Forebrain, diencephalon.
Meninges of the brain.
Cerebro-spinal fluid.
The diencephalon
• The diencephalon is the region of the embryonic
vertebrate neural tube that gives rise to posterior
forebrain structures including the thalamus,
hypothalamus, posterior portion of the pituitary
gland, and pineal gland.
• The hypothalamus performs numerous vital
functions, most of which relate directly or
indirectly to the regulation of visceral activities by
way of other brain regions and the autonomic
nervous system.
THE DIENCEPHALON
•
•
•
•
EPITHALAMUS
THALAMUS
SUBTHALAMUS
HYPOTHALAMUS
Diencephalon
•
•
•
•
•
•
•
•
•
•
Thalamus  dorsal thalamus
Hypothalamus
pituitary gland
Epithalamus
habenular nucleus and commissure
pineal gland
Subthalamus  ventral thalamus
subthalamic nucleus (STN)
field of Forel
Diencephalon
Hypothalamus
Thalamus
•Command for the
•Chief relay centre for
control of autonomic
directing sensory messages functions such as heart
Helps regulate awareness
rate, blood pressure,
•Relays commands going
hunger, thirst.
to the skeletal muscles
•Role in emotions and
from the motor cortex.
motivation (e.g., thoughts
about fear get translated into
arousal through hypothalamus.)
Classification of Thalamic Nuclei
• I. Lateral Nuclear Group
• II.Medial Nuclear Group
• III.
Anterior Nuclear Group
• IV.
Posterior Nuclear Group
• V.
Metathalamic Nuclear Group
• VI.
Intralaminar Nuclear Group
• VII.
Thalamic Reticular Nucleus
Summary of Thalamic
Connectivity
• I. Sensory Input
•
general sensation
•
special sensation
•
taste, equilibrium, hearing, vision
• II.
Motor Input
•
cerebellum, basal ganglia
• III.
Reticular Formation
• IV.
Limbic System
•
mammillary nucleus
•
hippocampal formation
• Thalamus
• Functions of the thalamus
• I. Relay functions
•
from the spinal cord, brainstem, cerebellum basal ggl.
•
to
the cortex
• II. Modulatory functions
•
Influences the excitability of the cx, synchronised vs.
desynchronised states (repetitive and burst firing)
• III. Integrative functions
•
1. Sensory connections (sensory relay station)
•
2. Motor coordination
•
3. Psychological functions (instinct, affection, limbic
functions etc)
•
4. Autonom function control
•
5. Cortical activation
Clinical Syndromes of the Thalamus
Posterolateral thalamic syndromes
sensory disorders
Thalamic (Dejerine-Roussy) syndrome
----- VP nucleus - pain
Medial thalamic syndromes
disorders of consciousness
thalamic neglect, thalamic amnesia,
akinetic mutism
Anterolateral thalamic syndromes
motor disorders
paresis, ataxia, motor incoordination, dysphagia
Visual (Optic) Pathway
Modality: Vision
Receptor: Photoreceptor Cell of Retina
Cranial Nerve: II (Optic nerve)
1st Neuron: Bipolar Cell
2nd Neuron: Ganglion Cell
optic nerve
optic chiasm
optic tract
3rd Neuron: Lateral Geniculate Nucleus
optic radiation
Termination: Visual Areas (V I, V II)
Brodmann area 17 (V I), 18, 19 (V II)
Visual
Pathway
1. Optic nerve
2. Optic chiasm
3. Optic tract
4. Lateral
geniculate
body
5. Optic radiation
6. Visual cortex
Visual (Optic) Pathway
Clinical Features of Visual Pathway Lesion
1. optic nerve
2. optic chiasm
3. optic tract
4. 5. optic radiation
A. unilateral blindness
B. bitemporal hemianopsia
C. left homonymous
hemianopsia
D. left inferior homonymous quadranopsia
E. left superior homonymous quadranopsia
Signs of Visual Pathway Lesion
Optic nerve
- ipsilateral blindness
Optic chiasm
- bitemporal hemianopsia
Optic tract
- contralateral homonymous hemianopsia
Optic radiation
- contralateral homonymous quadranopsia
- intact light reflex
Visual Cortex
- contralateral homonymous quadranopsia
- macular sparing
Visual Field Defect
left inferior optic radiation lesion
right superior quadranopsia
Hypothalamus  Limbic System
Diencephalon3rd ventricle
Surrounded by cerebrum
Intermediate
mass
Hypothalamus
Pituitary gland
Mammillary body
Thalamus
Pineal body
Epithalamus
epithalamus Located at dorsal part of the diencephalons, it includes the
pinieal body. It secretes melatonin which signals the nighttime stage of the
sleep-wake cycle.
pineal body — internal secretion gland
habenular triangle— habenular nucleus
habenular commissure
thalamic medullary stria
posterior commissure
subthalamus
subthalamic nucleus
participate in the function of extracorticospinal tract