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Neuroanatomy > Diencephalon > Flashcards

Diencephalon Flashcards

1
Q

Components of diencephalon

A

Thalamus

Hypothalamus

Epithalamus (pineal gland, habenular nuclei and habenular commissure)

Subthalamus

(optic nerve and optic tracts)

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2
Q

Internal medullary lamina divides thalamus into what portions?

A

Anterior

Medial

Lateral

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3
Q

Divisions of lateral thalamus

A

Ventral and dorsal parts

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4
Q

What are the additional grey matter components associated with the thalamus?

A

Internal laminar nuclei (found within internal medullary lamina)

Interthalamic adhesion (mass intermedialis)

Lateral geniculate body

Medial geniculate body

Reticular nucleus

(External to external medullary lamina but intimately related to thalamus)

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5
Q

The sheet of white matter superior to thalamus?

A

Stratum zonale

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6
Q

Sheet of white matter lateral to thalamus?

A

External medullary lamina

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7
Q

What is found at the tip of the tail of the caudate nucleus?

A

Amygdala

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8
Q

Where is the hypothalamic sulcus?

A

Between thalamus and hypothalamus

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9
Q

What is the dorsal free margin of the thalamus, which is not related to the more medially located epithalamus?

A

Pulvinar

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10
Q

Of which part of the thalamus is the pulvinar?

A

Lateral dorsal thalamus

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11
Q

What is the principal function of the anterior thalamic nuclei?

A

Adjustment of mood in response to recent memory

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12
Q

Afferent connections of anterior thalamic nuclei

A

Mamillothalamic system (originally from fornix which is originating from hippocampal/parahippocampal portion of temporal lobe)

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13
Q

Where do most of the fibres from fornix which enter the hypothalamus terminate?

A

Mamillary body

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14
Q

Efferent connection of anterior thalamic nuclei

A

Cingulate gyrus

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15
Q

Papez circuit

A

Hippocampal-> fornix-> mamillary body-> anterior thalamic nucleus-> cingulate gyrus

Involved in recent memory

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16
Q

Which part of the Papez circuit is affected in Wernicke’s syndrome?

A

Mamillary bodies undergo degeneration or ischaemia

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17
Q

The function of the dorsal medial nucleus of the thalamus?

A

Adjust behaviour and psychological/physical state in response to mood

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18
Q

Afferent connections of the dorsal medial nucleus of the thalamus

A

All other internal thalamic nuclei

Basal ganglia

Lentiform nucleus

Hypothalamus

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19
Q

Efferent connections of the dorsal medial nucleus of thalamus?

A

Prefrontal cortex

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20
Q

Which thalamic nuclei are concerned with the limbic system?

A

Anterior thalamic

Dorsal medial nuclei

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21
Q

Important afferent connections of the intralaminar thalamic nuclei

A

Ascending reticular formation of the brainstem

All other thalamic nuclei

Ascending pain pathways:

Spinothalamic tract (which also activates reticular formation)

Trigeminothalamic tract

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22
Q

Efferent connections of intralaminar nuclei

A

The whole cerebral cortex

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23
Q

What is the function of intralaminar thalamic nuclei?

A

Cortical arousal

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24
Q

What is the largest intralaminar nucleus?

A

Centromedian nucleus

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25
Q

Connections of the centromedian nucleus

Significance?

A

All other thalamic nuclei

Motor cortex

Basal ganglia

Striatum

Motor activity can regulate levels of arousal.

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26
Q

Which part of the thalamus is affected in Wernicke’s syndrome?

A

Dorsal median nucleus

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27
Q

What are the three lateral dorsal tier thalamic nuclei from ventral to dorsal?

DPP

A

Lateral dorsal nucleus

Lateral posterior nucleus

Pulvinar

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28
Q

Connections of lateral dorsal nucleus

A

Similar to the anterior nucleus of thalamus, can be thought of posteriorly displaced anterior nucleus.

Mamillothalamic and thalamocingulate connections.

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29
Q

Connections of the lateral posterior nucleus

A

Two-way connection with superior parietal lobule and all other thalamic nuclei

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30
Q

Connections of pulvinar

A

Connections with all thalamic nuclei including strong connections with LGN and MGN

Two-way connections with sensory association cortices.

