Hormones - class-XI

Growth hormone secreted by the anterior pituitary has a widespread effect in the body. It stimulates growth of various body cells, promotes protein anabolism, absorption of calcium from bowel and conversion of glycogen to glucose.

• Blood is the medium of transport of animal hormones. The tissues that produce the hormones are known as the effectors while those tissues that are influenced by the effectors are called targets. Hormones are of low molecular weight and they diffuse readily. 
• The effects brought about by the hormones are not permanent as they get readily oxidized. 

Hormones are a diverse group of biochemicals, which perform a variety of roles in biological systems. Hormones are produced in endocrine glands. Hormones are responsible for maintenance of internal balance and developmental changes in the animal body. 

Insects go through a process of moulting during their life cycle. The process is controlled by hormones like moulting hormone and juvenile hormones. Ecdysone is a steroidal prohormone of the major insect molting hormone, which is secreted from the prothoracic glands. Insect molting hormones (ecdysone and its homologues) are generally called as ecdysteroids.

Hormones are powerful. It takes only a tiny amount to cause big changes in cells or even whole body. Hormones are chemicals produced by special cells in glands and other organs of the body; most hormones are produced by cells in the endocrine glands. These hormones, which are produced in very small amounts, are released into the bloodstream and travel to the target organ or tissue where they exert their effect. That is why too much or too little of a certain hormone can be serious. Not all the hormones are easily diffusible. Among the diffusible lipid-soluble molecules are steroid hormones. Hormones are nonantigenic that is no antibody formation occurs against hormones.

Hormones are special chemical messengers in the body that are created in the endocrine glands like Thyroid gland produces thyroxine and calcitonin. 

Hormone is a chemical messenger produced in the body that controls and regulates the activity of certain cells or organs. Hormones are secreted from the endocrine glands in the body. The glands are ductless, so hormones are secreted directly into the bloodstream. 

Vitamin D is a hormone produced by the kidneys that help to control the concentration of calcium in the blood and is vital for the development of strong bones. Thyroxine, also called as 3,5,3,5-tetraiodothyronine, or $T _ 4$, is one of the two major hormones secreted by the thyroid gland. Epinephrine, more commonly known as adrenaline, is a hormone secreted by the medulla of the adrenal glands.

The hormone is a regulatory substance produced in an organism and transported in tissue fluids, such as blood or sap to stimulate specific cells or tissues into action. Usually, it is a class of signaling molecules, produced by glands in multicellular organisms, that are transported by the circulatory system to target distant organs to regulate physiology and behaviour.

Rickets is defective mineralization or calcification of bones before epiphyseal closure in immature mammals due to deficiency or impaired metabolism of vitamin D, phosphorus or calcium, leading to fractures and deformity. 

The local hormones are known as kinins, which are released to overcome changes in body tissues. Kinins help in vasodilation and increase blood supply to the affected part, causing a mild local pain. Thus, they act as the first aid of the body. The sensation of pain at the time of stinging by a poisonous insect, burning or internal injury is due to kinins. So, they are called, first aid hormones.

Pheromones are the chemicals or compounds which have peculiar odour. These are secreted and released by the organisms with the help of glands present on the skin surface at various locations. These pheromones have odour which help in attracting the other member of the same species. The pheromone initiates a neuronal response and there is change in the physiolodical behaviour of the organism. There are various forms of pheromones like alarm pheromeones, food trail phereomeones and sex phereomones.

The chemical substances that are secreted by cells/tissues or glands are categorised as biological substances. It includes digestive juices, hormones and other secretions. Gastrin, thyroxin and oxytocin are the hormones secreted by stomach, thyroid gland and posterior pituitary respectively. These are biochemical substances. Creatinine is a breakdown product of creatine phosphate and does not fall under the biological category of chemical substances. Thus, the correct answer is D.

Juvenile hormone (JH), produced by the corpora allata, regulates two important processes in insects. The first is development; as an insect develops, the degree juvenility of the next stage is determined by the amount of JH in the blood; the lower the JH, the more adult the next stage. The other function of JH is, in many insects, to regulate the production of eggs in the female's ovaries. Because mating behavior is often synchronized with the ovarian cycle, the mating behaviour and pheromone production to be linked with JH.

