Chapter 11, Section 4
The Diencephalon, Brainstem, and Cerebellum
Diencephalon
• The diencephalon is located between cerebral
hemispheres and superior to the midbrain
• It surrounds the third ventricle
Structures within the diencephalon:
• Thalamus
• Epithalamus
• Hypothalamus
• Optic tracts & Optic chiasm
• Mammillary bodies
• Pituitary Stalk (infundibulum)
• Pineal gland
Structures within the diencephalon:
Figure 11.21. A sagittal section
showing the diencephalon in brown
and the brainstem in yellow.
The thalamus is a sensory
relay center:
• Receives all sensory
impulses (except smell)
• The thalamus relays
Thalamus
• The thalamus relays
impulses to appropriate
areas of the cerebral cortex
for interpretation
Example: Figure 12.42. The lateral
geniculate nucleus (LGN) within the
thalamus relays impulses from the retina
to the visual cortex for interpretation.
Hypothalamus
The hypothalamus regulates a variety of visceral activities including:
1. Body temperature 2. Heart rate and blood pressure
3. Hunger and thirst 4. Sex drive
5. Influences moods and emotions 6. regulates endocrine system
The Limbic System
The limbic system is a region of the diencephalon and the deeper regions of the
cerebrum important for controlling emotions and memory.
Functions of the Limbic System
1. Memory1. Memory
2. Reproduction
3. Emotions
(fear, anger, pleasure, sorrow)
4. Hunger and feeding
1. Cingulate Gyrus – Satisfaction Center
• Feeling satisfied after a meal or after
sexual intercourse
• Damage may result in voracious appetite
or unusually high sex drive
2. Hippocampus
• Within deep temporal lobe
The Limbic System
• Within deep temporal lobe
• Role in memory and spatial cognition
• Alzheimer's results in degeneration of
hippocampus
3. Amygdala
• Assigns emotion to a memory (pleasant
or unpleasant)
• Like or dislike a person you see
• Fear of heights
Brainstem
The brainstem connects the brain to the spinal cord.
It includes three parts:
1. Midbrain
2. Pons
3. Medulla Oblongata
Figure 11.15a. Sagittal section of the brain. The
three portions of the brainstem are shown in yellow.
Midbrain
The midbrain is located between the diencephalon and the pons.
Fibers of the midbrain join lower parts of brainstem and
spinal cord with higher part of brain
• Corpora Quadrigemina “Body of 4 twins”
• Superior Coliculi – visual reflexes
• Inferior Coliculi – auditory reflexes
• Cerebral Peduncles
•Ventral surface of midbrain
•Main motor pathway from cerebrum to
lower CNS
Midbrain
• Substantia nigra
• Involved in coordinating voluntary movements
• Secretes dopamine – inhibitor neurotransmitter
• Communicates with Basal Nuclei within cerebrum
Cross section through midbrain. Dark portions
are substantia nigra. Opening in center is
cerebral aqueduct.
•Parkinson’s disease results in degeneration of substantia
nigra and basal nuclei.
Pons
• The pons appears as a rounded bulge on the ventral aspect
of the brainstem
• Located between the midbrain and medulla oblongata
• Dorsal aspect – Longitudinal fibers
connect medulla oblongata and cerebrum
The Pons is a “Bridge”
connect medulla oblongata and cerebrum
•Ventral aspect- Transverse fibers
connect cerebellum and cerebrum
Figure 11.20a. Ventral
view of the brainstem.
•Pontine Respiratory Center – functions
with medulla to maintain basic rhythm of
breathing
Medulla Oblongata
• The medulla is an enlarged extension of the spinal cord.
•Conducts ascending and descending impulses between brain and
spinal cord
Structures:Structures:
1. Pyramids
• Site of motor tract decussation
(crossing over)
2. Olives
• Passages for fibers to cerebellum
Nuclei of Medulla:
1. Cardiac center – regulates heart rate
2. Vasomotor center – regulates blood pressure
3. Respiratory center – regulates rhythmic breathing
Medulla Oblongata
1 = cerebral peduncles.
2 =pons with transverse fibers leading
towards cerebellum.
Ventral surface of brainstem.
towards cerebellum.
3 & 4 = pyramids on the medulla
Cerebellum
The cerebellum “little brain” is inferior to occipital
lobe of the cerebrum, and posterior to the pons.
Functions of the cerebellum include:
1. Integrates sensory information
2. Balance and posture
3. Coordinates motor activity
4. Learning and practicing4. Learning and practicing
Cells within the cerebellum
1. Purkinje cells – larges cells in CNS
• Gatekeepers of impulses leaving
the cerebellum
2. Dentate Nucleus – balance and
proprioception
Cerebellum
The cerebellum communicates with the CNS by means of tracts, called cerebellar
peduncles:
1. Inferior peduncles – relays sensory impulses of the actual position of limbs
and joints from medulla to cerebellum
2. Middle peduncles – transmits impulses from the cerebral cortex to the
cerebellum of the desired position of these body parts.
3. Superior peduncles – sends correcting impulses from dentate nucleus of
cerebellum to midbrain, adjusting the position of a limb.
Damage to cerebellum may result in loss of balance,
tremors, and inaccurate movements
Figure 11.22 the cerebellum communicates with other
parts of the CNS by means of the cerebellar peduncles.
End of Chapter 11, Section 4