Human Hormone System : Important Biochemicals That Controls Our Body Organs

3D Picture of Position and Names Of Different Glands of Human Body. Created by Me (Manash Kundu)

ENDOCRINE SYSTEM:

Major glands of the human endocrine system. The hypothalamus stimulates the  gland and influences food intake, weight regulation, fluid intake and balance, thirst, body heat, and the sleep cycle.  hormones stimulate growth, egg and sperm development, milk secretion, and release of hormones by other glands. The pineal gland may play a significant role in sexual maturation and the circadian rhythm. Thyroid hormones regulate the metabolic rate of tissues, stimulate the contraction of heart muscle, and are necessary for normal growth and brain development before birth and during infancy. Parathyroid hormone regulates calcium, phosphorus, and magnesium levels. The adrenal glands regulate salt and water retention, some reactions of the immune system, and blood pressure. The islets of Langerhans regulate blood sugar levels. The ovaries and testes produce hormones that regulate the reproductive system and that produce male and female secondary sex characteristics.

Position and Names Of Different Glands of Human Body

This system consists of glands widely separated from each other with no direct links.Endocrine glands consists of groups of secretory cells surrounded by an extensive network of capillaries that facilitates diffusion of hormones(Chemical messengers) from the secretory cell into the bloodstream.They are commonly referred to as the ductless glands because hormones  diffuse directly into the bloodstream. The hormone is then carried in the bloodstream to target tissues and organs that may be quite distant,where they influence cellular growth and metabolism.

3D Picture of Position and Names Of Different Glands of Human Body created by me (Manash Kundu)

Homeostasis of the internal environment is maintained partly by the autonomic nervous system and partly by the endocrine system.The autonomic nervous system is concerned with rapid changes,while hormones of the endocrine system are mainly involved in slower and more precise adjustments.

    

This system consists of a number of distinct glands and some tissues in the other organs. Although the hypothalamus is classified as a part of the brain and not as an endocrine gland it controls the pituitary gland and has an indirect effect on many others.The ovaries and testes secrete hormones associated with the reproductive system after puberty.

    

When a hormone arrives at its target cell,It binds to a specific area,The receptor,where its act as a switch influencing chemical or metabolic reactions inside the cell.The receptor of peptide hormone are situated  on the cell membrane and those for lipid based hormones are inside the cell. 

3D Pictures of Different Hormones and their affecting organs created by me (Manash Kundu)

Hormones:

Organic compound (often a steroid or peptide) that is produced in one part of a multicellular organism and travels to another part to exert its action.

Hormones regulate physiological activities including growth, reproduction, and homeostasis in vertebrates; molting and maintenance of the larval state  in insects; and growth, bud dormancy, and leaf shedding in plants. Most vertebrate hormones originate in specialized tissues  and are carried to their targets through the circulation. Among the many mammalian hormones are ACTH, sex hormones, thyroxine, insulin, and epinephrine. Insect hormones include ecdysone, thoracotropic hormone, and juvenile hormone. Plant hormones include ethylene, abscisin, auxins, gibberellins, and cytokinins.

Peptide hormone:

1) Adrenaline(epinephrine)

2) Noradrenaline (Norepinephrine)

3) Insuline

4) Glucagon

Lipid based hormone:

1) Steroid:  glucocorticoid, mineralocorticoid.

2) Thyroid hormones.

3D Picture of Pituitary Gland , its components and its Hormones (With Affecting Organs) created by me (Manash Kundu)

PITUITARY:

Endocrine gland lying on the underside of the brain that plays a major role in regulating the endocrine system. Major Hormones are secreted from this main Gland Therefore it also call "Master Gland".

ANTERIOR PITUITARY:

Some of the hormones secreted by the anterior lobe (adenohypophysis) stimulate or inhibit secretion by other endocrine glands(Target galnds) while others have a direct effect on target tissue.

