S1) Topography of the Nervous System Flashcards

1
Q

What are the four basic components of the central nervous system?

A
  • Cerebral hemispheres
  • Brainstem
  • Cerebellum
  • Spinal cord
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2
Q

What are the four basic components of the peripheral nervous system?

A
  • Dorsal and ventral roots
  • Spinal nerves
  • Peripheral nerves
  • Ganglia
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3
Q

Distinguish between the composition of grey matter and white matter

A
  • Grey matter is composed of cell bodies and dendrites (highly vascular)
  • White matter is composed of axons with no cell bodies(+ supporting cells) connects ares of grey matter
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4
Q

Why does grey matter contain axon terminals?

A

Grey matter contains axons to allow communication with white matter

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5
Q

Why is white matter white?

A

White matter is white due to the presence of fatty myelin

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6
Q

In the peripheral nervous system, identify the equivalent structures of the following:

  • Grey matter
  • White matter
A
  • The PNS equivalent of grey matter is a ganglion
  • The PNS equivalent of white matter is a peripheral nerve
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7
Q

How many segments does the spinal cord consist of?

A

The spinal cord is composed of 31 segments

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8
Q

Describe the structure of a spinal cord segment

A
  • Central core of grey matter
  • Outer shell of white matter

Each segment connects with a mixed spinal nerve through dorsal sensory roots and ventral motor roots

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9
Q

Identify three components of white matter

A
  • Funiculus
  • Tract
  • Fasciculus
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10
Q

What is a funiculus?

A
  • A funiculus is a segment of white matter containing multiple distinct tracts
  • Impulses travel in multiple directions, up and down
  • dorsal funiciulus contains dorsal column tract (ascending)
  • lateral funiciulus contains contains lateral corticospinal trac t (descending)
  • spinothalamic tract (ascending)
  • ventral funiculus contains ventral corticospinal tract (descending)
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11
Q

What is a tract?

A
  • found within each funiculus
  • A tract is an anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter
  • Impulses travel in one direction, either up or down (sensory or motor)
  • eg spinothalamic tract (connects spinal cord dorsal horn to thalamus)
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12
Q

What is a fasciculus?

A

A fasciculus is a subdivision of a tract supplying a distinct region of the body

  • eg gracile fasciculus supplying lower half of body, cuneate fasciculus supplying upper half
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13
Q

Identify the three different regions of grey matter

A
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14
Q

What is a nucleus?

A

A nucleus is a collection of functionally related cell bodies (grey matter)

eg thalamus

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15
Q

What is a cortex?

A

A cortex is a folded sheet of cell bodies found on the surface of a brain structure (grey matter)

outer shell of grey mater found on cerebral hemispheres and the cerebellum

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16
Q

What is a fibre?

A

A fibre is an axon in association with its supporting cells e.g. oligodendrocytes (synonymous with axon)

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17
Q

What are the three types of fibres found in the nervous system?

A
  • Association fibres
  • Commissural fibres
  • Projection fibres
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18
Q

What do association fibres do?

A

Association fibres connect cortical regions within the same hemisphere

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19
Q

What do commisural fibres do?

A

Commissural fibres connect left and right hemispheres or cord halves

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20
Q

What do projection fibres do?

A

Projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa

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21
Q

What are the three components of the brainstem?

A
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22
Q

What is the function of the midbrain (mesencephalon)?

A

The midbrain regulates eye movements and reflex responses to sound and vision

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23
Q

Which processes are regulated by the pons?

A
  • Feeding
  • Sleep
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24
Q

Which key centres are found in the medulla?

A
  • Cardiovascular and respiratory centres
  • Major motor pathway (medullary pyramids)
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25
Q

Where is the central sulcus found?

A

Central sulcus is a key landmark separating the frontal and parietal lobes (coronal plane)

26
Q

Which cortices are found in the following locations:

  • Precentral gyrus
  • Postcentral gyrus
A
  • Precentral gyrus: contains primary motor cortex
  • Postcentral gyrus: contains primary sensory cortex
27
Q

Where is the lateral fissure found?

A

The lateral fissure is a key landmark separating the temporal lobe from the frontal/parietal lobes

28
Q

Where is the parieto-occipital sulcus found?

A

Parieto-occipital sulcus is a key landmark separating the parietal lobe from the occipital lobe

can only see this in the middle of the brain

29
Q

Where is the calcarine sulcus found?

A

The calcarine sulcus is a key landmark surrounded by the primary visual cortex

30
Q

What is the optic chiasm?

A

The optic chiasm is a site where fibres in the visual system cross over

31
Q

What is the uncus?

A
  • The uncus is a part of the temporal lobe that can herniate, compressing the midbrain
  • It has an important olfactory role (smell)

part of hippocampus, emotions

32
Q

What are the medullary pyramids?

