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Year 3 - Neuro > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the four components into which a cell is divided?

A

Dendrite
Soma
Axon
Synapse

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2
Q

What does the soma of a nerve cell contain?

A

Mitochondria, ribosomes, ER, nucleus

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3
Q

What does the soma of a nerve cell do?

A

Integrates all the signals until an AP is generated

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4
Q

What does an axon do?

A

Conducts output signals to presynaptic terminals

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5
Q

What is a synapse?

A

Point of chemical communication between neurones

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6
Q

What are the four types of neuron?

A

Unipolar
Pseudounipolar
Bipolar
Multipolar

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7
Q

Which type of neuron is a peripheral autonomic neuron?

A

Unipolar

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8
Q

Which type of neuron is a dorsal root ganglion neuron?

A

Psuedounipolar

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9
Q

Which type of neuron is a retinal neuron?

A

Bipolar

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10
Q

Which type of neuron is a lower motor neuron?

A

Multipolar

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11
Q

Which Golgi type of neurons have short /no axon?

A

Golgi type II

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12
Q

Why does a membrane potential “leak”?

A

Ion channels along the axon which lets current out

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13
Q

What is lambda in terms of the nervous system?

A

The distance which a change in membrane potential can travel before diminishing to 37% of the original

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14
Q

What equation defines lambda

A

Rm/Ri ^0.5

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15
Q

How can Ri be decreased and what effect does this have on lambda?

A

Increases lambda

Increase axon diameter (not viable in vertebrae)

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16
Q

How can Rm be increased and what effect does this have on lambda?

A

Increases lambda

Add myelin

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17
Q

How do Schwann cells myelinate cells?

A

Send out processes to wrap around the axon several times, many surround one axon

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18
Q

How do oligodendrocytes myelinate cells?

A

Each oligodendrocyte surrounds many axons

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19
Q

What is a chemical synapse, structurally?

A

Matric of fibrous extracellular proteins within the cleft that holds synaptic membranes together

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20
Q

What are the three classifications of presynaptic terminal, based on structure?

A

Axodendritic
Axosomatic
Axoaxonic

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21
Q

What is an axodendritic synapse?

A

Axon synapses with a dendrite (most common)

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22
Q

What is an axosomatic synapse?

A

Axon synapses with the soma

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23
Q

What is an axoaxonic synapse?

A

Axon synapses with another axon

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24
Q

What are the classifications of synapse based on function?

A

Excitatory

Inhibitory

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25
Q

How does an excitatory synapse work?

A

Uses glutamate

When released, generates a brief excitatory post-synaptic potential (EPSP)

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26
Q

How does an inhibitory synapse work?

A

Uses GABA and glycine (GABA higher in brain)

Released these to generate a hyperpolarising response or inhibitory post-synaptic potential (IPSP)

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27
Q

What are the two types of synaptic integration?

A

Spatial summation

Temporal Summation

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28
Q

Describe spatial summation

A

Several inputs converge on one neuron to determine its output (whichever type there is more of)

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29
Q

Describe temporal summation

A

Single input of the same type, if enough occur in a short enough time frame it changes the membrane potential

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30
Q

What are the 5 sensations (not including special sensory) ?

A 
Fine touch
Proprioception
Thermosensation
Nociception
Pruriception
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31
Q

Where does the “exteroceptive” division pick up sensation from?

A

Cutaneous sense, from surface of body

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32
Q

What does the proprioceptive division sense?

A

Posture and movement through sensors in muscles, tendons and joints

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33
Q

Where does the enteroceptive division pick up sensation from?

A

Internal body

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34
Q

Where are the first order neurons in the somatosensory pathway found?

A

Dorsal root ganglia
or
Cranial ganglia

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35
Q

Where are the 2nd order neurons in the somatosensory pathway found?

A

Dorsal horn of spinal cord
or
Brainstem nuclei

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36
Q

Where are the 3rd of neurones in the somatosensory cortex found?

A

Thalamic nuclei

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37
Q

How is the signal passed from the first order neuron to the second order neuron in the somatosensory pathway

A

Stimulus opens cation selective ion channels in peripheral terminal or primary sensory afferent, creating depolarising receptor potential
Triggers an AP, frequency is increased with increased membrane potential
APs arrive at central terminal causing graded released of neurotransmitter on second order neurons

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38
Q

What is the sensory unit for touch, pressure and vibration?

A

Skin mechanoreceptors

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39
Q

What is the sensory unit for proprioception?

