process information from other neurones and bring it to the soma

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7
Q

what is the function of the axon

A

conducts signals to other neurones via synapses at the axon terminal

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8
Q

what is a nerve

A

bundle of axons in the pns

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9
Q

what is a nerve tract/pathway

A

bundle of axons in the CNS

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10
Q

what is the soma (cell body)

A

houses the cell nucleus (genetic info)

responsible for cell metabolic maintenance

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11
Q

what is a ganglion

A

group of neurone cell bodies in the peripheral ns

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12
Q

what is the nucleus

A

group of neurone cell bodies in the cns

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13
Q

what are the factors that determine the function of the neurone

A

shape of neurones
chemicals used to communicate with other neurones
reaction to neurotransmitters

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14
Q

what are multipolar neurones

A

they have many processes emanating from the cell body (e.g. spinal motor neurones, purknje fibres)
interneurones & motor neurones

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15
Q

what is the function of interneurones

A

form all the neural wiring within the cns

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16
Q

what are motor neurones

A

cell body located in the motor cortex- carries signals from the cns to muscles or glands (efferent)

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17
Q

what are bipolar sensory neurones

A

where one axon communicates with the sense organ and one with the cns (dorsal root ganglion cells in the spinal cord)

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18
Q

what are glial cells & what is their function

A

nerve cells that do not carry nerve impulses

they digest part of dead neurones, manufacture myelin and provide physical & nutritional support

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19
Q

what are they types of glial cells

A

astrocytes
oligodendrocytes
microglia
schwann cells

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20
Q

what is the function of astrocytes

A

they help in regulating extracellular ionic concentrations.
provide physical and metabolic support to the neurones of the cns.
scar forming cells of the cns

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21
Q

what is the function of oligodendrocytes

A

form myelin around axons for electrical insulation in the cns
fewer & shorter processes

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22
Q

what is the function of schwann cells

A

form myelin in the pns

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23
Q

what is the function of microglia & what is their origin

A

phagocytic cells, they clean up dead tissue in case of damage
mesodermal origin

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24
Q

what are the advantages of the golgi method (silver impregnation method)

A

neurones can be studied in isolation from their neighbours (only 1% of cells are stained)
neurones well delineated (outlined)

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25
Q

what is a neurite

A

a projection from the cell body of a neurone

either a dendrite or axon

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26
Q

how many dendrites does a neurone possess

A

one to several
primary dendrites may branch into secondary or tertiary
some dendrites are covered with spines

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27
Q

how many axons does a neurone have & where does it originate

A

as a rule each neurone only has one axon which originates from the axon hillock
they do not taper but may branch

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28
Q

why are dendrites important

A

they receive and process info from other cells making synaptic contacts with them

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29
Q

how do dendrites act as neural integrators

A

neurones with many dendrites can fine tune synaptic inputs (no of dendrites determines no of synaptic contacts received by the same cell)

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30
Q

what tasks is the cerebellum concerned with? are they conscious?

A

“automatic” motor tasked

unconscious coordination of movement

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31
Q

what is the function of the cerebellar purkinje cell

A

makes decisions about which muscles need to be contracted & by how much to keep us in balance

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32
Q

what is the importance of dendrite growth

A

they grow, branch & prune during development allowing establishment & refinement of many connections with other neurones

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33
Q

what is the lipid & protein content of myelin

A

70-80% lipids

20-30% proteins

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34
Q

what is the difference in terms of location and function of oligodendrocytes & schwann cells

A

oligodendrocytes
cns- provide myelin to several axons

schwann cells
pns- provide myelin to only one axon

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35
Q

what are the 3 types of connection between axon terminals & post synaptic cells

A

axosomatic
axoaxonic
axodendritic

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36
Q

what are synaptic boutons

A

small, bulb shaped swellings at the end of axon or along the course of their branches

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37
Q

what are the three axonal transport mechanism & which element of the cytoskeleton do they use

