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Limbic System

Limbic System

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This lesson will identify, explore and describe the role and functions of the thalamus and hypothalamus. Also, explored is the role of the amygdala and hippocampus within the limbic system. The limbic system as the conduction and switching center will be explained.

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Tutorial

What's Covered

Welcome to today's lesson on the limbic system. Just below the cerebral cortex (the outer layer of wrinkled material) are several other important structures that make up the forebrain. This tutorial will focus specifically on the:

  1. Thalamus & Hypothalamus
  2. Amygdala
  3. Hippocampus

1. THALAMUS & HYPOTHALAMUS

The internal structures in the forebrain is called the limbic system, which is an area of the brain involved in things such as emotions, motivation, and memory formation. This area acts as an intermediary system to the cerebral cortex, as it passes on a lot of the information and processes it in different ways.

The thalamus is a smaller, football-shaped structure that's located at the center of the brain. It is a type of conduit or switching center for all the sensory information that's being set up to the cerebral cortex.

Injury to the thalamus can lead to a loss of senses in general like deafness or blindness. The thalamus is also related to control of movement and sleep as well.

The hypothalamus, which is the even smaller and more circular-shaped gland that's located right in front of the thalamus, is involved in things like motivation and emotion within people. One of the major duties of the hypothalamus is to regulate food, water, and sleep motivations. Damage to specific areas of the hypothalamus can result in different aspects of over or under-eating, drinking, or sleeping. This has been shown in rats as well as in humans.

The hypothalamus regulates the autonomic nervous system and controls all of those kinds of regular bodily functions that keep us alive. So the things that we don't necessarily consciously deal with, like heartbeat and digestion, are helpfully regulated by the hypothalamus.

Terms to Know

    • Limbic System
    • Areas of the forebrain involved in emotions, motivation, and memory formation.
    • Thalamus
    • A small, football-shaped structure central to brain; acts as conduction and switching center for sensory information being sent to the cerebral cortex.
    • Hypothalamus
    • A smaller, circular center in front of thalamus, involved in motivation and emotions in people.

2. AMYGDALA

The amygdala is a small almond-shaped structure that's down towards the bottom of the brain. It is related to emotional responses within people, especially related to emotions that have to do with survival; the fight-or-flight response, where it motivates us to survive in some kind of way. So these would include fear, anger, or pleasure-seeking kinds of things.

While it is a basic structure that develops in animals as well people, it really serves a powerful function.

The amygdala can lead to the creation of a lot of irrational fears or phobias. And if you have any kind of phobia you know that these are the kinds of things that are very difficult to shake. It's hard to get rid of a phobia. So you can see how intrinsic and powerful this organ can be to the formation of different kinds of thoughts and ideas.

Term to Know

    • Amygdala
    • A small, almond-shaped structure related to emotional responses in people, especially fear.

3. HIPPOCAMPUS

The hippocampus is sort of crescent-shaped structure that appears on both sides of the brain. Remember, we have two different hemispheres. So we're talking about two of these crescent shapes that are moving-- that are inside of our brain. And this is related to the formation of memories.

Now, remember that as with all parts of the brain, the parts of the limbic system also work together in lots of ways. So the thalamus and the hypothalamus help to bring all of that sensory information to our higher levels of the brain. The amygdala attaches emotions and helps to create those quick-thinking sorts of responses. And they all act as conduits to relay that information up to the cerebral cortex.

Similarly, with all of that working in conjunction, the hippocampus takes all the sensory information and the emotions that these three other organs are using, and then attaches it to different kinds of events, and helps to create these strong long-lasting memories in our minds. This is why a lot of sensory information can trigger memories in people.

Example The smell of smoke can automatically trigger a memory of camping trips when you were a child.

It explains why memories have very strong emotions attached to them. So if you're remembering, say, a traumatic event from your childhood, you can still feel those same kinds of emotions because the hippocampus plays that central role in attaching those memories and creating meaning out of them so that they can last longer within our brains.

Term to Know

    • Hippocampus
    • Crescent-shaped structures on both sides of the brain, related to the formation of memories.

    Summary

    The hypothalamus regulates the autonomic nervous system and controls regular bodily functions that keep us alive. The amygdala can lead to the creation of a lot of irrational fears or phobias. The hypothalamus regulates food, water, and sleep motivations, while the thalamus is a switching center for all the sensory information. More importantly, the hippocampus plays a central role in attaching memories to meaning.

    Good luck!

Source: This work is adapted from Sophia author Erick Taggart.

TERMS TO KNOW
  • Limbic System

    Areas of the forebrain involved in emotions, motivation, and memory formation.

  • Thalamus

    A small, football-shaped structure central to brain; acts as conduction and switching center for sensory information being sent to the cerebral cortex.

  • Hypothalamus

    A smaller, circular center in front of thalamus, involved in motivation and emotions in people.

  • Amygdala

    A small, almond-shaped structure related to emotional responses in people, especially fear.

  • Hippocampus

    Crescent-shaped structures on both sides of the brain, related to the formation of memories.