Telencephalon, Limbic System, Diencephalon

Emotions/Emotional Drive

*Amygdala* -Emotions have both mental and physical components that are expressed as visceral motor changes and stereotyped somatic motor behavior >Behavioral and physical changes along with the emotions-> So angry want to punch someone >Stereotyped: There are stereotypical facial and behavioral response to emotions we have learned to read-> See someone crying know that they are upset >*Cognition*: The AWARENESS of sensations and their cause. >*Affect*: The feeling itself (how do you feel) >*Conation*: The URGE to take action-> "Yes, I will bake a cake!!!" >Physical changes: HTN, tachycardia, and sweating-> SNS stereotypical responses (treatment is to get patient to PNS) -Emotions of rage, fear, and aggression

Limbic System

*Concerned with EMOTIONAL expression and genesis* -Limbic System is an arbitrary term used to describe the collection of interconnected cortical and subcortical structures that provide for the integration of body homeostasis, olfaction, learning and memory, and emotional expression. >*HOME = homeostasis, olfaction, memory, and emotion* ->Homeostasis: Hypothalamus for temperature, eating, drinking, sex, etc ->CN I: olfactory -The Limbic System is the anatomic substrate for the integrative role of these structures in the EMOTIONAL input to motor activity and autonomic function

Memory

*Hippocampal Formation*

Magnocellular Neurons

*Magnocellular neurons* of the *supraoptic and paraventricular nuclei* of the hypothalamus (MEDIAL nuclei within the hypothalamus) regulate *water and electrolyte balance* - Individual neurons in the posterior pituitary secret either ADH (antidiuretic hormone) or oxytocin, both are small nine amino acid peptides, action potentials in these neurons release the peptides at the axon terminals >These hormones are released into the systemic circulation in the capillary network of the posterior lobe: ->*ADH* promotes *water reabsorption* from late distal tubule and collecting duct in the renal nephrons through aqua pores in the principal epithelial cells. ->*Oxytocin* promotes smooth muscle contraction

DA Pathways

*Mesolimbic DA pathway*: VTA= basal forebrain and Nucleus Accumbens (ventral striatum part of basal ganglia) *Mesocortical DA pathway*: VTA-PFC and temporal cortex (Amygdala and Hippocampus) -Elevated dopamine can lead to increased emotional stability and motor movements-> treat be decreasing DA levels

OCD

*Obsessive-Compulsive Disorder* -Recurrent intrusive OBSESSIVE thoughts -Performance of REPETITIVE compulsive behaviors that provide TEMPORARY relief. -Improvement seen with pharmacological (*serotonin enhancement*) and behavioral treatment.

Olfaction

*Olfactory Cortex* Unique in that there is *no thalamic relay* -Secondary sensory neurons innervate the primary olfactory cortex (*medial anterior tip of temporal lobe-> piriform and periamygdaloid cortex*-> O1) >Fibers of the olfactory tract also project directly to the *amygdala*(corticomedial nucleus) and olfactory tubercle (anterior perforated substance) >These inputs are thought to be important in *emotional, memory, and motivational aspects* of olfaction.

Telencephalon

*Prosencephalon, endbrain, 2 cerebral hemispheres* Cerebral cortex -Neocortex: 6 layers -Occipital lobe -Parietal lobe -Temporal lobe >Hippocampus >Amygdala -Frontal lobe >Prefrontal Cortex >Basal Forebrain

Fornix (Parts)

-After info reaches the maxillary bodies-> goes to the ANTERIOR nucleus of thalamus (*mammillothalamic tract*)

