Question

A hormone (LO 35.1)

Answer 1

Hormones are defined as chemical substances that affect the activity of another part of the body. (Or)

Hormones are Organic compounds that are synthesized in glands which are secreted into the blood and having an action in a distance on target cells

Hormones serve as messengers, controlling and coordinating activities throughout the body. It can act as a neurotransmitter.

A hormone can be made from many starting molecules, but every hormone has a specific receptor it is made for. Many hormones travel through the bloodstream to their target cell, which has a specific receptor necessary to receive the signal.

Functions :

The neuroendocrine system is a complex arrangement of cells in animals which can pass messages via hormones. From the time of conception to the time of death, different hormones will affect the body and alter its development and course. These chemical signals operate on a variety of levels in animals.

A hormonal response in animals starts with input to the sensory systems. Light, touch, smell, taste and other physical inputs are processed by the central nervous system. The brain decides what to make from these inputs based on genetics and past experiences.

In response to the inputs, the brain sends a signal to the hypothalamus, the central processing center for hormonal instructions. For instructions which need to be delivered quickly, the hypothalamus contacts the posterior pituitary gland through nerve connections. These impulses signal the posterior pituitary to quickly release a hormone. Arteries within the gland carry the released hormones directly through the blood to the tissues they are meant for.

*3 categories of hormones :

1. Steroid hormones:

Activate gene transcription and regulate the enzymes created from genes.eg: Androgens, testosterone, progesterone and the corticosteroids including aldosterone and cortisol etc
2. Peptide hormones :

Insulin, Glucagon, ACTH, TSH, MSH, LH, FSH, Growth hormone etc
3. Amino acid derivatives hormones:

Catecholamine(NE&E), and thyroid hormones(thyroxine and triiodothyronine etc

Neurotransmitters are a special form of hormones, which travel only short distances between neurons.