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Head and Neck Anatomy > Anatomy of the Diacephalon > Flashcards

Anatomy of the Diacephalon Flashcards

1
Q

Describe the diencephalon and its location?

A
  • Paired structure
  • Located between the brain stem and the cerebral hemisphere
  • Continuous with the rostral part of the midbrain
  • Forms the lateral wall of the 3rd ventricle
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2
Q

What are the 3 structures that make up the diencephalon?

A
  1. thalamus
  2. hypothalamus
  3. epithalamus
    > these structures effectively enclose the 3rd ventricle
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3
Q

What parts of the diencephalon are seen externally on the base of the brain?

A
  1. Infundibulum
  2. Tuber cinerium
  3. Mamillary bodies
    > caudal to the optic chiasma
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4
Q

Describe the medial surface of the diencephalon?

A

is subdivided, by hypothalamic sulcus into:
1. Dorsal part
2. Ventral part

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5
Q

The dorsal part of the diencephalon is made of?

A

thalamus and epithalamus

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6
Q

The ventral part of the diencephalin is made of?

A

subthalamus and hypothalamus

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7
Q

Describe the epithalamus and its location?

A

Relatively small part, located in most caudal and dorsal region
Lies immediately rostral to superior colliculus

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8
Q

The epithalamus consists of?

A

Pineal gland
Habenular nuclei

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9
Q

Describe the pineal gland and its function?

A
  • An endocrine organ
  • Synthesizes melatonin
  • Controls:
    1. Sleep/awake cycle
    2. Regulation of onset of puberty
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10
Q

Describe the habenular nuclei and its function?

A
  • Located in habenular triangle
    > area in the posterior part of the diencephalon, just anterior to pineal gland
  • Have connections with limbic system
  • Serves autonomic function and emotional drives
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11
Q

Describe the thalamus and its location?

A
  • Large mass of grey matter
  • in shape and size, resembles small hen’s egg
  • Forms the lateral wall of the 3rd ventricle
  • Separated from hypothalamus by hypothalamic sulcus
  • May be connected to opposite thalamus by interthalamic adhesion (massa intermedia)
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12
Q

Why is the thalamus at different levels in the 2 hemispheres?

A
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13
Q

Describe the structural components of the thalamus?

A
  1. tubercle of thalamus > narrow anterior end that lies in the posterior boundary of the interventricular foramen
  2. pulvinar > The expanded posterior end lies above the superior colliculi
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14
Q

Describe the superior surface of the thalamus?

A
  • Bounded laterally by caudate nucleus, thalamostriate vein and a nerve fiber bundle called stria terminalis
  • Lateral part lies in the floor of the lateral ventricle & is covered by ependyma
  • Medial part is related to the choroid plexus of the 3rd ventricle
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15
Q

Describe the lateral surface of the thalamus?

A

related to the internal capsule

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16
Q

Describe the inferior surface of the thalamus?

A

rests on the subthalamus and hypothalamus

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17
Q

Describe the medial surface of the thalamus?

A
  • Stria medullaris thalami (a fascicle of nerve fibers) courses along its dorsomedial margin
  • Below is limited by hypothalamic sulcus
  • Forms the upper part of the lateral wall of the 3rd ventricle
  • Covered by ependyma
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18
Q

Describe the internal organization of the thalamus?

A

the thalamus is composed of grey matter, interrupted by two vertical sheaths of white matter called medullary laminae.

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19
Q

Describe the external medullary lamina of the thalamus?

A
  • Located laterally, separates reticular nucleus from the rest of the thalamic mass
  • Contains thalamocortical & corticothalamic fibers
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20
Q

Describe the internal medullary lamina of thalamus?

A
  • Y- shaped band, divides thalamus into Anterior, Medial & Lateral nuclear groups
  • Contains:
    1. Fibers connecting thalamic nuclei with one another
    2. Neuronal collections called intralaminar nuclei
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21
Q

Name all the nuclear groups of the thalamus?

A
  1. Anterior nuclear group
  2. Lateral nuclear group
    > dorsal
    > ventral tiers
  3. Medial nuclear group
  4. Intralaminar nuclei
  5. Reticular nucleus
  6. Midline nuclei
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22
Q

Describe the functional organization of the nuclei of the thalamus?

A
  • All the nuclei of the thalamus except reticular nucleus, project to ipsilateral cerebral cortex
  • The whole of the cerebral cortex receives input from the thalamus
  • All thalamic nuclei receive corticofugal fibers in a basically reciprocal fashion
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23
Q

The thalamic nuclei are divided into?

A
  1. specific nuclei
  2. non specific nuclei
    > Based on their connection with the cerebral cortex
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24
Q

Describe specific nuclei and where they are located?

A
  • Have well-defined sensory and motor functions
  • Have highly organized point-to-point connection with sensory & motor regions of cerebral cortex
  • Lie within the ventral group of the lateral nuclear group
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25
Q

Describe non-specific nuclei?