A

fast anterograde
slow anterograde
fast retrograde

microtubules

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38
Q

where does fast anterograde transport from & to

A

from cell body to synaptic terminal

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39
Q

at what pace are chemicals and chemicals transported in fast anterograde

A

100-400 mm/day in mammals

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40
Q

why do active neurones require require fast anterograde flow

A

for quick supply to their axon terminals to replace used neurotransmitters or organelles

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41
Q

what is the role of cytoskeleton in fast anterograde axonal transport

A

entire length of axonal transport is threaded with microtubules
organelles/chemicals transported along microtubule tracks by small kinesin molecules

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42
Q

what are the two different rates of slow anterograde axonal transport

A

type A: 0.2-1mm/day

type B: 2-5mm/day

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43
Q

what is the function of fast retrograde axonal transport & what is its pace

A

movement of surplus membrane particles & neurotoxins and viruses into cns
200-300mm/day

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44
Q

what is the carrier for fast retrograde

A

ATPase dyenin

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45
Q

what is resting potential

A

electrical potential that exists across the membrane when cell is in resting conditions

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46
Q

what is nernst potential used to calculate

A

exact V generated by a specific ion for a known conc difference across a membrane potential permeable to that ion

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47
Q

what does Vnernst reflect

A

balance between electrical and chemical forces (electrochemical gradient) acting on a given ion)

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48
Q

what happens when Vm is exactly Vnernst

A

no net flow of that ion across the membrane

each ion will try to pull Vm to its Vnernst & the ion with the highest permeability (more open channels) will win

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49
Q

what influences Vrest

A

Pk predominantly

Pna ana Pcl to a lesser extent

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50
Q

why is Vrest not identical to Ek

A

there is leakage through Na+ and Cl- channels

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51
Q

what does the Goldman-Hodgkin-katz constant field equation do

A

combines the nernst equations for all ions and takes permeabilities into consideration
gives a better approximation of vrest

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52
Q

what is meant by passive propagation

A

that of which occurs in an electric wire where static membrane properties do not change during electrical signalling

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53
Q

what is meant by active propagation in neurones

A

unlike wires electrical properties in neurones are triggered by changes in Vm which enable conduction of electrical signals without decrement over large distances

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54
Q

what is the difference in signal propagation along a cable and axon

A

along a cable the signal decreases away from point of generation where in an axon the signal does not change with distance

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55
Q

what happens to the current when the axon diameter is increased

A

the current will propagate further

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56
Q

what factors influence signal propagation

A

larger axon

myelin

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57
Q

what is the all or nothing principle

A

if the stimulus too low there is no action potential and if over threshold its same size

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58
Q

how many gates do Na+ channels have

A 
2 
internal (h) - inactivation 
external (m)- activation
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59
Q

how many gates to K+ channels have

A

1

n gate

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60
Q

what is the state of the gates during resting condition of the cell

A

Na+
70% internal (h) open
external (m) gates closed

K+
n gates closed

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61
Q

do the Na+ or K+ channels contribute to Vm under resting conditons

A

no

Vrest is close to Ek (bc of Pleak) and far from Ena

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62
Q

what happens when electrical membrane potential (Vm) decreased to threshold

A

external (m) gates open

Na+ flows inside axon decreasing Vm causing more m gates to opening - rising phase of action potential

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63
Q

what is the effect of sodium permeability on action potential - goldman equation

A

increased Na+ permeability causes Vm to shift towards Ena. the action potential overshoots and reaches its peak value

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64
Q

how is further depolarisation of a membrane stopped after an action potential

A

internal (h) gates on Na+ channels begin to shut down

responsible for the absolute refractory period

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65
Q

how are K+ channels involved in repolarisation of action potential

A

K+ channel slowly open allowing K+ to flow out of cell

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66
Q

why does an undershoot of the action potential occur

A

Pk higher than at rest
membrane more positive on the inside
hyperpolarisation causes K+ channels to close & membrane settles back to rest
internal (h) na+ gates repopen

