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YEAR 2 - The Nervous System > 18. CNS Morphology > Flashcards

18. CNS Morphology Flashcards

1
Q

At what levels do the efferent sympathetic and parasympathetic neurons emerge from the spinal cord?

A
  • Sympathetic -> T1-L2
  • Parasympathetic -> S2-S4
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2
Q

At what point does closure of the neural tube start and end?

A

It starts in the middle, then proceeds in both the the anterior and posterior directions.

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3
Q

Describe what happens if the posterior end of the neural tube fails to close.

A
  • Spina bifida
  • Not typically fatal but varies in degree of disability, with some individuals experiencing no symptoms but a hairy patch on the lower back, while others have difficulty with walking and bowel control, as well as hydrocephalus.
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4
Q

How can the incidence of neural tube defects be reduced? [EXTRA]

A

Folic acid supplementation during pregnancy can reduce the likelihood of developing NTDs, but there is little evidence to suggest it can prevent other defects, such as cleft palate. (De-Regil, 2015)

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5
Q

Describe the patterning of the neural tube in the anteroposterior axis.

A
  • The node (at the posterior end of the tube) secretes signals to lead to the rhythmic ‘clock’ creation of somites through early development.
  • Somites regulate the emergence of the peripheral nerves from a continuous set of nerve roots into a segmentally arranged pattern of spinal nerves.
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6
Q

At what end of the neural tube is the node found?

A

Posterior

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7
Q

Give some clinical relevance for dermatomes. [EXTRA?]

A

Shingles infections show symptoms along dermatomes.

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8
Q

What is the name for the end of the spinal cord?

A

Conus medullaris

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9
Q

What is the name for the bundle of nerves that continues after the spinal cord ends?

A

Cauda equina (horse’s tail) -> These are dorsal and ventral nerve roots

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10
Q

Below where the spinal cord ends, what is the name for the space?

A

Subarachnoid space

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11
Q

At what level does the subarachnoid space end? [IMPORTANT]

A

S2

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12
Q

What are the meninges?

A
  • The membranous coverings of the brain and spinal cord.
  • There are three layers of meninges, known as the dura mater, arachnoid mater and pia mater.
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13
Q

ADD FLASHCARDS ON THE FUNCTIONS OF EACH OF THE MENINGES.

A

Do it.

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14
Q

Which space does lumbar puncture sample from?

A

Subarachnoid space (which contains the CSF).

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15
Q

At what height is lumbar puncture done and in what position?

A

L4/L5 level in the foetal position

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16
Q

Name three reasons why you might do lumbar puncture.

A
  • Injection of spinal anaesthetic
  • Sampling of the CSF
  • To decrease intracranial pressure
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17
Q

What is the artery of Adamkiewicz?

A
  • It is a reinforcing artery for the lumbo-sacral region of the spinal cord
  • Arises from a left posterior intercostal artery at the level of the 9th to 12th intercostal artery, which branches from the aorta

Aorta -> Posterior intercostal artery -> Artery of Adamkiewicz

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18
Q

How can you identidy what level a cross-section of the spinal cord is taken from?

A

Look at the proportions of grey and white matter.

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19
Q

Describe how the white matter changes in shape along the length of the spinal cord.

A

As you go from cranial to caudal, both the ascending and descending tracts get smaller, as fewer axons are still running at this point.

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20
Q

At what points does the spinal cord have enlargements? What parts are enlarged? Why?

[IMPORTANT]

A
  • Cervical enlargement (C3-T2)
  • Lumbar enlargement (L1-S2)
  • These are due to enlargements in the grey matter
  • This is because these regions supply the limbs, which reflects the greater innervation of the limbs
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21
Q

What neurons does the lateral horn of the grey matter contain in the thoracic region?

A

Pre-ganglionic sympathetic

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22
Q

What is the intermediolateral nucleus?

A

The intermediolateral nucleus (IML) is a region of grey matter found in one of the three grey columns of the spinal cord, the lateral grey column. This is Rexed lamina VII.

The intermediolateral cell column exists at vertebral levels T1 – L2 and mediates the entire sympathetic innervation of the body, but the nucleus resides in the grey matter of the spinal cord.

