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Cortex & pyramidal motor system Flashcards

1
Q

What are the features of the cortex?

A
  • 2-4mm thick (very thin) layer that covers the whole of the brain
  • When spread out flat it is around 1m^2 (large SA), folds to inc SA
  • Cortex lines all of the white matter
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2
Q

What makes up most of white matter?

A

Myelin (oligodendrocytes) is the main componenet - makes it white

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3
Q

Define the cortex

A

A thin mantle of cells that make up the outer surfacde of the brain

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4
Q

What is the cortex composed of?

A

Grey matter (cell bodies)

Many of these cells are neurones, whose myelinated projections constitute the cerebral white matter

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5
Q

What is the most abundant cell in the cortex?

A

Pyramid cells (75-85%)

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6
Q

Where are pyramidal cells found?

A
  • Abundant in the cortex (75-85%)
  • Also in other structures (hippocampus)

Cell bodies make up cortex surrounding brain Their axons =white matter

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7
Q

What is the structure of pyramidal cells?

A
  • Pretty large
  • Soma 10-50um
  • Have one rlly large dendrite that grows upwards & many others that branch off
  • Appear spiny as they have many projections off of the dendrites to communicate w many other cells
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8
Q

Are pyramidal cells exitatory or inhibitory?

A

Excitatory (glutamergic)

It is a major cortical output

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9
Q

Where are granule cells found?

A

In other structures (cerebellum)

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10
Q

What is the structure of granule cells like?

A
  • Soma is <10um
  • Have a smooth stellate (no spines)
  • Small round shaped body
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11
Q

Are granule cells inhibitory or excitatory?

A

Inhibitory cells –> GABAergic interneurones (many inhibitory neurones are called interneurones)

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12
Q

Name 3 types of glial cells:

A
  • Astrocytes
  • Microglia
  • Oligodendrocytes
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13
Q

What is the structure of astrocytes like?

A
  • Characteristic star shape
  • Many dendrites & large cell body
  • Very abundant in brain
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14
Q

What is the role of astrocytes?

A
  • Maintian homeostasis (sequestering K+ ions and glutamine)
  • End feet –> maintain BBB & contribute to blood flow reg
  • Reapir & scarring in brain
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15
Q

What is the structure of microglia cells like?

A

Smaller than astrocytes –> can swell when they are activated by something negative

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16
Q

What is the role of microglia?

A
  • Resident immune cells, fine processes during rest
  • Ramified amoeboid (can swell), mobile when activated
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17
Q

What is the structure of oligodendrocytes?

A

Small cells whose processes form individual nodes of myelin around axon

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18
Q

What is the role of oligodendrocytes?

A

Make up the white matter as they ensheath axons

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19
Q

What are the 6 cortical layers?

A

1 - Molecular

2 - External granular

3 - External pyramidal

4 - Internal granular

5 - Internal pyramidal

6 - Multiform

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20
Q

What is found in the molecular (1) cortical layer?

A

Neurons

Glial cells

Apical dendrites

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21
Q

What is found in the external granular (2) cortical layer?

A

Small pyramidal

Granual neurons

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22
Q

What is found in the external pyramidal (3) cortical layer?

A

Small and medium pyramidal cells & granular cells

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23
Q

What is found in the Internal granular (4) cortical layer?

A

Mostly stellate neutrons, but some pyramidal cells

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24
Q

What is found in the internal pyramidal (5) cortical layer?

A

Large pyramidal neurons

Apical & basilar dendrites

Projections neurons

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25
Q

What is the multiform (6) cortical layer?

A

Small spindle like pyramidal neurons

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26
Q

What does golgi stain do?

A

Impregnates some cells, not all cells but will impregnate the whole cell

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27
Q

What does nissle stain do?

A

Stains all cells but only DNA material so we see the cell body

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28
Q

What are the main ones of Brodmann’s areas we need to know?

A

1-3

4

5&7

6

22

41

44,45

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29
Q

What is the location and name/function of Brodmann’s area 1-3?

A

Location = Postcentral gyrus

Name/function = Primary somatosensory area

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30
Q

What is the location and name/function of Brodmann’s area 4?

A

Location = Precentral gyrus

Name/function = Primary motor area

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31
Q

What is the location and name/function of Brodmann’s area 5, 7?

A

Location = Superior parietal lobule, supramarginal gyrus

Name/function = Somatosensory association areas

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32
Q

What is the location and name/function of Brodmann’s area 6?

A

Location = Middle frontal gyrus

Name/function = Premotor area

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33
Q

What is the location and name/function of Brodmann’s area 22?

A

Location = Superior temporal gyrus

Name/function = Wernicke’s area

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34
Q

What is the location and name/function of Brodmann’s area 41?

A

Location = Superior temporal gyrus

Name/function = Primary auditory area

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35
Q

What is the location and name/function of Brodmann’s area 44, 45?

A

Location = Inferior frontal gyrus

Name/function = Broca’s area

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36
Q

What is the order of signals around the motor areas of the brain?

A
  • Primary somatosensory (1-3)
  • Then to secondary somatosensory cortices (5,7)
  • The to prefrontal cortex (8-10)
  • To premotor cortex (6)
  • Then motor cortex (4)
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37
Q

What happens in the primary somatosensory cortex?