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67
Q

what does the refractory period do

A

limits the firing frequency

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68
Q

why is the refractory period important

A

info about strength of stimulus is encoded in the firing frequency of action potentials

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69
Q

what is meant by the absolute refractory period

A

a second AP can not be generated regardless of the strength

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70
Q

in which situations can a 2nd AP be generated (relative refractory period)

A
  1. increased threshold to overcome hyperpolarisation

2. reduced amplitude because there are fewer na+ channels are available to open so less na+ can flow into the cell

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71
Q

why does the AP only propagate forwards

A

ahead of ap, Na+ channels are closed ready to be opened

behind ap Na+ channels inactive and so cant be opened (spreading current has no effect)

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72
Q

why do membrane areas covered with myelin not become depolarised

A

myelin means they cannot create APs
the current is forced to travel down to nodes of ranvier where the conc of Na+ channels is high
the AP jumps from node to node

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73
Q

what is the benefit of saltatory conduction

A

ap jump from node to node so increased conduction velocity

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74
Q

what is the speed of large myelinated axon conduction

A

120m/sec

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75
Q

what is the speed of small myelinated axon conduction

A

0.25m/sec

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76
Q

what would happen to axon propagation without myelin

A

it would be delayed

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77
Q

what are the two types of synapses

A

electrical

chemical

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78
Q

which type of synapse is the fastest

A

electrical- no chemical transduction involved

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79
Q

where are electrical synapses found

A

escape reflex neurones
cardiac muscle cells
epithelial cells

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80
Q

where are chemical synapses found

A

neurones

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81
Q

what are gap junctions

A

protein pores that bridge the gap between 2 cells

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82
Q

how are gap junctions different from channels

A

channels allow communication between the cell and the extracellular space

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83
Q

what are the pores in gap junctions made of

A

6 subunits of the protein connexin

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84
Q

of up to what molecular weight will gap junctions allow substances to pass through

A

1000

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85
Q

what is the distance between the membranes in an electrical & chemical synapse

A

electrical- 3.5nm

chemical- 20-40nm

86
Q

which synapse has cytoplasmic continuity

A

electrical

87
Q

what is the structural unit for an electrical synapse

A

gap-junction channel

88
Q

what is the structural units for a chemical synapse

A

vesicles
docking/fusion proteins
channels
postsynaptic receptors

89
Q

what is the transmitter for an electrical synapse

A

ionic current

90
Q

what is the transmitter for a chemical synapse

A

chemical transmitter

91
Q

in which synapse is there a transmission delay and by how long is it

A

chemical

1-5ms

92
Q

what is the direction of transmission in an electrical synapse

A

can be bidirectional

93
Q

what is the transmission direction in a chemical synapse

A

unidirectional

94
Q

what are the two types of receptors to neurotrasmitters

A

ionotropic

metabotropic

95
Q

what is a ionotropic receptor & give an example

A

one that is linked to an ion channel (ligand gated)

ionotropic nicotinic cholinergenic receptor

96
Q

what is a metabotropic receptor & give an example

A

g-protein coupled receptors one that is not directly linked to an ion channel, uses a second messenger

metabotropic muscarinic cholinergic receptor

97
Q

outline the sequence of events in synaptic transmission

A

ap propagated in presynaptic neurone
Ca2+ entry into synaptic knob
release of neurotransmitter by exocytosis
binding of nt to postsynaptic receptor
opening of specific ion channels in subsynaptic membrane

98
Q

what is SNARE

A

vesicle docking and calcium sensing proteins which enable vesicle fusion with the terminal membrane

99
Q

what are V-SNARE proteins

A

vesicle membrane protein

100
Q

what are the 2 types of V-SNARE proteins

A

synaptobrevin

synaptotagmin

101
Q

what is the function of synaptobrevin (V-SNARE)

A

SNARE complex binding protein

102
Q

what is the function of synaptotagmin (V-SNARE)

A

calcium sensory which helps with the fusion when calcium enters the synaptic terminal so the vesicle with neurotransmitter can fuse with the membrane

