15 - Hypothalamus and Limbic System Flashcards by Jason Yin

Hypothalamus and Limbic System

Hypothalamus: HOMEOSTASIS; receiving stimuli
both exogenous and endogenous sources and responding with endocrine, autonomic and cognitive mechanisms
Drive Related Behaviors: Hunger, thirst, sleep, reproduction, emotions…
Limbic System: Integration between neocortex and hypothalamus and generating singularity of function (whole brain working together)

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Hypothalamus anatomy 2

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Hypothalamus anatomy 3

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Hypothalamus anatomy 4

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Medial preoptic nucleus

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: anterior nucleus

Somatostatin → Inhibits release of GH

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Supraoptic nucleus

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Paraventricular nucleus

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Ventromedial nucleus

Growth hormonereleasing hormone→Growth hormone

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Dorsomedial nucleus

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Arcuate nucleus

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hypothalamic nucleus, their releasing hormones (chemical messengers), and the hormone they cause to be released from the pituitary: Lateral hypothalamic zone

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Supraoptic and Paraventricular nucleus

magnocellular neurons produce ADH/VP and oxytocin and
secrete in posterior pituitary (neurohypophysis, only two hormones released from posterior)

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Suprachiasmatic nucleus

circadian rhythms… efferent projections innervate the pineal for melatonin production; VIP, GRP, ADH maintain clock and help regulate feeding and thirst behaviors in
circadian patterns. VIP/GRP (vasoactive intestinal peptide and gastrin releasing peptide)

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Anterior nucleus

temperature regulation (cooling/sweating and vasodilation)

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Medial/Lateral Preoptic nucleus

gonadotropins, sexual behavior, sexually dimorphic

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Ventromedial nucleus

Satiety center. Stimulation inhibits feeding, lesion leads to hyperphagia

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Dorsomedial nucleus

Olfactory, behaviors; fear, rage , aggression, aversion. Stimulate in cats: piloerection, arching of back, biting, hissing. Similar results with amygdala, and PAG.

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Arcuate nucleus

Dopamine inhibition of prolactin. Site of neurokinin system targeted with FDA approved drug for HOT FLASHES

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Mammillary Bodies

termination site of fornix, initiation site of mammilothalamic tract.
Involved with recall memory of aversive vs pleasurable stimuli

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Posterior nucleus

rostral extension of PAG, related to fear, aggression, and analgesia. Temperature regulation (heating/vasoconstriction and shivering).

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Tuberomammilary nucleus:

(just below mammillary bodies) histamine, attention and wake states

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Periventricular Region

Produces somatostatin, thyroid releasing hormone,
somatostatin, leptin, gastrin, GnRH and neuropeptide y. Part of endogenous analgesia system with connections to PAG

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Lateral Nucleus

**Hunger center**. Stimulation in animals leads to feeding, lesion leads to anorexia. **OREXINS** – related to **feeding behavior** and **Sleep/Wake cycles**

AFFERENTS TO THE HYPOTHALAMUS (diagram)

EFFERENTS FROM THE HYPOTHALAMUS

hypothalamic pathways: cranial nerves, spinothalamic tract, lower motor neurons, and spinal cord

Lesions of the Hypothalamus

Hypothalamus and Pituitary Function - Hormonal Deficiencies: ADH/VP deficiency

**Diabetes insipidus**, excessive thirst, drinking and urine production

Hypothalamus and Pituitary Function - Hormonal Deficiencies: Growth hormone deficiency

**Adults:** Increased cardiovascular disease, obesity, reduced muscle strength and exercise capacity, and increased cholesterol. **Infants:** Hypoglycemia. **Children:** Decreased height and growth rate

Hypothalamus and Pituitary Function - Hormonal Deficiencies: Gonadotrophin deficiency

**Men:** Diminished libido and impotence; testes shrink, spermatogenesis is preserved. **Women and Adolescent Girls:** Diminished libido and dyspareunia; breast atrophy in chronic deficiency. **Children:** Delayed or frank absence of puberty.

Hypothalamus and Pituitary Function - Hormonal Deficiencies: Thyrotropin deficiency

Malaise, weight gain, lack of energy, cold intolerance, and constipation

Hypothalamus and Pituitary Function - Hormonal Deficiencies: Corticotrophin deficiency

Mineralocorticoid function (angiotensin-renin axis dependent) is not affected; deficiency limited to glucocorticoids and adrenal androgens. Initially symptoms nonspecific (weight loss, lack of energy, malaise); severe adrenal insufficiency may present as a medical emergency

Hypothalamus and Pituitary Function - Hormonal Deficiencies: Panhypopituitarism

Refers to deficiency of several anterior pituitary hormones; may occur in a slowly progressive fashion (eg, pituitary adenomas)

Hypothalamus and Pituitary Function - Hormone Overproduction: Prolactin

Hypogonadism, if hyperprolactinemia sustained. **Women:** amenorrhea, galactorrhea, and infertility. \ **Men:** decreased libido, impotence, and rarely galactorrhea

Hypothalamus and Pituitary Function - Hormone Overproduction: Growth Hormone

**Children**: pituitary gigantism. **Adults**: acromegaly, large hands and feet, face coarseness, prognathism, changes in voice, and hirsutism. Glucose intolerance with 20% of patients progressing to diabetes mellitus. Respiratory difficulty, sleep apnea, cardiomyopathy and myopathy, carpal tunnel, lumbar canal stenosis, colonic polyps

Hypothalamus and Pituitary Function - Hormone Overproduction: Thyrotropin

Can lead to hyper or hypo-thyroid, cardiac, respiratory and CN III, IV and VI dysfunction

Bitemporal hemianopsia

Tumors of the pituitary that compress the optic chiasm leads to a pathognomonic visual field deficit

Blood supply to the hypothalamus is from circle of Willis branches especially posterior cerebral, posterior communicating, anterior cerebral, anterior communicating.

