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MD4001 > Cerebral Cortex - from cells to function > Flashcards

Cerebral Cortex - from cells to function Flashcards

1
Q

What is the principle axonal target?

A

The dendritic spines

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2
Q

What is a unipolar neuron?

A

Single extension: There is a peripheral sprout that collects sensory information and there is a central sprout.

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3
Q

What is a bipolar neuron?

A

There is a single dendrite which senses and sends info to the cell body and there is an axon

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4
Q

What is a multipolar neuron?

A

Lots of dendrites and a single axon

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5
Q

What is an interneuron?

A
  • A type of multipolar neuron
  • local processing
  • Short axon
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6
Q

What is a pyramidal cell?

A

• Multipolar cell with a long axon

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7
Q

Describe myelination in the PNS

A
  • Schwann cells make a wrapping around a single axon
  • you can find the nucleus
  • One Schwann cell builds one internode
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8
Q

Describe myelination in the CNS

A
  • Oligodendrocytes have multiple processes to wrap around different neurones
  • One oligodendrocyte builds a number of internodes
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9
Q

Describe the non myelinated neurones in both the CNS and the PNS

A
  • In the CNS: unmyelinated neurones are not associated with any glial cells
  • In the PNS: Schwann cells envelope the unmyelinated axons, contacting one or more of the axons
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10
Q

Describe conduction in non myelinated neurones

A
  • Continuous conduction because of passive current flow

* example: sensory fibres carrying pain, itch and temperature

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11
Q

What is multiple sclerosis?

A
  • A phasic disease which results in demyelination
  • Caused by an immune attack/ inflammation of T cells (macrophage mediated)
  • This can result in a conduction block (slowing of propagation) and cross talk
  • Paraesthesia and crosstalk
  • Some re-myelination can occur
  • There will be some permanent loss (due to cell death/axonal loss)
  • Plaques and lesions will be seen throughout the CNS
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12
Q

What is white matter?

A

Collection of nerve fibres, many of which are coated with insulating fatty myelin

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13
Q

What is grey matter?

A

Contains neuron cell bodies, synapses and processes

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14
Q

What are the glial cells of the CNS?

A
  • Oligodendrocytes
  • Astrocytes
  • Microglia
  • Ependyma (lining cells of the CNS cavities)
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15
Q

What are the glial cells of the PNS?

A
  • Schwann cells

* Satellite cells (support the cells in the ganglia)

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16
Q

What are astrocytes?

A
  • ‘star cells’

* They offer metabolic and structural/mechanical support

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17
Q

What are the roles of astrocytes?

A
  • Water distribution
  • Potassium buffering
  • ROS (reactive oxygen species) Scavenging
  • Define architecture
  • Regulate migration/pruning of synapses/synaptogenesis
  • Help maintain (but don’t make up) the blood brain barrier
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18
Q

What type of astrocyte is present in white matter?

A

Fibrous astrocyte

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19
Q

What type of astrocyte is present in grey matter?

A

Protoplasmic astrocyte

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20
Q

What is the blood brain barrier?

A

A barrier composed of endothelial cells and their tight junctions

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21
Q

What is the integrity of the blood brain barrier highly dependent on?

A

The ‘end feet’ (or foot processes) of astrocytes

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22
Q

What are microglia?

A

• Resident macrophages of the central nervous system

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23
Q

What are the functions of microglia?

A
  • Phagocytosis and antigen presentation (immune response)

* Synaptic pruning

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24
Q

Where do microglial cells originate?

A

• They are blood series cells (unlike the other glial cells, they don’t originate from the epithelium in the neural tube)

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25
Q

What are ependymal cells?

A
  • Ciliated cuboidal epithelial cells that line the ventricle as part of a plexus and secrete and reabsorb CSF
  • Specialised ependyma secrete CSF on the choroid plexus
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26
Q

What are the lobes of the brain and where are they located

A
  • Frontal (anterior superior part of the brain)
  • parietal (middle superior part of brain)
  • Occipital (posterior part)
  • Temporal (middle inferior part of the brain)
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27
Q

What is the neocortex?

A

Part of the cerebral cortex (which is the external grey matter)where the cells are arranged into 6 layers

28
Q

How many cell layers are there in the paleocortex?

A

3

29
Q

How many layers are there in the archicortex (hippocampus)?

A

4

30
Q

What are the 6 layers in the neocortex?

A
  • Molecular layer
  • External granular layer
  • External pyramidal layer
  • Internal granular
  • Internal pyramidal layer
  • Multiform layer
31
Q

Describe the granular layer of the neocortex

A
  • Contain granule (stellate) neurones which are multipolar with short axons
  • Local processing occurs
  • There is more receiving in this layer
32
Q

Describe the pyramidal layer of the neocortex

A
  • Contain pyramidal cells
  • Multipolar neurones with long axons
  • More output/sending in this layer
33
Q

What gives a striated appearance to the primary visual (striate) cortex?