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31
Q

Brodman area- Primary occipital cortex

A

17

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32
Q

Brodman areas- Visual association cortex

A

19, 20

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33
Q

What is the difference between primary visual cortex and secondary/tertiary?

A

Initial sensory information is received in the primary cortex.

Subsequently, it is projected to the secondary area of visual association cortex where it is processed

Tertiary cortex compares new visual experience with previous information and tries to recognise it.

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34
Q

Function of primary sensory cortices

A

Receive information

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35
Q

Function of secondary sensory cortices?

A

Process information

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36
Q

Function of tertiary sensory cortices?

A

Compare to previous experiences to recognise object.

E.g. with written text

Primary receives image

Secondary identifies that it is English

Tertiary reads it

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37
Q

Secondary and tertiary sensory cortices together are known as?

A

Association areas

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38
Q

Consequence of pulvinar damage

A

Sensory aphasia

Unable to make sense of sensory information though the primary cortices are able to receive it.

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39
Q

What is the general arrangement of ventral tier nuclei

A

5 ventral tier nuclei

Two in front

Then three combined nuclei dorsally.

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40
Q

What is the most anterior ventral tier nucleus?

A

Ventral anterior nucleus

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41
Q

What is the second most anterior ventral tier nucleus?

A

Ventral lateral nucleus

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42
Q

Which of the ventral tier nuclei are concerned with motor function?

A

Ventral anterior nucleus

Ventral lateral nucleus

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43
Q

What are the three nuclei that make up the ventral posterior nucleus?

A

Ventral intermediate nucleus

Ventral posteromedial nucleus

Ventral posterolateral nucleus

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44
Q

Connections of the ventral anterior nucleus of the thalamus

A

Ventral anterior nucleus receives fibres from basal ganglia (specifically pallidothalamic fibres) and projects to the prefrontal cortex and premotor area.

Involved in planning motor movements

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45
Q

Connections of the ventral lateral nucleus?

A

Receives fibres from the corticopontocerebellar loops either via dentorubrothalamic pathway or dentothalamic pathway

Projects to SMA and 1o motor area

Again involved in planning and executing motor functions

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46
Q

Connections of ventroposterolateral nucleus

A

Receives medial lemniscus (dorsal columns)

Spinothalamic tract

Fibres ascend to the primary somatosensory cortex

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47
Q

Features of the thalamic syndrome

A

Thalamic injury, especially to sensory nuclei of VPN initially presents with contralateral hemianaesthesia

This may progress to intractable hemibody pain due to aberrant new intrathalamic connections.

Patients will often become depressed and may commit suicide.

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48
Q

Thalamic hand

A

Can be a consequence of damage to the motor component of the thalamus

The hand becomes pronated, and flexed, MCPJ flexed, ICPJ extended

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49
Q

The function of the ventral posteromedial nucleus of the thalamus?

A

Similar to ventral posterolateral but for head and neck

Receives afferents from the trigeminothalamic tract and tractus solitarius

Sends fibres to primary sensory cortex.

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50
Q

Function of VIM

A

The relay nucleus of the thalamus for the cerebellum, receiving input from the opposite cerebellum via the superior cerebellar peduncle. Output is to the primary motor cortex (Brodmann’s area 4) and premotor cortex

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51
Q

Connections of the reticular nucleus

A

Main regulator of thalamic activity

Receives information from the whole cerebral cortex

Receives information from ascending reticular formation

Sends fibres to all nuclei of the thalamus

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52
Q

3 basic functions of the hypothalamus

A

Part of the limbic system

Intimately related with the function of ANS

Endocrine function

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53
Q

AP extent of the hypothalamus

A

From midbrain to the optic chiasma

Sheet of grey matter

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54
Q

Swelling on the undersurface of the hypothalamus

A

Tuber cinereum

Mamillary bodies

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55
Q

What divides the hypothalamus into right and left areas?

A

The ventral part of the third ventricle

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56
Q

From which part of the parahippocampal formation do most of the fibres of the fornix originate?

A

Subiculum

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57
Q

Divisions of hypothalamus

A

Can be divided into medial and lateral side by an imaginary plane which is in line with the entry of the fornix and exit of the mamillothalamic tract

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58
Q

What fibres run from the frontal-orbital and septal area through the lateral hypothalamus into the brainstem

A

Medial forebrain bundle

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59
Q

What is the septal area of the brain?

