The Amazing Human Brain and Human Development

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Lesson 2: Brain Organization and Function
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Brain Organization and Function

The diencephalon has four main substructures: thalamus, hypothalamus, epithalamus, and subthalamus. We'll focus on the first two.

In Latin, thalamus means little room. In the brain, the thalamus is located deep inside and between the two cerebral hemispheres, so it is indeed a little room. The thalamus is a nuclear mass of great importance in both sensory and motor systems. No sensory information, with the exception of olfactory information, reaches the cerebral cortex without first passing through and being processed by thalamic nuclei.

The thalamus functions as a way station between the brain and the spinal cord. If you experience sensations such as pain, pressure, or temperature, you have your thalamus to thank! Senses such as taste, sight, sound, and touch also must pass through the thalamus as they make their first stops in the brain.

The prefix hypo means under, so consider the hypothalamus as being located under the thalamus. In medical lingo, the hypothalamus is referred to as inferior to the thalamus. The lower, or inferior, surface of the hypothalamus is actually one of the very few parts of the diencephalon visible on an intact brain. (Remember, the thalamus is the inner room.)

The hypothalamus is tiny, about the size of a small bean, and comprises about 1/300th of the brain's total weight. Despite its unimpressive size, the hypothalamus is the major visceral control center of the brain. It is your hypothalamus that regulates your body temperature. And it is your hypothalamus that sends you a signal to let you know that you're hungry, thirsty, tired, mad, or sad. The hypothalamus is involved in limbic system function as well.


Thalamus or Hypothalamus?

Experiencing sensations such as pain or pressure? That's the job of your thalamus. Feeling hungry, tired, or irritable? Your hypothalamus is busy sending you those types of signals.

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