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

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

hypophysiotropic hormone

• Hypothalamiopituitary 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

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 SystemThe 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 BrainThe 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 BrainThe 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 BrainThe 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 BrainThe 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