A

Septal nuclei (medial olfactory area) structures below he rostrum of the corpus callosum, anterior to the lamina terminalis

.The septal nuclei are composed of medium-size neurons which are classified into medial, lateral, and posterior groups. The septal nuclei receive reciprocal connections from the olfactory bulb, hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus, and thalamus.

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60
Q

What are these hypothalamic nuclei?

A

Pre-optic nuclei

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61
Q

What is the function of the pre-optic nucleus?

A

Contains dimorphic nucleus which is thought to be involved in determining sexuality

Involved in the regulation of sexual function via the mediation of release of adenohypophyseal gonadotrophs through GnRH

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62
Q

What is this nucleus?

A

Lateral hypothalamic nucleus

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63
Q

The function of the lateral hypothalamic nucleus

A

Involved in the regulation of hunger

Excessive stimulation can provoke anger

Involved in regulation of thirst

Located close to sympathetic outflow of the hypothalamus

64
Q

What is the green nucleus?

A

Ventromedial nucleus of hypothalamus

65
Q

What is the function of the ventromedial nucleus of the hypothalamus

A

Satiety

Happiness

66
Q

Divisions of medial hypothalamus from anterior to posterior

A

Pre-optic region

Supra-optic region

Tuberal region

Mamillary region

67
Q

What is the nucleus in the pre-optic region of hypothalamus?

A

Pre-optic nucleus

68
Q

Which nuclei are in the supra-optic region of the medial hypothalamus?

A

Suprachiasmatic nucleus

Anterior thalamic nucleus

Supraoptic nucleus

Paraventricular nucleus

69
Q

What is the function of the suprachiasmatic nucleus?

A

Involved in the regulation of circadian rhythms (biological clock)

Receives afferent fibres from optic chiasm- allows to determine light exposure, using ratio of light and darkness can be used to determine season

Connected to epithalamus

Pineal gland involved in circadian rhythmn

70
Q

Function of the anterior hypothalamic nucleus?

A

Involved in the regulation of body temperature- helps with cooling

Sends efferents to the spinal cord and is involved in sweat production and cutaneous vasodilation

Involved in PNS

71
Q

Functions of the supraoptic nucleus

A

Produces ADH which is stored in and released after traversing axons from the neurohypophysis

72
Q

Function of the paraventricular nucleus?

A

Involved in the production and release of oxytocin by the neurohypophysis

73
Q

How is the suprachiasmatic nucleus involved in circadian rhythms?

A

Receives efferents from the optic chiasma and has projections to the habenular nuclei and subsequently to the pineal gland.

74
Q

Which substances are secreted by the pineal gland?

A

Melatonin

5HT

CCK

75
Q

What is the name for the bundle of neurones projecting from the supraoptic and PVN of the hypothalamus?

A

Supraopticohypophyseal tract

76
Q

What are the three important nuclei of the tuberal region?

A

Arcuate nucleus

Ventromedial nucleus

Dorsomedial nucleus

77
Q

Location of the arcuate nucleus?

A

In the median eminence of the tuberal region of the hypothalamus

78
Q

Function of the arcuate nucleus?

A

Projects axons to the hypothalamic hypophyseal portal system.

Releases substance release factors to stimulate the anterior pituitary to produce its endocrine mediators.

79
Q

What is the name of the bundle of fibres projecting from the arcuate nucleus to the portal system?

A

Tuberohypophyseal tract

80
Q

Function of the ventromedial nucleus of the hypothalamus?

A

Satiety and happiness centre

When stimulated, inhibits the nucleus of the lateral hypothalamus that is involved in hunger.

81
Q

Function of the dorsomedial nucleus

A

Punishment centre

Connects with lateral hypothalamus and is involved in the regulation of hunger.

82
Q

Important nuclei of the mammillary region of the hypothalamus

A

Mamillary nuclei

Posterior hypothalamic nucleus

83
Q

Function of the mamillary nuclei?

A

Involved in eating mechanisms

Involved in Papez circuit

84
Q

What is the effect of vitamin B1 deficiency on the brain?