A
  • Receive less functionally distinct afferent input
  • Connect with wider area of cortex, including associative and limbic regions
  • Include nuclei of the dorsal tier of lateral group, and whole of the anterior and medial group
26
Q

Name the components of the ventral tier of the lateral nuclear group?

A
  1. Ventral anterior
  2. Ventral lateral
  3. Ventral posterior:
    > VPL
    > VPM
  4. Lateral geniculate
  5. Medial geniculate
27
Q

Describe the components of the ventral anterior nucleus and its function?

A

Ipsilateral globus pallidus & substantia nigra
Motor cortex
Premotor & supplementary motor cortex
> influences motor activity

28
Q

Name the components of the ventral lateral nucleus and its function?

A

Ipsilateral globus pallidus &
substantia nigra
Contralateral dentate nucleus
Primary motor cortex
> influences motor activity

29
Q

Name the components of the ventral posterior nucleus and its function?

A

General sensory afferents from the contralateral half of the Head & neck (VPM) and Body (VPL)
Primary somatosensory cortex
> chief sensory relay station

30
Q

Name the components of the lateral geniculate body?

A

Ipsilateral temporal hemiretina
Contralateral nasal hemiretina
Optic radiation to the primary visual cortex
> part of the visual pathway

31
Q

Name the components of the medial geniculate body and its function?

A

Inferior colliculus
Auditory radiation to the primary auditory cortex
> part of the auditory pathway

32
Q

Name the parts of the dorsal tier of the later nuclear group?

A
  1. Lateral Dorsal
    > part of limbic system
  2. Lateral Posterior
    > sensory association cortex of parietal lobe
  3. Pulvinar
    > Sensory association cortices of parietal, temporal & occipital lobes
33
Q

Describe the basal ganglia?

A

large interconnected nuclear masses (grey matter) located deep within:
1. Cerebral hemispheres
2. Diencephalon
3. Mid brain

34
Q

What is the function of basal ganglia?

A

They play an important role in the control of posture and voluntary movement

35
Q

Name the group of nuclei of the basal ganglia?

A
  1. Corpus striatum (in the cerebral hemispheres)
  2. Subthalamic nucleus (in the Diencephalon)
  3. Substantia nigra (in the Mid brain)
36
Q

Abnormalities of the basal ganglia result in?

A
  1. Parkinson’s disease
  2. Huntington disease
37
Q

Describe the structure of the corpus striatum?

A

Subdivided by internal capsule into two nuclei:
1. Caudate nucleus – in the wall of lateral ventricles
2. Lentiform nucleus

38
Q

Describe the caudate nucleus?

A
  • Large C-shaped or comma-shaped mass of grey matter.
  • Lies in close relation to lateral ventricle.
  • It has a Head, Body, and Tail
39
Q

Describe the parts of the caudate nucleus?

A
  1. Head :(Anterior) Large, & rounded and forms the lateral wall of anterior horn of lateral ventricle.
    It is continuous inferiorly with putamen of lentiform Nucleus.
  2. Body : Long & narrow continuous with head at the interventricular foramen.
    It forms part of the floor of body of lateral ventricle.
  3. Tail : Long & narrow, and lies in the roof of inferior horn of lateral ventricle.
    It is connected anteriorly with Amygdaloid nucleus
40
Q

Describe the lentiform nucleus?

A
  • wedge shaped/ lens shaped
  • It is a mass of grey matter wedge-shaped or (biconvex lens).
  • It has 2 capsules, external capsule laterally & internal capsule medially.
    > Internal capsule separates between lentiform nucleus laterally & caudate nucleus and thalamus medially.
    > External capsule separates between lentiform nucleus and Claustrum.
  • Inferiorly putamen is continuous with the head of caudate nucleus
41
Q

Name and describe the segments of the lentiform nucleus?

A
  1. The Putamen - Larger darker lateral portion. located laterally between external capsule and globus pallidus
  2. The Globus pallidus – Smaller, lighter medial portion.
    located btween putamen and internal capsule.
    - Further subdivided into :
    > Lateral segment (outer)
    > Medial segment (inner)
42
Q

What is the amygdaloid nucleus?

A
  • Almond-shaped small mass of grey matter lies in temporal lobe close to the Uncus.
  • Lies Anterosuperior to inferior horn of lateral ventricle.
  • It is connected to the tail of caudate nucleus.
  • It is the smell center & part of limbic system
43
Q

What is the claustrum?

A

Thin sheet of gray matter which lies lateral to external capsule & medial to the Insula

44
Q

What is the subthalamic nucleus?

A
  • Large nucleus in the subthalamus
  • Located ventral to the thalamus
  • Wedge shaped division of the diencephalon
45
Q

Name the 3 nuclei contained in the subthalamic nucleus?