Both statements are true so (c) will be the correct answer. All the extra water, excess salts and the nitrogenous wastes such as Urea have to be sent to the excretory system to be thrown out of the body.

• A hormone is derived from Greek"impetus" which is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism.
•  Hormones in animals are often transported in the blood.
•  Cells respond to a hormone when they express a specific receptor for that hormone. Hence, Hormones are also known as Impetus. 
 So, the correct answer is 'Impetus'.

Chemically, hormones may be proteins, polypeptide's, amino acid derivatives or steroids. They help the body to cope up with infections, stress. trauma, starvation and extreme temperatures.

• Hormones have diverse chemical structures, mainly of three classes: eicosanoids, steroids, and amino acid/protein derivatives (amines, peptides, and proteins). 
• The glands that secrete hormones comprise the endocrine signalling system. The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell (autocrine or intracrine signalling) or nearby cells (paracrine signalling). Hence, Chemically, hormones are Proteins and Steroids.

• Hormones are derivative of protein, amino acids, and steroids. Hormones are the chemical messenger that provide signals to the cell for performing the particular function. Hormones are used up completely in the metabolism.
• Enzymes are the catalyst, which enhances the biochemical reactions. Enzymes act at the place where they are formed. And enzymes do not get used up in the reaction. Hence, Hormones differ from enzymes in the respect that they are used completely in metabolism.

• A hormone may be defined as a specific product (organic substance) of an endocrine gland secreted into the blood which carries it to a specific part of the body where it produces a definite physiological effect. 
• Hormones exert their effects not where they are locally produced, but on other tissues of the body. And never stored in the body and synthesized at once.  Hence,  They have a high molecular weight and not found in plants is not the property of hormones.

• A hormone receptor is a receptor molecule that binds to a specific hormone.
• Hormone receptors are a wide family of proteins made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a variety of other receptors for various ligands, such as fatty acids and prostaglandins. Hence, Hormones affect distant cells by controlling Receptor proteins.  

A hormonal control is always involuntary. We cannot control its action by our wish. Eg$:$ Growth of height of an individual.

FSH and LH are collectively known as gonadotropic hormone because they regulate the growth and functioning of gonads.

The calorigenic effect is a result of the increased metabolic rate and increased oxygen consumption by cells. When the metabolic rate increases, more heat is generated.T1 and T1 are hormones that have a calorigenic effect.

Hypothalamus secretes both releasing and inhibitory hormones controlling the secretion of some anterior pituitary hormones(LH, ACTH, and TSH etc.)

IAA (auxin), GA3 (gibberellin), and ABA (abscisic acid) are naturally occurring plant hormones. Synthetic hormones include 2,4-D and NAA.

Hormones of protein nature binds to specific receptor molecules located on the plasma membrane to form the hormone receptor complex.

• The functions of Hormones are : 

•  Hyposecretion- too little of any hormone in the body can be caused by a large pituitary tumour, which interferes with the pituitary gland's ability to produce hormones. Hence, Deficiency of hormones is caused to due to Hyposecretion.

Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amount. They are released from the ductless glands called as endocrine glands. They affect the activity of another part of the body called as target site. They are not stored in the body.

Hormones can be classified based on their solubility into hydrophilic and lipophilic hormones. Hydrophilic hormones are soluble in water. They are mostly amino-based proteins. Examples include epinephrine, norepinephrine, insulin. Lipophilic hormones are soluble in lipids. They are steroids and thyroxine. Examples includes aldosterone, steroid hormones, iodothyronines.

Atrial natriuretic factor cause dilation of the afferent arterioles and constriction of the efferent arterioles leading to a primary increase in GFR.

• Water-soluble hormones include glycoproteins, catecholamines, and peptide hormones composed of polypeptides. Receptors for peptide hormones are located on the plasma membrane because they have bound to a receptor protein located on the plasma membrane.
  
• Thyroxine, Aldosterone, Cortisol, Testosterone are lipid soluble hormones.
  
