Limbic System
II: Amygdala, Hypothalamus
Competencies:
- Explain how the anatomy of the amygdala provides a model for the integration of visceral and gustatory sensory information and the behavioral (e.g. affect, goal oriented) responses to those stimuli.
- Discuss the role of the ventral stiratum and basal forebrain working in concert with the prefrontal cortex with respect to drive, reward and motivation.
- Describe the neuroendocrine and central regulatory roles of the various regions of the hypothalamus.
- Identify the medial forebrain bundle and its relationship to the extended limbic system.
To master the material presented in this
lecture:
Read ...
Purves text, pp 456-458
Haines pp 284-287.
Look at the Review Questions below ...
Listen to the lecture and focus on the
following points ...
Revisit the Points Regarding the Amygdala Provided for the Previous Lecture.
-
The hypothalamus is more that just
the “master endocrine gland”. It is a critical locus
for the regulation of autonomic function and the integration of
autonomic function with goal directed behaviors. A critical pathway,
the medial forebrain bundle, courses through the lateral hypothalamus.
This “bundle” is important for communication and coordination
between limbic forebrain, hypothalamic and brainstem consummatory
centers.
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Key centers include:
-
Preoptic - sexual differentiation,
reproductive function and behavior
-
Anterior - parasympathetic
regulatory center
-
Magnocellular paraventricular
and supraoptic nuclei - vasopressin and oxytocin synthesis and
release
-
Suprachiasmatic - circadian
and seasonal rhythm generator
-
Parvocellular paraventricular,
arcuate nucleus and median eminence - pituitary releasing factors
-
Parvocellular paraventricular,
ventromedial and arcuate nuclei and lateral regions - metabolism,
eating and drinking behaviors
-
Parvocullular paraventricular
and lateral regions - origen of "stress" pathways
to brainstem and spinal cord that utilize corticotropin releasing
hormone as the chemical transmitter.
-
In animal models, lesions
of the lateral hypothalamus (lateral to the fornix) produce a syndrome
characterized by aphagia and adipsia. Of course, it is impossible
to distinguish between effects induced by damage to cell bodies
vs damage to the medial forebrain bundle. Recently, a neurochemically
distinct population of neurons has been identified in the lateral
hypothalamus that utilize the unique neuropeptide orexin (also known
as hypocretin) that appear to be involved in a circuit that regulates
feeding behavior.
Consider the Following Questions ...
-
Which hypothalamic nucleus is involved?
- Circadian activity rhythm.
- Diabetes insipidis.
- Synthesis of oxytocin.
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A patient is periodically spiking a high temperature, has ceased menstruating, and has excessive mood swings. She might be suspected of having a tumor in what part of the hypothalamus? What would be an effective way to image the suspected tumor?
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What is the medial forebrain bundle? Where do you find it?
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What is the role of the amygdala in limbic system function? Is it considered a single functional unit, or is it better to associate subunits of this region with different neural systems? Why?
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What is the functional significance of the ventral striatum/nucleus accumbens? What region of the cortex is antomically associated with these striatal regions?
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