22-CHEMICAL COORDINATION & INTEGRATION

CHAPTER NO.22 CHEMICAL COORDINATION & INTEGRATION

A215

HUMAN ENDOCRINE SYSTEM NEED FOR ENDOCRINE SYSTEM:As we have already learnt,Neural system provides point-to-point rapid coordination among organs.Neural coordination is fast but short-lived.

As the nerve fibres do not innervate all cells of the body The cellular functions need to be continuously regulated; a special kind of coordination and integration has to be provided.

This function is carried out by hormones. The neural system and the endocrine system jointly coordinate and requlate the physiological functions in the body.

ENDOCRINE GLANDS AND HORMONES

Endocrine Glands:The endocrine system is a network of glands in your body that make the hormones that help cells interact with each other.They’re responsible for almost every cell, organ, and function in your body.A gland is an organ that makes hormones that do a specific job in your body.Endocrine glands lack ducts and are hence called ductless glands. Their

- secretions are called hormones.

Types of Endocrine Glands:There are many types of endocrine glands in human body such as

Hypothalamus

Pituitary

Thyroid

Parathyroids

Adrenals

Pineal body

Pancreas (Heterocrine; both

endocrine & exocrine)

Ovaries (in females)

Testes (in males)

Hormones:Hormones are chemical messengers secreted by endocrine glands upon a

stimulus (other hormones, neural stimulus, change in concentration of extracellular fluid, etc.) , transported to target cells by means of circulatory system to target cells which have specific receptors for a specific hormone.Secreted in blood in very minute quantities.May be secreted within seconds of gland stimulation (epinephrine &

norepinephrine) or may take more time (thyroxine) Cleared from blood by metabolic destruction by the tissues, binding with the tissues, excretion by the liver into the bile, and excretion by the kidneys into

the urine.Target cells have_specific receptor molecules. No. of receptor molecules may be increased or decreased in a cell.

chemical Nature of Hormones: Hormones are broadly classified into three types based on chemical nature.

A. Peptide & Protein Hormones Peptide hormones consists of chains of amino acids (up to 100) e.g.

TSH, LH Protein hormones have numerous amino acids ( more than 100) e.g.

Insulin

B. Steroid Hormones derived from lipids such as linoleic acid and arachidonic acid

phospholipids , cholesterol and the eicosanoids e.g. Testosterone

C.Amino Acid Derivatives derived from amino acids like tyrosine e.g. Thyroxine

HYPOTHALAMUS Hypothalamus is the basal part of diencephalon, forebrain contains several groups of neurosecretory cells called nuclei which produce hormones.These hormones regulate the synthesis and secretion of pituitary hormones.

These are of two types, the releasing hormones (which stimulate secretion of pituitary hormones) and the inhibiting hormones (which inhibit secretions of pituitary hormones).

PITUITARY GLAND Called as Master Gland

Location: The pituitary gland is located in a bony cavity called sella turcica

and is attached to hypothalamus by a stalk.

1. Adenohypophysis consists of two portions, pars distalis and pars intermedia.The pars distalis region of pituitary is commonly called anterior pituitary.

a) Pars distalis secretes hormones like growth hormone (GH), prolactin {PRLi, thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH)

b) Pars intermedia secretes only one hormone called melanocyte stimulating hormone (MSH).

2. Neurohypophysis (pars nervosa) is also known as posterior pituitary.stores and releases two hormones called oxytocin and

vasopressin.

DISORDERS

1. Dwarfism Growth hormone deficiency (GHD), also known as dwarfism or pituitary

dwarfism.caused by insufficient amounts of growth hormone in the body.Children with GHD have abnormally short stature with normal body proportions.

2. Gigantism caused by hypersecretion of growth hormone during childhood.condition characterised by excessive growth and height significantly above average.

3. Acromegaly develops when the pituitary gland produces too much growth hormone

during adulthood.Common signs are enlarged hands and feet, enlarged facial features,

including the facial bones, lips, nose and tongue

LET US KNOW WHAT WE HAVE LEARNT!