LIMBIC SYSTEM

Limbic System Overview

* Connects Neocortex to Hypothalamus * Coordinates Emotional, Behavioral, and Autonomic Response to External Stimuli * Contributes to Learning and Memory * Contains Brain Regions Associated with Pleasure and Aversion

Papez Circuit 1937

Limbic Structures

Limbic Structures - * Hippocampus

* Widespread inputs and outputs * Short term and declarative memory * Site of adult neurogenesis * Highly excitable, linked to common forms of focal epilepsy

Limbic Structures - Amygdala:

* Widespread inputs/outputs; informs cortical response to external stimuli * Associated with fear, anger, aversion, recognizing threats in faces, sounds

Limbic Structures - Septal Area/ Basal Forebrain

Limbic Structures - Cingulate Gyrus:

Access to all regions of neocortex and relays information to and from the hippocampus via the **cingulum**

Limbic Structures - Parahippocampal/Entorhinal/Piriform/Uncus

* Ventral cortical regions provide input to amygdala and hippocampus from septal, olfactory nuclei and cingulum

Limbic structure anatomy - fornix, hippocampus, amygdala

Limbic structure anatomy - hippocampus and amygdala

hippocampus, fornix - structure

hippocampus surrounds structures - anatomy

hippocampal cortex proximity

**Hippocampal Formation**

hippocampal anatomy - Cingulate Gyrus 13 Septal nuclei 17 Nucleus Accumbens 16 (aka ventral striatum 16)

hippocampal anatomy - Fornix (body 19, Columns 18)

hippocampal anatomy - Fornix 30, 23 Anterior nucleus of thalamus 16 Mammilothalamic tract 18 Stri Terminalis/Terminal Vein 17 Amygdala 6

hippocampal anatomy - Mammilothalamic tract 25 Amygdala 13 Stria Terminalis/Terminal Vein 20 Hippocampus 9

hippocampal anatomy - Stria Medularis Thalami 37 Hippocampus 11 Stria Terminalis 22 Crua of Fornix 18

hippocampal anatomy - Crua of Fornix 4 Fimbria of Fornix 9 (alveus of fornix 24) Habenula 31 Habenulointerpeduncular tract 29 Stria Terminalis 20

hippocampal anatomy - Hippocampus proper 21 Dentate gyrus 22 Subiculum of hippocampus 23 Stria Terminalis 17

hippocampal anatomy - Hippocampus proper 18 Dentate gyrus 19 Subiculum of hippocampus 20 Crua of Fornix 12

Connections of the Amygdala

Hippocampal Connections

Septal Region and Reticular Formation

amygdala function (diagram)

amygdala functions

Limbic Structure Main Functions

Limbic Structure Main Functions - Hippocampus

* Learning, short-term memory, processing for long term memory, spatial memory: site of early damage in Alzheimer.

Limbic Structure Main Functions - Amygdala

* Stimulation generates fear, aggression, rage; recognition of emotion in others. * Lesion leads to apathy, placid, tame attitude. Inappropriate response to threat. * Discrimination of aversive versus pleasing stimuli.

Limbic Structure Main Functions - Septal Nuclei including basal forebrain groups and nucleus accumbens

* Accumbens linked to pleasure center! Animals self stimulating this region will not stop! * Lesions lead to anhedonia, flat affect. * Cholinergic basal forebrain nuclei = cognition

Limbic Structure Main Functions - Cingulate/Cingulum:

* The cingulate gyrus has access to all neocortical regions. The cingulum is the main fiber tract connecting neocortical association areas to the hippocampal system

Limbic Structure Main Functions - Parahippocampal/Entorhinal/Piriform/Periamygdaloid/Uncus

* Olfactory and gustatory input to amygdala and hippocampus * Processing of input from cingulum

hypothalamus and limbic - Clinical Correlations: Wernicke Encephalopathy-Kosakoff Psychosis

* Thiamine deficiency; malnutrition, chronic alcoholism, bariatric surgery * Damage to mammillary bodies: Hypothalamus * Acute confusion, memory deficits, confabulation

hypothalamus and limbic - Clinical Correlations: Encephalopathy

* HSV-1 and temporal lobe infection

hypothalamus and limbic - Clinical Correlations: Temporal Lobe Epilepsy

* Circuit loops between hippocampus and temporal cortex * Sclerosis of mesial temporal structures (hippocampus, amygdala)

hypothalamus and limbic - Clinical Correlations: Emotion, Behavior, Learning, Memory:

* Perception of Facial Emotion * Social Exchange, “cheating” * Probabilistic Learning: outcomes and consequences for actions

hypothalamus and limbic - Clinical Correlations: Addictive behaviors:

* Ventral tegmental area to nucleus accumbens is main reward circuit * Drugs, alcohol, food, gambling, sex… * Dopaminergic system alterations linked to addictions

Kluver- Bucy Syndrome (1937)