Question

Describe the order of events in the activation of steroid hormone receptors. Start with the hormones that are in the circulatory system and end with a change in activity in the nucleus.

Answer 1

Answer:

Hormones are the non nutrient chemical substances which are produced from the endocrine glands in trace amounts. They are known to perform and regulate a number of physiological responses within our body and they get transported throughout the body via the blood being the medium.

Depending on their composition and solubility, hormones are classified into two groups namely;

Fat/Lipid soluble and: These hormones are soluble in lipids

Water soluble: These hormones are soluble in water

Lipid soluble hormones: Steroids and their activation

Steroids are the class of the hormones which are soluble in lipids. They are called steroids as they remain derived from the cholesterol precursor.

Receptor for steroid hormones and their mechanism of action:

As the hormones are soluble in lipids, they can easily cross the plasma membrane which forms a protective barrier surrounding the cell from all the sides. This is due to the reason that the plasma membrane also is made of lipids and proteins. Being soluble in the lipids, these hormones can easily pass the cell membrane and then enters inside the cell.

Once inside the cell, the hormone gets bound to their receptors which are located intracellularly. Likewise the formation of hormone receptor complex is intracellular and the hormone now gets activated. After their activation, they enter inside the nucleus of the cell through the nuclear pores and likewise they can modify the DNA present within the nucleus. Once the DNA within the nucleus gets modified, the proteins formed from them also are modified bringing about the different physiological responses within our body.

Summary for hormone action: The steroid hormone modifies the DNA, and also thus the modified proteins are formed due to which the different physiological responses are exhibited by the human body.

Example: Progesterone

Progesterone is a steroid hormone which is present in the human females and it remains associated with the regulation of reproductive events like regulation of menstrual cycle, and also for maintaining pregnancy. The hormone is released from the temporary endocrine glands like corpus luteum, and placenta.

Since, this is a steroid hormone; it can easily cross the cell membrane and then enter the nucleus of the cell. Due to which the DNA present within the nucleus gets modified, also thus modifying the proteins. This gets reflected in terms of thickening of the uterine walls supporting the implantation of the fetus.

Thus, this is how a steroid hormone facilitates its action by crossing the cell membrane, binding to an intracellular receptor, and modifying the DNA and the proteins.