PART: A-_ VERY SHORT ANSWER TYPE QUESTIONS

a. MCQs:

1 FSH is produced by

a) Thyroid gland

b) Anterior pituitary gland

c) Posterior pituitary gland

d) Gonads

2. Which of the following is an accumulation and releasing centre of

neurohormone?

a) Hypothalamus

b) Anterior lobe of pituitary gland

c) Posterior pituitary gland

d) Intermediate lobe of pituitary

3. Gigantism and acromegaly are due to

a) Hyperthyroidism

b) Hyperpituitarism

c) Hypopituitarism

d) Hypothyroidism

4. Which of the following glands is regarded as a master gland?

a) Adrenal gland

b)Pancreas

c) Pituitary gland

d) Thyroid

5. Which hormone causes the contraction of labour?

a) Prolactin

b) Estrogen

c) Progesterone

d) Oxytocin

b. TRUE/ FALSE:

1. FSH is released by the anterior pituitary gland.

2. Pituitary Gland is called the master gland of the human body.

3. Growth hormone is secreted by neurohypophysis.

c. FILL UPS:

1. Testosterone is anexample of ___—_—s sex hormone.

2. TSH has its effect on__ gland.

3. Dwarfism is caused due to hyposecretion of ss hormone.

ANSWER KEY: PART- A

a. MCQ's

1.B

2. C (Neurohormones are formed in hypothalamus but secreted in

posterior pituitary)

3. B (Hypersecretion of GH in children cause gigantism and in adults

causes Acromegaly)

4. B (As pituitary gland’s hormones controls secretions of other glands)

5. D.

b. TRUE/ FALSE:

1. True,

2. True (As pituitary gland’s hormones controls secretions of other

glands)

3. False (Growth hormone is secreted by Anterior pituitary)

c. FILL UPS:

1. Male

2. Thyroid (TSH has receptors on Thyroid)

3. Growth Hormone

PART : B~ SHORT ANSWER TYPE QUESTIONS

1. Write difference between Neural and Endocrine control and integration.

2. Write a note on hormones secreted by Hypothalamus.

3. Write a note on disorders caused by abnormal secretion of Growth Hormone.

PART : C— LONG ANSWER TYPE QUESTIONS

1. Write a note on hormones secreted by Anterior Pituitary.

A216

PINEAL GLAND:

Position: - Pineal gland or epiphysis cerebri is located on the dorsal side of the forebrain.

Structure: - It is small, reddish —grey, pine cone shaped and solid endocrine

gland.It is ectodermal in origin.

Histologically it is formed of a lobular parenchyma of pinealocytes.It is surrounded by connective tissue and covered by a capsule.

FUNCTIONS:Pinealocytes secrete, MELATONIN hormone.It plays a very important role in of 24 hour rhythm of our body that is sleep

wake cycle. Melatonin also influences Metabolism & Pigmentation.It regulates the Sexual and Reproductive function.

THYMUS GLAND:Position and Structure:

It is a soft, pinkish triangular lobular mass of lymphoid tissue located on dorsal

side of the heart and the aorta. It grows maximum size at puberty and then atrophies

gradually. It is formed of outer cortex and central medulla. Internally it has many

lobes and held together by connective tissue.

Hormone:Thymus gland secretes a polypeptide hormone called Thymosine.

Function:-Thymus is the site of differentiation of T- lymphocytes which provides cell mediated immunity.It has Hassall corpuscles which act as phagocytes.

Thymosin also promotes production of antibodies to provide humoral immunity.

In old age thymus degenerated, thyroxin decreased and immune response become weak.

THYROID GLAND:-Position and Structure:#

Itisa. gland, that it secretes only hormones.Itisa oo corse lieson... and... ew, of inthe below the .Itis a are shieldand = = bilobed. a o by a transverse band called Histoligically it is consists of small rounded . : held together by

stromal tissue.Each thyroid follicles is composed of follicular cells enclosing a cavity.The follicular cells synthesise two hormones; and Thyrocalcitonin is a long peptide hormone which Se:

2. Its level is regulated by increased plasma level of calcium.Thyroxine occur in two forms Tetraiodothyronine (T4) & Triiodothyronine (Ts)These are iodine containing amine hormone derived from tyrosine amino acid.These hormones regulate (BMR), c These hormones help in at

These hormone also help in moeioe is in infant caused due to ce - during pregnancy of mother,so ow,My xoedema is disease of adult due to Hypothyroidism, Low BMR, reduced Temperature , Heart rate.

Simple Goitre:-It is due to iodine deficiency in diet .it is a non-cancerous enlargement of thyroid gland.

PARATHYROIDS GLANDS:-Position & Structure:

These are four in number, pea shaped glands which are wholly or partially embedded on the back side of the thyroid gland, each lobe contain one pair gland.