A

Joint and muscle mechanoreceptors

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40
Q

What is the sensory unit for temperature?

A

Thermoreceptors

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41
Q

What is the sensory unit for pain?

A

Mechanical, thermal and polymodal nociceptors

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42
Q

What is the sensory unit for itch?

A

Itch receptors

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43
Q

Which receptors mediate fine discriminatory touch?

A

Low threshold mechanoreceptors

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44
Q

Which receptors respond to cold, cool, warm and hot but not dangerous stimuli?

A

Low threshold thermoceptors

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45
Q

Which receptors respond to high pressure mechanical stimuli?

A

High threshold mechanoreceptors

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46
Q

Which temperatures do thermal nociceptors respond to?

A

> 45 or

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47
Q

What do chemical nociceptors respond to?

A

Substance in tissue

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48
Q

Which type of receptors constantly fire signals?

A

Stretch receptors

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49
Q

Which type of receptor (based on adaption rate) gives continuous information to the CNS?

A

Slow adaption

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50
Q

What kind of information do fast adaption fibres give to CNS?

A

Acute change

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51
Q

What do very fast adapting fibres respond to?

A

Rapid movement such as vibration

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52
Q

Describe the myelination on A-alpha axons

A

Thick

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53
Q

Describe the myelination on A-beta axons

A

Moderate

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54
Q

Describe the myelination on A-delta axons

A

Thin

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55
Q

Describe the myelination on C fibres

A

None

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56
Q

What is the approx. conduction velocity of A-alpha axons?

A

80-120m/s

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57
Q

What is the approx. conduction velocity of A-beta axons?

A

35-75m/s

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58
Q

What is the approx. conduction velocity of A-delta axons?

A

5-30m/s

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59
Q

What is the approx. conduction velocity of C axons?

A

0.5-2m/s

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60
Q

What is the sensory receptor of A-alpha axons?

A

Proprioceptors of muscle

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61
Q

What is the sensory receptor of A-beta axons?

A

Mechanoreceptors of skin

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62
Q

What is the sensory receptor of A-delta axons?

A

Pain and temp

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63
Q

What is the sensory receptor of C axons?

A

Temperature, pain, itch

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64
Q

What is the receptive field?

A

Territory from which a sensory unit can be excited defined by a “two-point” threshold

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65
Q

Give an example of where receptive field is small on the body

A

Fingertips

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66
Q

Describe the relationship between receptive field and acuity

A

Inversely proportional

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67
Q

What are the four types of low threshold mechanoreceptors?

A

Fast adapting 1 (small RF)
Fast adapting 2 (wide RF)
Slow adapting 1
Slow adapting 2

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68
Q

What is a slow adapting 1 unit otherwise known as?

A

Merkel cell - neurite complex

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69
Q

Where are slow adapting 1 units found?

A

Basal epithelium on hands and soles of feet mostly

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70
Q

Describe the sensory acuity of slow adapting 1 units?

A

High

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71
Q

What are fast adapting 1 units otherwise known as?

A

Meissner corpuscles

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72
Q

What do fast-adapting 1 units sense?

A

Low frequency vibration, stroking and flutter

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73
Q

Describe the acuity of fast-adapting 1 units?

A

High

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74
Q

What are slow adapting 2 units otherwise known as?

A

Ruffini endings

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75
Q

Where are slow adapting 2 units found?

A

Dermis and joint capsules

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76
Q

Describe the core of slow adapting 2 units?

A

Collagenous so axons can branch into it

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77
Q

Where are fast adapting 1 units found?

A

Close to basal epithelium

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78
Q

What is the role of slow adapting 1 units?

A

Signal sustained pressure, sense texture

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79
Q

What are fast-adapting 2 unit otherwise known as?

A

Pacinian corpuscles

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80
Q

Where are fast-adapting 2 units found?

A

Close to periosteum

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81
Q

What do fast adapting 2 units sense?

A

High frequency vibration

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82
Q

Describe the acuity of fast-adapting 2 units

A

Low

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83
Q

Which receptors does hairy skin contain?

A

FA2, SA1, SA2

84
Q

Which two types of fibre do hair units have?

A

Circumferential fibres

Palisade fibres

85
Q

What does grey matter make up in the spinal cord?

A

Dorsal and ventral horns and laminae of Rexed

86
Q

In which laminae of Rexed do nociceptors terminate?

A

Laminae I and II

87
Q

In which laminae of Rexed do low threshold mechanoreceptors terminate?

A

Laminae III, IV, V, VI

88
Q

In which laminae of Rexed do proprioceptors terminate?

