Understanding the Limbic System: Key Functions and Components

Table of Contents

1. Introduction
2. Components of the Limbic System
3. Histology
4. Connections
5. Functions

Introduction

The limbic system is derived from the word ‘Limbus’, meaning a ring. The word limbic was first used to describe the border structures around the basal region of the cerebrum.

Now the limbic system describes the entire neuronal circuitry that controls emotional, behavioral, and motivational drives and more.

Components of the Limbic System

1. The limbic lobe and the related subcortical nuclei.

The limbic lobe includes the cingulate gyrus, isthmus, hippocampal gyrus, and uncus.

2. The related subcortical nuclei are the hypothalamus, amygdala, septal nuclei, portion of the basal ganglion,paraolfactory area, and anteriorthalamic nucleus.

The hypothalamus is located in the middle of all these structures and plays a vital role in the limbic system.

The limbic cortex surrounds these subcortical limbic areas. The limbic cortex is composed of a ring of cerebral cortex on each side of the brain. The limbic cortex begins.

1. In the orbitofrontal area on the ventral surface of the frontal lobes,

2. Extends upwards into the subcallosal gyrus,

3. Then over the top of the corpus callosum onto the medial aspect of the cerebral hemisphere in the cingulate gyrus, and finally

4. Passing behind the corpus callosum and downward onto the ventromedial surface of the temporal lobe to the parahippocamal gyrus and uncus.

The neocortex sits with the legs on each side of the limbic system, like a rider on a horse without complete control. It can modify emotional behavior, but cannot initiate or terminate emotional behaviors.

Histology

The limbic cortex is made up of Allocortex (allo means old). The limbic cortex is the phylogenetically oldest part of the cerebral cortex.

Connections

The limbic cortex functions as a two-way communication and association linkage between the neocortex and the lower limbic structures.

1. Reticular nuclei in the brainstem and their associated nuclei

2. Medial forebrain bundle- main

3. Through short pathways among the reticular formation of the brainstem, thalamus, hypothalamus, and other areas of the basal brain.

Functions

1. Controls autonomic functions

2. Emotional behaviours like pleasant or unpleasant, reward or punishment, satisfaction or aversion.Emotion of rage, fear.

3. Motivation.

4. Memory.