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The Brain and
Behavior
PART III
Chemical Control of
the Brain and Behavior
Chapter 15
Point to Point Communication
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The brain uses precise and specific pathways
to communicate.
Synaptic Transmission is Tightly Confined in
Time and Space.
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Neurons communicate with only one or a small
subset of neurons.
Transmission is rapid
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Minute quantities of neurotransmitters are used.
Transmitters are quickly destroyed or taken up.
The Nervous System also Communicates
Over Great Distances and Time.
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Hormonal communication
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Networks of neurons in ANS
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Secretes chemicals into the blood stream to affect the
entire body.
Simultaneously controls responses in many internal
organs.
Diffuse modulatory systems extend their reach with
widely divergent axonal projections.
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Each modulatory system uses a specific neurotransmitter
or set of neurotransmitters.
Use metabotropic postsynaptic receptors to prolong their
action.
Regulate arousal, mood, motivation, sexual behavior,
emotion, sleep, etc.
Point to Point Communication
Hormonal Communication
Interconnected neurons
of the ANS
Diffuse modulatory systems
Hypothalamus &
Pituitary
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Hypothalamus is located
below the thalamus and
forms the walls of the third
ventrical.
It can be divided into
several nuclei using
cytoachitectonics.
Each nucleus has a very
specific function.
The pituitary is connected to
the base of the
hypothamlamus.
The Secretory Hypothalamus
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Integrates somatic and visceral responses in
accordance with the needs of the brain.
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A tiny lesion in the hypothalamus can be lethal
Homeostasis – the hypothalamus maintains
the body’s internal environment in a narrow
physiologic range.
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Temperature, blood volume and pressure,
osmolarity, pH, and oxygen levels are all regulated
by hormonal mechanisms.
Structure and Connections of the
Hypothalamus
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Three zones: Lateral, Medial, Periventricular
Connections are extensive (discussed later).
Periventricular is most highly connected to the pituitary.
Controls:
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Circadian rhythms
ANS to viscera.
Posterior Pituitary
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Neurohormones are
produced in the
magnocelluar
hypothalamus and
released at the pituitary
Oxytocin
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Released to initiate uterine
contraction or milk letdown.
Can be triggered by somatic,
visual or auditory stimuli or
inhibited by stress.
Antidiuretic Hormone
(vasopressin)
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Regulated blood volume,
pressure and osmolarity
ADH
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The Subfornical organ
detects Angiotensin II
and activates the
release of ADH and
initiates thirst
responses.
ADH acts at the level of
the kidney to decrease
urine production and
thus increase blood
volume.
Anterior Pituitary
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Parvocellular
neurosecretory cells release
tropic factors that cause the
production of hormones in
the anterior pituitary
Hormones include:
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Follicle Stimulating Hormon
Luteinizing Hormone
Thyroid Stimulating
Hormone
Adrenocorticotropic
hormone
Growth Hormone
Prolactin
The Autonomic Nervous System
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The autonomic nervous system works
independently to initiate typically multiple,
widespread and relatively slow responses to
our environment.
Sympathetic N.S. – fight or flight response.
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Increase in heart rate, blood pressure, glucose
mobilization, sweating, etc.
Parasympathetic – decreases heart rate,
blood pressure, increases digestion, etc.
Organization of Neural Outputs of the CNS
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CNS uses a
monosynaptic
pathway
ANS uses a
disynaptic pathway.
Cell bodies of ANS
located in Ganglion
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Preganglionic
neurons lead to
postganglionic
neurons.
PNS vs ANS
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Operate in parallel but
pathways and
neurotransmitters are
distinct.
Sympathetic
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Parasympathetic
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Emerge from T1-L3
Preganglionic neuron is
short.
Cranial nerves, cervical
and sacral origin.
Long preganglionic and
shot postganglioic neuron.
Each system innervates a
wide variety of tissues.
Actions tend to be
reciprocal.
Enteric Division
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Lines the digestive system
Consists of the myenteric
(Aurbach’s) plexus and the
submucosal (Meissner’s)
plexus.
Controls the transport and
digestion of food.
Has sensory and ANS
components.
Monitors tension and stretch
of digestive system and
works independently to
control movement, digestive
enzyme secretion, and
mucous production.
Central Control of ANS
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Hypothalamus is the main regulator of the ANS
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It coordinates information from the body and other
parts of the brain and provides a coordinated set of
both neuronal and hormonal outputs
The periventricular nucleus (PVN) is central to
control of the ANS
The nucleus of the solitary tract (located in the
medulla) is also important in the control of
autonomic function.
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Controls output to other autonomic brain stem nuclei
including those necessary for cardiac and
respiratory function.
Neurotransmitter and Pharmacology of
Autonomic Function
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Preganglionic Neurotransmitters
 Acetylcholine (ACh) binds to fast nicotinic receptors that initiate
EPSP or slower muscarinic (G-Protein coupled ) receptors.
 NPY and VIP Triggers slow responses that can last several
minutes. (Effects are mostly modulatory)
Postganglionic
 Parasympathetic
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ACh that bind muscarinic receptors.
Very localized
Activated by either mAChR agonists or NE antagonists propranolol.
Sympathetic
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Norepinepherine
Wide spread throughout body.
Activated by either NE agonists or mAChR antagonists (atropine).
Adrenal medulla releases NE and EPI and acts like a nonspecific
postganglionic cell.
The Diffuse Modulatory Systems
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Messages that must be widely broadcast through the
brain use diffuse modulatory systems.
The brain uses many of these mechanisms each
requiring a specific neurotranmitter.
Connections are widely dispersed throughout the
brain.
Modulatory system affect wide areas to make them
more or less excitable or more or less synchronously
active etc.
Like volume, treble and bass controls – don’t change
lyrics or melody but do change how they are
preceived.
Important in motor control, memory, mood, motivation,
and metabolic state.
Heavily involved in many psychiatric disorders.
Anatomy and Functions of the Diffuse
Modulatory Systems.
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Core of each system has a small number of
neurons.
Neurons of the diffuse system arise from this
central core (usually found in brain stem)
Each neuron has tremendous affect because
it can connect to as many as 100,000
neurons.
Neurotransmitters are released into the
extracellular fluid and can diffuse to many
neurons.
The Noradrenergic
Locus Coeruleus
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Makes some of the most
diffuse connections in the
brain.
“Involved” in regulation of
attention, arousal, sleep wake
cycles, learning and memory,
anxiety, pain, mood and brain
metabolism
Activated by new, unexpected,
nonpainful sensory stimuli.
General arousal to interesting
events in the outside world.
Functions generally to
increase brain
responsiveness, speeding
information processing.
Serotonergic Raphe Nuclei
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Caudal innervate spinal cord
and modulate pain-related
sensation
Rostral innervate brain.
Fire most during
wakefulness.
Part of reticular activating
system
Involved in sleep wake
cycles and stages of sleep.
Important in control of mood
and emotional behaviors (Ch
21).
Dopaminergic Substantia Nigra and Ventral
Tegmental Area.
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Neurons project from
Substantia nigra to
striatum.
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Control voluntary
movements
Degeneration results in
Parkinson’s disease.
VTA projects to frontal
cortex and limbic
system
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Reward system that
reinforces adaptive
behaviors.
Cholinergic Basal Forebrain and Brain
Stem Comlexes
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General function not
completley understood.
First cells to die in the
course of Alzheimer’s
disease.
Implicated in arousal,
sleep wake cycles,
learning and memory