A

Laminae VII, VIII, IX

89
Q

Describe who fine touch, pressure, vibration and proprioception get to brain via dorsal column medial lemniscal pathway

A

Enters dorsal horn and synapses with 2nd order neurons
Ascends cord on same side
Synapses in either dorsal column gracile nucleus or cuneate nucleus
Desiccates from 2nd order neuron
Travels to medial lemniscus and ascends to ventral posterior lateral nucleus of thalamus
Synapses in 3rd order neurons
Signal travels to somatosensory cortex via posterior internal capsule

90
Q

What is stereognosis?

A

Ability to recognise an object through touch

91
Q

Describe who crude touch, itch, tickle gets to brain via spinal cord

A

Enters spinal cord, immediately crosses

Ascends spinal cord to synapse in thalamus

92
Q

Where does input from T6 and below run in the dorsal column?

A

Fasciculus gracilis

93
Q

Where does input from T5 and above run in the dorsal column?

A

Fasciculus cuneatus

94
Q

Which is more lateral in the dorsal column, fasciculus gracillis or cuneatus?

A

Fasciculus cuneatus

95
Q

What is lateral inhibition?

A

When one neuron is active, it inhibits the activity of the adjacent neurons via inhibitory interneurons

96
Q

How is somatic information from the anterior head mediated?

A

By two trigeminothalamic pathways

97
Q

Describe the trigeminothalamic pathways

A

Impulses originate at terminal of trigeminal nerves
Synapse on second order neurons in spinal nucleus (pain, temp) or chief sensory nucleus
Projected to the ventroposteriomedial nucleus of the thalamus via trigeminal lemniscus
Sent to cortex via thalamocortical neurons

98
Q

Where is the somatosensory cortex located?

A

Post central gyrus of the parietal cortex posterior to central sulcus and adjacent to posterior parietal cortex

99
Q

What is the central sulcus split into?

A

Brodmann areas 1, 2, 3a, 3b

100
Q

Where does Brodmann area 3a get information from?

A

Muscle spindles

101
Q

What type of information does Brodmann area 3a receive?

A

Proprioceptive information

102
Q

Where does Brodmann area 3b get it’s information from?

A

Cutaneous receptors: Merkel cells and Meissner’s corpuscles and area 3a

103
Q

What type of information does Brodmann area 3b receive?

A

Touch

104
Q

Where does Brodmann area 1 get information from?

A

Cutaneous mechanoreceptors and area 3b

105
Q

What type of information does Brodmann area 1 receive?

A

Texture discrimination

106
Q

Where does Brodmann area 2 get information from?

A

Joint afferent, Golgi tendon organs, areas 3a and 3b

107
Q

What type of information does Brodmann area 2 receive?

A

Object perception

108
Q

What would be the affect of a lesion in Brodmann area 3b?

A

Deficits in texture, shape and dsicrimination

109
Q

What would be the affect of a lesion in Brodmann area 1?

A

Loss of texture discrimination

110
Q

What would be the affect of a lesion in Brodmann area 2?

A

Impaired grasping and size and shape discrimination

111
Q

How many cell layers does the somatosensory cortex have?

A

6

112
Q

Where does most of in the information in the somatosensory cortex terminate?

A

Layer IV

113
Q

What is the role of the posterior parietal cortex?

A

Receive and integrate information from cortical and sub-cortical areas
Interprets all of the sensory information to give a full picture of the environment

114
Q

What can damage to the posterior parietal cortex cause?

A

Agnosia, astereognosis, hemi-spatial neglect

115
Q

Which drugs are examples of Na channel antagonists?

A

Local anaesthetics

116
Q

How are transmitters released at cell synapses?

A

AP depolarises axon terminal
Causes opening of voltage gated Ca2+ channels
Ca2+ enters cell and triggers exocytosis of synaptic vesicle content
Diffuses across synaptic cleft and binds with post synaptic cell

117
Q

What happens to neurotransmitters after response is initiated in post-synaptic cell?

A

Either:
Returned to axon terminal or transported into glial cells
Inactivated by enzymes
Diffuse out of synaptic cleft

118
Q

What is the major inhibitory neurotransmitter?

A

GABA

119
Q

On which receptors does GABA act?

A

Ionotropic (to allow Cl into cell)

120
Q

Which neurotransmitter do interneurons typically use?

A

GABA

121
Q

What neurotransmitters do projection neurons typically use?

A

Glutamate (excitatory)

122
Q

What is the resting membrane potential normally?