A

May develop haemorrhagic lesions in the mammillary body.

The dorsal medial nucleus of the thalamus

Periaqueductal region of brainstem

Superior and inferior colliculi

Wernicke-Korsakoff syndrome.

85
Q

Function of the posterior hypothalamic nucleus

A

SNS

Generation of heat through shivering and minimising heat loss through peripheral vasoconstriction.

86
Q

Arrangement of the fornix

A

Alveus

Fimbriae

Crus

Body

Columns

87
Q

Connection of amygdala to the hypothalamus is via what WM structure?

A

Striae terminalis

and second pathway ventral amygdaloid fugal pathway

88
Q

What is the dorsal longitudinal fasciculus?

A

A descending pathway from the anterior hypothalamus carrying PNS efferents to the PNS nervous outflow- craniocaudal.

89
Q

From what does adenohypophysis develop?

A

Rathke’s pouch which is a diverticulum of orally derived tissue

90
Q

Cranipharyngioma

A

Meant to be an embryological neoplastic remnant of Rathke’s pouch

91
Q

What is the most common supratentorial tumour in children?

A

Craniopharyngioma

92
Q

What is the only sensory pathway not to synapse in the thalamus before reaching the cerebral cortex?

A

Olfactory

93
Q

White matter sheets of the thalamus

A

Rostrally covered with stratum zonale

Laterally with external medullary lamina

Divided into three parts by internal medullary lamina

94
Q

Divisions of the lateral thalamus

A

Into two tiers:

Dorsal tier containing lateral dorsal, lateral posterior, pulvinar nuclei

Ventral tier containing the ventral anterior nucleus, ventral lateral nucleus, ventral posterior nucleus, medial and lateral GN.

95
Q

What thalamic nuclei are not included in the three part schematic

A

Reticular nucleus

Intralaminar nuclei

Midline nuclei located in the medial surface of the thalamus in the interthalamic connection

96
Q

Categorisation of thalamic nuclei

A

Specific relay nuclei

Non-specific thalamic nuclei

Association nuclei

97
Q

Specific relay nuclei

A

Anterior nucleus

Ventral tier of lateral nucelar group: ventral anterior, lateral, posterior, MGN, LGN)

98
Q

Anterior nucleus

A

Receives input from the hypothalamus (mamillary bodies and mamlliothalamic tract) and projects to the cingulate gyrus

99
Q

Ventral anterior and ventral lateral nuclei

A

Basal ganglia and cerebellar input

Project to motor and premotor cortices

100
Q

Ventroposterolateral nucleus

A

Receives somatosensory input from medial leminscus and spinothalamic tract

101
Q

Ventroposteromedial nucleus

A

Somatosensory information from the sensory nuclei of the trigmeinal nerve

102
Q

Medial geniculate nuclei

A

Receive input from the cochlear nuclei projecting to the transverse gyrus of Heschl

103
Q

Lateral geniculate nucleus

A

Receives input from retinal ganglion cells and projects to the calcarine sulcus

104
Q

Nonspecific thalamic nuclei

A

Centromedian

Reticular

Midline nucleus

105
Q

Centromedian nucleus

A

Largest intralaminar nuclei

Receives input from cortex and globus pallidus

Projects to the caudate and putamen

Involved in reticular activating system

106
Q

Reticular nucleus

A

Receives input from collateral branches of thalamocortical and corticorthalamic fibres and projects to other thalamic nuclei

Modulates influence of thalamus on cortex

107
Q

Midline nucleus

A

Receives input from brainstem reticular formation and projects to limbic structures such as the amygdaloid nucleus and cingulate gyrus

108
Q

What are the association nuclei of the thalamus

A

Medial nucleus (dorsomedial nucleus)

Dorsal tier of lateral nuclei (lateral dorsal nucleus, lateral posterior nucleus, pulvinar)

109
Q

Dorsomedial nucleus

A

Receives input from olfactory cortex, amygdaloid nucleus, the hypothalamus.

Reciprocal connections with association cortex of frontal lobe

Concerned with affective behaviour

110
Q

Lateral dorsal nucleus

A

Part of the limbic system

Receives afferents from hippocampal formation, projects to cingulate gyrus

111
Q

Lateral posterior nucleus

A

Unknown afferents

Projects to somatosensory cortex of the parietal lobe

112
Q

Pulvinar

A

Receives input from the superior colliculus

Also from sensory association areas of parietal, temporal, and occipital lobes, projecting back to the same areas.