A

The sensory info arrives here

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38
Q

What happens in the secondary somatosensory cortex?

A

Info is recieved from the primary somatosensory cortex & sends onto the Prefrontal cortex

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39
Q

What does the prefrontal cortex do?

A

Recieves info from secodnary somatosensory cortices

Plans movement

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40
Q

What does the premotor cortex do?

A

Recieves info from the prefronal cortex

Organises movement

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41
Q

What happens in the motor cortex?

A

Recieves info from the premotor cortex

Produces movement

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42
Q

How many layers do the motor & sensory cortex have?

A

6 each

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43
Q

What is layer 4 of the motor & sensory cortices, and how do they differ?

A

Input of sensory info

Layer 4 is a granular layer

It’s much larger in the sensory cortex as this is where the sensory info enters

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44
Q

What is layer 5 of the motor & sensory cortices, and how do they differ?

A

Output to other parts of the brain

Much larger in the motor cortex as this is where movement is produced so more cells needed here

45
Q

What is another name for the primary motor cortex?

A

Precentral gyrus

46
Q

What is another name for the primary sensory cortex?

A

Postcentral gyrus

47
Q

What is the role of these following 5 brain areas:

Prefrontal -
Premotor -
Primary motor -
Primary somatosensory -
Secondary somatosensory -

A

Prefrontal - Planning movement
Premotor - Organising movement
Primary motor - Producing movement
Primary somatosensory - Recieving sensation
Secondary somatosensory - Interpreting sensation

48
Q

How are the motor and somatosensory cortices layers arranged?

A

In cellular layers & are organised SOMATOTOPICALLY in an inverted fashion

49
Q

What is Aphasia?

A

Disruption of lanuage and/or speech

50
Q

What are the 2 main language centres we focus on?

A

Broca’s and Wernicke’s area

51
Q

What sort of aphasia happens in Broca’s area?

A

Expressive aphasia

Failure to formulate

52
Q

What sort of aphasia happens in Wernicke’s area?

A

Receptive aphasia

Failure to comprehend

53
Q

How did Broca discover Broca’s area in the brain?

A

He was studying patients suffering from aphasia - language was appropriate but speech was choppy, some words come out abnormally & they were aware of this

He noticed damage in motor cortex (production of movement) & failure to formulate speech properly

54
Q

How was the role of Wernicke’s area discovered?

A

Patients would use completely inappropriate language - had no idea what they were saying was inappropriate

Next to primary auditory cortex so auditory processing was wrong

55
Q

How does brain lateralisation work?

A

There is a tendancy towards lateralisation of some functions in the human brain

56
Q

Give 2 examples of lateralisation:

A

Handedness & language abilities

  • 70% of ppl are right-handed
  • 95% of right handed ppl have left hemisphere lang dominance
  • 60-70% of left-handed ppl have left hemisphere language dominance
57
Q

What is the role of Wernicke’s area?

A

Interprets spoken word

58
Q

What is the role of Broca’s area?

A

Produces speech

59
Q

What is multiple sclerosis (MS)?

A

Auto immune disease that attacks the myelin & thus can produce symptoms of upper & lower motor neurone sydromes

60
Q

How many people does MS affect?

A

160/100 000 people

61
Q

What are the symptoms of MS?

A

Can vary dramatically & can include tingling in the legs, fatigue, balance & coordination problems, blurred vision, diffculties speaking or swallowing

62
Q

What is the most common form of MS?

A

It results symptomatic & asymtomatic periods

63
Q

What is the order of info travelling around the motor system?

A

1 - Visual info req to locate target

2 - Frontal-lobe motor areas plan the reach & command the movement

3 - Spinal cord carries

4 - Motor neurons carry message to muscles of the hand and forearm

5 - Sensory receptors on the fingers send message to sensory cortex saying that the cup has been grasped

6 - Spinal cord carries sensory info to brain

7 - Basal ganglia judge grasp forces & cerebellum correct movement errors

8 - Sensory cortex recieves the message that the cup has been grasped

64
Q

What does the cortex do?

A

It integrates info & produces movement via the pyramidal system

65
Q

What carries motor signals?

A

They’re carried by upper motor neurones

These synapse w lower motor neurons in the brain stem & spinal cord

66
Q

What do lower motor neurons do?

A

Bring motor signals to the muscles

67
Q

What are some components of extrapyramidal systems?

A

Basal ganglia & cerebellum

68
Q

What are the pyramidal tracts?

A

They are projection fibres (also upper motor neurons) that originate in layer 5 of pri,ary motor cortex

69
Q

Revise the motor system compartments diagram

A

fndnof

70
Q

Look at brain scans of white matter

A

fnjfonow

71
Q

What are the 3 types of white matter tracts?

A
  • Association fibres
  • Commissural fibres
  • Projection fibres
72
Q

What does white matter refer to?

A

Myelinated axons & groups of myelinated axons that form white matter tracts

73
Q

What are association fibres?

A

Exchange info within one hemisphere (ipsilateral)

74
Q

What are commissural fibres?

