Limbic System I Flashcards
What does the limbic system control?
Mood, emotion, feelings, motivation, critical for memory
What is the clinical relevance of limbic system?
Over 50% of patients have mood disorders they are treated for
What structures are involved in the limbic system?
- Amygdala
- Hippocampus
- Septal Nuclei
- Nucleus accumbens
- Medial prefrontal cortex and Anterior cingulate cortex
- Ventral segmental area
- Anterior and Dorsomedial nuclei of the thalamus
- Mammillary nuclei
In limbic system, what do all circuits involve?
Hypothalamus!!
All limbic areas receive rich innervation by which monoaminergic and cholinergic axons?
NE & 5HT
Where is NE made?
Locus ceruleus (pons)
Where is Serotonin (5HT) made?
Raphe nuclei (Ra - midbrain)
What are norepinephrine and serotonin important for in the limbic system?
Arousal & Sleep-wake cycles
Where are the dopamine producing neurons in the limbic system?
Ventral Tegmental Area (VTA)
Where do the dopaminergic neurons in the VTA travel to?
- Nucleus Accumbens
- Medial prefrontal cortex
- Amygdala
- Septal nuclei
What is dopamine involved in?
Major role in motivation
-Associated with Mesolimbic system - Midbrain area
What area is implicated in drug addiction?
Dopamine area (VTA - ventral tegmental area)
Where do cocaine and amphetamine work?
Dopamine neurons
-Block DA reuptake (Inc. DA in synapse)
What happens if you lesion the VTA or Nucleus Accubins?
Dec. in drug seeking behavior.
What types of drugs decrease drug seeking behavior?
DA receptor blockers!
What are some natural rewards and what system do they travel through?
Sex & Food
Mesolimbic system
Where is acetylcholine (ACh) found most often in the limbic system?
Nucleus basalis and Septal Nucleus
-These are damaged/lost in Alzheimer’s disease
What plays a role in fear conditioning (hearing bell before you’re hurt)?
Amygdala
-Animal studies done looking at increase in heart rate and freezing
What do lesions in the amygdala cause?
-Prevent fear conditioning! (getting response form tune, not entire stimulus)
How might fear conditioning relate to clinical aspects of human medicine?
PTSD & fear conditioning/increased amygdala activity
Who was Phineas Gage?
Railroad foreman injured on site by explosion = sent rod through his brain (he had most normal function, but his personality changed a lot)
What are symptoms of prefrontal lobe damage (Phineas Gage)?
- Impairment of goal directed behavior
- Lack of emotion in decision-making (lack of risk aversion)
- Poor social judgement (antisocial behavior)-> no more church
- Poor emotional control (increased impulsivity) -> very responsive to criticism
What parts of the brain were injured in Phineas Gage?
- Dorsolateral PRC (DLPFC)
- -> involved in working memory
- -> Executive functions - Orbital frontal cortex (OFC)
- -> Amygdala projection
How does the prefrontal cortex influence the amygdala?
It inhibits it!