113
Q

Describe the vascular territories of the thalamus

A

Four vascular territories

Chiefly supplied by small perforating end-arteries from the PCA

Anterior: polar arteries, PComm

Paramedian: thalamoperforating branches from the P1 segment of the PCA (either unilateral or bilateral)

Lateral: Thalamogeniculate artery from P2

Posterior: Medial posterior choroidal artery or posterior branch of lateral posterior choroidal artery

May also receive additional blood supply form the anterior choroidal artery

114
Q

Draw the blood supply of the thalamus

A
115
Q
A

Bilateral medial thalamic nuclear group infarction

Artery of Percheron occlusion

116
Q

Gerard Percheron

A

French neurologist

117
Q

Epidemiology of artery of Percheron

A

Estimated prevalence of 33%

4-18% of all thalamic strokes

118
Q

Gross anatomy of artery of Percheron

A

Solitary arterial trunk that branches from proximal PCA to supply paramedian thalami and rostral midbrain bilaterally

Occasionally it may supply the anterior thalamus, esp if polar arteries absent

119
Q

Sensory disturbance in thalamic pathology

A

Results from lesions affecting VPL and VPM

Can be positive or negative, either sensory loss or hemibody pain affecting the contralateral side.

Most frequently involves proprioceptive input can be distinguished from cortical sensory loss due to loss of vibratory sense which is often spared in the parietal sensory loss.

Pain often felt close to skin and can occur spontaneously

Thalamic paraesthesia predominantly affects the circumoral region and distal part of limbs.

120
Q

Motor disturbance in thalamic lesions

A

Result from lesions in ventral anterior and ventral lateral nuclei interrupting connections between the thalamus and extrapyramidal motor system

Thalmic disturbances to motor function may result in hemiataxia and abnormal involuntary movements e.g. action tremor or choreoathetosis

The affected hand may assume abnormal posture- thalamic hand

May involve transient contralateral hemiparesis (thought to be due to extension into internal capsule rather than isolated thalamic pathology.

121
Q

Thalamic hand

A

Wrist pronated and flexed at CMC and MCPJ with hyperextension at the IPJ

122
Q

How to distinguish thalamic lesions causing coma vs midbrain

A

If there is midbrain involvement then there may be presence of oculomotor nerve paresis whereas pure thalamic lesions exhibit small, diencephalic pupils

123
Q

Affective disturbances in thalamic lesions

A

Tend to result from lesions in anterior and dorsomedial nuclei that interrupt connections with limbic system structures and frontal cortex

May result in apathy, disinterest, lack of initiative or drive.

Less often, agitation or confusion may develop

124
Q

Memory disturbance with thalamic lesions

A

Lesions in dosromedial nucleus may result in memory loss

125
Q

Visual disturbance in thalamic lesions

A

Contralateral hemianopia

126
Q

Broad division of hypothalamus

A

Into a medial hypothalamic region containing the majority of nuclei

Lateral hypothalamic region containing major fibre tracts and a group of diffuse nuclei

127
Q

Borders of the hypothalamus

A

Rostral border- anterior commissure and lamina terminalis

Caudal border merges with midbrain tegmentum

128
Q

Subdivisions of medial hypothalamic area

A

Supraoptic region (most anterior)

Tuberal region

Mamillary region

129
Q

Supraoptic region nuceli

A

Supraoptic

Suprachiastmatic

Anterior nucleus

Paraventricular nuclei

130
Q

Nuclei of the tuberal region of the hypothalamus

A

Ventromedial

Dorsomedial

Infundibular

131
Q

Nuclei of mamillary region

A

Mamilllary body

Posterior nucleus

132
Q

Major afferent connections of the hypothalamus

A

Olfactory and septal areas

Hippocampus

Amygaloid nucleus

Midbrain tegmentum

Dorsomedial and midline thalamic nuclei

133
Q

Olfactory and septal afferents to the hypothalamus

A

Areas are concerned with smell and basic emotional drives

Afferents via the medial forebrain bundle

134
Q

Hippocampal afferents to hypothalamus

A

Sends axons to mamillary bodies via the fornix

135
Q

Amygdaloid afferents to hypothalanus

A

Sends afferents to the hypothalamus via the stria terminals

Associated with complex behaviours

136
Q

Midbrain afferents to the hypothalamus

A

Reticular formation with diffuse network of fibres

Sends axons via the medial forebrain bundle

Raphe nucleus and nucleus coeruleus also project fibres via the dorsal longitudinal fasciculus