The release of an anterior pituitary hormone follows stimulation of the gland by a specific releasing hormone produced by the hypothalamus and carried  to the gland through the pituitary portal system of blood vessels.When  there is a low level of a hormone in the blood supplying the hypothalamus it produces the appropiate releasing hormone that stimulates release of a trophic hormone by the anterior pituitary.This in turn stimulates the target gland  to produce and release its hormone. As a result the blood level of that hormone rises and inhibits the secretion of releasing factor by the hypothalamus.

Hormones From Pituitary Gland Created By Me (Manash Kundu)

 Hormones of Anterior Pituitary Lobe:

1)THYROID STIMULATING HORMONE(TSH):

This hormone is synthesised by the anterior pituitory and its release is stimulated by TRH from the hypothalamus.It stimulate growth and activity of the thyroid gland, which secretes the hormones thyroxine(T4) and triiodothyronine(T3). Release is lowest in the early evening and highest during night.Secretion is regulated when the blood level of thyroid hormones is high, secretion of TSH is reduced and vice versa.

2) GONADOTROPHINS:

After puberty two gonadotrophins(sex hormones) are secreted by the anterior pituitory in response to luteinising hormone releasing hormone(LHRH) also known as gonadotrophin releasing hormone(GnRh). In both males and females these are

a) Follicle stimulating hormone:(FSH)

b) Luteinising hormone:(LH)

In Females:

LH and FSH are involved in secretion of the hormones osetrogen and pogesterone during the menstral cycle as the level of oestrogen and pogesterone rise, secretion of LH and FSH is supressed.

In Males:

LH also called interstitial cell stimulating hormone(ICSH) stimulates the interstitial cells of the testes to secrete the hormone testosterone.

3) ADRENOCORTICOTROPHIC HORMONE (ACTH):

Corticotrophin releasing hormone(CRH) from the hypothalamus promotes the synthesis and release of ACTH by the anterior pituitory.This increases the concentration of cholesterol and steroids within the adrenal cortex and the output of steroid hormones, especially cortisol. ACTH levels are highest at about 8 a.m. and fall to their lowest about midnight,although high levels sometimes occur at midday and 6 p.m..This circardian rhythm is maintained throughout life.It is associated with the sleep pattern and adjustment to changes takes several days following, e.g. changing work shifts taveling to a different time zone. It is supressed when the blood level of ACTH rises.Other factors that stimulate secretion include hypoglycaemia, exercise and stressors, e.g. emotional states and fever.

4) PROLACTIN:

This hormone stimulate the lactation(milk production) and has a direct effect on the breast immediately after childbirth.The blood level of prolactin is stimulated by prolactin relaesing  hormone(PRH) released from the hypothalmus and it is lowered by prolactin.After birth sucking stimulates prolactin secretion and lactation. The resultant high blood level is a factor in reducing the incidence of conception during lactation.

  

Prolactin together with oestrogens ,corticosteroids,insulin and thyroxine is involved in initiating and maintaining lactation.Prolactin secretion is related to sleep, i.e. it is raised during any period of sleep,night or day.Emotional stress increases production.

5) GROWTH HORMONE (GH):

This is the most abundant hormone synthesised by the anterior pituitory.It stimulates growth and division of most body cells but especially those in the bones and skeletal muscles.Body growth in response to the secretion of GH maintains the mass of bones and skeletal muscles.It also regulates aspects of metabolism in many organs, e.g. liver,intestine, and pancreas; stimulates protein synthesis; promotes break-down of fats and increses blood glucose level. It releases is stimulated by growth hormone releasing hormone(GHRH) and supressed by growth hormone release inhibiting hormone(GHRIH). Both of which secreted by the hypothalamus. Secretion og GH is greater during sleep and is also stimulated by hypoglycaemia,exercise and anxiety.

3D Picture of Pituitary Gland , its components and its Hormones (With Affecting Organs) created by me (Manash Kundu)

POSTERIOR PITUITARY:

The structure of the posterior pituitary gland and its relationship with the hypothalamus is same as anterior pituitary.Oxytocin and antidiuretic hormone (ADH or  vasopressin) are the hormones synthesised in the hypothalamus and then stored in the axon terminals within the posterior pituitary gland.These hormones acts directly on non-endocrine tissue and their release from synaptic vesicles by exocytosis is stimulated by nerve impulses from the hypothalamus.

