what is the most hormone action give reason in support of your answer
Answers
Answer:
1. Identify the three major classes of hormones on the basis of chemical structure
2. Compare and contrast intracellular and cell membrane hormone receptors
3. Describe signaling pathways that involve cAMP and IP3
4. Identify several factors that influence a target cell’s response
5. Discuss the role of feedback loops and humoral, hormonal, and neural stimuli in hormone control
Explanation:
Learning Objectives
By the end of this section, you will be able to:
Identify the three major classes of hormones on the basis of chemical structure
Compare and contrast intracellular and cell membrane hormone receptors
Describe signaling pathways that involve cAMP and IP3
Identify several factors that influence a target cell’s response
Discuss the role of feedback loops and humoral, hormonal, and neural stimuli in hormone control
Although a given hormone may travel throughout the body in the bloodstream, it will affect the activity only of its target cells; that is, cells with receptors for that particular hormone. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. Hormones play a critical role in the regulation of physiological processes because of the target cell responses they regulate. These responses contribute to human reproduction, growth and development of body tissues, metabolism, fluid, and electrolyte balance, sleep, and many other body functions. The major hormones of the human body and their effects are identified in Table 2.
Endocrine Glands and Their Major Hormones (Table 2)
Endocrine gland Associated hormones Chemical class Effect
Pituitary (anterior) Growth hormone (GH) Protein Promotes growth of body tissues
Pituitary (anterior) Prolactin (PRL) Peptide Promotes milk production
Pituitary (anterior) Thyroid-stimulating hormone (TSH) Glycoprotein Stimulates thyroid hormone release
Pituitary (anterior) Adrenocorticotropic hormone (ACTH) Peptide Stimulates hormone release by adrenal cortex
Pituitary (anterior) Follicle-stimulating hormone (FSH) Glycoprotein Stimulates gamete production
Pituitary (anterior) Luteinizing hormone (LH) Glycoprotein Stimulates androgen production by gonads
Pituitary (posterior) Antidiuretic hormone (ADH) Peptide Stimulates water reabsorption by kidneys
Pituitary (posterior) Oxytocin Peptide Stimulates uterine contractions during childbirth
Thyroid Thyroxine (T4), triiodothyronine (T3) Amine Stimulate basal metabolic rate
Thyroid Calcitonin Peptide Reduces blood Ca2+ levels
Parathyroid Parathyroid hormone (PTH) Peptide Increases blood Ca2+ levels
Adrenal (cortex) Aldosterone Steroid Increases blood Na+ levels
Adrenal (cortex) Cortisol, corticosterone, cortisone Steroid Increase blood glucose levels
Adrenal (medulla) Epinephrine, norepinephrine Amine Stimulate fight-or-flight response
Pineal Melatonin Amine Regulates sleep cycles
Pancreas Insulin Protein Reduces blood glucose levels
Pancreas Glucagon Protein Increases blood glucose levels
Testes Testosterone Steroid Stimulates development of male secondary sex characteristics and sperm production
Ovaries Estrogens and progesterone Steroid Stimulate development of female secondary sex characteristics and prepare the body for childbirth
TYPES OF HORMONES
The hormones of the human body can be divided into two major groups on the basis of their chemical structure. Hormones derived from amino acids include amines, peptides, and proteins. Those derived from lipids include steroids (Figure 1). These chemical groups affect a hormone’s distribution, the type of receptors it binds to, and other aspects of its function.
This table shows the chemical structure of amine hormones, peptide hormones, protein hormones, and steroid hormones. Amine hormones are amino acids with modified side groups. The example given is norepinephrine, which contains the NH two group typical of an amino acid, along with a hydroxyl (OH) group. The carboxyl group typical of most amino acids is replaced with a benzene ring, depicted as a hexagon of carbons that are connected by alternating single and double bonds. Peptide hormones are composed of short chains of amino acids. The example given is oxytocin, which has a chain of the following amino acids: GLY, LEU, PRO. The PRO is the bottom of the chain, which connects to a ring of the following amino acids: CYS, CYS, TYR, ILE, GLU, and ASP. Protein hormones are composed of long chains of linked amino acids. The example given is human growth hormone, which is composed of a bundle of amino acid strands, some thread-like, some coiled, and some in flat, folded sheets. Finally, steroid hormones are derived from the lipid cholesterol. Testosterone and progesterone are given as examples, which each contain several hexagonal and pentagonal carbon rings linked together.
Figure 1. Amine, Peptide, Protein, and Steroid Hormone Structure
AMINE HORMONES
Hormones derived from the modification of amino acids are referred to as amine hormones. Typically, the original structure of the amino acid is modified such that a –COOH, or carboxyl, group is removed, whereas the −NH3+−NH3