103
Q

what is a synaptic terminal

A

the ending of a presynaptic neurone where the electrical signal is converted into chemical

104
Q

what are T-SNARE protein and name the 2

A

target membrane proteins
voltage transducer

syntaxin
SNAP-25

105
Q

where are V-SNAREs located

A

on the vesicle

106
Q

where are T-SNAREs located

A

on the membrane of the pre-synaptic membrane

107
Q

what is the importance of recycling neurotransmitters

A

if they remained in the synaptic cleft there would be uncontrolled signalling

108
Q

what does EPSP stand for

A

excitatory post synaptic potential

109
Q

what is the main differences between AP and EPSPs

A

EPSP only reaches threshold
EPSP is decremental
EPSP is much longer (15-20msec)

110
Q

why does temporal summation occur in EPSPs

A

as the time taken is much longer for a single EPSP the signals adduct at high frequency to each other reaching the threshold

111
Q

why is temporal summation id EPSPs important

A

otherwise the EPSP would decrement allowing for an AP to generated

112
Q

what is spatial summation

A

signals come from different inputs

this ‘collects’ signals together allowing for threshold to be met for AP

113
Q

what does IPSP stand for

A

inhibitory post synaptic potential

114
Q

what does IPSP do

A

causes hyperpolarisation of post synaptic neurones

115
Q

what is the importance of IPSPs

A

makes it much harder to generate an AP as you are further away from the threshold

116
Q

what neurotransmitters can cause hyperpolarisation in the post synaptic neurone

A

GABA

glycine

117
Q

what is the function of first order neurones

A

conduct impulses from receptors to spinal cord or brainstem

118
Q

do first order neurones enter on the same or opposite side of the body that the peripheral receptor is located

A

same

119
Q

where are the cel bodies on first order neurones located

A

dorsal root ganglion of spinal nerve

trigeminal ganglion of trigeminal nerve

120
Q

within the cns do 1st order neurones remain on the same side or opposite?

A

same

121
Q

what is the function of second order neurones

A

carry signals from the spinal cord/brainstem to the thalmus

122
Q

what are afferent nerves

A

sensory nerve fibres travelling towards the cns from sensory modalities such as pain, touch, temp etc

123
Q

what afferent nerves

A

motor nerve fibres travelling away away from the cns to effector organs

124
Q

what are the two types of peripheral neurones

A

multipolar

unipolar

125
Q

what are multipolar neurones

A

more than 2 processes emanating from the neurone cell body

located in the cns

126
Q

what are unipolar neurones

A

sensory neurones with cell bodies located in the dorsal root ganglion that enters the spinal cord

127
Q

are sensory neurones myelinated?

A

both myelinated and unmyelianted

128
Q

where are the cell bodies of motor neurones

A

spinal cord

129
Q

where are the cell bodies of sensory neurones

A

dorsal root ganglion

130
Q

does the letter system include sensory or motor fibres

A

both

131
Q

does the roman numeral system include sensory or motor fibres

A

sensory

132
Q

what properties do both the roman numeral and letter system include

A

size of fibres

conduction velocity

133
Q

what do Ia (Aα) fibres do

A

sensory from muscle spindle to the CNS

134
Q

What do Ib (Aα) fibres do?

A

golgi tendon organ to CNS

135
Q

What do II (Aβ) fibres do?

A

muscle spindle, touch pressure, to CNS

136
Q

What do III fibres (Aδ) do?

A

pain, pressure, temperature to cns

137
Q

What do IV fibres (C) do?

A

pain, touch, temperature to cns

138
Q

What do B fibres do?

A

part of the ANS, preganglionic autonomic fibres towards effector organ

139
Q

what do C fibres do

A

part of ANS

postganglion autonomic fibres towards effector organ

140
Q

What do Aα fibres do?

A

signals from cns to skeletal muscles

141
Q

What do Aγ fibres do?

