Limbic system

Limbic System

The word “limbic” means “border.” It means the border structures around the basal regions of the cerebrum, the functions of the limbic system, controls and supports a variety of functions including emotional behavior and motivational drives, long term memory, fear searching for food or drinking water , olfaction and other functions

A major parts of the limbic system are the cortical and subcortical structures

subcortical structures includes hypothalamus, the septum, the araolfactory area, the anterior nucleus of the thalamus, portions of the basal ganglia, the hippocampus, and the amygdala.





limbic cortex surrounding the subcortical limbic structures it is composed of a ring of cerebral cortex in each side of the brain (1) beginning in the orbitofrontal area is the portion over the orbits , (2) extending upward into the subcallosal gyrus, (3) then in the cingulate gyrus, and finally (4) to the parahippocampal gyrus and uncus.

Function of the hypothalamus,

hypothalamus its very small size located Above the pituitary gland and below the thalamus ,send output signals in three directions:
(1) downward to the brain stem, mainly into the reticular areas from these areas into the peripheral nerves of the autonomic nervous system;
(2) upward to the thalamus and limbic cortex
(3) to the hypothalamic infundibulum to control the posterior and the anterior pituitary glands.
In addition to their roles in behavioral control, these areas control many internal conditions of the body, such as body temperature, osmolality of the body fluids, and the drives to eat and drink and to control body weight.
Functions of the Hippocampus
The hippocampus has numerous connections with the cerebral cortex as well as with the basal structures of the limbic system.
Stimulation of the hippocampus can cause different behavioral patterns such as pleasure, anger
hippocampus is critically involved in many declarative memory functions.

Functions of the Amygdala

The amygdala is a complex of multiple small nuclei located in the anterior pole of each temporal lobe. It has connections with the other areas of the limbic system the Amygdala concern with the fear
Amygdala stores simple significance codes mainly for fear .a fight-or-flight reaction may be generated via projections to the higher centers
Effects initiated from the amygdala include
(1) increases or decreases in arterial pressure, (2) increases or decreases in heart rate, (3) increases or decreases in gastrointestinal motility and secretion, (4) defecation or micturition, (5) pupillary dilation or, rarely, constriction, (6) piloerection, and (7) secretion of various anterior pituitary hormones, especially the gonadotropins and adrenocorticotropic hormone.
Stimulation of the amygdala is believed to make the person’s
behavioral response appropriate for each occasion

Function of the Limbic Cortex

The most poorly understood portion of the limbic system is the ring of cerebral cortex called the limbic cortex that surrounds the subcortical limbic structures.the limbic cortex in effect functions as a cerebral association area for control of behavior
cingulate gyrus, responsible for satisfaction
.