A

Exchange info between hemispheres (contralateral)

75
Q

What are projection fibres?

A

Carry info from the cortex to other regions of the brain & spinal cord (upper motor neurons)

76
Q

What type of cells form white matter?

A

Oligodendrocytes

77
Q

Name some key association fibres

A
  • Cingulum
  • Cingulum (parahippocampal)
  • Superior longitudinal fasciculus
  • Inferior longitudinal fasciculus
  • Fasciculus occipito-frontalis
  • Uncinate fasciculus
78
Q

Where are association fibres found?

A

Only in a single hemisphere, not between them

79
Q

Where are commissural fibres found?

A

Connect the cortices of the two hemispheres

80
Q

Give an example of some commissural fibres?

A
  • Corpus callosum
  • Fornix
  • Anterior commissure
  • Posterior commissure
81
Q

What is the main commissural fibre?

A

The corpus callosum

Runs anterior to posterior direction

Largest of white matter structures

82
Q

What does the corpus callosum do?

A

Connects the cortices

83
Q

What does the fornix do?

A

Connects the hippocampus (temporal lobe) to the hypothalamus & mammillary bodies near the diencephalon

Ppts in memory

84
Q

What does the anterior commissure do?

A

Connects the temporal lobes (amygdala), puts in emotion

85
Q

What does the posterior commissure do?

A

Connects bilateral midbrain nuclei, ppts in the pupillary light reflex

86
Q

What do projection fibres do?

A

Connect the cortices to the other brain structures & the spinal cord

This includes the upper motor neurons

87
Q

What are the pyramidal tracts?

A

Are a sub-population of upper motor neurons that produce movement

88
Q

Where do the pyramidal tracts originate?

A

In layer 5 of the primary motor cortex & converge to form the INTERNAL CAPSULE b4 cont to spinal cord

89
Q

Why are cerebral penducles important for the motor pathway?

A

Its where all the motor neurones converge & project to rest of body

90
Q

What is the internal capsule a part of ?

A

Part of the pyramidal tracts

All motor fibres merge here –> 2nd largest white matter area

Strokes happen here often & can severly affect movement

91
Q

Where do pyramidal tracts originate, pass thru & go to?

A

In the primary motor cortex

Descend & converge into the internal capsule

Pass thru midbrain (cerebral peduncles)

Synapes w lower motor neurons in brain stem & spinal cord

92
Q

Where do pyramidal tracts originate?

A

Layer V of pirmary motor cortex

1 million nerve fibres w a conduction velocity of 60m/s

93
Q

Which 2 tracts make up the pyramidal tracts?

A
  • Corticobulbar tract
  • Corticospinal tract
94
Q

What is the corticobulbar tract?

A

Terminates in the brain stem

Produces head, neck & face movement

95
Q

What is the corticospinal tract?

A

Terminates in the spinal cord

Lateral –> crosses over

Ventral –> remains on the same side

96
Q

Where does corticobulbar tract run?

A

Come from face, head, tongue etc

All motor pathways pass thru cerebral peduncles

Terminates in brain stem & priduces head, brain etc movements

97
Q

Where does the corticospinal tract run?

A

80% crosses over to the other side of body when it reaches spine

98
Q

How is white & grey matter arranged in the spinal cord?

A

White matter on outside & grey matter on inside

99
Q

How are the dorsal and ventral orientations of the spine arranaged & what do they do?

A

Doral = back (motor info) –> flexors

Ventral = front –> extensors

Both make connections in the lower motor neurons

100
Q

What does the lateral corticospinal tract do?

A

Synapses with interneurons & motor neurons that invigorate muscles of the LIMBS and DIDGITS

101
Q

What does the ventral corticospinal tract do?

A

Synapses w interneurons & motor neurons that inntevate the TRUNK (midline of the body)

102
Q

What are some symptoms of upper motor neuron sydrome?

A
  • Muscle weakness and/or stiffness
  • Inc muscle tone (hypertonia)
  • Exaggerated stretch reflexes & clonus (invol contractions), or spasticity (velocity sep reactions)
103
Q

What are some symptoms of lower motor neuron sydrome?

A
  • Muscle weakness
  • Dec muscle tone
  • Inhibited stretch reflexes & spontaneuos firing that cause individual muscle fibre contractions (recordable) & potentially twitching
104
Q

What is amytrophic lateral sclerosis (ALS)?

A

Degeneration of upper & lower motor neurons

105
Q

What is primary lateral sclerosis?

A

Slow degeneration of the corticospinal tract

Begins as weakness & stiffness of the legs that causes balance & walking problems

106
Q

What is pseudobulbar palsy?

A

Degeneration of the cortcobbulbar tract

Facial paralysis, inl the tongue, persistant dribbling or difficulty w speaking, chewing & swallowing

107
Q

What is progressive muscluar atrophy?

A

Lower motor neuron degeneration

Begins as weakness & stiffness of the hands that spreads to the lower body & muscles lose tone

108
Q

How is the spinal cord ventral horn generally organised?

A

Organised topographically

Medial aspects innervate proximal & lateral aspects innervate distal muscles

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