• Epinephrine, Non-epinephrine, Thymosin, Melatonin and Calcitonin are water-soluble hormones.
  

Overproduction of growth hormone causes excessive growth. In children, the condition is called gigantism. In adults, it is called acromegaly. Overproduction of growth hormone is almost always caused by a noncancerous (benign) pituitary tumor (adenoma). 

• The central nervous system and the peripheral nervous system are the two major parts of the nervous system.
• The peripheral nervous system is further divided into two types- the somatic nervous system and the autonomic nervous system. 

1. The somatic system controls the sense organs and voluntary muscles. 
   
2. The autonomic nervous system controls the internal organs and regulates the secretion from the endocrine glands of the body. 

• Hence, the nervous system is capable of controlling the endocrine glands, but the endocrine glands cannot regulate the functioning of the nervous system.
• So, the correct answer is 'Neurons regulate endocrine activity, but not vice versa'.

• The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.
• Hormones act on nearby tissues or are carried in the bloodstream to act on specific target organs and distant tissues. 
  
• Hence Provides chemical integration through hormones is the correct function of the endocrine system with reference to chemical coordination.
• So, the correct answer is 'Provides chemical integration through hormones '.

$\Rightarrow$ Properties of Hormones

Oestrogen is secreted by the ovary, glucagon is secreted by alpha cells of the pancreas to raise blood sugar, and growth hormone is secreted by the anterior pituitary.

Nuclear receptors are typically used by steroid hormones and thyroid hormones. Among the list, Thyroxine and Cortisol have nuclear receptors. Catecholamines, Cholecystokinin, and Growth hormone use cell surface receptors.

Parathormone and thyrocalcitonin are directly involved in calcium homeostasis. Aldosterone indirectly affects calcium by regulating sodium and water balance. Cortisol is a glucocorticoid and is not primarily involved in calcium balance.

• The plant hormone abscisic acid (ABA) has been shown to promote abscission and dormancy, to inhibit cell elongation and to be involved in several hormones mediated plant responses
• ABA inhibits seed germination.It also inhibits morphogenesis(It is the biological process that causes an organism to develop its shape).
• So, the correct answer is 'ABA'.

Hormones are chemically diverse group of molecules produced in endocrine glands. The secretions of these glands are not conducted through special ducts but are just poured into circulating blood. Specific organs also called as target tissues have special receptors on their cell surface, which binds to specific hormones. Those tissues which do not have receptors for a particular hormone will not respond to that hormone.

Hormones are our body's chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including- growth and development, metabolism that derives energy from the foods we eat, sexual function, reproduction, mood. All of these is achieved by coordination of functions. Thus, answer is- 'co-ordination of functions'.

• Hypersecretion means excessive production of a bodily secretion. 
• Hypersecretion - too much of any hormone in the body is caused by a secretory pituitary tumour. Hyposecretion- too little of any hormone in the body can be caused by a large pituitary tumour, which interferes with the pituitary gland's ability to produce hormones. Hence, Excess of hormones is caused due to Hypersecretion.

The word "hormone" was coined by the English physiologist Ernest H. Starling in connection with the discovery of secretin, the first hormone, in 1902.

A hormone is a regulatory chemical that is secreted into the blood by an endocrine gland or an organ of the body exhibiting an endocrine function. The blood carries the hormone to every cell in the body, but only the target cells for a given hormone can respond to it. Thus Hormones are stable, long lasting chemicals released from glands.

All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones. They are biochemical messengers, secreted in very low amounts with considerably small half - life.

Hormone is a regulatory substance produced in an organism by glands and transported in tissue fluids such as blood to stimulate specific cells or tissues into action.

Hypersecretion of growth hormones or catastrophic hormone during adulthood causes acromegaly. Acromegaly patient has a gorilla like appearance with huge hands and legs.

