Welcome back to our lesson on the nervous system.
In this video, we will discuss the thalamus and the hypothalamus.
These two structures are responsible for many bodily functions.
Some of which include: regulating body temperature; regulating our circadian rhythm; integrating
functions of the autonomic nervous system; and even causing our bodies to respond to
different emotional states. For the rest of this video, we will discuss the details
of these functions and more.
Great, so let’s begin.
The thalamus, resides in the diencephalon portion of the forebrain, and it is located
superior to the hypothalamus and inferior to the cerebrum. Many sensory neuron pathways,
except those concerned with smell, pass through the thalamus, and therefore many functions
of the thalamus are related to processing sensations.
In particular the thalamus is thought to consolidate, or group sensory inputs, into a cohesive feeling or experience.
For example, holding a cup of hot tea would stimulate receptors that detect sensations
of heat, texture, and also the shape of the cup.
Yet, we don’t experience each of these sensations separately because the thalamus combines these,
initially separate, sensations into a whole complete feeling or experience.
Though the thalamus can process feelings, such as pain, it would not know which part
of the body is experiencing that pain.
Said another way, the thalamus cannot localize our sensations.
In fact, it relies on “the sensory areas of the cerebrum” to do so.
As a result, after the thalamus combines sensory inputs, it then relays this packaged information
to the parietal lobe of the cerebral cortex, where we gain more precise awareness of our sensations.
Some other functions of the thalamus include, regulation of consciousness, stimulating feelings
of wakefulness and alertness, and also temporarily suppressing unimportant sensations.
By temporarily blocking minor sensations, the thalamus allows the cerebrum to concentrate on important tasks.
For example, when you focus on a task such as reading a book or writing a paper,
you are less likely to notice small occurrences such as someone else walking into the room.
The last part of the diencephalon that we will discuss is located below or inferior
to the thalamus and is called the hypothalamus.
The hypothalamus is thought to play a role in many bodily functions.
First, the hypothalamus is thought to integrate autonomic responses to different emotions.
Basically, when the hypothalamus detects a change in emotional state, the autonomic nervous
system triggers a reflex response. Certain emotions, such as anger or embarrassment, cause a more noticeable response.
For instance, when we get angry, our heart rate will increase; or when we are embarrassed we tend to blush.
Another major function of the hypothalamus is the regulation of our body rhythms.
These are processes that occur in sync with the day, or a 24-hour period.
These rhythms, often referred to as our biological clock, are regulated by the hypothalamus, and affect your day-to-day life.
Secretion of hormones, sleep-cycles, changes in mood, and our mental alertness can all fluctuate with our bodily rhythm.
For instance, mental alertness fluctuates depending on one’s circadian rhythm; consequently,
a person who usually sleeps at night would be more alert in the morning and less alert at night.
The next major function of the hypothalamus is the regulation of food intake.
The hypothalamus regulates food intake by controlling peristalsis, which is the movement
of food through the digestive tract; and it also controls feelings of satiety and fullness.
The hypothalamus is able to perform these functions by responding to changes in blood nutrient
levels, to chemicals secreted by fat cells, and to hormones secreted by the our intestines.
Perhaps the most vital function of the hypothalamus is being the nervous system’s link to the endocrine system.
The hypothalamus performs this function via its connection to the anterior pituitary gland.
This connection is important because it allows the hypothalamus to regulate the pituitary gland.
By producing special hormones called “releasing hormones”, the hypothalamus can directly affect
hormone secretion of other organs.
In fact, releasing hormones, also known as releasing factors, stimulate the secretion
of other hormones. For example, GHRH, or growth hormone-releasing hormone, stimulates the
anterior pituitary to secrete GH or growth hormone.
Further, since the pituitary gland produces its own releasing factors, the hypothalamus
indirectly affects other organs in the endocrine system, such as the adrenal cortex and the
thyroid. One analogy that might simplify this concept is if you think of the pituitary gland
as being the “parent” of the endocrine system, and the hypothalamus as being the “grandparent”.
Lastly, the hypothalamus acts as its own center for hormone production.
It produces ADH (Antidiuretic hormone), which helps the body maintain proper blood volume;
and it produces Oxytocin, which triggers uterary contractions during labor.
Because of these functions the hypothalamus is considered crucial to maintaining body
homeostasis, and many of our autonomic responses.
This concludes our discussion on the thalamus and hypothalamus.
Please be sure to check out our other videos on the nervous system.
Thanks for watching!