A

-70mV

123
Q

What effect do K channel agonist have?

A

Inhibitory

As opens K channel, causes outflow, makes cell more negative

124
Q

What effect do K channel antagonists have?

A

Excitatory

As closes K channel, causes retention, makes cell more positive

125
Q

What type of receptor is responsible for direct gating?

A

Ionotropic receptor

126
Q

What type of receptor is responsible for indirect gating?

A

GPCR

127
Q

What do GPCR do with regards to gating?

A

Modulate neurotransmitter release
Regulate the size of the post-synaptic potential
Modulate channels in soma

128
Q

What is the structure of a glutamate channel?

A

Tetrameric

129
Q

What is the structure of GABA, glycine and nicotinic ACh receptors?

A

Pentameric

130
Q

What are the two GABA receptors in the CNS?

A

GABA(A) - activates Cl- channels

GABA(B) - activates K channels

131
Q

Name a drug which can enhance the action of GABA?

A

Benzodiazepines, baclofen

132
Q

What is “quanta”?

A

Release of neurotransmitter from a single cell

133
Q

What is quanta released by?

A

Purkinje cell - Olivary neuron synapses

Inhibitory basket cell

134
Q

Where are upper motor neurons located?

A

In the motor cortex

135
Q

Where are lower motor neurons located?

A

In spinal cord or brainstem

136
Q

Where are the two enlargements of motor neurons in the spinal cord?

A

Cervical C3-T1

Lumbar L1-S3

137
Q

What is a motor unit?

A

Single alpha-neuron and all of the skeletal muscle is innervates

138
Q

What are smaller motor units for?

A

Fine movements, eg fingers and EO eye muscles

139
Q

What is each muscle fibre innervated by?

A

Single motor axon at the endplate/NMJ, usually at the centre of the fibre

140
Q

What is the motor neuron pool?

A

Collection of alpha-motor neurons which innervate a single muscle

141
Q

How is muscle contraction graded?

A

Through the recruitment of additional synergistic motor units
or
Chance in frequency of AP discharge from alpha motor neuron

142
Q

Which lower motor neurons are more dorsal, flexor or extensor?

A

Flexor

143
Q

Where do lower motor neurones receive input from?

A

Central terminal of dorsal root ganglion
UMNs in motor cortex
Spinal interneurons

144
Q

What does muscle strength depend on?

A

Firing rates of LMNs, number of LMNs and co-ordination of movement
Fibre size and phenotype

145
Q

Which alpha motor neurons are larger, for fast or slow type muscles?

A

Fast type

146
Q

Describe the myotatic reflex

A

Muscle is stretched
Activates Ia afferent stimulating excitatory post-synaptic transmission
Activates alpha motor neuron
Contraction of muscle

147
Q

What are intrafusal fibres?

A

Non-contractile equatorial regions in muscle innervated by Ia (sensory afferent)

148
Q

What supply intrafusal fibres?

A

Gama motor neurons

149
Q

How are intrafusal fibres subdivided?

A

Bag 1/dynamic

Bag 2/static

150
Q

Describe a dynamic intrafusal fibre

A

Sensitive to the rate of change of muscle length, innervated by gamma motor neurons

151
Q

Describe a static intrafusal fibre

A

Sensitive to current length of muscle, innervated by static gamma motor neurons

152
Q

Where do Ia afferent fibres come from?

A

Annulospinal nerve

153
Q

Which is the slower afferent fibre, Ia or II?

A

II

154
Q

What do type II afferent fibres form on intrafusal fibres?

A

Flowerspray endings

155
Q

Which type of intrafusal fibre do type II afferent fibres NOT innervate?

A

Bag 1

156
Q

What do static motor neurons sense?

A

Slow muscle length changes ie sitting -> standing

157
Q

What do dynamic motor neurons sense?

A

Fast muscle length changes like shaking hands

158
Q

Where are Golgi tendon organs found?

A

Between collage fibres between tendon and bone

159
Q

What happens when tension is applied to Golgi tendon organs?

A

Mechanoreceptors are activated

160
Q

What innervated Golgi tendon organs?

A

Groub Ib fibres

161
Q

What is the function of the Golgi tendon organs?

A

To protect muscle from overload

162
Q

Where are proprioceptive axons found?

A

In connective tissue of joints

163
Q

What do proprioceptive axons respond to?

A

Changes in angle, direction, velocity of movement

164
Q

What do horizontal cells in the eye receive input from?

A

Photoreceptors

165
Q

Where do horizontal cells in the eye project to?