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23
Q

Describe the formation of the spinal cord.

A

Neurulation:

  • The notochord signals to induce the ectoderm above it to become the neural plate (neuroectoderm)
  • Due to mass proliferation, the neural plate starts to fold, forming a neural groove
  • The two sides of the neural groove come together, forming the neural tube (with a ventricle in the middle)
  • This forms the spinal cord
  • The cells just above the neural tube are the neural crest cells, which form the PNS
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24
Q

Describe what happens if the anterior end of the neural tube fails to close.

A
  • Anencephaly
  • This occurs in about 1 in every 1000 births
  • It is usually fatal
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25
Q

Describe some experimental evidence for the importance of the notochord in patterning the neural tube. [EXTRA]

A

Holtfreter 1933:

  • In a normal neural tube, motor neurons develop bilaterally near the notochord
  • When an additional notochord was transplanted near the side of the neural tube, extra motor neurons differentiated near it
  • When the notochord was removed, no motor neurons differentiated in the spinal cord
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26
Q

Describe the patterning of the spinal cord in the dorsoventral axis.

A
  • BMPs (bone morphogenic proteins) from the overlying ectoderm -> Specify the roof plate and subsequent dorsal horn formation
  • Shh from the notochord -> Specifies floor plate and ventral motor neurons
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27
Q

What does the spinal cord supply motor information to and where does each originate from?

A
  • Skeletal muscles (motor) -> From ventral horn
  • Blood vessels, glands and viscera (sympathetic and parasympathetic) -> From lateral horn
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28
Q

Give some experimental evidence for the patterning of the neural tube by Shh. [EXTRA]

A

(Briscoe 2000) - “A homeodomain protein code specifies progenitor cell identity and neuronal fate in the ventral neural tube”

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29
Q

During development, what are the dorsal and ventral halves of the neural tube called? What separates them?

A
  • Dorsal side is the alar plate
  • Ventral side is the basal plate

They are separated by a groove called the sulcus limitans.

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30
Q

How do somites affect the emergence of peripheral nerves from the spinal cord?

A

Somites are involved in axon guidance:

  • Axons grow out through the anterior part of the somite (S) only.
  • The posterior part repels, while the anterior attracts axon growth cones.
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31
Q

What height does the spinal cord end in humans and newborns? [IMPORTANT]

A
  • L1/L2 in adults
  • L3/L4 in newborns
  • This is due to differential growth during development
  • This means that spinal cord segments do not correspond to vertebral segments in adults but the spinal nerves for each segment exit at the level of the corresponding vertebra.
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32
Q

What are the different layers and spaces covering the spinal cord? [IMPORTANT]

A
  • Pia mater -> Covers the spinal cord
  • Subarachnoid space -> Between the pia and arachnoid maters, Contains the CSF
  • Arachnoid mater
  • Subdural space -> Potential space between the arachnoid and dura maters
  • Dura mater
  • Epidural space -> Contains fat
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33
Q

Draw the arrangement of the meninges in the skull.

A
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34
Q

Describe the blood supply to the spinal cord. [IMPORTANT]

A
  • Aortic arch gives off the right and left subclavian arteries
  • These give rise to a vertebral artery each
  • The vertebral arteries give rise to the anterior (x1) and posterior (x2) spinal arteries
  • The artery of Adamkiewicz branches from the descending aorta (via a posterior intercostal artery) and is an important reinforcing artery for the lumbo-sacral part of the spinal cord (NOTE: There are reinforcing arteries for all segments of the spinal cord)
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35
Q

How many anterior and posterior spinal arteries are there?

A
  • 1 anterior
  • 2 posterior
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36
Q

What are the dorsal and ventral horns of the spinal cord?

A

They are the tips of the H-shaped grey matter in the spinal cord.

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37
Q

What are dorsal and ventral roots?

A

The two parts emerging from the spinal cord that join to make a spinal nerve.

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38
Q

What is a dorsal root ganglion?

A

A cluster found in the dorsal root of a spinal nerve, containing the cell bodies of sensory neurons.

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39
Q

Which section of the spinal cord has a distinct shape?

A

The thoracic region has a distinct H-shaped grey matter, with small ventral and dorsal horns, as well as distinct LATERAL horns.

