Glands, Organs, and Hormonal Signaling in the Human Body

1.Describe endocrine glands:

Endocrine system consists of endocrine glands and endocrine organs that are present throughout the body. Endocrine glands are the glands without ducts that secrete their production such as hormones directly into the blood (Tsang et al, 2016).

The major endocrine glands in the endocrine system are as follows:

Pituitary gland

Hypothalamus

Pineal gland

Pancreas (it also has exocrine function)

Thyroid gland

Testis

Overy

Parathyroid gland

Adrenal gland

Endocrine glands can be compared to nerves of the nervous system, which transmit the electrical signal through neurotransmitter (Ahsan et al. 2020). In case of endocrine system, endocrine glands are actively involved in regulating functions of different body parts by secreting the chemical messenger, hormones. Hormones perform specific functions such as regulating temperature, controlling growth, carrying out metabolism and triggering reproductive development.

Hormones are the main products of endocrine glands that are secreted directly into the blood stream and then transported to various organs of body to instigate them to perform their functions. Specific hormones are secreted from different endocrine glands that work on the specific target organs. For example, insulin and glucagon the two hormones secreted from pancreas and work on the muscle cells and tissues to maintain the normal range of glucose in blood stream.

The entire function of the endocrine system is maintained and controlled by the hypothalamus, which is known as the control centre of the endocrine glands.

3. Regulation of hormone secretion:

Hormone secretion is regulated and controlled by the feedback loops that stimulate the initialization of hormone secretion and regulating the additional hormone secretion when needed

There are two types feedback loops that regulate the hormone secretion, the positive feedback and negative feedback loop (Schoor and Shaikh, 2018). The positive feedback loop is associated with releasing additional hormone in blood steam thereby enabling the hormone to stimulate the target organ to perform its functions. On the other hand, negative loop is associated with inhibition of further hormone secretion. Through maintaining synchronise action, these two loops assist the bloodstream to enable hormones to be regulated within the narrow range.

For example, when oxytocic is secreted to stimulate the uterine muscle for contraction in terms of pushing foetus towards cervix thereby causing it to be stretched. This initial release of oxytocin into bloodstream stimulates the pituitary gland to secrete more oxytocin to develop more labour contraction in the uterine muscle to facilitate child birth. After birth, negative feedback loop then send signal to the pituitary gland to stop oxytocin secretion thereby reducing the oxytocin level in the bloodstream.

4. Role of adrenaline?

Adrenaline is called as the activation hormone which is generally secreted while intense situation comes in which an individual in highly exited.

This chemical substance plays dual roles in which it acts as neurotransmitter (in Brain) and as hormone (in rest of the body) (van den Beld et al 2018.). Under normal condition there is no secretion of adrenaline. In normal condition adrenaline is stored in adrenal medulla. When body feels threats, the neurotransmitter released from brain into the bloodstream that opens the Ca+ channel thereby stimulating adrenal gland to release adrenaline hormone to maintain equilibrium state inside the body.

Adrenaline assists body to combat the issue which is called ‘fight’ to overcome the threats which is known as ‘flight’

Adrenaline provides support to the body during the emergency situation through:

Regulating the blood pressure

Maintaining heart rate

Regulating body temperature

5. Describe function of thyroid gland:

1. Thyroid gland secrets two important hormones, triiodothyronine or T3 and thyroxine or T4 (Kloas and Kirschbaum, 2019). These two hormones together are associated in maintaining blood pressure, body temperature and metabolism.

2. Low level of T3 and T4 in blood stream stimulates secretion of thyrotropin-releasing hormone (TRH) from the control centre of endocrine system, the hypothalamus. Then TRH stimulates secretion of Thyroid stimulating hormones [TSH] from pituitary gland which then simulates the thyroid gland for secreting T3 and T4.

T3 and T4 together performs the following functions:

Regulating and controlling metabolism

Regulating breathing

Impacting nervous system

Maintaining body temperature

Maintaining cholesterol level

Promoting growth and development

Regulating heart rate, body weight and muscle strengths

Controlling digestion and intestinal flow

Reference list:

Ahsan, A., Khan, A., Farooq, M.A., Naveed, M., Baig, M.M.F.A. and Tian, W.X., 2020. Physiology of Endocrine System and Related Metabolic Disorders. In Endocrine Disrupting Chemicals-induced Metabolic Disorders and Treatment Strategies (pp. 3-41). Springer, Cham.

Kloas, W. and Kirschbaum, F., 2019. Endocrine System. The Histology of Fishes, p.373.

Schoor, M.E. and Shaikh, S., 2018. Physiology of the Endocrine System and Metabolic complications in Anesthesia. In Basic Sciences in Anesthesia (pp. 405-426). Springer, Cham.

Tsang, A.H., Astiz, M., Friedrichs, M. and Oster, H., 2016. Endocrine regulation of circadian physiology. J. Endocrinol, 230(1), pp.R1-R11.

van den Beld, A.W., Kaufman, J.M., Zillikens, M.C., Lamberts, S.W., Egan, J.M. and van der Lely, A.J., 2018. The physiology of endocrine systems with ageing. The Lancet Diabetes & Endocrinology, 6(8), pp.647-658.

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