Lecture 4- The Neuromodulatory System Flashcards
What is the neuromodulatory system
A collection of various types of neurons that produce specific neurotransmitters that act to modulate the level of activity of neurons at a distance
Neurotransmitters involved
Serotonin Acetylcholine Dopamine Noradrenaline Adrenaline
Neuromodulatory system characteristics
The origin is subcortical
Each system is the locus of a particular chemical transmitter that is projected to broad areas of the brainstem, thalamus and cortex
All systems are reciprocally connected with frontal cortex and parts of limbic system
The effects of these systems on downstream targets is similar
Functions of neuromodulatory systems
Cognitive abilities Developments and growth Levels of arousal Muscular activity Neuro plasticity Pleasure and pain Sleep/wake cycle
Serotonergic system
Located in the midbrain, pons and medulla oblongata (Brainstem), close to the midline
Consists of a rostral cluster in midbrain and pons and a caudal cluster in the medulla
Projects to the majority of the CNS
Neurons produce serotonin
Projections of rostral subsystem of serotonergic cluster
Strongest to striatopallidal complex, hippocampus and cerebral cortex
Functional correlations of serotonergic system
Inhibition in forebrain, specifically cerebral cortex, but can also be excitatory
Excitation in brainstem
Can induce co-transmission of other transmitters, especially hormones and neuropeptides
Modulator of neural activity
Cholinergic system
Location: mostly in striatopallidal complex, basal forebrain, hypothalamus, epithalamus, midbrain tegmentum, cranial nerve motor nuclei, spinal cord motor neurons
Projects to majority of CNS
Many subdivisions
Neurons produce acetylcholine
Functional correlates of cholinergic system
Neurons are interconnected at their distal dendrites, allowing correlated activity of groups of neurons
Continuous subsystems, therefore continuation of spinal cord to basal forebrain
Enhanced capacity to mediate behaviour and cognition
Can fire in correlation with wake and REM sleep
Contribute to complex motor programs, volitional behaviour, cog activity and conscious experience
Catecholaminergic systems
Include dopamine, noradrenaline, adrenaline
Up to 20 nuclei in CNS from olfactory bulb to spinal cord
Delineation of catecholamine system
Dopamine= Midbrain and forward/rostral Noradrenaline= Pons and rostral/upper medulla Adrenaline= Caudal/lower medulla
Hypothalamic DA neurons
Sexual reproductive behaviour
Feeding
Modulation of other hypothalamic functions
Midbrain dopaminergic system
2 main groups
- nigral
- ventral tegmental (substantia nigra/ A9/A10)
A9 nuclei
From the niggropallidal projection
Dopaminergic fibres project heavily upon corpus striatum, important for movement control
Loss of this input slows and impairs initiation of movement (parkinsons)
A10 nuclei
Form from the meso-limbic projection
DA neurons project heavily upon limbic system and cortex (meso-cortical projection)
Plays major role in modulation of limbic function, especially in reward behaviours