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40
Q

Draw how the spinal cord changes along its length.

A
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41
Q

Draw and compare the cross-section of the spinal cord in the cervical, thoracic and lumbar regions.

A

Note:

  • There is the distinct H-shaped grey matter in the thoracic region, with the lateral horn
  • There are lots of large alpha fibres in the cervical and lumbar regions (circled in red)
  • There is the spinocerebellar tract in the cervical and thoracic regions (circled in blue). This is not so distinct in the lumbar region, since the afferent fibres that eventually join the spinocerebellar tracts via Clarke’s column
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42
Q

Describe the organisation of the neurons in the ventral horn of the spinal cord. [IMPORTANT]

A

As mentioned earlier, the ventral horn contains the lateral and medial motor columns (as well as the interneurons):

  • The medial motor neurons innervate the axial muscles (more proximal), while the lateral motor neurons innervate the limb muscles (more distal)
  • Neurons innervating extensor muscles are more ventral, while neurons innervating flexor muscles are more dorsal

This means that the lateral motor columns are only found in the lumbar and branchial regions of the spinal cord [CHECK THIS].

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43
Q

What sort of fibres originate in the ventral horn of the spinal cord? What do they innervate?

A
  • Aα -> Somatic efferent fibres to extrafusal muscles
  • Aγ -> Somatic efferent fibres to intrafusal muscles (Skeletal muscle fibers that serve as specialized sensory organs in proprioception that detect the amount and rate of change in length of a muscle.They constitute the muscle spindle.)
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44
Q

Draw the Rexed laminae.

A
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45
Q

What are the Rexed lamina?

A

They are bands of neurons in the grey matter of the spinal cord, with the neurons in each lamina possessing a different function.

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46
Q

What are the important zones in the dorsal horn of the grey matter and what laminae do these include? [IMPORTANT]

A
  • Lamina 1 -> Marginal zone (a.k.a. posteromarginal zone)
  • Lamina 2 -> Substantia gelatinosa
  • Laminae 3-5 -> Nucleus proprius (a.k.a main sensory nucleus)
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47
Q

Draw the main nuclei and laminae in the grey matter of the spinal cord. [IMPORTANT]

A

Dorsal horn:

  • Marginal zone
  • Substantia gelatinosa
  • Nucleus proprius

Lateral horn (in thoracic region?):

  • Thoracic nucleus (Clarke’s column)
  • Intermediolateral nucleus

Ventral horn:

  • Lateral motor pool
  • Medial motor pool
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48
Q

Label this spinal cord cross-section.

A
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49
Q

What does the brainstem consist of?

A
  • Midbrain
  • Pons
  • Medulla
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50
Q

What do the telencephalon (cerebrum) consist of?

A
  • Cerebral cortex
  • Basal ganglia
  • Hippocampus
  • Amygdala
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51
Q

What are the main divisions of the brain (in terms of development)?

A
  • Prosencephalon gives rise to:
    • Telencephalon (cerebrum) -> Cerebral cortex and subcortical structures (hippocampus, amygdala and basal ganglia)
    • Diencephalon -> Thalamus and hypothalamus
  • Mesencephalon -> Midbrain
  • Rhombencephalon gives rise to:
    • Metencephalon -> Pons and cerebellum
    • Myelencephalon -> Medulla
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52
Q

What is confusing about the cerebellum?

A

It is part of the hindbrain (rhombencephalon) and develops adjacent to the pons, but it is not part of the brainstem (while the midbrain is).

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53
Q

Label the different embryonic origins of parts of the brain on a diagram.

A
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54
Q

Where in the brain are the thalamus and hypothalamus?

A
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55
Q

Label this image of the brain.

A
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56
Q

What are the main lobes of the brain you need to know about?

A
  • Frontal
  • Parietal
  • Occipital
  • Temporal
  • Insular
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57
Q

What is this and what is the function?

A
  • Frontal lobe
  • Functions:
    • Movement
    • Language
    • Executive functions -> A collection of cognitive skills including the ability to plan, organise, initiate, self-monitor and control one’s responses in order to achieve a goal.
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58
Q

What is this and what is the function?