A

Other photoreceptors and bipolar cells

166
Q

What do amacrine cells in the eye receive input from?

A

Bipolar cells

167
Q

Where do amacrine cells in the eye project to?

A

Ganglion cells, bipolar cells and other amacrine cells

168
Q

What does “the Dark Current” refer to?

A

When light stimulus hits the retina, membrane potential is inhibited and there is an influx of sodium

169
Q

What does light convert 11-cis-retinal to?

A

All-trans-retinal

170
Q

What does all-trans-retinal activate?

A

Rhodopsin

171
Q

What does rhodopsin activate?

A

G proteins which activate phosphodiesterase

172
Q

If there is more light is there more or less cGMP?

A

Less because phosphodiesterase hydrolyses it

173
Q

Where are cones located?

A

In the fovea

174
Q

What are cones for?

A

Fine and colour vision, seeing in daylight

175
Q

Where are rods found?

A

Along the whole retina excluding fovea

176
Q

What are rods for?

A

Seeing in dim light (ie night)

177
Q

Why is parallel processing important?

A

Compared in the cortex to perceive depth

178
Q

If there is a lesion on the optic tract what is the visual defect?

A

Monocular blindness

179
Q

If there is a lesion at the optic chiasm what is the visual defect?

A

Bitemporal hemianopia

180
Q

If there is a lesion at the striate cortex what is the visual defect?

A

Contralateral hemianopia with foveal sparing

181
Q

If there is a lesion at the optic radiation what is the visual defect?

A

Quadrantanopia

182
Q

Where do spinal interneurons receive input from?

A

Primary sensory axons
Descending axons from the brain
Collaterals of LMNs
Other interneurons

183
Q

What is reciprocal inhibition?

A

When muscles which antagonise the desired movement are inhibited to allow agonist movement to be unopposed

184
Q

What can inhibit Renshaw cells?

A

Strychnine

185
Q

What are Renshaw cells?

A

Inhibitory collateral cells

186
Q

What is pain?

A

An unpleasant, sensory and emotional experience a/w actual tissue damage or described in such terms

187
Q

What are the 3 classifications of pain?

A

Nociceptive, inflammatory and pathological

188
Q

Describe the characteristic of pain which originates in the skin

A

Well localised, pricking, stabbing, burning

189
Q

Describe the characteristic of pain which originates in the muscle

A

Poorly localised, aching, tender, cramping, stabbing

190
Q

Describe the characteristic of pain which originates in the viscera

A

Very poorly localised, dull, vague, nauseating

191
Q

What are nociceptors?

A

Peripheral primary sensory afferent neurons normally activated by intense stimuli

192
Q

What happens when nociceptors relay pain to second order neurons?

A

AP causes voltage activated Ca2+ channels to open
Ca2+ influx causes glutamate release which activates post-synaptic AMPA and NMDA receptors
Influx of Na and Ca into postsynaptic cell
EPSP occurs opening voltage activated Na+ channels

193
Q

What information do A-delta fibres receive?

A

Mechanical and thermal

Stabbing, pricking, lancinating sensation

194
Q

What temperatures do type I and II A-delta fibres activate at?

A

Type I - very hot, 53

Type II - hot, 43

195
Q

What information do C-fibres receive?

A

All noxious stimuli

196
Q

What is hyperalgesia?

A

Increased response/perception of a painful stimulus

197
Q

What is allodynia?

A

Perception of pain with a non-painful stimulus

198
Q

Which receptors perceive noxious heat?

A

TRPA1, TRPC3, TRPV1

199
Q

What pathology can affect TRPV1 receptors?

A

Activated by inflammatory conditions and become sensitised to normal body temperature

200
Q

How do afferent C-fibres carry information to the CNS?

A

Via glutamate release and peptides in the dorsal horn

201
Q

What effect does long term stimulation have on C-fibres?

A

Increases overall excitability

202
Q

What do efferent C-fibres do when stimulated?

A

Release pro-inflammatory mediators from peripheral terminal

203
Q

Where do C-fibres synapse in the spinal cord?

A

Laminae of Rexed I and outer part of II

204
Q

What do C-fibres in laminae of Rexed I do?

A

Excite nociceptive cells

205
Q

What do C-fibres in laminae of Rexed II do?

A

Synapse on interneurons and travel to V to synapse at the wide dynamic range neuron

206
Q

When does viscerosomatic pain occur?

A

When internal organs ruptures and exudate comes into contact with a body wall structure

Year 3 - Neuro (19 decks)

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