1. Chapter 15: Chemical Control of the Brain and Behavior
Neuroscience: Exploring the Brain, 4e
Chapter 15: Chemical Control of the Brain and Behavior

2. Introduction Synaptic connections Point to point
Restrict synaptic communication
Brain areas with expanded influence in space and time
Secretory hypothalamus
Autonomic nervous system (ANS)
Diffuse modulatory systems

3. The Secretory Hypothalamus
Function
Differences between hypothalamus and dorsal thalamus
Hypothalamus defects
Often fatal disruption to body functions
Dorsal thalamus defects
Discrete sensory or motor deficit

4. The Secretory Hypothalamus—(cont.)
Homeostasis
Regulatory processes: regulates body temperature and blood composition
Hypothalamus commands in cold weather.
Shiver, goose bumps, turn blue
Hypothalamus commands in hot weather.
Turn red, sweat

5. Functional Zones of the Hypothalamus

6. The Pituitary Two neurohormones Oxytocin
Lactation, suppress hypothalamic function.
Vasopressin
Regulates blood volume and salt concentration

7. Communication between Kidneys and the Brain

8. Hypothalamic Control of the Anterior Pituitary
Controlled by parvocellular neurosecretory cells
Secrete hypophysiotropic hormones
Hypothalamo-pituitary portal circulation
Pituitary cells secrete or stop secreting hormones.

9. Stress Response
Periventricular hypothalamus secretes CRH into portal circulation.
ACTH released into circulation
ACTH stimulates cortisol release from adrenal cortex.

10. Divisions of Autonomic Nervous System
Sympathetic division: “fight or flight”
Increased heart rate and blood pressure
Depressed digestive function
Mobilized glucose reserves
Parasympathetic division
Slower heart rate, fall in blood pressure
Increased digestive functions
Stop sweating

11. ANS Circuits versus Somatic Motor System

12. Sympathetic and Parasympathetic Divisions

13. The Enteric Division
Location: lining of esophagus, stomach, intestines, pancreas, and gallbladder
Two complicated networks: myenteric (Auerbach's) plexus and submucous (Meissner's) plexus
Function: control physiological processes involved in transport, digestion of food
Input indirectly from brain via axons of the sympathetic and parasympathetic divisions

14. Central Control of the ANS
Connections for autonomic control
Periventricular zone connections to brain stem and spinal cord nuclei
Nucleus of solitary tract
Function of solitary nucleus
Integrates sensory information from internal organs and coordinates output to autonomic brain stem nuclei

15. Neurotransmitters
Neurotransmitters and the pharmacology of autonomic function
ANS better understood than the CNS—e.g., drug mechanisms influencing synaptic transmission
Preganglionic neurotransmitters
ACh binds to nAChR, evokes fast EPSP.
Ganglionic ACh activates mAChR, causes slow EPSPs and IPSPs.
Some preganglionic terminals release NPY, VIP— trigger small EPSPs.

16. Postganglionic Neurotransmitters
Parasympathetic: release Ach
Local effect
Sympathetic: most release NE
Far-reaching effects
Parasympathomimetic: mimic or promote muscarinic actions of ACh or inhibit actions of NE
Sympathomimetic: mimic or promote NE actions or inhibit muscarinic actions of ACh

17. The Diffuse Modulatory Systems of the Brain
Anatomy and functions differ:
Four systems with common principles
Small set of neurons at core
Neurons arise from brain stem.
One neuron influences many others.
Synapses release transmitter molecules into extracellular fluid.

18. The Noradrenergic Locus Coeruleus

19. The Noradrenergic Locus Coeruleus —(cont.)
Path: Axons innervate cerebral cortex, thalamus, hypothalamus, olfactory bulb, cerebellum, midbrain, and 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

20. The Serotonergic Raphe Nuclei

21. 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
Particularly involved in sleep–wake cycles, mood
Other transmitters involved in coordination
Most active during wakefulness, when aroused and active

22. Dopaminergic Substantia Nigra and Ventral Tegmental Area

23. Dopaminergic Substantia Nigra and Ventral Tegmental Area—(cont.)
Axons project to the striatum.
Facilitates the initiation of voluntary movements (degeneration causes Parkinson’s disease)
Ventral tegmental area
Innervates circumscribed region of telencephalon
Mesocorticolimbic dopamine system: dopaminergic projection from midbrain

24. The Cholinergic Diffuse Modulatory Systems

25. Cholinergic Systems Basal forebrain complex
Core of telencephalon, medial and ventral to basal ganglia
Function: mostly unknown, participates in learning and memory
Pontomesencephalotegmental complex
Utilizes ACh
Function: regulates excitability of thalamic sensory relay nuclei

26. Drugs and the Diffuse Modulatory Systems
Psychoactive drugs act on CNS.
Interfere with chemical synaptic transmission
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

27. Stimulant Drug Action on Catecholamine Axon Terminal
Stimulants: block catecholamine reuptake
Cocaine targets DA reuptake.
Amphetamine blocks NE and DA reuptake and stimulates DA release.

28. Concluding Remarks
Three components of nervous system with great reach of influences:
Secretory hypothalamus (all over the body)
Autonomic nervous system (all over the body)
Diffuse modulatory systems (all over the brain)
At detailed level
Each system performs different functions.
At general level
All work maintain brain homeostasis.