Hormones & Behavior | Noba
The skeletal system also protects internal organs and produces blood cells. provide calcium that is essential for the proper functioning of the nervous system. The autonomic nervous system controls the function of our organs and The endocrine system consists of a series of glands that produce chemical . but the reciprocal relation also occurs; that is, behavior can affect hormone concentrations. This module describes the relationship between hormones and behavior. the division between the nervous system and the endocrine system is becoming more receptors must be available for a specific hormone to produce any effects .
The process of protein hormone synthesis begins when a hormone or an active metabolite stimulates a receptor in the cell membrane.
- Endocrine system and influence on behavior - Part 1
- Hormones & Behavior
This leads to the activation of specific molecules of DNA in the nucleus and the formation of a prohormone. The prohormone is transported through the endoplasmic reticulum, is packaged into secretory vesicles in the Golgi apparatus, and is ultimately secreted from the cell in its active, hormone form. In some cases, protein hormone synthesis can be stimulated by the entrance of a metabolite into the cytoplasm or nucleus of a target cell. This type of stimulation occurs when glucose enters insulin-producing beta cells in the islets of Langerhans of the pancreas.
There are also hormones and metabolites that lead to the inhibition of specific cellular activities.
For example, dopamine is released from neurons and binds to receptors on lactotrophs in the anterior pituitary to inhibit the secretion of prolactin. The islets of Langerhans contain alpha, beta, and delta cells that produce glucagon, insulin, and somatostatin, respectively.
A fourth type of islet cell, the F or PP cell, is located at the periphery of the islets and secretes pancreatic polypeptide. These hormones regulate one another's secretion through paracrine cell-cell interactions.
The stimulation of a receptor at the cell surface is followed by a series of complex events within the cell membrane.
Events that occur within the cell membrane then stimulate activities within the cell that lead to the activation of specific genes in the nucleus. Genes contain unique sequences of DNA that code for specific protein hormones or for enzymes that direct the synthesis of other hormones. The transcription of genes results in the formation of messenger ribonucleic acid mRNA molecules.
In the case of hormone stimulation, the mRNA molecules contain the translated code required for synthesis of the target protein hormone or enzyme. When mRNA leaves the nucleus and associates with the endoplasmic reticulum in the cytoplasm, it directs the synthesis of a relatively inert precursor to the hormone, called a prohormone, from amino acids available within the cytoplasm. The prohormone is then transported to an organelle called the Golgi apparatuswhere it is packaged into vesicles known as secretory granules.
As the granules migrate to the cell surface the prohormone is cleaved by a special enzyme called a proteolytic enzyme that separates the inactive region from the active region of the hormone.
Through a process known as exocytosis, the active hormone is discharged through the cell wall into the extracellular fluid.
Putting It All Together: The Nervous System and the Endocrine System
It should be noted that the same signal that increases the synthesis of a protein hormone usually also increases the immediate release of hormone from already synthesized secretory granules into the extracellular fluid. The precursor of all steroid hormones, cholesterolis produced in nonendocrine tissues e.
The cholesterol is then taken up by the adrenal gland and the gonads and is stored in vesicles within the cytoplasm. Through the actions of several enzymes, cholesterol is converted into steroid hormones. The first step in steroid hormone synthesis is the conversion of cholesterol into pregnenolonewhich occurs in mitochondria organelles that produce most of the energy used for cellular processes.
The two main classes of tyrosine derivatives are thyroid hormones and catecholamines. Catecholamines, I hope I spelled that right. Catecholamines are the hormones that are made in the adrenal medulla and they include epinephrine and nor epinephrine. A little bit more common name outside of the medical community for epinephrine is adrenaline.
Adrenaline is a little bit more familiar because we hear it when you're really excited and your fight or flight response. These are the three main classes of hormones and we see that they're classified by structure but they're also classified by function in a separate system. Even though all these hormones are functioning in the endocrine system not all of them have endocrine function. There's a class of hormones that are considered to have autocrine function and these are hormones that elicit a response at the cell that they're made or the cell immediately next to the cell that makes the hormone.
In addition to autocrine signalling there's paracrine signals. This is more the regional effect. One example of paracrine signals are between the hypothalamus and the pituitary gland which I'll show you in a second. Those are really close. Yeah, there's not a hard line that gets drawn with where paracrine signal function ends but generally these are regionally acting signals.
Then the last class are the endocrine signals. Those are the classic hormones that are set to function at a distance in the body and their response is elicited somewhere far away. Let's say the pituitary gland traveling all the way down to the gonads. That's a pretty long distance in terms of hormone size and blood vessel length. Those are called endocrine glands. Now that we've covered how hormones are classified I want to talk about the main organs of the endocrine system that use these hormones to communicate.
I went ahead and pre wrote out to save a little bit of time.
The first organ that I want to talk about in the endocrine system is the hypothalamus. The hypothalamus is a member of the endocrine system but it's also a member of the nervous system.
It's right here in the brain.
It's about the size of a grape. As a member of the nervous system it's taking in the signals that are being stimulated by the sensory nerves. It takes those signals and it kind of funnels them into the endocrine system through the pituitary gland by controlling the pituitary gland.
3.4 Putting It All Together: The Nervous System and the Endocrine System
The pituitary gland is often known as the master gland. It's situated right here below the hypothalamus and if the hypothalamus is about the size of a grape in the body, the pituitary gland is about the size of a green pea and it's tiny but it's role is huge in that it is principally involved in stimulating the other endocrine glands which are ultimately gonna cause any of the effects that are happening in the body.
The first organ that it stimulates going down the list here is the thyroid gland. It stimulates the thyroid gland through thyroid stimulating hormone.
The thyroid gland is a gland that wraps around the trachea which is your windpipe and you can feel it when you swallow, but the thyroid gland's main role is regulating our body's metabolism. Up regulating or down regulating the entire body and it does that through the thyroid hormones T3 and T4.
Another name for T3 is triiodothyronine and another name for T4 is thyroxine, but those are the thyroid hormones that are a member of the thyrosine derivatives that I was talking about a little bit earlier. Behind the thyroid gland are four spots that are kind of collectively known as the parathyroid gland.
I'm drawing them on the front but I want to be clear that these spots are on the back of the thyroid gland and the parathyroid gland is principally or chiefly involved in regulating our body's calcium levels. It does that through its hormone parathyroid hormone. Moving down the list we have the adrenal glands right here on top of the kidneys. They're called adrenal glands because they're adjacent to the kidneys and another name for the kidneys are the, the whole kidney system is the renal system.
The adrenal glands are stimulated by the pituitary's release of adrenocorticotropic hormone and then they ultimately release their hormones. There are two separate areas of the adrenal glands. You've got the cortex of the adrenal glands which is the outside and the medulla which is the inside of the adrenal glands.The Chemical Mind - Crash Course Psychology #3
The cortex is where the adrenal steroid hormones come from and so you got your glucocorticosteroids and your mineralocorticosteroids and those are things like cortisol and aldosterone. Those have a lot of functions in the body as far as regulating fluid volume and the stress response and in the medulla that's where the catecholamine hormones are made.
Again, those catecholamines were the second class of thyrosine derivatives that I mentioned earlier.