A

The medullary pyramids are a location of descending motor fibres

this is a major pathway

33
Q

What is the parahippocampal gyrus?

A

The parahippocampal gyrus is a key cortical region for memory encoding

34
Q

What is the corpus callosum?

A

The corpus callosum consists of fibres connecting the two cerebral hemispheres otherwise left and right are not in coordinaton

35
Q

What is the thalamus?

A

The thalamus is a sensory relay station projecting to the sensory cortex

the final point that sensory information has to pass to reach the thalamus

36
Q

What is the cingulate gyrus?

A

The cingulate gyrus is a cortical area important for emotion and memory, grey matter

37
Q

What is the hypothalamus?

A

The hypothalamus is an essential centre for homeostasis

38
Q

What is the fornix?

A

The fornix is a major output pathway from the hippocampus

39
Q

What is the tectum?

A

The tectum is the dorsal part of the midbrain involved in involuntary reflex responses to auditory and visual stimuli

40
Q

What is the cerebellar tonsil?

A

The cerebellar tonsil is a part of the cerebellum that can herniate and compress the medulla

if there is an increase in intracranial pressure then this will force this area down and crush the medulla

41
Q

Having developed from a hollow tube, the brain is itself hollow.

What are the cavities in the brain called?

A

The cavities in the brain are called ventricles

42
Q

Describe the layout of the ventricular system

A
43
Q

What is found inside the brain ventricles?

A

The ventricles each contain choroid plexus (highly vascular0 , which makes a total of 600-700ml of cerebrospinal fluid per day

44
Q

What types of functions does CSF have?

A

CSF has both metabolic and mechanical functions

  • it is important in supporting the brain and making it weightless
  • contains glucose and good for immunity
45
Q

Describe the circulation of cerebrospinal fluid

A

CSF circulates through the ventricular system and subarachnoid space before being reabsorbed at the arachnoid granulations in the superior sagittal sinus (and some other sites) and then gets reabsorbed into the venous system

46
Q

what is a gyrus and a sulcus

A
  • gyrus → raised fold of cerebral cortex
  • sulcus → valley between adjacent gyri
47
Q

what is a fissure?

A
  • large groove in between adjured hemispheres (lobes)
48
Q

pathway of the CSF through the brain ventricles

A
  1. choroid plexus makes CSF
  2. most CSF made in the lateral ventricles
  3. CSF then circulates through intraventricular foramen → third ventricle
  4. then drained to the fourth ventricle via the cerebral aqueduct
  5. CSF drains through 2 lateral apertures and median aperture in the 4th ventricle
49
Q

blockage of the ventricular system

A
  • blockage of a part of the system → upstream dilation and damage to surrounding structures
  • cerebral aqueduct is a common sight due to stenosis or a tumour
  • blockage of the cerebral aqueduct = dilation of 3rd and 2nd ventricles but normal 4th ventricle
50
Q

what are cerebral peduncles (white matter) in the midbrain

A
  • contain descending corticospinal fibres from ipsilateral hemispheres
51
Q

what is substantia Nigra (grey matter) in the midbrain

A
  • contains dopaminergic neurones that project to striatum
52
Q

what is the red nucleus (grey matter) in the midbrain

A
  • well distinct and gives rise to axons that travel to the cord in vestigial rubrospinal tract (controlling muscle tones and flexion)
53
Q

what is the oculomotor nucleus (grey matter) in the midbrain

A
  • contains lower motor neurone cell bodies projecting through oculomotor nerve to all bar two of extra ocular muscles
54
Q

what is Edinger-Westphal nucleus (grey matter) in midbrain

A

contains parasympathetic preganglionic neurones that project to the ciliary ganglion in the orbit to cause pupillary constriction

55
Q

what is Periaqueductal grey matter in the midbrain

A

Periaqueductal grey matter is an area surrounding the cerebral aqueduct that has roles in pain transmission and micturition

56
Q

what are medial lemniscus and spinothalamic tract

A

medial lemniscus (connecting gracile/cuneate nucleus to thalamus) and spinothalamic tract (connecting spinal dorsal horn to thalamus) path through the midbrain (they have to get to the thalamus!

57
Q

what is Superior/inferior colliculus (grey matter)

A

Superior/inferior colliculus (grey matter) regulate reflex responses to visual and auditory stimuli respectively

58
Q

how are cell bodies in the grey matter cord organised

A

in columns

organised into laminae

59
Q

which space do bridging veins traverse

A

subdural

60
Q

what is another term for crus cerebri

A

cerebella peduncles that connect the cerebral hemispheres to the brainstem

61
Q

what layer is the falx cerebri covered in

A

meningeal dura

62
Q

what dura covers brain and the spinal cord

A
  • occipital - cervical junction where the periosteal layer covering the brain turns into meningeal dura