HORMONE: - Para Thyroid Hormone (PTH) is secreted by gland.It is regulated by circulating levels of calcium ions.

FUNCTION:-Parathyroid hormone increases the calcium ions level in the blood.PTH acts on bone and stimulate the process of bone reabsorption.It reduces excretion of calcium in urine as increase reabsorption of calcium.PTH also stimulates reabsorption of calcium ions by the renal tubule from

digested food.

LET US KNOW WHAT WE HAVE LEARNT!

PART A SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. Goitre is a pathological condition associated with:

(a) Glucagon

(b) progesterone

(d) testosterone

2. A person is having problem with calcium metabolism in his body.Which of the following gland is defective?

(a) Parotid

(b) pancreas

(d) parathyroid

3. Thymosin is responsible for:

(a) raising the blood sugar level

(b) raising the blood calcium level

(d) decrease in blood RBC

4 A hormone responsible for normal sleep wake cycle is:

(a) epinephrine

(b) gastric

(d) insulin

5. Which glands atrophy in adult?

(a) pancreas

(b) thymus

(d) thyroid

2. FILL UPS:

1. Thyroxine and tri iodo thyroxin, produced by the thyroid gland , are

synthesized from iodine and ................4.

2. Metamorphosis is tadpole larva is controlled by...................

3. TRUE /FALSE:

1. Both Myxoedema and cretinism are caused by hypothyroidism

2. Grave disease is characterised by low BMR.

ANSWER KEY - PART: A

A. MCQs:

1. (c) Thyroxine: Goitre is disease of hypothyroidism which is caused by low

iodine in body.

2. (d) Parathyroid: This hormone maintains the calcium and phosphorus level

in the body

3. (c) Differentiation of T- lymphocytes: This hormone stimulate the development and differentiation of T cells increasing resistance to infections.

4. (c) Melatonin: Hormone responsible for normal sleep wake cycle, informing

the brain when it's day and night.

5. (b) Thymus: Itis a prominent at birth and degenerates gradually in adults

B. FILL UPS:

1. Tyrosine Amino Acid

2. Thyroxin hormone

C. TRUE /FALSE:

1. True: both are due to deficiency of Thyroxin hormone.

2. False: Myxoedema and Cretintism are characterised by low BMR

PART-B SHORT ANSWER TYPE QUESTIONS:

1. Old people have weak immune system .What could be the reason?

2. What is the effect of hypothyroidism on the development of baby during

pregnancy?

3. Enlist the functions of: a. Thymosine b. Parathyroid hormone

PART —C LONG ANSWER TYPE OF QUESTION:

1. Give the structure and function of Thyroid Gland.

A217

INTRODUCTION:ADRENAL GLAND:

It is a small gland that makes steroid hormones, Adrenaline and Noradrenaline.

These hormones help control heart rate, blood pressure, and other important

body functions.There are two adrenal glands, one on top of each kidney, also called, Supra-renal Gland. The adrenal glands are located in the posterior abdomen, between the supramedial kidney and the diaphragm. They are retroperitoneal, with parietal peritoneum covering their anterior surface only. The right gland is

pyramidal in shape, contrasting with the semi-lunar shape of the left gland.

They control many important functions, including:

1. Metabolism

2. Blood sugar levels

3. Blood Pressure

4. Salt and water balance

5. Pregnancy

6.Sexual development before and during puberty

7. Stress response

8. Balance of sex hormones, including estrogen and testosterone

PANCREAS:A glandular organ located in the abdomen. It makes pancreatic juices,

which contain enzymes, that, aid in digestion, and it produces several

hormones, including INSULIN. The pancreas is surrounded by the stomach,intestines, and other organs. The pancreas is an elongated, tapered organ located across the back of the belly, behind the stomach. The right side of the organ-called the HEAD-is the widest part of the organ and lies in the curve of the duodenum, the first division of the small intestine.

The pancreas has DIGESTIVE and HORMONAL functions:The enzymes secreted by the exocrine gland in the pancreas help break

down carbohydrates, fats, proteins. and acids in the duodenum. These

enzymes go down the pancreatic duct into the bile duct in an inactive form.

TESTES:Testis (plural testes) is the male reproductive gland or gonad in all animals,

including humans. It is homologous to the female ovary. The functions of the

testes are to produce both sperm and androgens, primarily testosterone.

Testosterone release is controlled by the anterior pituitary Luteinizing Hormone(LH), whereas Sperm Production is controlled both by the anterior pituitary Follicle-Stimulating Hormone(FSH) and Gonadal Testosterone.