•  E.H. Starling in 1905 discovered a signalling molecule or chemical secretin, from pancreatic secretions and named this signalling molecule as hormone.
•  G.W. Harris is known as the father of neuroendocrinology. He worked on the neural control of endocrine system

The question asks which hormones regulate growth and metamorphosis. Both juvenile hormone (maintains larval state, inhibits metamorphosis) and ecdysone (causes molting, triggers metamorphosis) regulate these processes. However, only option A (Juvenile hormone) is marked correct, which is incomplete - the question likely meant which SINGLE hormone. Based on the options, A is the best answer among those listed.

A.Insulin – hormone stimulates the breakdown of glycogen in the liver into glucose.

B.Adrenaline – hormone increasing the heart rate, increasing blood pressure, expanding the air passages of the lungs, enlarging the pupil in the eye (see photo), redistributing blood to the muscles and altering the body's metabolism, so as to maximise blood glucose levels (primarily for the brain).

C.Glucagon - The pancreas releases glucagon when the concentration of insulin (and indirectly glucose) in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. High blood-glucose levels, on the other hand, stimulate the release of insulin.

D.Thyroxine - It plays vital roles in digestion, heart and muscle function, brain development and maintenance of bones.

So, the correct option is ‘Insulin’.

(A) Prolactin regulates the growth of the mammary glands and formation of milk in them. 

(A) Oxytocin initiates vigorous uterine contractions in females at the time of the childbirth, milk secretion by mammary glands, contraction of smooth muscles.

Local hormones - A number of hormones are secreted by the cells but not in glands and widely dispersed in the body are called local hormones. Example are histamine, prostaglandins, etc.

(A) Thyroid stimulating hormone (TSH) promotes growth and function if thyroid gland. 

Hormones are nonnutrient chemicals which act as intercellular messengers and are produced in trace amounts. All hormones produce their specific effects on target tissue/cells by binding to the specific proteins called as hormone receptors. The normal functioning of endocrine glands and the level of hormones in the body needs to be regulated. This is possible through a feedback mechanism.

Hormones which interact with membrane-bound receptors normally do not enter the target cell but generate second messengers (eg, cyclic AMP, IP3, Calcium Ions etc) which in turn regulate cellular metabolism. Hormones which interact with intracellular receptors (eg, steroid hormones, iodothyronines, etc) mostly regulate gene expressions or chromosome function by the interaction of hormone receptor complex with the genome. 

Endocrine gland lack ducts and are called ductless glands. Their secretions are called hormones. Adrenal cortex secrets many hormones commonly called as corticoids. Anterior pituitary secretes many hormones such as GH, PRL, TSH, ACTH etc. The pineal gland secretes three hormones namely, melatonin, serotonin, adrenoglomerulotropin.

Human sex hormone is steroid hormones. The natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands. These forms of hormones are lipids. 

The endocrine system consists of organ, tissue and cells that produce a small amount of non-nutrient chemicals which sends signals to other cells or acts as an intercellular messenger. These chemicals are known as hormones which are transported to their target site through blood.

Hormones do not provide energy or building materials but they effect growth, differentiation and metabolic activities of their target cell.

Most of the body functions are regulated by hormones like growth, vegetative and sexual development, thermal regulation, cellular oxidation, metabolism of carbohydrates, proteins, fats, etc. Hormones are needed in very small quantity to carry out these functions. Some hormones are proteinaceous eg: insulin (regulates sugar metabolism), growth hormone of pituitary, parathyroid hormone parathormone (regulates calcium and phosphate transport).

(A)Calmodulin is a multifunctional intermediate calcium binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the binding of Ca2+ is required for the activation of calmodulin. 

Steroid hormones and thyroid hormones do not bind to the cell surface receptors. Being lipid soluble, these are able to enter the cells and their nuclei and influence the gene action. The hormone binds to the receptors forming a hormone-receptor complex. It binds to the transcription factors that in turn to DNA and a particular gene is activated. Their transcription leads to the synthesis of a specific protein to influence the metabolism of the recipient cell. Thus, the peptide hormones activate existing enzymes in the cell while steroid hormones bring about the synthesis of new enzymes.

• Nervous system is a coordinated network of nerve cells and fibres by which nerve impulses are transmitted throughout the body.
• Endocrine system consists of glands that produce hormones.