A
  • Occipital lobe
  • Functions:
    • Vision and integrating visual information
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59
Q

What is this and what is the function?

A
  • Parietal lobe
  • Functions:
    • Sensory inputs such as touch, pressure, heat, cold, and pain
    • Sense of space and time
    • Reading and comprehension
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60
Q

What is this and what is the function?

A
  • Temporal lobe
  • Functions:
    • Auditory information
    • Language
    • Memory
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61
Q

What is this and what is the function?

A
  • Insular lobe
  • Functions (not that well-known):
    • Sensory processing
    • Feelings and emotions
    • Autonomic control
    • Decision-making
    • Self-awareness
    • Social functions like empathy.
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62
Q

What is this?

A

Insular lobe (a.k.a. insula)

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63
Q

Where is the insular lobe found?

A

It is deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes).

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64
Q

What are the main brain sulci you need to know?

A
  • Longitudinal (sagittal)
  • Lateral
  • Central
  • Parieto-occipital
  • Calcarine
  • Cingulate
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65
Q

What is this?

A

Longitudinal (sagittal) sulcus

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66
Q

What is this?

A

Lateral sulcus

(Separates the frontal and parietal lobes from the temporal lobe)

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67
Q

What is this?

A

Central sulcus

(Separates the parietal lobe from the frontal lobe)

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68
Q

What is this?

A

Central sulcus

(Separates the parietal lobe from the frontal lobe)

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69
Q

What is this?

A

Parieto-occipital sulcus

(Note that is is mostly visible from the medial side, as shown)

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70
Q

What is this?

A

Calcarine fissure

(Note that it is mostly only seen from the medial side)

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71
Q

What is the importance of the calcarine fissure?

A

The primary visual cortex (V1) is split across the banks of the fissure.

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72
Q

What is this?

A

Cingulate sulcus

(Separates the cingulate gyrus from the frontal and parietal lobes)

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73
Q

What are the main braingyri you need to know?

A
  • Pre-central (M1)
  • Post-central (S1)
  • Insula
  • Uncus
  • Parahippocampal
  • Hippocampal
  • Dentate
  • Cingulate
  • Superior temporal (A1)
  • Orbitofrontal
  • Wernicke’s and Broca’s areas
  • V1 on banks of post-calcarine sulcus
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74
Q

What is this and why is it important?

A
  • Pre-central gyrus
  • It contains M1 (the motor cortex)
75
Q

What is this and why is it important?

A
  • Post-central gyrus
  • It contains S1 (the primary somatosensory cortex)
76
Q

What is this and why is it important?

A
  • Parahippocampal gyrus (a.k.a. hippocampal gyrus)
  • It is part of the limbic system. The region plays an important role in memory encoding and retrieval.
77
Q

What is this and why is it important?

A
  • Uncus (it is part of the parahippocampal gyrus)
  • It contains the primary olfactory cortex
78
Q

Check the difference between the hippocampal and parahippocampal gyrus.

A

The hippocampal gyrus might just refer to the hippocampus itself?

79
Q

What is this and why is it important?

A
  • Dentate gyrus
  • It is involved in the formation of new episodic memories, the spontaneous exploration of novel environments and other functions.

Note that is is adjacent to the hippocampus and parahippocampal gyrus, so it can be hard to see.

80
Q

What is this and why is it important?

A
  • Hippocampus
  • It is involved in learning and memory.

It is named after a seahorse.

81
Q

What is this and why is it important?

A
  • Cingulate gyrus
  • It is part of the limbic system. It is involved in emotion and behaviour. It also helps to regulate autonomic motor function.
82
Q

What is this and why is it important?

A
  • Superior temporal gyrus
  • It contains A1 (auditory cortex).
83
Q

What is this and why is it important?

A
  • Orbitofrontal gyrus
  • It is involved in decision-making.
84
Q

What are these and why are they important?

A
  • Broca’s area (in left inferior frontal gyrus) -> Involved in speech
  • Wernicke’s area (in left posterior superior temporal gyrus) -> Involved in comprehension of written and spoken langauge
85
Q

What is the importance of the banks of the post-calcarine sulcus?

A

This is where V1 is.