Males have two testicles of similar size contained within the scrotum,

which is an extension of the abdominal wall. Scrotal asymmetry is not unusual:

one testicle extends farther down into the scrotum than the other due to differences in the anatomy of the vasculature.The volume of the testicle can be estimated by palpating it and comparing it to ellipsoids of known sizes.They fulfil two key functions, the production of gametes (sperm) and the secretion of hormones, particularly the male hormone Testosterone.

OVARY:The ovary is an organ found in the female reproductive system that produces an ovum. When released, OVUM travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary (from Latin ovarium ‘egg, nut') found on each side of the body. The ovaries

also secrete hormones that play a role in the menstrual cycle and fertility. The

ovary progresses through many stages beginning in the prenatal period

through menopause.The ovaries are considered the female gonads. Each ovary is whitish in color and located alongside the lateral wall of the uterus in a region called the ovarian fossa. The ovarian fossa is the region that is bounded by the external iliac artery and in front of the ureter and the internal iliac artery. This area is about 4 cm x 3. cm x 2 cm in size.

The ovaries are surrounded by a capsule, and have an outer cortex and an inner medulla. The capsule is of dense connective tissue and is known as the Tunica Albuginea. Usually, ovulation occurs in one of the two ovaries releasing an egg each menstrual cycle. The side of the ovary closest to the fallopian tube is connected to it by Infundibulopelvic Ligament, and the other side points downwards attached to the uterus via the Ovarian Ligament.

Other structures and tissues of the ovaries include the HILUM.

FUNCTION:At puberty, the ovary begins to secrete increasing levels of hormones.

Secondary sex characteristics begin to develop in response to the hormones.

The ovary changes structure and function beginning at puberty. Since the ovaries are able to regulate hormones, they also play an important role in pregnancy and fertility. When egg cells (oocytes) are released from the fallopian tube, a variety of feedback mechanisms stimulate the endocrine system which cause hormone levels to change. These feedback mechanisms

are controlled by the Hypothalamus & Pituitary Gland.Messages from the HYPOTHALAMUS are sent to the PITUITARY

GLAND. In tum, the pituitary gland releases hormones to the ovaries. From

this signal, the ovaries release their own hormones.

LET US KNOW WHAT WE HAVE LEARNT !

PART-A VERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. Adrenal gland consists of:

a) ACTH and BCTH

b) Inner and outer layer of kidney

c) Inner medulla and outer cortex

d) Lower adrenal and upper adrenal

2. Adrenaline hormone increases:

a) Blood pressure

b) Blood glucose level

c) Arteriosclerosis

d) Oxygen uptake

3. Pancreas secretes:

a) Insulin

b) Glucagon

c) Somatostatin hormones

d) All the above

4. Which one of the followings are male sex hormones?

a) Insulin

b) Aldosterone

c) Androgen

d) Pheromone

5. Adrenal gland is derived from:

a) Endoderm

b) Mesoderm

c) Ectoderm

d) Ectoderm and mesoderm

FILL UPS:

1. Males have two testicles of similar size contained within the----—-—

2. the ovary begins to secrete increasing levels of hormones at -----—---

TRUE / FALSE:

1. The ovaries are surrounded by a capsule is of dense connective tissue and is known as the tunica albuginea.

2. The enzymes secreted by the exocrine gland in the pancreas do not help break proteins.

ANSWER KEY: PART-A

A. MCQs:

1. B: Adrenal gland consists of Inner and outer layer of the kidney.The outer part is called adrenal cortex and inner region is known as adrenal medulla.

2. A: Adrenaline hormone increases blood pressure. It sends a message in the form of an impulse to different parts of the body.

3. D: Pancreas secretes Insulin, Glucagon, and Somatostatin hormones.

4. C: Androgens

5. D: Adrenal gland is derived from Ectoderm and mesoderm. They are endocrine glands. They are found above the kidneys.

B. FILL UPS:

1. Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall.

2. (At puberty), the ovary begins to secrete increasing levels of hormones. Secondary sex chara cteristics begin to develop in response to the hormones.

C. TRUE / FALSE:

1. True

2. False - The enzymes secreted by the exocrine gland in the pancreas help break down carbohydrates, fats, proteins, and

acids in the duodenum.