Main nuclear divisions of the thalamus

-All thalamic nuclei are GLUTAMATERGIC except *reticular nucleus* -Hypothalamus helps with homeostasis: Connected to everything (BS, diencephalon, forebrain) >South of diencephalon= homeostasis >North of diencephalon= Thalamus=connects entire cortex->Tell how things are going (motor, sensory, etc) -Anterior Nuclear Group: Memory= Hippocampus-> fornix-> mamillary bodies-> Anterior nucleus -Thalamic reticular nucleus-> ALL GABA! >Flat on top of other nuclei, on lateral surface -VA/VL: Gets motor input >Cerebellum DCN and Basal ganglia GPi go to VA/VL -Lateral geniculate nucleus= 6 layered structure >Info from retina (ganglion cells) >IPSI eye info: Layers 2,3, and 5 >CONTRA eye info: 1,4, and 6 >Optic tract goes to LGN -Medial geniculate nucleus: UNCONCIOUS AUDITORY info from lateral lemniscus tract-> goes to inferior colliculus via brachium-> goes to MGN >BILNORAL-> Both ears -Intralaminar nuclei: PANIC button-> arous the entire cortex so know what's going one (wake up dummy!) -Medial nuclear group (Mediodorsal nucleus MD): Part of BG loop that is involved in emotion and cognitive awareness >Projects to PFC

Integration of neuroendocrine/ behavioral/autonomic responses by hypothalamus:

-Blood pressure / body electrolyte composition -Energy and body metabolism -Sexual and parenting behaviors (reproduction) -Body temperature -Stress response: fight or flight -Sleep-wake cycle regulation *Functional grouping of neurons in the hypothalamus regulate body functions*

White matter (axon) pathways (Picture)

-Cingulate gyrus-> Part of the LIMBIC system -Cingulum: Fibers are coming out towards you-> connects cingulate gyrus anterior to posterior-> stay IPSIlateral/do not cross over -See optic chiasm: Nasal fibers cross (temporal visual fields)

Coronal Section of brain (Myelin stain)

-Cingulate gyrus: Limbic system -Medial temporal lobe= Amygdala + Hippocampus -Uncus herniation-> into tentorium cerebelli-> CN 3 affected

Anxiety Disorder

-Large variety of conditions: panic, posttraumatic stress, generalized anxiety, obsessive-compulsive. -Thought to be associated with NE, EPI, and 5-HT (metabotropic) INCREASED activity in CNS. -Improvement seen with pharmacological (*benzodiazepines*) stimulation of *GABAA receptors*-> ionotropic

Medial Hypothalamic nuclei (Picture)

-Lateral group of nuclei: Sandwhiched between lateral + PERIventricular groups= medial group >Fornix runs between late and medial group

Fornix (Picture)

-Medial temporal lobe has the hippocampus-> both almost join -Fornix travels POSTERIOR, MEDIAL and ANTERIOR to mammilary bodies (MEMORY-> posterior of hypothalamus) -Mammilary body goes to thalamus then cortex

Adult brain (Sagittal Cut)

-Pineal gland: ONLY 1 present in diencephalon >Pineal tumor: DORSAL surface of midbrain-> problems with looking UP >Calcification occurs here due to age-> will see in CT scan >Determine if mass/hemorrhage occurring

Diencephalon (Picture)

-Red nucleus= RST-> stimulation will cause upper limbs to flex

Temperature Regulation

-Temperature regulation is under the control of the *anterior and posterior hypothalamic nuclei* -Activation of the SYMPATHETIC nervous system and adrenal medullary hormones secretion regulated by the DORSAL and POSTERIOR hypothalamus. -Thirst and regulation of drinking in the LATERAL hypothalamus >Tissue osmolality and vascular fluid volume control DRINKING behavior >Osmoreceptors (circumventricular organs-> around the ventricle) are located in the ANTERIOR hypothalamus >Hypertonicity >285 mOsm / kg, osmoreceptors will stimulate the RELEASE of ADH and initiate *drinking behavior* due to thirst. >LOW blood volume promotes secretion of RENIN from the kidney with ultimate formation of *Angiotensin II* that will cause INCREASED thirst and the RELEASE of ADH --- 2 osmoreceptors that produce ADH released from nerve terminal is PPG: 1.) Subfornical organ (SFO) 2.) Organ vasculosum Lamina Terminalis (OVLT) -Circumventricular organs in front of the BBB to sample the blood concentration (NOT in BBB) -Receptors are VERY sensitive and fire with slight elevation (300 mOsm/L to 301 will fire!)