86
Q

Summarise where each of these is found:

  • A1
  • S1
  • V1
  • M1
A
  • A1 -> Superior temporal gyrus (temporal lobe)
  • S1 -> Post-central gyrus (parietal lobe)
  • V1 -> Banks of post-calcarine sulcus (occipital lobe)
  • M1 -> Pre-central gyrus (frontal lobe)
87
Q

What are the main tracts in the cerebral hemispheres that you need to know about?

A
  • Internal capsule
  • Optic radiation
  • Cerebral peduncles
88
Q

What is the internal capsule?

A

A region deep in the cerebral hemispheres that functions as a communication pathway between areas of the cerebral cortex and areas of the brainstem.

89
Q

What are the cerebral peduncles?

A

The two stalks that attach the cerebrum to the brainstem. They are structures at the front of the midbrain which arise from the front of the pons and contain the large ascending (sensory) and descending (motor) nerve tracts that run to and from the cerebrum from the pons.

90
Q

What are commissures?

A

Fibre tracts that connect corresponding areas in the two cerebral hemispheres.

91
Q

What are the brain commissures you need to know about?

A
  • Anterior commissure
  • Corpus callosum
92
Q

What is this and what is the importance?

A
  • Anterior commissure
  • It is a white matter tract that connects the two temporal lobes.
93
Q

What is this and what is the importance?

A
  • Corpus callosum
  • It is a white matter tracts that connects the two cerebral hemispheres.
94
Q

What is this?

A

Olfactory tracts

95
Q

What is this?

A

Olfactory bulbs

96
Q

What is this?

A

Optic chiasm

97
Q

What is this?

A

Optic nerves

98
Q

What is this?

A

Optic tracts

99
Q

What is this and what is the importance?

A

Mamillary bodies -> Important relay nuclei connecting parts of the limbic system and are a major terminus of the fibres of the fornix.

100
Q

What is this?

A

Stalk of the pituitary gland

101
Q

What is this?

A

Pons

102
Q

What is this?

A

Cerebral peduncles

103
Q

What is this?

A

Medulla

104
Q

What is this?

A

Pyramid -> This is part of the medulla that forms the major descending control pathway from the cortex to the spinal cord (i.e. corticospinal tract)

105
Q

What are the different parts of the corpus callosum?

A
  • Most anterior = Rostrum
  • Middle = Body
  • Most posterior = Splenium

(The rostrum is labelled on the diagram)

106
Q

What is this and what is the importance?

A
  • Fornix
  • The major output tract of the hippocampus and also carries some afferent fibres. Also part of the limbic system, so it is also involved in memory and emotions.
107
Q

What is this?

A

Thalamus

108
Q

What is this?

A

Epithalamus

109
Q

What is this?

A

Superior colliculus

110
Q

What is this?

A

Inferior colliculus

111
Q

What is this?

A

Third ventricle

112
Q

What is this?

A

Cerebral aqueduct

113
Q

What is this?

A

Fourth ventricle

114
Q

What is this?

A

Cerebellum

115
Q

Label this.

A
116
Q

What is this and what is the importance?

A
  • Amygdala
  • It is involved in memory, decision-making and emotional responses (as part of the limbic system).
117
Q

If you have time, go on Michaelmas week 2 CAL and look at the different cross-sections of the brain.

A

Do it.

118
Q

Draw a diagram of the locations of the different sensory and motor cortices.

A
119
Q

What are the true functions of the cerebral cortex?

A

Highr cognitive functions:

  • Episodic, procedural, recognition memory
  • Planning, emotion, judgement
  • Generation and understanding language
  • Reading
  • Maths

Functions like motor skills, etc. can be performed with just the brainstem and spinal cord (even though the cortex is also involved), so these are not true functions of the cortex.

120
Q

What are the main features of the three main parts of the brainstem?

A
121
Q

What side of the brainstem is this?

A

Anterior

122
Q

What side of the brainstem is this?

A

Posterior

123
Q

Label this brainstem.

A
124
Q

Label this brainstem.

A
125
Q

How is the brainstem positioned relative to the thalamus?

A

Note how this means that the midbrain is pretty small and hard to see, consisting mostly of the cerebral peduncles.

126
Q

How does the brainstem appear from the inferior side of the brain?