137
Q

Thalamic afferents to hypothalamus

A

Axns from dorsomedial and midline thalamic nuclei to the hypothalamus via thalamohypothalamic tract

138
Q

Efferent connections of the hypothalamus

A

Olfactory and septal areas

Anterior thalamic nuclei

Preganglionic autonomic neurones of brainstem and SC

Posterior pituitary

Anterior pituitary

139
Q

Olfactory and septal efferents of hypothalamus

A

These areas receives hypothalamic efferents via the medial forebrain bundle

Concerned with smell and basic emotional drive

140
Q

Hypothalamic efferents

Anterior thalamic nuclei

A

This thalamic nucleus is part of the limbic system

Receives hypothalamic axons via the mamillothalamic tract and projects in turn to the cingulate gyrus

141
Q

Hypothalamic efferents:

Preganglionic autonomic neurones

A

Include dorsal nucleus of vagal nerve

Intermediolateral cell column

Both receive input from the hypothalamus via the dorsal longitudinal fasciculus.

The hypothalamic projections to the intermediolateral cell column are relayed in reticulospinal pathways

142
Q

Hypothalamic efferents:

Posterior pituitary gland

A

Receives direct axonal projections from large neurosecretory cells in PVN and supraoptic nuclei of the hypothalamus

Carried in the supraoptic hypophyseal tract

Involved in the synthesis of ADH and oxytocin

143
Q

Hypothalamic efferents:

Anterior pituitary

A

Neurosecretory cells in infundibular nucleus of the hypothalamus, secretory and inhibitory factors to the pituitary

Axoplasmic transport in the tuberoinfundibular tract and are secreted into a capillary bed in the median eminence.

From the median eminence, they are transported in the hypophyseal portal veins to a second capillary bed in the anterior pituitary.

144
Q

Autonomic function of hypothalamus

A

Cardiovascular regulation

Body temperature

Water balance

Food intake

145
Q

Cardiovascular regulation by hypothalamus

A

Exerts both sympathetic and parasympathetic influences on CV system

Posterior hypothalamus -> sympathetic

Anterior hypothalamus-> PNS

These effects are mediated by cardiovascular control centres in reticular formation of brainstem

146
Q

Body temperature regulation by hypothalamus

A

Anterior hypothalamus contains heat sensitive neurones that sense temperature of blood. Simtualte vasodilation and sweating via PNS

Cold-sensitive in posterior hypothalamus increase rate of firing when cold, sympathertic

147
Q

Where is the thirst centre in the hypothalamus

A

Lateral hypothalamus

148
Q

Location of hypothalamic hunger centre

A

Lateral hypothalamus

149
Q

Location of hypothalamic satiety centre

A

Ventromedial nucleus

150
Q

Emotional behaviour regulation by hypothalamus

A

Integrates limbic and controls autonomic nervous systems

Stimulation of lateral hypothalamus-> fear

Ventromedial hypothalamus stimulation-> placidity and tameness

151
Q

Body temperature

Anterior hypothalamic lesion

A

Hyperthermia

152
Q

Body temperature

Posterior hypothalamic lesion

A

Hypothermia

153
Q

Body weight

Destructive lesion of the ventromedial hypothalamus

A

Obesity

154
Q

Ventromedial hypothalamic lesions, impact on behaviour

A

May cause episodic outbursts of rage and fear with prominent autonomic component

155
Q

Etymology of thalamus

A

Comes from greek “thalamos” meaning bedroom or inner chmaber

156
Q

Etymology of die-encephalon

A

From greek “dia” meaning through

Encephalon meaning brain

157
Q

Etymology of pituitary gland

A

From “pituia” meaning mucous because the gland was thought to bring mucous to the nose

Neuroanatomy (18 decks)

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