amygdaloid nuclei (Fear and apprehension)

-The fear reaction is absent in those animals in which the *amygdala is destroyed.* >A behavior thought of as placidity >Can be due to calcification and atrophy of the anterior-medial temporal lobes >Cannot recognize the emotion fear (scared, fearful, afraid) ->Can't draw or pick out fear -Also: The amygdala is involved with the *encoding of memories that evoke FEAR* and other emotions (love, etc)

Major site of integration of autonomic reflexes of the brainstem and spinal cord

-The hypothalamus maintains body homeostasis >Homeostatic functions include regulation of body temperature, water and electrolyte balance, and plasma glucose level. -AFFERENT (incoming) innervation to the hypothalamus is from *all levels of the CNS* -EFFERENT (outgoing) innervation of the hypothalamus: >DIRECT neural innervation to the POSTERIOR pituitary. >*Releasing factors* to the ANTERIOR pituitary. >DIRECT innervation of the limbic system by the *mammillothalamic tract* >Hypothalamic innervation of the brainstem, including the reticular formation and medullary brainstem centers (vagus DN, Solitary, etc), and spinal cord allows for regulation of cardiovascular, respiratory, genital-urinary and gastrointestinal function. -SNS: T1-L2 -PNS: CN 3, 7, 9, and 10; S2-S4

Limbic System additional structures

1. AMYGDALA: Emotional significance; subcortical= not conscious 2. hippocampal formation: Memory 3. subcortical structures: >*Thalamic nuclei*: mediodorsal (MD) (output of BG-limbic part) and anterior nuclei (output of mammillary bodies) >*Midbrain nuclei*: Ventral Tegmental Area (VTA): DOPAMINE (input to BG) (REWARD SYSTEM-> metabotropic) >*Basal ganglia*: Ventral striatum (*nucleus accumbens*)

Neocortex

6 layers! Thalamus: Comes to Layer IV (release Glu) and layer VI talks to thalamus (Layer IV IN, Layer VI OUT) UMNs: Layer 5 is major output to subcortical regions >LMN >BG >Cerebellum -Layer 2-3: Superficial layers go to cortex (cortico-cortex fibers)-> to other sides of cortex >Cells communicate with cortex: Ipsi and contra using *corpus callosum* for corticocortico tract

Characteristic of the limbic system

Allocortex (three-layer cortex) is the paucity of the connections between it and the neocortex (six-layered cortex) -Neocortical activity can MODIFY emotional behavior and visa versa. >Not many connections to the neocortex (higher functioning) to allocortex -However, one of the characteristics of emotion is that it CANNOT be turned on and off at will.

Emotions of rage, fear, and aggression

Animals with *bilateral lesions* of limbic structures in the temporal lobes displayed specific emotional and behavioral DEFICITS -*Placidity*: Fierce animals became docile (destruction of amygdala)-> no more rage, fear, etc -*Hypersexuality*: Mounting inanimate objects, different species, indiscriminate choice of sex partners (destruction of *piriform cortex*-> O1 cortex) -*Visual agnosia*: Animals could not recognize objects (destruction of visual association areas in the temporal lobe - "What" pathway-> Path from V1 to V4)

Limbic cortex (picture)

Anterior insular cortex is in the lateral fissure (Sylvian fissure) >Heschl's gyri (primary cortex) within the fissure: Process incoming auditory info -Uncus anterior to parahippocampal gyrus

Hypertonicity and Blood

As blood goes by: -SFO will SHRIVEL-> causes ion channels to OPEN-> sodium goes in (DEPOLARIZES)-> get a receptor potential (since it is sensory)-> Glutamate released on MEDIAL hypothalamus nuclei-> get APs and release ADH in posterior pituitary-> ADH enters capillaries and goes to the rest of the body (ADH receptors in the nephron) --- Shrink gated mediated ion channel -Sodium comes in when cell shrivels