A
127
Q

What are some important sensory pathways that pass through the brainstem?

A
  • Somatosensory system
  • Auditory system
  • Taste
  • Autonomic system
128
Q

What are the cerebellar peduncles?

A

They are connections between the cerebellum and the brainstem:

  • Superior cerebellar peduncles -> Join cerebellum to midbrain
  • Middle cerebellar peduncles -> Join cerebellum to pons
  • Inferior cerebellar peduncles -> Join cerebellum to medulla
129
Q

What are the cerebral peduncles? What side are they more visible from?

A

They are more visible from the anterior side.

130
Q

What are the tectum and tegmentum?

A

They are the two parts of the midbrain:

  • Tectum -> Dorsal side (containing the superior and inferior colliculi)
  • Tegmentum -> Ventral side
131
Q

What important structures does the tectum contain?

A

Superior colliculus and inferior colliculus

132
Q

Name all the brainstem nuclei you need to know.

A
  • Dorsal column nuclei
  • Pontine nuclei
  • Inferior olivary nuclei (olives)
  • PAG
  • Locus coeruleus
  • Nucleus raphe
  • Cranial nerve nuclei:
    • Oculomotor (III)
    • Edinger-Westphal (III parasympathetic)
    • Trochlear (IV)
    • Abducens (VI)
    • Trigeminal (V) -> Mesencephalic nucleus, principle sensory nucleus and spinal nucleus, motor nucleus)
    • Facial (VII)
    • Cochlear & Vestibular (VIII)
    • Nucleus ambiguous + Nucleus solitarius (IX)
    • Vagal (X)
    • Hypoglossal (XII)
133
Q

Where are the dorsal column nuclei?

A
  • At the junction of the spinal cord and medulla
  • They are at the end of the dorsal columns
134
Q

Where are the pontine nuclei and what is their function?

A
  • They are in the ventral pons -> They are not very visible on any specimen, so you are unlikely to need to identify them
  • They receive input from the primary motor cortex via the corticopontine tract (ipsilaterally)
  • They output via the pontocerebellar tract to the contralateral cerebellum (via the middle cerebellar peduncle)
135
Q

Where are the olives (a.k.a. olivary bodies) and what is their function?

A
  • They are oval-shaped structures in the lower medulla
  • They contain the inferior and superior olivary nuclei
136
Q

Where is the superior olivary nucleus and what is its function?

A
  • Technically in the pons, but is considered as part of the olives in the medulla
  • Couldn’t find a cross-section of its location, so probably not important
  • Involved in the perception of sound (see appropriate lecture)
137
Q

Where is the inferior olivary nucleus and what is its function?

A
  • In the olives of the ventral medulla
  • Has a distinct wavy appearance in cross-section
  • Involved in the cerebellar motor-learning (see lecture on the cerebellum)
138
Q

Where is the periaqueductal grey (PAG) and what is its function?

A
  • Found surrounding the cerebral aqueduct in the midbrain
  • It outputs to the 5-HT cells of the raphe nucleus and noradrenergic cells of the locus coeruleus, which are involved in pain control
139
Q

Where is the locus coeruleus and what is its function?

A
  • It is on the posterior side of the cranial pons (near the PAG)
  • It contains noradrenergic
  • It is involved in descending pain control, stress response, the formation of memory, attention and arousal.
140
Q

Where is nucleus raphe and what is its function?

A
  • The raphe nuclei are a cluster of nuclei in the dorsal pons and medulla -> They are found along the midline
  • They release 5-HT and the nucleus raphe magnus is involved in descending pain control
141
Q

Where is the nucleus raphe magnus?

A
  • It is located in the caudal pons and the most rostral portion of the medulla, along the midline
142
Q

Summarise the main tracts in the brainstem that you need to know.

A
  • Corticospinal
  • Corticobulbar
  • Corticopontine
  • Dorsal columns
  • Internal arcuate/medial lemniscus
  • Lateral lemniscus
  • Anterolateral column -> Spinoreticular, spinomesencephalic, spinothalamic
  • Medial longitudinal fasciculus
  • Spino-cerebellar
  • Ponto-cerebellar
  • Superior cerebellar peduncle
  • Spinal tract of the trigeminal
  • Posterior commissure
143
Q

Draw the path of the corticospinal tract and corticobulbar tract through the brainstem, including any decussation.