PART-B SHORT ANSWER TYPE QUESTIONS:

1. Adrenal gland secretes which type of hormones?

2. Define pancreas.

PART-C LONG ANSWER TYPE QUESTION:

1. Draw labelled diagram of ovary and write its function.

A218

INTRODUCTION:What are Hormones?

Hormones are chemical messengers that are produced by the endocrine glands

and are released into the bloodstream directly instead of through ducts. They

regulate various body functions such as growth, reproduction, digestion, etc.

They are of two types based on their chemical composition:

Protein Hormones- These hormones are soluble in water.e.g. Adrenaline, Noradrenaline.

Steroid Hormones- These hormones are not soluble in water.e.g. thyroid hormone.

since we protein hormones are soluble in water, they are easily transported in —

the blood. The steroid hormones which are not water soluble bind to plasma

proteins and are transported to their target organs. Before we understand

the mechanism of hormone action, let's look at what are hormone receptors.

Each hormone has receptors that are found on the cell membrane of the target

organ. Once the hormone binds to its designated receptor, a series of actions

are initiated to release secondary messengers inside the cell. These secondary

messengers are responsible for relaying information to the nucleus or other

organelles. Based on their structure, receptors are of different types:

Internal receptors— they can be either nuclear or cytoplasmic. Nuclear

receptors are found on the nuclear membrane while the cytoplasmic receptors

are found in the cytoplasm of the cell. These receptors are for the steroid

hormones.

External receptors— These are the transmembrane receptors which are

embedded in the lipid layer of the cell membrane. These receptors are for the

protein ones.The mechanism of action hormone can be of two types: First, where the receptors are fixed and the second, where the receptors are mobile.

Fixed Receptor Mechanism:This mechanism of action hormone is seen in the protein hormones such as Adrenaline, insulin, ADH, TSH etc. As mentioned earlier, since they are water soluble, they cannot pass through the cell membrane as it is made up of a lipid layer. So, they bind to their extracellular receptors present on the membrane.Once the protein hormone binds to the receptor, a series of reactions occur

beginning with the production of adenyl cyclase enzyme. This enzyme leads to

the production of cyclic AMP or cAMP which is the secondary messenger. This

cAMP can now enter the cell and cause the effect it was meant to bring about.

MOBILE RECEPTOR MECHANISM:This kind of mechanism is seen in the steroid hormone that is insoluble in water. They are made up of fats and therefore can freely cause the lipid layer of the cell membrane. Their receptors are intracellular and not extracellular like those for the protein ones. The intracellular receptors can be floating in the cytoplasm, on the nuclear membrane or inside the nucleus. For this reason,their receptors are known as mobile receptors.

We know the nervous system and the endocrine system are the two controlling systems of the body. The endocrine system controls the body with the help of hormones they release. These hormones bind with specific receptors on target cells which further proceed to trigger intracellular signals either by altering membrane permeability, acting through second messenger system or activating specific genes to form new proteins.To better understand the mechanism of hormone action, it is crucial to

comprehend various definitions.

HORMONE ACTION In reality there are numerous hormones that perform an immense number of functions for various purposes. Their sensitivity and responsiveness are

dependent on both, the number of receptors and its affinity. Also, the site of the

receptor might be:Present in or on the surface of the cell membrane e.g. protein or peptide hormones and catecholamines.

In the cytoplasm. e.g. steroid hormones;

In the cell nucleus. e.g. thyroxine.

Furthermore, hormones can be divided into groups on the basis of their chemical nature:Peptide, polypeptide, protein hormones.Steroids lodothyronines (thyroid hormone).Amino acid derivatives.The hormones that interact with membrane-bound receptors generally don't enter target cells, rather generate second messengers that proceed to regulate cellular metabolism.On the other hand, hormones which interact with intracellular receptors mostly regulate gene expression or chromosome function by the interaction of

hormone receptor complex with the genome.

MECHANISM OF HORMONE ACTION:The mechanism of hormone action is grouped into two classes:

1.) Fixed Membrane Receptor Mechanism: This type of mechanism is shown by the water-soluble hormones that are amines or proteins in composition such as the growth hormone, oxytocin, ADH, etc. These hormones can't pass through the lipid membrane. They have their target receptor on the cell

membrane to which the hormone, cAMP acts as the secondary messenger. It diffuses through the cell membrane and activates several enzymatic reactions to cause biochemical changes.

2.) MOBILE RECEPTOR MECHANISM: This type of mechanism is shown by lipid soluble hormones such as fatty acids and steroids that can easily pass through the plasma membrane. They possess intracellular receptors.The mRNA is translated into protein. This protein causes biochemical changes inside the cell.

