Higher level limbic system

What is the limbic system and what is it generally involved in?

The limbic system is a collection of brain structures near the top of the brainstem and boarding the ventricles that are involved in emotion and memory and compete to influence the hypothalamus.

What does the reptilian brain of the triune brain model represent and what is its general function?

Brainstem

Reflexes and primitive survival functions (i.e., autonomic functions, feeding/digestion, and sexual development/reproduction)

What does the paleomammalian brain of the triune model represent and whats its function?

The limbic system

Emotion and memory - fear, anger, love, anxiety, and aggression

What does the neomammalian brain of the triune model represent and what’s its function?

Neocortex

Highest level functions - thought, reasoning, analysis, and self-regulation; overcoming motor plans dictated by lower areas.

Orbitofrontal cortex

social and emotional decision making

cingulate gyrus

Anterior part involved in motivation, and other areas involved in emotional expression

medial prefrontal cortex

inhibiting learned emotional responses

function and location of parahippocampal gyrus

memory

medial temporal lobe

Insula / Insular cortex

mapping of emotions on to the body - “feelings”

Describe the olfactory pathway

• odorants dissolve in the nasal cavity and bind to olfactory receptors, causing the opening of ion channels and depolarization of olfactory neurons

• action potentials get carried on olfactory nerve to the olfactory bulb (through cribriform plate)

• synapses on neurons from olfactory bulb that form olfactory tract and travel into the brain

• bypasses the thalamus and directly synapses to limbic areas

True or false - olfactory receptor cells are first-order neurons

True

True or false - Olfactory neurons are pseudounipolar

False - olfactory neurons are bipolar

True or false - olfactory neurons are continually replaced and renewed

True - olfactory neurons have a lifespan of 60 days, are are one of the few examples of neurons that are capable of regenerating (this would be interesting for discussion board)

Where are the cell bodies of 2nd order olfactory neurons found?

The olfactory bulb

Where do axons of olfactory tract synapse?

• Primitive/limbic cortex (prepiriform cortex) - awareness of smell

• medial dorsal nucleus of thalamus - relays to orbitofrontal cortex for discrimination of smell and identification of smell

• hypothalamus and limbic areas via entorhinal cortex and hippocampus - memory and emotional componenets

cortical and noncortical inputs into the hippocampus?

• most association areas

• cholinergic from basal forebrain (via fornix)

• Noradrenergic from locus coeruleus (via median forebrain bundle)

• Serotonergic from raphe nucleus (via median forebrain bundle)

• dopaminergic from the midbrain tegmentum (via median forebrain bundle)

The fornix carries information between which brain areas

Hippocampus, basal forebrain, and hypothalamus (mammillary bodies)

Basal forebrain nuclei - consists of what and functions generally in what?

Nucleus Accumbens, BNST, septal nuclei, nucleus basalis of Myenert

Involved in production of acetylcholine, affecting alertness, wake, and memory

Which region of the hippocampus is active when viewing novel information?

Anterior hippocampus

Which region of the hippocampus is active when viewing familiar information (long term memory formation)?

Posterior hippocampus

The left hippocampus is involved in encoding what type of information?

Language related information

The right hippocampus is involved in encoding what type of information?

Spatial relationships

Efferent fibers from the amygdala travel on what tract? They project where?

Stria terminalis

Bed nucleus of stria terminalis (BNST) - involved in acute stress response

Hypothalamus - regulates autonomic outputs (mod of heart rate and blood pressure via CN X and sympathetic nervous system) and pituitary/hormonal/endocrine response

Nucleus accumbens

A part of reward/pleasure pathways and involved in substance abuse

Stimulated by dopaminergic neurons from VTA - stimulations causes profound sense of wellbeing, the “feeling” of reward

Septal nucleus

Involved in reward and reinforcement of pleasurable behaviors

Stimulation gives sexual sensations

Ventral to septum pallucidum near anterior commissure

Connected with amygdala via ST, habenula via SMT tract, hippocampus via fornix

Nucleus basalis of Myenert

Involved in arousal and attention to novel stimuli

Has cholinergic projections to cortex cognition

Inferior to anterior commissure