A
144
Q

For the corticopontine tract, state:

  • Origins
  • Pathway (inc. decussation)
  • Functions
A
  • Origins: Motor, somatosensory and visual cortices
  • Pathway: Ipsilateral to pontine nuclei in ventral pons
  • Functions: Carries motor, sensory and visual information to the pontine nuclei, for relay to the cerebellum, where it is used for motor coordination
145
Q

For the ponto-cerebellar tract, state:

  • Origins
  • Pathway (inc. decussation)
  • Functions
A
  • Origins: Pontine nuclei in ventral pons
  • Pathway (inc. decussation): Decussates and enters the contralateral
  • Functions: Carries motor, sensory and visual information to the cerebellum, where it is used for motor coordination
146
Q

Where are the dorsal columns in the brainstem and where do they end?

A
  • They are at the dorsal end of the medulla
  • End at the junction of the spinal cord and medulla (this is where the dorsal column nuclei are)
147
Q

Draw the path of the internal arcuate and medial lemniscus.

A
148
Q

Draw the position of the medial lemniscus at each level of the brainstem.

A
149
Q

Draw the pathway of the lateral lemniscus. Where does it start and end?

A
  • Starts: Superior olivary complex
  • Ends: Inferior colliculus
150
Q

Draw the path of the spinothalamic tract in the brainstem.

A
151
Q

Draw the path of the spinoreticular and spinomesencephalic tracts in the brainstem.

A
152
Q

What structures does the medial longitudinal fasciculus link? Draw its surface position.

A
  • Oculomotor nerve, trochlear nerve and abducens nerve
  • It passes from the pons to the mibrain (not all nuclei shown on diagram)
153
Q

Draw the position of the medial longitudinal fasciculus in cross section in the midbrain.

A
154
Q

Draw the position of the spinocerebellar tract in the spinal cord.

A
155
Q

Describe the pathway of the spino-cerebellar tract in the brainstem.

A
  • Exits in the medulla/pons and enters the inferior cerebellar peduncle.
156
Q

What is the spinal tract of the trigeminal nerve and what is its function?

A

It is a descending tract from the trigeminal ganglion and sensory nucleus to the spinal nucleus.

157
Q

Draw the position of the spinal tract of the trigeminal nerve in cross section.

A
158
Q

Where is the posterior commissure and what is its function?

A
  • On the dorsal aspect of the rostral end of the cerebral aqueduct.
  • It is important in the bilateral pupillary light reflex.
159
Q

Label these cranial nerve nuclei.

A

(The afferent nuclei are on the left and the efferent nuclei are on the right)

160
Q

Draw the positions of the cranial nerve nuclei at different levels in the brainstem.

A
161
Q

State the main cranial nerve nuclei and other nuclei in the midbrain.

A
  • PAG
  • Red nucleus
  • Oculomotor nucleus (CN 3)
  • Edinger-Westphal nucleus (CN 3)
  • Trochlear nucleus (CN 4)
  • Trigeminal mesencephalic nucleus (CN 5)
162
Q

State the main cranial nerve nuclei and other nuclei in the pons.

A
  • Pontine nuclei
  • Superior olivary nuclei
  • Locus coeruleus
  • Raphe nuclei (inc. nucleus raphe magnus)
  • Trigeminal principle sensory, spinal and motor nuclei (CN 5)
  • Abducens nucleus (CN 6)
  • Facial nucleus (CN 7)
  • Vestibular and cochlear nuclei (CN 8)
163
Q

State the main cranial nerve nuclei and other nuclei in the medulla.

A
  • Dorsal column nuclei
  • Inferior olivary nuclei
  • Raphe nuclei (inc. nucleus raphe magnus)
  • Spinal trigeminal nuclei (CN 5)
  • Nucleus tractus solitarius (CN 7, 9, 10)
  • Nucleus ambiguus (CN 9, 10)
  • Dorsal (motor) nucleus of the vagus (CN 10)
  • Hypoglossal nucleus (CN 12)
164
Q

What is the function of the Edinger-Westphal nucleus? Which cranial nerves is it related to?

