Thalamus, Hypothalamus and Limbic System

2. The limbic system
• The limbic system, also known as the
paleomammalian cortex, is a set of brain
structures located on both sides of the thalamus,
immediately beneath the medial temporal lobe of
the cerebrum primarily in the forebrain.[1]
• It supports a variety of functions including
emotion, behavior, motivation, long-term
memory, and olfaction.[2] Emotional life is largely
housed in the limbic system, and it critically aids
the formation of memories.

4. Limbic System Structures
• Amygdala: the almond-shaped mass of nuclei
involved in emotional responses, hormonal
secretions, and memory. The amygdala is
responsible for fear conditioning or the
associative learning process by which we learn
to fear something.
• Cingulate Gyrus: a fold in the brain involved
with sensory input concerning emotions and the
regulation of aggressive behavior.
• Fornix: an arching, band of white matter axons
(nerve fibers) that connect the hippocampus to
the hypothalamus

5. Hippocampus: a tiny nub that acts as a memory indexer –
sending memories out to the appropriate part of the
cerebral hemisphere for long-term storage and retrieving
them when necessary.
Hypothalamus: about the size of a pearl, this structure
directs a multitude of important functions. It wakes you up
in the morning and gets the adrenaline flowing. The
hypothalamus is also an important emotional center,
controlling the molecules that make you feel exhilarated,
angry, or unhappy.
Olfactory Cortex: receives sensory information from the
olfactory bulb and is involved in the identification of odors.
Thalamus: a large, dual lobed mass of gray matter cells
that relay sensory signals to and from the spinal cord and
the cerebrum

6. Disorders of the limbic system
• Anxiety and high amounts of stress (including
increased cortisol levels) also have an impact on
inflammation levels, digestion and gut health,
cardiovascular functions, your immune system,
and the reproductive system — sometimes
contributing to disorders like diabetes, insomnia,
high blood pressure, higher susceptibility to
infections and infertility.

8. Hypothalamus
• Hypothalamus- region of the brain lying below
the thalamus and making up the floor of the third
cerebral ventricle. The hypothalamus is an
integral part of the brain. It is a small cone-
shaped structure that projects downward from
the brain, ending in the pituitary (infundibular)
stalk, a tubular connection to the pituitary gland.
The hypothalamus contains a control centre for
many functions of the autonomic nervous
system, and it has effects on the endocrine
system because of its complex interaction with
the pituitary gland.

9. Anatomy of Hypothalamus
• The hypothalamus and pituitary gland are
connected by both nervous and chemical
pathways. The posterior portion of the
hypothalamus, called the median eminence,
contains the nerve endings of many
neurosecretory cells, which run down through
the infundibular stalk into the pituitary gland.
Important structures adjacent to the median
eminence of the hypothalamus include the
mammillary bodies, the third ventricle, and the
optic chiasm (a part of the visual system). Above
the hypothalamus is the thalamus.

11. Hypothalamic Dysfunctions
• Injuries or diseases affecting the hypothalamus
may produce symptoms of pituitary dysfunction
or diabetes insipidus; in the latter disorder, the
absence of vasopressin, which promotes the
reabsorption of water in the kidneys, induces the
rapid loss of water from the body through
frequent urination. Hypothalamic disease can
also cause insomnia and fluctuations in body
temperature. In addition, the optic chiasm is
particularly susceptible to pressure from
expanding tumours or inflammatory masses in
the hypothalamus or the pituitary gland.
Pressure on the optic chiasm can result in visual
defects or even blindness.

12. Thalamus
• Thalamus, plural thalami, either of a pair of
large ovoid organs that form most of the lateral
walls of the third ventricle of the brain. The
thalamus translates neural impulses from
various receptors to the cerebral cortex. While
the thalamus is classically known for its roles as
a sensory relay in visual, auditory,
somatosensory, and gustatory systems, it also
has significant roles in motor activity, emotion,
memory, arousal, and other sensorimotor
association functions.

14. Thalamic nuclei
• The major nuclei of the thalamus include the
relay nuclei, association nuclei,
midline/intralaminar nuclei, and the reticular
nucleus. With the exception of the reticular
nucleus, these nuclear groups are divided
regionally (i.e., anterior, medial, and lateral) by
sheets of myelinated neural fibres known as the
internal medullary lamina. The reticular nucleus
is separated from the remainder of the thalamic
nuclei by the external medullary lamina.

16. Functions of Thalamus
• The thalamus functions as an anatomical
region of the brain, located in the center of the
brain, between the cerebral cortex and the
midbrain. The thalamus is involved in several
cognitive functions, such as serving as a central
hub to relay sensory information to the brain,
regulating sleep and consciousness, and the
regulation of anger and aggression. Like most
areas of the brain, the thalamus is
multifunctional in nature so it handles a number
of different

17. Thalamic Dysfunctions
• Thalamic Diseases: Disorders of the centrally
located thalamus, which integrates a wide
range of cortical and subcortical information.
Manifestations include sensory loss,
MOVEMENT DISORDERS; ATAXIA, pain
syndromes, visual disorders, a variety of
neuropsychological conditions, and COMA.
Relatively common etiologies include
CEREBROVASCULAR DISORDERS;
$CRANIOCEREBRAL TRAUMA$; BRAIN
NEOPLASMS; BRAIN HYPOXIA;
INTRACRANIAL