Homeostasis

Autonomic and neuroendocrine control via *hypothalamus*: Very important component as most structures input to the hypothalamus and the info will come right t back out -Sexual behavior >Including the behavioral components of copulation, urge to copulate, and events leading to pregnancy -Basic sexual responses are thought to be INNATE

Diencephalon: Hypothalamus

By responding to signals generated within the hypothalamus, brain stem, or higher centers, such as the limbic system, the hypothalamus can ACTIVATE the endocrine and somatic motor system

Prefrontal Cortex

Cerebral cortex ANTERIOR to the motor cortex -Planning, decisions, expression, etc. -Dorso-lateral cortex: Cognitive awareness and goal setting >MCA -Medial Prefrontal Cortex: Emotional significance >ACA -Orbitofrontal >Cognitive >ACA

Amygdala

Collection of nuclei just BENEATH the UNCUS of the temporal lobe, dorsal to the anterior tip of the hippocampus. -Required for EMOTIONS and behavioral drives -Attaches *emotional significance* to stimuli from association cortices >Happy, fear, excitation, etc -Anterior tip of hippocampus

White matter (axon) pathways

Comes in ALL lengths Some connect hemispheres together (*commisural fibers*). -*Corpus callosum*: pathway interconnecting the two cerebral hemispheres. >Layers 2/3 to Layers 2/3 on other hemisphere-> cortico-cortico tracts -*Anterior commissure*: Links the two TEMPORAL cortices together and some crossing fibers of the *anterior olfactory nucleus* -Association fibers present: Cingulum and arcuate fasciculus -Some interconnect cortex with *subcortical structures*-> Fornix

Basal Ganglia

DEEP NUCLEI -Striatum = caudate and putamen >VENTRAL striatum (LIMBIC portion of the striatum) -> *Nucleus accumbens* -> Adjacent parts of the caudate, striatum, and basal forebrain. -*Globus pallidus* = internal and external segments

Intralaminar Nuclei

DIFFUSE to entire cortex-> Arouse the entire cortex -Similar to diffuse relay nuclei but they are involved in inputs and outputs from the *BASAL GANGLIA and LIMBIC system* Ex.) If someone chasing you, the entire cortex will light up! Two functional regions: -*Caudal intralaminar nuclei*: Centromedian nucleus -*Rostral intralaminar nuclei*: Relay for the Ascending Reticular Activating System (ARAS)= AROUSAL --- Main point to know: INTRALAMINAR NUCLEI are involved in ARAS (AROUSAL of ENTIRE cortex)

Multisystem Atrophy (MSA)

Degenerative neurological disorder -Cerebellum atrophy >Ataxia -Basal Ganglia atrophy >Parkinson's -ANS Atrophy >Autonomic insufficiency ->Impotence, incontinence, constipation, orthostatic HTN, temperature issue -MSA-C: Cerebellum + ANS -MSA-P: Basal Ganglia + ANS >Shy Drager Syndrome

Schizophrenia

Disorder of thought and affect = *emotional pathology* -Fairly common: 1% of population worldwide >2-3% of population have schizotypal personality disorder-> MILDER form of schizophrenia) -Schizophrenia has been shown to have significant GENETIC basis, based on twin studies and family pedigrees, and adoption studies. -High cost to society financially and emotionally. -Schizophrenia is one major cause of *psychosis* -Other disabling features of schizophrenia include an impoverishment of content in speech, thought or action, INABILITY to socialize and to maintain employment, and a split between how the person feels and how they appear to feel, LACK of motivation.

Fornix

Efferent pathway from hippocampus to mammillary bodies of the hypothalamus. -Hippocampus-fornix-Mamillary bodies: Consolidation of NEW INFO -Damage=CANNOT form memories

Limbic System (Picture)

Function: HOME -Homeostasis -Olfactory -Memory -Emotion

Most common location for abnormal electrical activity (seizure)?