Hormones of Posterior Pituitary Lobe:

1) OXYTOCIN:

Oxytocin stimulates two target tissues during and after childbirth: uterine smooth muscle and the muscle cells of the lactating breast. During childbirth increasing amounts of oxytocin are released by the posterior pituitory into the bloodstream in response to increasing distension of sensory streach receptors in the uterine cervix by the baby`s head.Sensory impulses is generated and travel to the control centre in the hypothalamus,stimulating the posterior pituitory to release more oxytocin.In turn this stimulates more forceful uterine contractions and greater steaching of the uterine cervix as the baby`s head is forced further downwards.Which stops soon after the baby is delivered when distension of the uterine cervix is greatly reduced.

    

Suckling generates sensory impulses that are transmitted from the breast to the hypothalamus.The impulses trigger the release of oxytocin from the posterior pituitory and oxytocin stimulate contraction of the myoepithelial cells around the glandular cells and ducts of the lactating braest to contract,ejecting milk.Suckling also inhibits the release of prolactin inhibiting hormone (PIH) , prolonging prolactin secretion and lactation.

2) Antidiuretic Hormone (ADH) or Vasopressin:

The main effect of this hormone is to reduce urine output. ADH increases the permeability to water of the distal convoluted and collecting tubules of the nephrons of the kidneys. As a result the reabsorption of water from the glomerular filtrate is increased. The amount of ADH secreted is influenced by the osmotic pressure of the blood circulating to the osmoreceptors in the hypothalamus. As the osmotic pressure rises, the secretion of ADH increases as in for example, dehydration and following haemorrhage. More water is therefore reabsorbed and the urine output is reduced. This means that the body retains more water and the rise in osmotic pressure of the blood is low for example after a large fluid intake, secretion of ADH is reduced, less water is reabsorbed and more urine is produced.

After Severe blood loss ADH causes smooth muscle contraction, especially vasoconstriction in the blood vessels of the skin and abdominal organs. This has a pressure effect, raising systemic blood pressure ; The alternative of this hormone, Vasopressin, reflects this effect.

3D Picture of Thyroid Gland and its Components created by me (Manash Kundu)

THYROID GLAND:

This gland is situated in the neck in front of the larynx and trachea at the level of the 5th, 6th and 7th cervical and 1st thoracic vertebrae.It is highly vascular gland that weighs anbout 25 g and is surrounded by a fibrous capsule.It resembles butterfly in shape,consisting of two lobes, one on either side of the thyroid cartilage and upper cartilaginous rings of the trachea.The lobes are joined by a narrow isthmuslying in front of trachea.The lobes are roughly cone shaped.

Hormones of Thyroid Gland:

1) THYROXINE AND TRI IODOTHYRONINE:

Iodine is essential for the formation of the thyroid gland hormones,Thyroxine(T4) and tri-iodothyronine(T3).The body`s main sources of iodine are seafood,vegetables grown in iodine rich soil and iodinated table salt in the diet.The thyroid gland selectively takes up iodine from the blood, a process called iodine trapping.

         

The thyroid hormones are synthesised as large precursor molecules called thyroglobulin, the major constituent is colloid.The release of T3 and T4 into the blood is regulated by thyroid stimulating hormone(TSH) from the anterior pituitary. Secretion of TSH is stimulated by thyroid releasing hormone(TRH) from the hypothalamus and secretion TRH is stimulated by exercise,stress, malnutrition, low plasma glucose and sleep.The level of secretion of TSH depends on plasma levels of T3 and T4 because these hormone affect the sensitivity of the anterior pituitary to TRH.When the supply of iodine is deficient,excess TSH is secreted and there is proliferation of thyroid gland cells and enlargement of the gland

(Goitre).

