HYPOTHALAMUS (part of diencephalon)

maintains HOMEOSTASIS (temperature, fluid balance, energy balance)

by regulating

the endocrine system the autonomic systemthe limbic system

Neural AND non-neural (humoral) inputs

Neural AND neuro-endocrine outputs

mammillary body

anterior commissure

infundibulum

hypothalamus

3rd ventricle

lateralventricle

4th ventricle

3rd ventricle

cerebralaqueduct

interventricular foramen

Hypothalamus: medial view and parts

mammillary body

tuber cinereummedian

eminence

infundibulum

Hypothalamus in horizontal section

hippocampus

cerebral peduncle

substantia nigra

inferior colliculus

amygdala

middle cerebral artery

interpeduncular fossa

hypothalamus

Hypothalamus in coronal section: anterior

Coronal planes

BA

hypothalamus

optic chiasm

anteriorcommissure

Sagittal View of Right Hemisphere

hypothalamus

A. Level of anterior commissure

septal nuclei

3rd ventricle

putamen

lateral ventricle

Basal forebrain

Coronal planes

BA

hypothalamusoptic chiasm

anterior commissure

Sagittal View of Right Hemisphere

hypothalamus

A. Level of anterior commissure

septal nuclei

third ventricle

putamen

lateral ventricle

caudate

Hypothalamus in coronal section: posterior

B: Level of mammillary bodies

mammillary body

hypothalamusthird ventricle

thalamus

internalcapsule

lateral ventricle

putamen

Hypothalamus: Antero-posterior regions

anterior (supraoptic)

posterior (mammillary)

middle (tuberal)

Preoptic area (not seen here) is antero-lateral to anterior region

TC: tuber cincereumME median eminanceINF infundibulum

optic chiasm

MAM

PV

VMH

DMH

AH

PH

INF SC

SO

fornix

anterior commissure

pineal

Hypothalamic nuclei

INF=ARC

SO: supraoptic nucSC: suprachasimaticPV: paraventricularINF: infundibular nuc AKA arcuate nucDMH: dorsomedial hypothalamic nucVMH: ventromedial hypothalamic nucPH: posterior hypothalamic nucAH: anterior hypothalamic nucMAM: mammilary bodies/nuc

Magnocellular cells: SO and PV.

Send axons to posterior pituitary which release oxytocin and ADH into the blood system

Oxytocin: parturition/lactationADH (antidiuretic hormone): conserves water at level of kidneys

Parvocelllular cells:

(PO, PV, AH, PH, VMH, INF)

Small cells involved in control of anterior pituitary. They are found throughout the hypothalamus and especially in the infundibular (arcuate) nucleus.

Hypothalamic Nuclei: Summary of Function

Anterior HypothalamusPO* (preoptic nucleus) water intake, sleep SC circadian rhythms, retina inputSO oxytocin, ADH productionPV* oxytocin, ADH productionAH* temperature (heat loss), sleep-waking

* These nuclei also have cells that control the anterior pituitary gland

Hypothalamic Nuclei: Summary of Function

Tuberal hypothalamusDMH feeding, rageVMH* feeding, rageINF* (ARC) endocrine control

Tuberomamillary nucleus: sleep/waking

Hypothalamic Nuclei: Summary of Function

Posterior Hypothalamus

MAM memory

PH* temperature, (heat conservation),

sleep-waking

Regulation of temperature:

AH: anterior hypothalamus (heat loss) think A/C “cooling”

PH: posterior hypothalamus (heat conservation)

Regulation of blood osmolarity:SO: anterior hypothalamus (ADH)PV: anterior hypothalamus (ADH)

Regulation of metabolism/emotion:VMH (tubal hypothalamus) feeding/rageTMH (tubal hypothalamus) feeding/rage

Regulation of pituitary gland (parvocellular cells):PO, PV, AH, VMH, INF, PH

Memory: MeMory = MaM

MAM (posterior hypothalamus)

Hypothalamus inputs: overview

Hyppocampus–(fornix)

Olfactory and limbicstructures –(MFB)

Amygdala –(stria terminalis)

Retina –(optic tract)

Brainstem (solitary nucleus) –(DLF)

Temperature, osmolarity, hormones –(non-neuronal)

HYPOTHALAMUS

Hypothalamus outputs: overview

--(fornix, MFB, VAF) limbic system

--(mammillothalamic tract) thalamus

--(DLF, hypothalamo-spinal tract) brainstem (autonomic efferents)

--(portal system and posterior system) pituitary

HYPOTHALAMUS

Pituitary gland = hypophysis

Anterior pituitary = endocrine cellsPosterior pituitary = axon terminals

of PV and SO nuclei

infundibulum

post. pituitary

supraoptic nucleus

paraventricular nucleus

Hypothalamic axons

Posterior pituitary: hypothalamic axons release vasopressin (ADH) and oxytocin to blood