A
  • It is the efferent parasympathetic pre-ganglionic nucleus for CN III (oculomotor nucleus).
  • It is involved in constricting the pupil, accommodating the lens, and convergence of the eyes.
165
Q

What are the different nuclei of the trigeminal nerve and what is the function of each? What do they relay to?

A

Sensory:

  • Mesencephalic -> Receives proprioceptive information from the peridontium and muscles of mastication, and passes these to the motor nucleus of the trigeminal nerve.
  • Principal sensory -> Receives touch information from the face and passes it to the contralateral VPM nucleus in the thalamus via the contralateral medial lemniscus.
  • Spinal -> Receives pain information from the face and passes this to the ventral posteriomedial (VPM) nucleus in the contralateral thalamus.

Motor:

  • Motor -> Innervates the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of the digastric.
166
Q

What is the function of the nucleus solitarius? Which cranial nerves is it related to?

A
  • It receives input from the facial (CN 7), glossopharyngeal (CN 9) and vagus (CN 10) nerves
  • This allows for sensation of taste and autonomic signals such as the baroreceptor reflex and chemoreceptor responses
167
Q

What is the function of the nucleus ambiguus? Which cranial nerves is it related to?

A
  • It contains motor neurons for the glossopharyngeal nerve (CN 9) and vagus nerve (CN 10)
  • These innervate the pharynx and larynx in phonation and swallowing processes
168
Q

Draw a labelled cross-section of the midbrain at the level of the superior colliculi.

A
169
Q

Draw a labelled cross-section of the midbrain at the level of the inferior colliculi.

A
170
Q

Draw a labelled cross-section of the medulla at the level of the decussation of the pyramids.

A
171
Q

Draw a labelled cross-section of the medulla at the level of the decussation of the medial lemniscus.

A
172
Q

Draw a labelled cross-section of the medulla at the level of the olives.

A
173
Q

What brainstem level is this? Label it.

A
174
Q

What brainstem level is this? Label it.

A
175
Q

What brainstem level is this? Label it.

A
176
Q

Describe the medio-lateral organisation of the cranial nerve nuclei in the brainstem.

A

Moving from lateral to medial the following pattern is followed: special sensory, somatic sensory, visceral sensory, autonomic motor and somatic motor.

177
Q

Summarise the blood supply to the brainstem.

A
178
Q

Summarise the blood supply to the different parts of the midbrain.

A
179
Q

Summarise the blood supply to the different parts of the medulla.

A
180
Q

What stroke could cause this?

A

Posterior inferior cerebellar artery (PICA), since the functions lost are enabled by:

  • Spinal trigeminal nucleus
  • Anterolateral system
  • Nucleus ambiguus
181
Q

What stroke could cause this?

A

Medial medullary syndrome:

  • Lesion of left pyramidal tract results in loss of corticospinal tract and complete right side paralysis and positive Babinski sign
  • Loss of RHS tactile sensation – dorsal column-medial lemniscus on left side.
  • Tongue deviation and wasting hypoglossal left side - ipsilateral
182
Q

Are cranial nerves innervated (by upper motor neurons) bilaterally? Does each nerve innervate its targets unilaterally or bilaterally?

A
  • Almost all the cranial nerves receive bilateral innervation from the brain via the UMNs. Two of the cranial nerves receive innervation from only one side of the brain (the contralateral side): CN XII (hypoglossal, which innervates the tongue) and CN VII (facial, which innervates the muscles of the face).
  • Each nerve innervates only ipsilaterally, except for the trochlear nerves which innervates the contralateral eye. Also, the optic nerve innervates both eyes.
183
Q

What is the filum terminale?

A
  • A strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris.
  • It is one of the modifications of pia mater.
  • It gives longitudinal support to the spinal cord.
184
Q

What is tabes dorsalis and what causes it?

[IMPORTANT]

A
  • A form of tertiary late neurosyphilis in which there is demyelination of the posterior columns of the spinal cord and DRG cells.
  • This leads to weakness, sensory ataxia (tabetic gait), lancinating pain, hypoaesthesia, and other manifestations of neurosyphilis such as personality changes.

YEAR 2 - The Nervous System (18 decks)

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