HIPPOCAMPUS

Basal Forebrain (BF)

INFERIOR surface of the telencephalon between the *hypothalamus and the orbital cortex* -*Basal nucleus (of Meynert)*: Major collection of basal forebrain cholinergic neurons (ACh cell bodies) -Send axons to ENTIRE cortex-> specifically to *hippocampus* -*Metabotropic cholinergic receptors*= EXECUTIVE MODULATORY -DEGENERATION of the ACh neurons of BN= *Alzheimer's Disease* >NO ACh to Hippocampus= DECREASED memory

Reticular Nucleus

In Thalamus (NOT talking about reticular formation!!!) -THIN sheet of neurons just lateral to the rest of the thalamus and medial to the internal capsule. -ONLY nuclei of the thalamus that does NOT project to the cortex. >Programmed rest put rest of thalamus on/off >Active in sleep state! ->Inhibit rest of thalamus -It gets its input from the cortex and thalamus and ARAS and the forebrain. -Its output is to the THALAMUS! -Pure inhibitory GABA-ergic neurons: REGULATES thalamic activity. -Reciprocal cortical- thalamic connections

Thalamus Inputs (Picture)

Internal capsule find tracts -CST: Posterior division -CBT: Genu -CPT: Anterior

Circuit Mediating Emotion (Pathway)

Known projections of the fornix to the hypothalamic region (mammillary bode and other hypothalamic areas) and of the hypothalamus of the prefrontal cortex are indicated. -A pathway interconnecting the amygdala to limbic structures is shown. -Finally: Reciprocal connections between the hippocampal formation includes the hippocampus proper and surrounding structures, including entorhinal cortex and the subicular complex. -Process info to cortex-> send info to hippocampus to consolidate the memory of that info-> send back to cortex for storage of memory

Frontal Lobe

LARGEST region of the brain (1/3 of the cerebral cortex) -Has three surfaces: dorso-lateral, medial and orbitofrontal. *Prefrontal cortex and Basal Forebrain*

PFC Stain

LEFT side -NOT see amygdala: TOO anterior -DARK= myelin stained axon -Cell bodies (white area)= 6 layers of cortex -ACA: Location of berry aneurysm-> must be clipped or you can infarct the PFC= *LOSS of emotional and cognitive behavior*

Lesions of the limbic system

Lesions of the limbic system can cause paroxysmal disorders (sudden attack, fit or outburst, etc) -Medial Temporal lobe common site of initiation of *epileptic seizures* -Disorders of the limbic system cause devastating, common psychiatric problems involving emotional (affective) disorders. (Dorsal lateral-Prefrontal cortex/DL-PFC and Temporal Cortex thin compared to normal). >Thin= atrophy as neurons are dying -> not plump and juicy! -SCHIZOPHRENIA -OCD -Anxiety Disorder

Limbic Cortex

Limbic cortex forms a ringlike "limbic" lobe around the edge of the cortical mantel and surrounds the corpus callosum and the upper-brain stem- diencephalic junction. -Main components of limbic cortex: Cingulate, parahippocampal (uncus), medial-prefrontal, and orbito-prefrontal gyri, temporal poles, and anterior insular cortex.

Relay Nuclei: Local Projections

Local, specific thalamic relay nuclei: Sensory and motor MOST localized (point in thalamus to point in cortex) -LATERAL location on the thalamus -All sensory modalities (EXCEPTION of olfaction) have specific relays in the *lateral thalamus* en route to their primary cortical areas

Depression and Mania

MOOD DISORDER -Depressed patients have sad mood and LACK enjoyment, impaired concentration, changes in sleep and eating, suicidal thoughts. -DECREASED levels or deficits in norepinephrine (NE) and serotonin (5HT) and /or dopamine (DA) are associated with depression. -Manic patients have elevated, irritable mood, racing thoughts and distractibility, and impulsive behavior.

