Thalamus and hypothalamus are both parts of the brain. Along with the epithalamus and perithalamus, they are both located in the region of the brain called the diencephalon.
Even though they have very similar names, which might make some people think they are similar, it’s actually the opposite – they vary significantly in both size and function, as will be discussed in more detail below. The only reason they have such similar names is their location. “Hypo” means under in Greek, and the hypothalamus is in fact located right beneath the thalamus, hence the name.
The thalamus’ function is to transfer the information it collects from other parts of the brain to the part called the cerebral cortex, which is the segment of the brain closest to the surface, consisting of gray matter, that then analyzes the information and sends instructions back.
On the other hand, the hypothalamus has a very close connection to the pituitary gland that is located near it. The pituitary gland can be considered the most important gland in the human body, since it sends hormones to all the other glands indicating when they should start or stop secreting other hormones.
In other words, it regulates the homeostasis of the body, which is its inner equilibrium. Since the hypothalamus sends signals instructing the pituitary gland as to what hormones to secrete, its importance is at least the same. These two segments of the brain vary in shape as well.
What is the Thalamus?
As I’ve mentioned, the thalamus is a part of the brain segment called the diencephalon, located between the cerebral cortex and the midbrain. It serves as a “bridge” between the two, therefore it is closely connected to both.
It transmits signals between the midbrain and the cerebral cortex, but it also regulates sleep, alertness and wakefulness. When looking at the cross-section of the human brain, the thalamus can be found almost at the very center of the brain, between the frontal lobe and the brain stem.
It consists of two bulbs, each about 6cm in length, one on each hemisphere of the brain. Since it’s located so close to the center, where the nerves go out in all directions towards the periphery of the brain, it has the optimal spot for the purpose that it fulfills (transmitting information between the midbrain and the cerebral cortex).
Its blood flow is facilitated through four branches of the posterior cerebral artery, allowing it just enough oxygen to function. Distinct segments of the thalamus have been discovered, such as the isothalamus or allothalamus, but they vary only slightly in structure and function, and therefore won’t be discussed in further detail.
The distinctive characteristics of the thalamus are:
- Part of the diencephalon, located between the cerebral cortex and the midbrain, near the center of the brain
- Transfers information between the cerebral cortex and the midbrain
- Regulates sleep, alertness and wakefulness
- Consists of two bulbs on each hemisphere, each around 6cm in length
What is the Hypothalamus?
The hypothalamus is an almond-sized part of the brain located beneath the thalamus, and is also a part of the diencephalon.
It consists of a large number of small bulbs, called nuclei. It regulates metabolic processes, body temperature, hunger, fatigue, etc… In addition, it plays a crucial role in the preservation of the body’s homeostasis, or inner equilibrium, since it dictates the secretion of different hormones from the pituitary gland that is located near the thalamus.
It sends signals which can trigger the pituitary gland to start or stop secreting a certain hormone, or just lower or increase the amount of hormones that are being secreted in the pituitary gland. In other words, it serves as the connection between the nervous and endocrine system. The substances it secrets are called neurohormones, and they are transferred to the pituitary gland which can then translate them into instructions described above.
Briefly covered, the main characteristics of the hypothalamus are:
- Part of the diencephalon, located beneath the thalamus
- Transfers information and serves as a connection between the nervous and endocrine systems
- Regulates body temperature, hunger, fatigue and metabolic processes in general
- Consists of many small nuclei, and in total is a small bulb the size of an almond
Differences Between the Thalamus and the Hypothalamus
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Location of Thalamus and the Hypothalamus
While the thalamus is located almost directly in the center of the brain, the hypothalamus is located beneath it (which is how it got its name), so their locations are different, although not by very much.
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Structure and size of Thalamus and the Hypothalamus
The thalamus consists of two bulbs for each brain hemisphere, each around 6cm in diameter. On the other hand, the hypothalamus consists of a large number of very small bulbs called nuclei, and in total is the size of an almond. This means that the thalamus is larger than the hypothalamus and has a different structure.
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Regulation of Thalamus and the Hypothalamus
The thalamus regulates sleep, alertness and wakefulness, whereas the hypothalamus regulates body temperature, hunger, fatigue and metabolic processes in general.
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Other tasks of Thalamus and the Hypothalamus
Although both thalamus and hypothalamus serve as “bridges”, they connect different pairs of things. While the thalamus connects the cerebral cortex with the midbrain, the hypothalamus connects the nervous system in general with the endocrine system. This makes another distinction between the two – the thalamus is a part of only the nervous system, while the hypothalamus can be regarded as both part of the nervous and endocrine system, since it plays an important role in both.
Thalamus vs. Hypothalamus: Comparison chart
| Thalamus | Hypothalamus |
| Located near the center of the brain | Located beneath the thalamus |
| Two 6cm-sized bulbs | Many small bulbs called nuclei, in total the size of an almond |
| Regulates sleep, alertness and wakefulness
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Regulates body temperature, hunger, fatigue and metabolic processes in general |
| Connects the cerebral cortex with the midbrain | Connects the nervous and endocrine systems |
Summary of Thalamus and Hypothalamus
- Both the thalamus and the hypothalamus are parts of the brain segment called the diencephalon
- Although they both serve the purpose of connecting different parts of the body, they are fundamentally different
- The thalamus connects the cerebral cortex with the midbrain, while the hypothalamus connects the nervous and endocrine systems
- Additionally, they vary in size – the thalamus consists of two, 6cm-sized bulbs, while the hypothalamus is an almond-sized cluster of small nuclei
- The thalamus regulates sleep, alertness and wakefulness, while the hypothalamus regulates body temperature, hunger, fatigue and metabolic processes in general