Download Nolte Chapter 23 – Drives and Emotions: The

Nolte Chapter 23 – Drives and Emotions: The Hypothalamus and Limbic System
Limbic system is interposed between the hypothalamus and the neocrotex, so limbic structures serve as
birdges between autonomic and voluntary responses to changes in the environment.
the hypothalamus is concerned with autonomic, endocrine, emotional, and somatic functions that
maintain our internal environment(homeostasis).
Three components: intereconnections with the limbic system, outputs that influence the pituitary, and
interconnection with various visceral and somatic nuclei.
Hypothalamic Divisions
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The inferior surface of the hypothalamus, excluding the mammillary bodies is the tuber
cinereum
o the median eminence protrudes from the ventral surface of this and is continuous with
the infundibular stalk, which is then continuous with the posterior pituitary.
 taken together (infundibular stalk and posterior pituitary) is known as the
neurohypophysis
the medial surface of the hypothalamus extends anteriorly to the lamina terminalis.
the hypothalamus can be subdivided from anterior to posterior as anterior, tuberal, and
posterior regions.
o the anterior is above the optic chiasm
o tuberal region is above and including the tuber cinereum
o posterior region is right above the including the mammillary bodies
longitudinally it can be subdivided into the
o perventricular (wall of the third ventricle) which is a rostral continuation of the
periaqueductal gray
 the dorsal longitudinal fasciculus is a bundle of hypothalamic afferents and
efferents
 suprachiasmatic nucleus
 a master clock that gets direct projections from the retina and releases
melatonin in conjunction with the pineal
 arcuate nucleus
 feeding behavior
o the lateral zone (lateral to the fornix) which is a rostral continuation of the reticular
formation
 has the medial forebrain bundle
 anteriorly it has the lateral preoptic nucleus that is a sleep-promoting area
 caudally it is continusous with the reticular formation
 also contains the lateral tuberal nuclei and the tuberomammillary nucleus which
is the source of histaminergic fibers that project widely to the cerebral cortex to
participate in the sleep-wake cycle.
o the medial zone
 has neurosecretory cells
 supraoptic and paraventricular
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secrete hormones that travel down the axons of these cells and
are released in the neurohypophysis
inputs to the hypothalamus include the forebrain (particularly the limbic system) and the brainstem and
spinal cord.
Brainstem conveys visceral and somatic sensory information and limbic structures convey information
relevant to the role of the hypothalamus in mediating many of the autonomic and somatic aspects of
affective states.
Major forebrain afferents include the septal nuclei, hippocampus, amygdala, insula, and the retina.
Septal nuclei project fibers to the hypothalamus in the medial forebrain bundle.
The major output of the hippocampus is the fornix
the amygdala projects to the hypothalamus via the stria terminalis, which accompanies the caudate
nucleus. Or they pass under the lenticular directly to the hypothalamus.
There are direct projections from the cerebral cortex to the hypothalamus that mainly arise in orbital
and medial prefrontal cortex and in the insula and join the medial forebrain bundle. There are also
contributions from the cingulate.
Afferents travel in the medial forebrain bundle. Others are contained in the dorsal longitudinal
fasciculus. VTA also projects to the hypothalamus.
Some cells in the hypothalamus are sensitive to the temperature of the hypothalamus itself and the
blood osmolality or the concentration of glucose or certain hormones.
Outputs from the hypothalamus largely reciprocate inputs
Their efferents blanket the cortex. Histaminergic fibers from the tuberomammillary nucleus and
orexinergic fibers from the tuberal and posterior hypothalamis do this.
mammilothalamic tract foes to the anterior nucleus of the thalamus.
There are branches to the midbrain reticular formation by way of the mammilotegmental tract.
Hypothalmic Control of the Pituitary Gland
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efferents of the hypothalamus control the hypophysis (pituitary gland)
The pituitary has an two lobes
o posterior lobe develops as a downward outgrowth of the diencephalon
o anterior lobe develops from the roof of the mouth
the pituitary has an upward extension around the infundibular stalk and constitutes the
adenohypophysis that is anterior to the neurohypohosis
Supraoptic and paraventricular propduce two peptide hormones
o vasopressin which increases reabsorption of water in the kidney and decreases the
production of urine
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oxytocin which causes contraction of uterine and mammary smooth muscle and is
important in parturition and milk ejection.
o these hormones travel down the axons of their parent cell bodys by axoplasmic flow in
what is called the supraopticohypophyseal tract
the hypophyseal support system is a vascular connection between the hypothalamus and the
adenohypophosis via the superior hypophyseal artery (a branch of the carotid)
o it breaks up into a capillary bed in the prximal part of the infundibular stalk then sends
vessels down the infundibular stalk to a second capillary bed in the adenohypophysis
 small peoptides called hypothalamic releasing hormones and inhibiting
hormones get released by the arcuate into this bloodstream.
the nuecleus of the solitary tract, the parabrachial nuclei, the reticular formation, and
periaqueductal gray all work together with the thalamus.
o nucleus of solitary tract is the principal viscery nucleus with primary afferent nerves in
VII, IX, and X conveying info about taste and internal organs.
o parabrachial have a more general role in visceral sensation and give the general
sensation of general well-ornotsowell-being since it receives inputs from the solitary
tract nucleus and deals with spinothalamic inputs of pain and temperature
o central pattern generators in the reticular formation help with cardiovascular, respitory,
and micruition.
o periaqueductal gray helps descending control of pain.
The hypothalamus has a maintained value at a set point that it likes to be. deviation of that creates an
error signal that then activates mechanisms to decrease that error signal.
medial preoptic nuclei are directly warm-sensitive, firing faster as their temperature increases
body water can also be regulated by the medial preoptic neurons. decreased water volume causes a
decrease in blood volume and an increase in its osmality. this stimulates receptors in an near the heart
which is transmitted via the flossopharyngeal and vagus nerves to the nucleus of the solitary tract and
then sent to preoptic neurons. medial preoptic can also get signals from the kidney and project to ADH
secreting neurons in the supraoptic and pareventricular nuclei which leads to increased reabsorption of
water by the kidnesy and signals to the cerebral cortex that say “I’m thirsty”.
arcuate nucleus is related to feeding behavior and receives projection from the nucleus of the solitary
about stomach contents and glucose content. Ghrelin is secreted by the stomach at rates that increase
with time since the last meal. it binds to arcuate neurons and stimulates feeding behavior. Leptin id
produces by adipocytes and cause the opposite effect.