Anterior pituitary gland: endocrine cells releasing hormones

median eminencecapillaries

RFsIFs

anterior pituitary sinusoids

hypophyseal portal vessels

Hormones from endocrine cells

releasing & inhibiting factors

Hypothalamus: Head Ganglion for ANS

• Inputs from – Viscera (afferents via CN X and IX to caudal

solitary nucleus) – somatic afferents– limbic system

• Outputs to – autonomic centers in brainstem– parasympathetic cranial nerve motor

nuclei (via DLF)– sympathetic spinal cord motor nuclei

(via hypothalamo-spinal tract)

dorsallongitudinal fasciculus

hypothalamo -spinal fibers

DMNX

hypothalamo-spinal fibers

IML=lateral horn

Lesion to descending hypothalamo-spinal fibers

(sympathetic pathway)

=

Horner’s Syndrome

Ptosis, miosis and anhydrosis

Limbic SystemPlays a role in emotions, emotional behaviors, learning, memory and navigation through space

Bilateral temperal lobectomy in monkeys: tame, fearless, placid, with a flat affect. Compulsive oral behavior, inappropriate hypersexuality and visual agnosia.

Patient HM = bilateral medial temporal lobectomy: demonstrated role of limbic system in learning and memories (hypothalamus important in committing new long term memories)

Emotions

Response patterns (emotional expression or behavior) measurable

Behavioral: muscle response (e.g. facial expression)ANS activationHormone secretion

Feelings (emotional experience)not easily measurable

Negative (anxiety, fear, anger)Positive (euphoria: rarely studied)

Limbic System

Anatomically speaking:• Limbic lobe• Hippocampus (fornix forms the

output fibers)

• Amygdala (stria terminalis forms the output tract)

• Septal nuclei• (Nucleus accumbens)

Limbic lobe: C-shaped medial border of hemisphere

septal nuclei

subcallosal gyrus

cingulate gyrus

isthmus of cingulate gyrus

parahippocampal gyrusuncus

Septal nuclei

H

fornix

HH

Basal Forebrain

ACH

Septal nuclei Play role in autonomic function and emotional behavior

Lesion = behavioral changes. Alterations in sexual behavior, rage behavior.

Referred to as the “pleasure center” because electrical stimulation is “positively reinforcing”

Nucleus accumbens• Implicated in addictive behavior.• Recieves dopaminergic input from ventral tegmental area

(VTA) • Is activated during reward/reinforcer situations

VTA

N.Acc

Reward pathway also includes: MFB, septal nuclei, hypothalamus and frontal cortex

Amygdala (deep to ucus)

Sensory input: prefrontal cortex, hippocampus, brainstem

Outputs: cortex, hippocampus, hypothalamus, brainstem

amygdala

• Responsible for learning and maintenance of link between a stimulus and its emotional value. (usually negative emotions)

• Also influence of smell on appetite

• Stimulation - fear and anxiety déjà vu

• Lesion –Kluver-Bucy syndrome• Placid, flat affect• Fearless• Inappropriate social and sexual behavior• Hyperoral and overly curious• Visual agnosia• Memory loss• Inability to recognize fear in facial expressions

Amygdala

Hippocampus

Major input is from the entorhinal cortex and goes to the dentate

Major output is back to the entorhinal cortex and to the hypothalamus

dentate gyrus

CA3

CA2

CA1Sub

EC

EC (entorhinal cortex)—funnels input from all sensory cortices to hippocampus

Hippocampus makes a question mark with an arrow head.

Question mark is hippocampus formation and arrowhead is dentate gyrus.

Hippocampus function:• learning and declarative memory (memory

for facts, events, faces, places etc). Memory of place-used for navigation

Lesion (patient HM):

• Unable to lay down (consolidate) new declarative memories

• Old memories intact

• No change in intellect

• No problems with procedural memory

Medial temporal lobe:hippocampus and amygdala

amygdala

hippocampus

hippocampus

amygdala

Hippocampal circuit (declarative memories)

cortex

limbic structure

hypothalamus

thalamus

mammillary nuclei

hippocampus

anterior nucleus

cingulate/PHGentorhinal

Papez circuit!!

mammillo-thalamic tract

fornix

Anterior limb of internal capsule

cingulum

mammillo-thalamic tract

fornix

Amygdala circuit

cortex

limbic structure

hypothalamus

thalamus

amygdala

non-mammillary nuclei

mediodorsal nucleus

prefrontal, temporalolfactory

stria terminalis, MFB,and VAF (ventralamygdalofugal) path

Anterior limb of internal capsule

Uncinate fasciculus and VAF