A
  1. Zona incerta- dorsolaterally
  2. Prerubral field –dorso medially
  3. Subthalamic nucleus - ventrally
46
Q

What is the sustantia nigra?

A

Largest nucleus in the midbrain

47
Q

What are the 2 parts of the sustantia nigra?

A
  1. Compact part – dorsal
    Contains neurones filled with melanin
  2. Reticular part - ventrally
48
Q

Describe the function of the substantia nigra?

A

produces dopamine
> control of movement via the signals it sends to the striatum
> enables precision movement

49
Q

The basal ganglia links with?

A
  1. thalamus
  2. cerebral cortex
50
Q

Connections of the basal ganglia are divided into?

A
  1. Input from sources outside basal ganglia
  2. Interconnections between nuclear masses within the basal ganglia.
  3. Output connections from basal ganglia to other parts of the brain.
51
Q

Describe the afferent fibers (input) of the corpus striatum?

A

I- Corticostriate Fibers: From all parts of cerebral cortex (mostly from sensory- motor cortex) axons pass to caudate nucleus and putamen.
Glutamate is the neurotransmitter of this fibers.

II-Thalamostriate Fibers : From intralaminar nuclei of thalamus axons pass to caudate nucleus and putamen.

III- Nigrostriate Fibers : Axons from Substantia nigra of midbrain pass to caudate nucleus and putamen.
Neurotransmitter is Dopamine.

IV_Brain stem Strial Fibers : Ascending fibers from brain stem end in caudate nucleus & putamen.
Serotonin is the neurotransmitter.
It is believed that the last 2 groups are inhibitory in function

52
Q

Name the efferent (output) fibers of the corpus striatum?

A

1-Striatopallidal fibers:
These fibers pass from corpus striatum (caudate nucleus & putamen) to globus pallidus.
Gamma-aminobutyric acid (GABA) is the neurotransmitter.

2-Striatonigral fibers:
These fibers pass from caudate nucleus & putamen to Substantia nigra.
Some fibers use GABA as a neurotransmitter, and others use Substance P.

53
Q

Describe the functions of the basal ganglia?

A
  1. Design of plans, which convert thoughts and ideas into motor actions
    > to produce a coordinated organized purposeful movement e.g. dressing.
  2. Determining the timing and scale of movement
    > to what extent the movement will be fast, and how long it will last.
  3. Storage of motor programs of familiar motor actions
    e.g. signature
54
Q

Describe the consequences of a lesion of the basal ganglia?

A
  1. Involuntary movement during rest
    Chorea, athetosis, hemiballismus, and tremor.
  2. Changes in muscle tone.
    A- Chorea: (Dance). Lesion: in caudate N
    > Features:
    - Involuntary, quick, Jerky, irregular, nonrepetitive and purposeless movement
    e.g. Swift grimaces, and sudden movement of head or limb.
55
Q

What is huntingtons disease?

A

deterioration of brain tissue usually begins age 30to 40
- no cure but have medications to cope with symptoms
- people usually die 15-20 years after onset of degeneration
- autosomal, dominant

56
Q

Describe the pathology of huntingtons chorea?

A
  • degenration of cerebral cortex and the basal ganglia
  • loss of GABAergic neurons in the striatum
  • severe striata; atrophy with resulting enlargement of ventricles
57
Q

Describe the clinical presentation of huntingtons chorea?

A
  1. twitching movements of head
  2. grimacing movements in face, lips and tongue
  3. gesticulating movements in distal parts of upper limbs
  4. jerking movements in distal parts of lower limbs
58
Q

Describe athetosis?

A

(Greek= Not fixed).
Lesion: Putamen & Globus pallidus.
Features: Involuntary, slow, sinuous, writhing movements involving distal part of limb (hand).

59
Q

Describe Hemiballismus?

A

(Greek= Jumping)
Lesion: Subthalamus
Features: Sudden, involuntary, spasmodic movements that involves one limb or one side of the body (Limb suddenly flies about in all directions out of control)

60
Q

Describe parkinsonism?

A

Lesion: Neuronal degeneration in substantia nigra leading to reduction of dopamine within corpus striatum

61
Q

Describe the pathophysiology of Parkinsons disease?

A
  1. loss of dopaminergic input to striatum
  2. degeneration of neurons in substantia nigra pars compacta
  3. disrupted signalling betweem basal ganglia, cortex and thalamus
62
Q

What are the features of Parkinsonism?

A

1- Tremors: Pill-rolling, involuntary, rhythmic, oscillating movements. It occurs during waking time during rest, it is called static tremors.
2- Rigidity: It occurs in both flexors, and extensors, but more in flexors giving flexion attitude.
> It is called lead pipe rigidity.
3- Akinesia: it means lack of movement; Absence of swinging arm during walking, mask face, low- volume slow monotonous speech, and shuffling gait

Head and Neck Anatomy (37 decks)

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