Function of diencephalon and limbic system

Major functions of hypothalamus

1. Control of ANS regulates contraction of smooth muscle and cardiac muscle secretions of many glands 2. Production of hormones produces several hormones known as Releasing and Inhibiting hormones that control anterior pituitary hormones release axons extend from paraventricular and supraoptic nuclei through infundibulum into posterior pituitary and they release two hormones (oxytocin and antidiuretic hormone) 3. Regulation of emotional and behavioral patterns Together with limbic system, participates in expressions of rage, aggression, pain, and pleasure, and sexual arousal 4. Regulation of eating and drinking regulates food intake contains • A feeding center, which promotes eating • A satiety center, which causes a sensation of fullness and cessation of eating • A thirst center, which senses rise osmotic pressure of extracellular fluid, and causes sensation of thirst 5. Control of body temperature thermostat, senses body temperature maintained at desired setpoint 6. Regulation of circadian rhythms and states of consciousness .suprachiasmatic nucleus of hypothalamus serves as body's internal biological clock because it establishes circadian (daily) rhythms, patterns of biological activity (such as the sleep-wake cycle) that occur on a circadian schedule (cycle of about 24 hours) nucleus receives input from eyes (retina) and sends output to other hypothalamic nuclei, reticular formation, and pineal gland

diencephalon

forms central core of brain tissue just superior to midbrain surrounded by cerebral hemispheres extends from brain stem to cerebrum surrounds third ventricle contains numerous nuclei involved sensory and motor processing between higher and lower brain centers includes thalamus,hypothalamus, and epithalamus • Projecting from hypothalamus is hypophysis, or pituitary gland • Portions of diencephalon in wall of third ventricle called circumventricular organs • optic tracts carrying neurons from retina enter diencephalon

basal nuclei (ganglia)

masses of grey matter located deep on each side of cerebral hemisphere, on either side of thalamus Include (caudate nucleus, )(Globus pallidum, and Putamencalled Lentiform nucleus) basal nuclei help initiate and terminate movements, suppress unwanted movements, and regulate muscle ton.and terminate some cognitive processes, such as attention, memory, and planning • with limbic system to regulate emotional behaviors • In Parkinson's disease, obsessive-compulsive disorder, schizophrenia, and chronic anxiety are thought to involve dysfunction of circuits between the basal nuclei and the limbic system

Limbic System: Amygdala

ring of structures on inner border of cerebrum and floor of diencephalon: is a rim of cerebral cortex on medial surface each hemisphere. includes cingulate gyrus, lies above corpus callosum, parahippocampal gyrus in temporal lobe below. hippocampus portion of parahippocampal gyrus extends into floor of lateral ventricle ,dentate gyrus lies between hippocampus and parahippocampal gyrus

Hypothalamus

small part of diencephalon located inferior to thalamus composed of dozen or so nuclei in four major regions controls many body activities and major regulators of homeostasis • Sensory impulses related to both somatic and visceral senses arrive at hypothalamus impulses from receptors for vision, taste, and smell • receptors withinhypothalamus itself monitor osmotic pressure, blood glucose level, certain hormone concentrations, and temperature of blood connections with pituitary gland and produces variety of hormone

functions of limbic system

"emotional brain" including pain, pleasure, docility, affection, and anger • Stimulation of a cat's amygdala or certain nuclei of hypothalamus produces a behavioral pattern called rage— cat extends its claws, raises its tail, opens its eyes wide, hisses, and spits , removal of amygdala produces an animal lacks fear and aggression with parts of cerebrum,functions in memory • Damage to limbic system causes memory impairment • For example: if hippocampus damaged, person lose ability to remember directions, locations, and orientations (spatial memory) • hippocampus,capable of responsible for some aspects of memory may develop new neurons, even in elderly

Limbic system

Amygdala several groups of neurons located close to tail of caudate nucleus septal nuclei located within septal area formed by regions under corpus callosum and paraterminal gyrus (a cerebral gyrus). mammillary bodies of hypothalamus two round masses close to midline near cerebral peduncles Two nuclei of thalamus, anterior nucleus and medial nucleus, participate in limbic circuits olfactory bulbs flattened bodies pathway rest on cribriform plate fornix, stria terminalis, stria medullaris, medial forebrain bundle, and mammillothalamic tract linked by bundles of interconnecting myelinated axons

epithalamus (pineal gland)

small region superior and posterior to thalamus, consists of pineal gland and habenular nuclei pineal gland is endocrine system because it secretes melatonin liberated during darkness promote sleepiness • orally, melatonin contribute to setting of body's biological clock by inducing sleep and helping body to adjust to jet lag • habenular nuclei involved in olfaction, especially emotional responses to odor, Circumventricular organs • Parts of diencephalon, wall third ventricle, monitor chemical changes blood because lack blood-brain barrier include part of hypothalamus, pineal gland, pituitary gland, nearby structures • Functionally, coordinate homeostatic activities of endocrine and nervous systems, regulation of blood pressure, fluid balance, hunger, and thirst sites of entry into brain of HIV cause dementia (irreversible deterioration of mental state)

Thalamus

thalamus makes up 80% diencephalon, 3 cm in length • paired oval masses of gray matter organized into nuclei with tracts white matter • bridge of gray matter (interthalamic adhesion) joins right and left halves of thalamus in about 70% of human brains Function: thalamus major relay station for sensory impulses from spinal cord and brain stem to primary sensory areas of cerebral cortex Also motor functions by transmitting information from cerebellum and basal nuclei to primary motor area of cerebral cortex • relays impulses between different areas of cerebrum • plays a role in maintenance of consciousness