Chapter 15 Chemical Control of the Brain and Behavior

Introduction Synaptic Connections –Point-to-point Restricts synaptic communication –Brain areas with expanded influence over space and time Secretory hypothalamus Autonomic nervous system (ANS) Diffuse modulatory systems

Ernst & Berta Scharrer – proposed that magnocellular neurosceretory neurons released chemicals into the capilary bed of the posterior lobe.

The Secretory Hypothalamus Function –Difference between hypothalamus and dorsal thalamus Hypothalamus defect –Fatal disruption to body function Dorsal thalamus defect –Blind spot, lack of feeling

Homeostasis –Regulatory process: Regulates body temperature and blood composition Hypothalamus commands in cold weather –Shiver, goosebumps, turn blue Hypothalamus commands in hot weather –Turn red, sweat The Secretory Hypothalamus

Structure of the Hypothalamus

Pathways to the Pituitary –Two neurohormones –Oxytocin Lactation, suppress hypothalamic function –Vasopressin Regulate blood volume and salt concentration The Secretory Hypothalamus

Communication between kidneys and brain The Secretory Hypothalamus

Hypothalamic Control of the Anterior Pituitary –Controlled by parvocellular neurosecretory cells Secrete hypophysiotro pic hormone Hypothalamio pituitary portal circulation –Pituitary cells secrete or stop secreting hormones The Secretory Hypothalamus

Stress Response –Periventricular hypothalamus secretes CRH into portal circulation. –ACTH released into circulation. –ACTH stimulates cortisol release from adrenal cortex. The Secretory Hypothalamus

Divisions of autonomic nervous system (ANS) –Sympathetic division Increased heart rate and blood pressure Depressed digestive function Mobilized glucose reserves –Parasympathetic division Slower heart rate, fall in pressure Increased digestive functions Stop sweating The Autonomic Nervous System

ANS Circuits versus Somatic Motor System The Autonomic Nervous System

Sympathetic and Parasympathetic Divisions

The Enteric Division –Location: Lining of esophagus, stomach, intestines, pancreas, and gallbladder –Composition: Two complicated networks- myenteric (Auerbach's) plexus and submucous (Meissner's) plexus –Function: Control physiological processes involved in transport, digestion of food –Inputs: From brain via axons of the sympathetic and parasympathetic divisions The Autonomic Nervous System

Anatomy and Functions –Four systems with common principles: Noradrenergic Locus Coeruleus Serotonergic Raphe Nuclei Dopaminergic Substantia Nigra and Ventral tegmental Area Cholinergic Basal Forebrain and Brain Stem Complexes The Diffuse Modulatory Systems of the Brain

Noradrenergic Locus Coeruleus The Diffuse Modulatory Systems of the Brain

The Nonadrenergic Locus Coeruleus –Path: Axons innervate cerebral cortex, thalamus, hypothalamus, olfactory bulb, cerebellum, midbrain, spinal cord –Function: Regulation of attention, arousal, sleep- wake cycles, learning and memory, anxiety and pain, mood, brain metabolism –Activation: New, unexpected, nonpainful sensory stimuli The Diffuse Modulatory Systems of the Brain

The Serotonergic Raphe Nuclei The Diffuse Modulatory Systems of the Brain

The Serotonergic Raphe Nuclei –Path: Innervate many of the same areas as noradrenergic system –Function: Together with noradrenergic system, comprise the ascending reticular activating system. Raphe system particularly involved in sleep/wake cycles. Also mood –Activation: New, unexpected, nonpainful sensory stimuli The Diffuse Modulatory Systems of the Brain

Dopaminergic Substantia Nigra and Ventral Tegmental Area The Diffuse Modulatory Systems of the Brain

Dopaminergic Substantia Nigra and Ventral Tegmental Area Substantia Nigra Projects to the striatum Facilitates the initiation of voluntary movements(Parkinson’s Disease) –Ventral tegmental area Innervates circumscribed region of telecephalon –Mesocorticolimbic dopamine system: Dopaminergic projection from midbrain The Diffuse Modulatory Systems of the Brain

Cholinergic Systems The Diffuse Modulatory Systems of the Brain

Cholinergic Systems –Basal forebrain complex Core of telencephalon, medial and ventral to basal ganglia Function: Unknown, participates in learning and memory –Pontomesencephalotegmental complex Releases ACh Function: Regulates excitability of thalamic sensory relay nuclei The Diffuse Modulatory Systems of the Brain

Drugs and the Diffuse Modulatory Systems –Psychoactive drugs: Act on CNS –Many drugs of abuse act on modulatory systems LSD, Psilocybe mushrooms, and peyote close to structure of serotonin Cocaine and amphetamine affect dopaminergic and noradrenergic systems - sympathomimetic The Diffuse Modulatory Systems of the Brain

Stimulants: Block reuptake –Cocaine targets DA reuptake –Amphetamine blocks NE and DA reuptake and stimulates DA release The Diffuse Modulatory Systems of the Brain