the brain and behavior part iii. chemical control of the brain and behavior chapter 15
TRANSCRIPT
The Brain and Behavior
PART III
Chemical Control of the Brain and Behavior
Chapter 15
Point to Point Communication
The brain uses precise and specific pathways to communicate.
Synaptic Transmission is Tightly Confined in Time and Space. Neurons communicate with only one or a small
subset of neurons. Transmission is rapid
Minute quantities of neurotransmitters are used. Transmitters are quickly destroyed or taken up.
The Nervous System also Communicates Over Great Distances and Time. Hormonal communication
Secretes chemicals into the blood stream to affect the entire body.
Networks of neurons in ANS Simultaneously controls responses in many internal
organs. Diffuse modulatory systems extend their reach with
widely divergent axonal projections. 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 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 Integrates somatic and visceral responses in
accordance with the needs of the brain. A tiny lesion in the hypothalamus can be lethal
Homeostasis – the hypothalamus maintains the body’s internal environment in a narrow physiologic range. Temperature, blood volume and pressure,
osmolarity, pH, and oxygen levels are all regulated by hormonal mechanisms.
Structure and Connections of the Hypothalamus Three zones: Lateral, Medial, Periventricular Connections are extensive (discussed later). Periventricular is most highly connected to the pituitary. Controls:
Circadian rhythms ANS to viscera.
Posterior Pituitary Neurohormones are
produced in the magnocelluar hypothalamus and released at the pituitary
Oxytocin Released to initiate uterine
contraction or milk letdown. Can be triggered by somatic,
visual or auditory stimuli or inhibited by stress.
Antidiuretic Hormone (vasopressin) Regulated blood volume,
pressure and osmolarity
ADH
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 Parvocellular
neurosecretory cells release tropic factors that cause the production of hormones in the anterior pituitary
Hormones include: Follicle Stimulating Hormon Luteinizing Hormone Thyroid Stimulating
Hormone Adrenocorticotropic
hormone Growth Hormone Prolactin
The Autonomic Nervous System 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. 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
CNS uses a monosynaptic pathway
ANS uses a disynaptic pathway.
Cell bodies of ANS located in Ganglion Preganglionic
neurons lead to postganglionic neurons.
PNS vs ANS Operate in parallel but
pathways and neurotransmitters are distinct.
Sympathetic Emerge from T1-L3 Preganglionic neuron is
short. Parasympathetic
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 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 Hypothalamus is the main regulator of the ANS
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. Controls output to other autonomic brain stem nuclei
including those necessary for cardiac and respiratory function.
Neurotransmitter and Pharmacology of Autonomic Function 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
ACh that bind muscarinic receptors. Very localized Activated by either mAChR agonists or NE antagonists propranolol.
Sympathetic 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 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. 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
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 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. Neurons project from
Substantia nigra to striatum. Control voluntary
movements Degeneration results in
Parkinson’s disease. VTA projects to frontal
cortex and limbic system Reward system that
reinforces adaptive behaviors.
Cholinergic Basal Forebrain and Brain Stem Comlexes 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