A

signals from cns to muscle spindle

142
Q

Whats the difference between B and C fibres in parasympathetic ANS.

A

B fibres are preganglionic longer than C fibres

143
Q

Whats the difference between B and C fibres in sympathetic ANS.

A

B fibres are shorter than C fibres as the preganglionic axons in the SNS synapse close to the spinal cord

144
Q

What are golgi tendon organs?

A

sensory receptor organ sensing changes in muscle tension

145
Q

How can you tell if a fibre is sensory/motor based on its name?

A

if its in the letter system its both but in the roman numeral its sensory only

146
Q

what does sensation mean

A

conscious/subconscious awareness of external environment

147
Q

what does perception mean

A

interpretation of sensation

148
Q

what are the 2 types of sensory modalities

A

general senses

special senses

149
Q

what are the types of general senses

A

somatic- tactile, thermal, pain, proprioceptive

visceral- conditions of internal organs

150
Q

what is involved in special senses

A

smell, taste, hearing, eqm, balance

151
Q

what are the microscopic features of peripheral nerves

A

free nerve endings
encapsulated nerve endings
separate cells

152
Q

what are the the types of sensory receptors based on location

A

exteroreceptors- outiside of body
interceptors- inside the body
proprioceptors

153
Q

what are the the types of sensory receptors based on stumi detected

A 
mechanoreceptors 
thermoreceptors
nociceptors 
chemoreceptors 
photoreceptors
osmoreceptors
154
Q

what modalities does the dorsal column-medial lemniscus (DC-ML) pathway sense

A

touch/proprioception

155
Q

the first order neurones of the DC-ML pathway terminate and synapse in the medulla, which nuclei do they synapse in

A

cuneate- upper half of body

gracile- lower half

156
Q

what is the dorsal column

A

the pathway on the same side that arises from the brainstem from touch/proprioception where the 1st order neurones ascend uninterruptedly

157
Q

what is the medial lemniscus

A

the pathway on the opposite side from second order neurones after synapsing with 2nd order neurones

158
Q

what modalities are received in the anterolateral system (ALS)

A

pain/temperature

159
Q

what happens to first order neurones in ALS

A

they terminate at the level of the brainstem & synapse with 2nd order neurones

160
Q

what happens to second order neurones in ALS

A

they decussate to the contralateral side and ascend to the thalamus (spinothalamic tract)

161
Q

where does the pain pathway cross over

A

spinal cord

162
Q

where do fine touch pathways cross over

A

brainstem

163
Q

what nerve senses facial sensory info and what is the name of the pathway

A

trigeminal nerve

trigeminothalmic

164
Q

at what level do first order neurones enter when sensory info is received from the face

A

enter through trigeminal ganglion at the level of the brainstem. they terminate here

165
Q

where do second order neurones cross over in the trigeminothalmic pathway

A

brainstem

166
Q

in what part of the thalamus do 2nd order neurones of the trigeminothalmic pathway cross synapse with third order

A

ventral posterior medial nucleus

167
Q

what happens to 1st order neurones in the pain and temp system for the trigeminothalmic pathway

A

they first pass down the brainstem to find their point in the trigeminal nucleus before they ascend

168
Q

what is acute pain

A

short term pain

169
Q

what is chronic pain

A

long term pain

170
Q

where is somatic pain and visceral pain

A

somatic- body

visceral- thorax =abdomen

171
Q

what are nociceptors

A

pain receptors

172
Q

where are nociceptors found

A

skin
muscle
joints

173
Q

what are the two types of pain fibres

A

a delta

c fibres

174
Q

which pain fibre is myelinated

A

a delta

175
Q

which pain fibres has the faster conduction

A

a delta (20m/s)

c fibres only 2m/s

176
Q

what is the size of a delta fibres

A

1-5 micrometers

177
Q

what is the size of c-fibres

A

2.5 micrometers

178
Q

what is the difference between the type of pain between the pain fibres

A

a delta
- sharp fast
c fibres
- dull, slow, ache

179
Q

what do a delta fibres & c fibres respond to

A

mechanical stimulation (pin prick) , painful heat/cold

180
Q

what else do c fibres respond to that a delta fibres dont

A

substances from damaged tissue

181
Q

what laminae do a delta fibres synapse in

A

1 and 5

182
Q

what laminae do c fibres synapse

A

1 and 2 (toward top)