·                     It increasing the basal metabolic rate and heat production:

·                     Regulating metabolism of carbohydrates,proteins and fats:

2) CALCITONIN:

This hormone is secreted by the parafollicular or C-cells in the thyroid gland.It acts on bone and the kidneys to reduce the blood calcium(Ca 2+) level when it is raised.It reduces the reabsorption of calcium by the renal tubules.Its effect is opposite to that of parathyroid hormone.The hormone secreted by the parathyroid glands.Release of calcitonin is stimulated by an increase in the blood calcium level.This hormone is important during childhood when bones undergo considerable changes in size and shape.

THYMUS GLAND:

Thymosin:

This is the hormone secreted by the thymus gland and is required for the development of T-Lymphocytes for cell-mediated immunity.

3D Picture of Parathyroid Gland and its Components created by me (Manash Kundu)

PARATHYROID GLANDS:

There are 4 small parathyroid glands,two embedded in the posterior surface of each lobe of the thyroid gland.They are surrounded by fine connective tissue capsules.The cells forming the glands are spherical in shape and are arranged in columns with channels containing blood between them.

3D Picture of Parathyroid Gland and its Components created by me (Manash Kundu)

         

It secretes parathyroid hormone(PTH), the main function is to increase the blood calcium level when it is low.This is achieved by indirectly increasing the amount of calcium absorbed from the small intestine and reabsorbed from the renal tubules.If inadequate supply provided then PTH stimulates Oestoclasts(Bone-destroying cells) and resorption of calcium from bones

3D Picture of Adrenal Gland created by me (Manash Kundu)

ADRENAL MEDULLA:

Picture of Adrenal Gland and its components

The medulla is completely surrounded by the adrenal cortex. It developed from nervous tissue in the embryo and is part of the sympathetic division of the autonomic nervous system.

1) Adrenaline (Epinephrine)

2) Noradrenaline (Norepinephrine)

Functions:

1) Increasing Heart rate.

2) Increasing Blood Pressure.

3) Diverting blood to essential organs including the heart, brain and skeletal muscles by dialting their blood vessel.

4) Increasing metabolic rate.

5) Dilating the pupil.

Picture of Adrenal Gland and its components

ADRENAL CORTEX:

The adrenal cortex produces three groups of steroid hormones from colesterol.They are collectivly called adrenocorti-

coids(Corticosteroid,corticoids) they are:

·                     Glucorticoids:

·                     Mineralocorticoids:

·                     Sex hormones(Androgens):

Glucocorticoids:

1) They have widespread metabolic effects and these include:

2) Gluconeogenesis: formation of new sugar from(for example protein) and hypoglycaemia(raised blood glucose level).

3) Lypolysis: (Breakdown of triglycerides into fatty acids and glycerol for energy production).

4) Stimulating breakdown of protein releasing amino-acids which can be used for synthesis of other protein.

5) Promoting absorption of sodium and water from renal tubules.

6) Anti-inflammatory actions.

7) Suppression of immune responses.

8) Delayed wound healing.

Mineralocorticoids:

Aldosterone is the main mineralocorticoid .Its functions are associated with the maintenance of water and electrolyte balance in the body.It stimulate the reabsorption of sodium (Na+) by the renal tubules and excretion of potassium(K+)in the urine. Sodium reabsorption is also accompanied by retention of water and therefore aldosterone is involved in the regulation of blood volume and blood pressure too.

Pineal Gland:

This is a small body attached to the roof of the 3rd Ventricle and is connected to it by a short stalk containing nerves, many of which terminate in the hypothalamus.

Melatonin:

1) Coordination of the circadian and diurnal rhythms of many tissues, possibly by influencing the hypothalamus.

2) Inhibition of growth and development of the sex organs before puberty, possibly by preventing synthesis or release of gonadotrophins.

LOCAL HORMONES:

Histamine:

This hormone are synthesised by the mast cells in the tissues and basophils in blood.It is released as a part of the inflammatory process, increasing capillary permeability and causing vasodilatation.It also causes contraction of smooth

muscle of the brochi and alimentary tract and stimulates the secretion of gastric juice.

Serotonin:

This  is present in platelets, in the brain and in the intestinal wall.It acuses intestinal secretion and contraction of smooth

muscle and its role in haemostasis(Blood clotting).