Motor Table

Superior cerebellar peduncle tracts cross in MIDBRAIN and go to VA/VL of the thalamus

Sagittal Section of brain

Posterior cingulate gyrus= MEMORY -Output from *Anterior Nucleus (AN) * of Thalamus goes to posterior cingulate gyrus->reciprocal to/from AN and cingulate gyrus -LAYER 4 IN to cortex, Layer 6 OUT of cortex -Ventral striatum-> medial dorsal (MD) of thalamus-> Medial PFC

Mains parts of the human CNS

Prosencephalon (forebrain) -Telencephalon (Cerebrum) >Cerebral cortex >Subcortical white matter: Internal capsule, cingulum, arcuate fasiculus-> strokes are common >Basal ganglia >Basal forebrain nuclei= Nucleus of Meynert-> RELEASE ACh! -Diencephalon >Thalamus >Hypothalamus >Epithalamus Mesencephalon (Midbrain) >Cerebral peduncles >Midbrain tectum >Midbrain tegmentum Rhombencephalon -Metencephalon >Pons >Cerebellum -Myelencephalon >Medulla Spinal Cord Know general idea

Psychosis

Psychosis is the presence of LOSS of the sense of reality. -Specific types of psychotic events are *hallucinations and delusions* -*Positive Symptoms*: >Hallucinations are sensory experiences which are perceived as real. >Delusions are fixed, false beliefs -*Negative Symptoms*: Deficits (absent/lacking) -Schizophrenia is reliably diagnosed based on evidence of the presence of longstanding psychosis in the absence of other known causes.

Antipsychotic treatment

Psychotic behavior responds to *neuroleptic (antipsychotic) drugs* such as *chlorpromazine* -These drugs have been demonstrated to be effective in treating the *POSITIVE symptoms of schizophrenia*: >Hallucinations, delusions, thought disorders, paranoia, excitement. >These drugs are antagonists of *dopamine receptors (D2 and D1)* ->Parkinson symptoms -*Negative symptoms* are LESS responsive to neuroleptic drugs - Those agents, which INCREASE dopaminergic activity, always EXACERBATE the symptoms of schizophrenia - Dopaminergic neurons are broadly represented in the limbic system, an area that is known to subserve emotion, reward, and motivation.

3 categories of Thalamic Nuclei...

RELAY nuclei INTRALAMINAR nuclei RETICULAR nucleus

Hypothalamus and ANS

Stimulation of the hypothalamus elicits autonomic reflexes. -Hypothalamus and limbic system influence the autonomic nervous system and emotional behavior -The hypothalamus is considered anatomically by dividing it into medial, lateral, anterior, tuberal, posterior, dorsal, and ventral regions. >Contrasting effects when stimulation ANTERIOR versus POSTERIOR hypothalamus

Diencephalon

ROSTRAL to the midbrain 1.)*Epithalamus*: Habenula, parts of the pretectum, and pineal body. 2.) *Thalamus*: Major group of RELAY nuclei -Bounded by the anterior and posterior commissures. >All but NOT olfactory 3.) *Hypothalamus*: Major regulation of autonomic, endocrine, homeostasis-> hunger, thirst, sexual desire, sleep-wake cycle, and limbic system. 4.) *Subthalamus*: Parts of the midbrain tegmentum continue into the subthalamus. -Contains the subthalamic nucleus of the *basal ganglia* just medial to the substantia nigra and cerebral peduncles. >Damage to BG on right-> See *hemiballismus* on LEFT-> look for CO issue

Arcuate fasciculus and cingulum (Picture)

RUNS IPSILATERAL: Does NOT cross other hemisphere

Relay Nuclei

Receive inputs from numerous pathways and project to *cerebral cortex* -Receive MASSIVE reciprocal connections back from the cortex. Corticothalamic (layer 6) fibers >>> Thalamocortical fibers (layer 4) >Cortex talks to thalamus A LOT more than the other way -Projections to the cortex can be *local or diffuse* Ex of thalamocortical tract: LGN to calcarine fissure= Geniculate-calcarine tract AKA optic radiations (very specific thalamocortical tract)

Hypothalamus: Circadian Rhythms

Regulation of circadian rhythms by the *suprachiasmatic nucleus* (medial group)

Hypothalamus: Sexual Behavior

Regulation of sexual behavior in the *anterior and preoptic area*

Sensory Table

Remember thalamus talks to cortex in LAYER 4 -Cortex sends info to Thalamus via LAYER 6