183
Q

which laminae correspond to the marginal zone

A

1

184
Q

which laminae correspond to the substantia gelitinosa

A

2 and 3

185
Q

which laminae correspond to nucleus proprius

A

4 and 5

186
Q

what is peripheral sensitisation

A

usually nociceptors have a high threshold and only respond to noxious stimuli however after damage they become sensitised

  • threshold is lowered
  • responsiveness increased
187
Q

why is peripheral sensitisation important

A

reduced likelihood of further damage

188
Q

after damage & inflammation of nociceptors, chemicals are released causing sensitised nociceptor, what are these chemicals?

A 
atp
histamine 
seretonin 
cytokines 
bradykinin
neuropeptides
189
Q

where can central sensitisation occur

A

spinal cord
thalamus
amygdala
anterior cingulate cortex

190
Q

what is central sensitisation and what can it lead to

A

cns receives prolonged stimulus of pain & becomes sensitised
it overacts pain pathways so non painful signals are amplified and the patient feels pain

191
Q

how does central sensitisation alter synaptic strength

A

more AMPA and NMDA receptors are added to the . membrane so more responsiveness to neurotransmitter. this is due to increased intracellular calcium activation 2nd msg system. TFs are activated causing an upregulation of proteins

192
Q

where does central sensitisation occur

A

lamina 1 and 5 (spinal cord)
thalamus
amydala
anterior cingulate cortex

193
Q

what is likely to occur in patients with TMJ disorders

A

increased pain sensitivity after contraction of facial muscles
increased likelihood of referred pain (head/ neck/ ear)
bilateral pain sensitivity- myofascial pain

194
Q

what does the gate theory of pain suggest

A

non noxious stimuli is able to close gates to painful input preventing pain sensation travelling up the cns

195
Q

what is the role of collateral branches in the gated theory of pain

A

act on interneurones to feedback on pain pathways to inhibit ascending pain pathways

196
Q

in which areas is pain perceived

A 
thalamus 
- ventral posteromedial 
- ventral posterolateral 
somatosensory cortex
hypothalamus 
limbic system
197
Q

what is referred pain

A

feeling pain away from the area of damage

198
Q

how does referred pain occur

A

convergence of sensory input from second order neurones due to signals from the viscera as well, as there are very few sent from spinal cord, causing confusion of the source of pain

199
Q

what are the components of the central control of pain- descending system

A

periaqueductal grey matter
locus coeruleus
raphe nucleus

200
Q

what is the function of the periaqueductal grey matter (around the cerebral aqueduct)

A

receive signals from hypothalamus, medulla and cortex

201
Q

what does the locus coerules do

A

secrete noradrenaline

202
Q

what does the raphe nucleus do

A

release serotonin

203
Q

what is the centrifugal pathways

A

descending system acting to reduce the pain response (release endorphins)

204
Q

where is sensory info received in the centrifugal pathway

A

sensory cortex

frontal limbic cortex

205
Q

at which point are endorphins released in the centrifugal pathways

A

spinal cord

206
Q

what is released at the synapse between the interneurones and the centrifugal pathway

A

gaba- an inhibitory neurotransmitter controlling centrifugal pathways

207
Q

what do opioids do

A

inhibit interneurones and stop the inhibition of the descending pathways

208
Q

what is an example of opioid

A

morphine, codeine

209
Q

what local anaesthetics block na channels in dental treatmetn

A

lidocaine
mepivincaine
articaine

210
Q

what are the COX enzyme inhibitors used to treat tooth aches

A

paracetamol

ibuprofen

Stage 1 (21 decks)

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