Diencephalon

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Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral heispheres
 Made of three parts
 Thalamus
 Hypothalamus
 Epithalamus
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Diencephalon
Figure 7.15
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Figure 4.8 The human brain stem
This composite structure extends from the top of the spinal cord into the
center of the forebrain. The pons, pineal gland, and colliculi
are ordinarily surrounded by the cerebral cortex.
The Brainstem: Medulla oblongata
Most inferior portion, functions as
a conduction pathway (descending
motor neuron pathways decussate
here)
Reflex centers for:
regulating heart rate
blood vessel diameter
coughing, sneezing
breathing
swallowing
The Brainstem: Pons
Superior to Medulla
oblongata.
Contains more ascending
and descending pathways.
Relays information from
cerebrum to cerebellum.
Also includes sleep and
respiratory centers.
The Brainstem: Midbrain
Small section superior to
the pons.
Part of the auditory
pathways and visual
reflexes
Also involved in regulating
muscle tone/activity and
coordination
The Brain: Reticular formation
2 types of nuclei:
Cranial nerves III-XII
and
Reticular Formation nuclei which
are scattered throughout
brainstem
Many pathways from RF project
directly to cerebrum to modulate
activity
Habituation (repetitive stimuli)
Reticular Activating System
The Diencephalon: Thalamus
“Gateway to cerebral cortex”
Most sensory stimuli project to
the thalamus, which in turn
projects to the cerebrum.
Thalamus also influences
moods and activities associated
with strong emotion.
(Two concepts: Sensory
integration and Mood)
The Diencephalon: Hypothalamus
Major control center of
autonomic nervous system
and endocrine system.
Centers associated with:
* Food/H2O intake
* Thermoregulation
* Cardiovascular regulation
* Hormone secretion
* Sleep/waking
* Emotional behavior
Thalamus
 Surrounds the third ventricle
 The relay station for sensory impulses
 Transfers impulses to the correct part of
the cortex for localization and
interpretation
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Slide 7.35
Hypothalamus
 Under the thalamus
 Important autonomic nervous system
center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
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Hypothalamus
 An important part of the limbic system
(emotions)
 The pituitary gland is attached to the
hypothalamus
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Epithalamus
 Forms the roof of the third ventricle
 Houses the pineal body (an endocrine
gland)
 Includes the choroid plexus – forms
cerebrospinal fluid
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Slide 7.37
Brain Stem
 Attaches to the spinal cord
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata
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Brain Stem
Figure 7.15a
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Midbrain
 Mostly composed of tracts of nerve
fibers
 Reflex centers for vision and hearing
 Cerebral aquaduct – 3rd-4th ventricles
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Slide 7.39
Pons
 The bulging center part of the brain
stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.40
Medulla Oblongata




The lowest part of the brain stem
Merges into the spinal cord
Includes important fiber tracts
Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.41
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