Association Fibers

Some axon pathways interconnect parts of the SAME cortex (IPSILATERAL)-> *Association fibers* -*Cingulum*: Fiber tract underlying the cingulate gyrus and interconnecting LIMIBIC cortical areas. *Arcuate fasciculus*: From frontal lobe fans out into the parietal, occipital and temporal lobes (PTO)

Hippocampus

Specialized temporal cortex (archicortex 3-4 layers) rolled into the *medial temporal lobe* -Required for the consolidation of *new memories and facts* during sleep >Consolidates the info

Stimulation of Anterior Hypothalamus

Stimulation of the *anterior hypothalamus results in Parasympathetic Nervous System activation and body heat LOSS* -Results in DECREASED heart rate and blood pressure, sweat gland stimulation, and INCREASED secretion and motility of the gut. -Electrical stimulation of the anterior hypothalamus leads to DILATION of skin blood vessels and SUPPRESSION of shivering.

Stimulation of Posterior Hypothalamus

Stimulation of the posterior hypothalamus results in *Sympathetic Nervous System activation and body heat RETENTION* -Results in INCREASED heart rate and BP, and constriction of cutaneous BVs. -Shivering -Electrical stimulation of posterior hypothalamus leads to actions that *conserve body heat*

Hypothalamus: Apetite and Energy

The hypothalamus is ESSENTIAL for regulation of appetite and energy balance -*"Feeding Center"* = Lateral hypothalamic area >Stimulation of the lateral hypothalamus elicits FEEDING >Lesion of the lateral hypothalamus leads to LOSS of appetite (*aphagia*), starvation, and death. -*"Satiety Center"* = Ventromedial hypothalamus -Stimulation of the ventromedial hypothalamus causes CESSATION of feeding (sense of fullness) -Lesions of in this region result in *hyperphagia* and if food supply is abundant the syndrome of hypothalamic obesity and decreased activity.

Hypothalamic Releasing Hormones

There are 6 hypothalamic releasing (4) and inhibiting (2) factors or hormones, which control the RELEASE of hormones from the ANTERIOR pituitary in the hypothalamus. -They are secreted into the *median eminence* of the hypothalamus. >Only for APG not for PPG -*CRH: Corticotropin releasing hormone 41 aa-> medial paraventricular nuclei -*TRH*: Thyrotropin releasing hormone 3 aa (smallest)-> medial paraventricular nuclei. -*LHRH*: Luteinizing hormone-releasing hormone 10 aa->also known as gonadotropin releasing hormone (GnRH)-> secreting neurons in the medial parts of the PREoptic area -> Reproduction -*GHRH*: Growth hormone releasing hormone 44 / 40 aa-> arcuate nuclei (medial group) INHIBITORY factors from *PERIventricular nuclei*: -GIH: growth hormone inhibiting hormone AKA *Somatostatin* and SIRF (somatotropin release inhibiting factor 14 aa)-> Secreting neurons in the periventricular nuclei. -*Dopamine* also called PIF (prolactin-inhibiting factor) -> SECRETING neurons periventricular nuclei.

Limbic System Pathway

Undestand the idea -Limbic cortex: cingulate gyrus -Basal ganglia: striatum-> Nucleus accumbens (ventral striatum) -To Medial dorsal thalamus -Basal forebrain: *Basal nucleus (of Meynert)*-> Release ACh -CNI have cilia on knob-> no thalamus-> olfactory cortex (O1)-> to amygdala (emotional significance of smell)-> Hypothalamus

Relay Nuclei: Diffuse Projections

WIDELY projecting (NON-specific) thalamic relay nuclei, allows for *behavioral orientation toward relevant stimuli* -Sensory and visual cortex (extrastriate tectum pathway): *Pulvinar and pre-processed sensory information* >Associated cortices: PTO (Parietal, Temporal, and occipital) -*Limbic inputs* (cognitive function) and PRE-processed information from association cortices >Limbic input and preprocessed info-> *Medial Dorsal Nucleus (MD)*: large bulge coronal sections (into 3rd ventricle)-> Pre-frontal association cortex One point to many!