Chemical Control of Brain and Behavior Flashcards
Overview of this chapter
Overview of diffuse modulatory systems
- Found only in CNS
- Highly divergent axonal projections
- Defined by the NT they use
What is the purpose of diffuse modulatory systems?
To coordinate activation states of neurons encompassing broad brain regions
Core neurons in the diffuse modulatory systems?
Small set (several thousand)
Origin of neurons in diffuse modulatory systems
Most arise from the brainstem nuclei
Most neurons in the diffuse modulatory systems arise in the ___
Brainstem nuclei
Axons of neurons in diffuse modulatory systems
Core neurons give rise to widely divergent axons that can form up to 100,000 synapses, each spreading throughout the brain
NT release in diffuse modulatory systems
Diffuse NT release affecting many neurons, and may also regulate NTs into extracellular fluid so they can mediate effects beyond a single synaptic cleft
Describe receptor activation in diffuse modulatory systems
Typically metabotropic receptors in the CNS
Classification of diffuse modulatory systems
Can be classified by NT (name of system is (NT)-ergic)
Diagram of projections in noradrenergic (NE) system
Origin of neurons noradrenergic system
Locus coeruleus
Projection of neurons in noradrenergic system
Throughout brain, including cortex, thalamus, and cerebellum (extremely wide projections)
Purposes of the noradrenergic system
- Locus coeruleus neurons strongly activated by novel, unexpected, nonpainful stimuli in the environment
- When activated, may generally increase brain responsiveness and increase speed/efficiency of information processing
- May be involved in sleep/wake cycles
NE system and stimulands
The noradrenergic system’s efficacy is enhanced by stimulants, such as cocaine and amphetamine
Peter the tiny horse is trying to severely impede the noradrenergic system by targeting one of its main nuclei.
Which would he target and why? What general effects would you see?
a) Raphe nuclei, slowed eating
b) Periventricular Hypothalamus, less sleep
c) Locus Coeruleus, generally less excitation
d) Substantia Nigra, less movement
Answer: C, this is the source nucleus for the Noradrenergic System
Diagram of projections in serotonergic (5-HT) system
Origin of neurons in the serotonergic system
Raphe nuclei throughout brainstem
Projections of neurons in serotonergic system
Large projections to forebrain & spinal cord
Purposes of the serotonergic system
- Rostral raphe nuclei innervate forebrain
○ Fires most during wakefulness and least during sleep
○ Controls sleep/wake cycles - Caudal raphe nuclei innervate the spinal cord
○ Modulates pain - Works with locus coeruleus for reticular activating system:
○ Arouses and awakens forebrain - Control of mood: SSRIs are effective drugs against clinical depression
When do the raphe nuclei innervating the forebrain fire the most and least? (Serotonergic system)
Fire most during wakefulness and least during sleep
Rostral raphe nuclei innervate the ___
Forebrain
Caudal raphe nuclei innervate the ___
Spinal cord
Serotonergic system and hallucinogens such as LSD
Hallucinogens such as LSD are 5-HT agonists:
- LSD binds to 5-HT receptors on raphe nuclei neurons → inhibits raphe firing → reduces outflow of serotonergic system (this also happens during dreaming!