A

The fourth layer is well developed (layers vary in thickness with function from region to region)

34
Q

Describe column/barrel representation in the somatosensory cortex

A
  • Columns appear as functional units linked to sensory input
  • Columns are associated with different modalities of sensation for a given part of the body
  • The barrels have more information flow up and down as opposed to side to side
  • their size is not fixed and is determined on the extent of the input
  • Columns arise from experience, not pre existing subunits
35
Q

Where is the primary visual cortex located?

A

In the occipital lobe, localised in a small area medially

36
Q

What is the function fo the primary visual cortex?

A

It responds to simple visual stimuli/simple patterns

37
Q

What makes up most of the occipital lobe?

A

The association cortex - for higher order processing

38
Q

Describe the visual cortex dorsal and ventral dual stream model

A

• There are 2 pathways, one is vision for action (movement) superiorly, and one for vision perception (recognition) towards the temporal lobe (where and what pathways)
• The vision for action pathway:
- integrates motion vs object locations
- co-ordinates visual guided action for skilled movements
- guides visual attention
• Vision perception:
- recognition (inferno-temporal cortex)
- Distinguishes spatial patterns, objects and faces
- stores visual memory
- recognises the significance of both objects and faces

39
Q

Where is the primary motor cortex?

A
  • Pre-central gyrus

* Frontal lobe just before the central sulcus

40
Q

What is the function of the primary motor cortex?

A
  • It has more direct control of motor activity than any other motor area
  • It is the director of force, speed and direction of muscle contraction
41
Q

Describe somatotopy

A
  • Body regions ‘map’ onto the motor cortex

* Certain parts of the body will have an enlarged representation e.g. the hand and the face (fine motor)

42
Q

What makes up the motor association cortex?

A
  • Supplementary motor area
  • Premotor cortex
  • Posterior parietal complex
43
Q

Describe the function of the supplementary motor area

A
  • Simple movement
  • Planning complex movement (especially with 2 hands)
  • Mental reversal of complex movement
  • Practice related, sequential movements
44
Q

Describe the function of the premotor cortex

A
  • Preparation for action
  • Posture and gait
  • Integration of spatial awareness and planned movement
45
Q

Describe the function of the posterior parietal complex

A

• Integrates visual information to formulate motor commands

46
Q

Broadly, what is the motor association cortex responsible for?

A

•The integration and complex processing of cognate primary cortex info. There are 2 types recognised:

  • Unimodal (one type of modality)
  • Polymodal (multiple modal input e.g. vision and somatic sensation in the dorsal stream)
47
Q

Where is the primary somatosensory cortex?

A

• Postcentral gyrus - motor and sensory are close together

48
Q

What are the functions of the association somatosensory cortex?

A
  • Awareness/perception in space (orientation)
  • Rearrangement of memories
  • Organising grasping movement
  • Number processing
  • Mirror neurons (fires both when doing and observing)
49
Q

What would damage to the superior parietal lobe lead to?

A

Problems with visumotor integration (optic integration)

50
Q

What would damage to the inferior parietal lobe lead to?

A

Contralateral neglect (patient ignores half of their body) and/or astereognosis (inability to recognise objects by touch)

51
Q

What are the functions of the pre-frontal region association cortex?

A
  • Morality
  • Contributes to attention
  • Planning
  • Working memory
  • Conscious decision making
  • Social behaviour regulation
52
Q

What are the features of pre-frontal lobe damage?

A
  • Personality changes
  • Deficits in planning
  • Perseveration (repetition of a response)
  • Primitive reflexes (suckling reflex)
  • Abuloa (slowness of intellect)
53
Q

What would happen as a result of a lesion in Broca’s area ?

A
  • Expressive aphasia
  • Language is reduced to disjointed words and sentence structure is poor
  • Comprehension is ok
54
Q

Where is Broca’s area?

A

In the frontal lobe next to the temporal lobe

55
Q

What would happen if there was a lesion in Wernicke’s area?

A
  • It could lead to repetitive aphasia

* Inability to understand/generate meaningful language

56
Q

What connects Broca’s area and Wernicke’s area?

A

DTI of arcuate fasciculus

57
Q

What would happen if there was damage to the DTI of arcuate fasciculus?

A

Conduction aphasia (difficulty repeating words/phrases)

58
Q

Where does 96% of language processing occur?

A

In the left hemisphere

59
Q

Dorsal stream of language specialisation

A

Maps acoustic speech to articulatory networks in the frontal lobe

60
Q

Ventral stream of language specialisation

A

Comprehension, bilateral

61
Q

What does repeated stimulation of neuronal pathways do?

A

Modifies dendritic spines

62
Q

What is long term potentiation

A

Synapses become strengthened

63
Q

Describe the specialisation of the hemispheres

A
  • Right: better at language and calculation

* Left: better at drawing, music and spatial perception

64
Q

Describe the feel the keys experiment

A

The left hand feels a set of keys and the right cortex recognises this but cannot activate the language centres in the left hemisphere to speak the word ‘keys’

65
Q

What are the 3 ways in which communication in the Brian occurs?

A
  • Commissural: cortex to cortex - crosses over the midline
  • Association: cortex to cortex - stays on the same side
  • Projection: communicates with the other structures inside and outside the brain
66
Q

What is the largest commissural bundle?

A

The corpus callosum

MD4001 (28 decks)

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