Prostaglandins(PGs):

·                     The inflammatory response.

·                     Potentiating pain.

·                     Fever.

·                     Regulating blood pressure.

·                     Blood clotting.

·                     Uterine contractions during labour.

Testosterone

Masculinizing sex hormone produced by the testes.

It is responsible for the development of the male sex organs and secondary sex characteristics (e.g., facial hair, masculine musculature, deep voice, and male-pattern baldness). Testosterone can be manufactured by modifying other, less expensive steroids. It is used in the treatment of hypogonadism, undescended testes (cryptorchism), and certain cancers.

3D Picture of Pancreas and its components created by me (Manash Kundu)

Hormones of Pancreas:

Picture of Pancreas and its Hormones

1) INSULIN:

Insulin is a polypeptide consisting of about 50 amino acids and fatty acids.When these nutrients, especially glucose, are in excess of immediate needs insulin promotes their storage by:

1) Acting on cell membrane and stimulating uptake and use of glucose by muscle and connective tissue cells.

2) Increasing conversion of glucose to glycogen.Specially in the liver and skeletal muscles.

3) Accelerating uptake of amino acids by cells, and the synthesis of protein.

4) Promoting synthesis of fatty acids and storage of fat in adipose tissue(Lipogenesis).

5) Decreasing glycogenolysis(braekdown of glycogen into glucose).

6) Preventing the breakdown of protein and fat and gluconeogenesis(Formation of new sugar from,e.g.,protein).

2) GLUCAGON:

The effects of glucagon increase blood glucose levels by stimulating:

1) Conversion of glycogen to glucose in the liver and skeletal  muscles(Glycogenolysis)

2) Gluconeogenesis.

3) SOMATOSTATIN (GHRIH):

The effect of this hormone,also produced by the hypothalamus,is to inhibit the secretion of both insulin and glucagon in addition to inhibiting the secretion of GH from the anterior pituitary.

Diseases Caused by Abnormal secretion of Hormones:

1) HYPERSECRETION OF ANTERIOR PITUITORY HORMONES:

Picture of a Person with Gigantism

Gigantism:

This occurs in children when there is excess GH while epiphyseal cartilages of long bones are still growing i.e. before ossification of bones is complete.It is evident mainly in the bones of the limbs and affected individuals amy grow to heights of 2.1 to 2.4 m, although body proportions remain normal.

Picture of a Person with Acromegaly

Acromegaly:

This occur in adults when there is excess GH after ossification is complete.The bones become abnormally thick and there is thickening of the soft tissues.

3D Picture of a Person with Acromegaly created by me (Manash Kundu)

2) HYPERTHYROIDISM:

Picture of a Person with Goitre

Graves` disease:

It effects more women than men and may occur in any age between 30 to 50 years.It is autoimmune disorder in which

an antibody that mimics the effects of TSH is produced,Causing:

 Goitre(Visible enlargement of gland) as the antibody stimulates thyroid growth.

Picture of a Person with Exophthalmos

                 


 Exophthalmos : Protrusion of the eyeballs due to the deposition of excess fat and fibrous tissue behind the eyes;

3D Picture of a Person with  Exophthalmos created by me (Manash Kundu)

3) HYPOPARATHYROIDISM:

Picture of a Person with Tetany

Tetany: There are very strong painful spasms of skeletal musclescausing characteristic bending inwards of the hands,forearms and feets

4) HYPERSECRETION OF GLUCOCORTICOIDS(CUSHING`S SYNDROME):

Picture of CUSHING`S SYNDROME

·                     Painfull adiposity of the face(Moon face) neck and abdomen.

·                     Excess protein breakdown,acusing thinning of subcutaneous tissue and muscle wasting,specially of the limbs.

·                     Diminished protein synthesis.

·                     Suppression of growth hormone causing arrest of growth in children.

·                     Osteoporosis.

·                     Pathological factures because of calcium loss from bone.

3D Picture of Position and Names Of Different Glands of Human Body. Created by Me (Manash Kundu)

                                                                                            3D Animation Showing the Human Gland System, Important Hormones etc.