HORMONES AS REGULATORS Hormones help in maintaining the internal environment of the body. When the secretion of hormones is under the control of other hormones, it is known as feedback control. It can be of two types:

1. POSITIVE FEEDBACK CONTROL: In this process, the end products of action cause more of the action to occur in a feedback loop.e.g. blood clotting, menstrual cycle.

2.NEGATIVE FEEDBACK CONTROL: In this type of regulation the end product of a process reduces the stimulus of that same process.

e.g. regulation of blood sugar, temperature regulation.

HORMONES as MESSENGERS The neurosecretory cells of the HYPOTHALAMUS secrete hormones known as NEURO HORMONES into the blood. These NEURO HORMONES are carried to the Pituitary Gland and stimulate it to release various hormones. Hence they are also known as “releasing factors”.

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

A. MULTIPLE CHOICE QUESTIONS:

Q1. Which is a secondary messenger of the mechanism of hormone action?

(a) ATP

(b) cAMP

(d) lipids

Q2. is produced by the alpha cells of the pancreas.

a) Calcitonin

b) Glucagon

c) Insulin

d) None of the above

Q3. controls the concentration of urine.

a) ADH

b) Oxytocin

c) ACTH

d) None of the above

Q4. Name the hormone that is responsible for milk secretion after parturition.

a) Insulin

b) Prolactin

c) Lactogen

d) Estrogen

Q5. Which of the following is not an endocrine gland?

a) Adrenal

b) Pituitary

c) Lacrimal

d) Thyroid

B. FILL IN THE BLANKS:

1. Hormones are of types based on their chemical composition.

2. accelerates conversion of glycogen into glucose.

3. are male sex hormones.

C. TRUE OR FALSE:

1. Protein hormones are not soluble in water.

2. Endocrine glands lack ducts and are called as ductless glands.

3. Insulin is a hormone produced by the pancreas.

A. MULTIPLE CHOICE QUESTIONS:

A1: (b) cAMP Explanation: cAMP or cyclic AMP is a common secondary messenger that participates in the hormone action. Once the hormone attaches itself to the extracellular receptor, a series of reactions begin and lead to the formation of cAMP which acts as the secondary

messenger.

A2: b) Glucagon

A3: a) ADH

A4: b) Prolactin

A5: (c) Lacrimal

B. FILL IN THE BLANKS:

1. Two

2. Glucagon

3. Androgens

C. TRUE/ FALSE:

1. False

2. True

3. True.

PART: B SHORT ANSWER TYPE QUESTIONS:

Q1. How does Hormones work as regulators?

Q2. Name some of the Hormones.

Q3. Define protein Hormone and steroid Hormone.

PART: C LONG ANSWER TYPE QUESTIONS:

Q1. Define Hormone Action and mechanism of hormone action.

A219

INTRODUCTION:Dear students we have done the chapter, 22- CHEMICAL COORDINATION &

INTEGRATION. Now we will discuss about the exercise questions given in your NCERT book.

Q. 1. Define the following:

(a) Exocrine gland

(b) Endocrine gland

(a) Exocrine gland: Glands that discharge their secretions into ducts are known

as exocrine glands.

(b) Endocrine gland: Glands that do not discharge their secretions into ducts are

known as endocrine glands. These glands discharge their secretions directly into

the blood.

messengers and are produced in trace amounts.

2. List the hormones secreted by the following:

(a) Hypothalamus (b) Pituitary (c) Thyroid

(d) Parathyroid (e) Adrenal (f) Pancreas

(g) Testis (h) Ovary (i) Thymus

(j) Atrium (k) Kidney (I) G-I Tract

(a) Hypothalamus

Thyrotropin Releasing Hormone (TRH)

Gonadotrophin releasing hormone (GnRH)

Somatotropin-releasing hormone

Adrenocorticotrophin-releasing hormone

Prolactin releasing Hormone

Growth-inhibiting hormone

Melanocyte-inhibiting hormone

(b) Pituitary

Growth Hormone (GH)

Prolactin (PRL)

Thyroid Stimulating Hormone (TSH)

Adrenocorticotrophic Hormone (ACTH)

Luteinizing Hormone (LH)

Follicle Stimulating Hormone (FSH)

Melanocyte Stimulating hormone (MSH)

Neurohypophysis also known as posterior pituitary Oxytocin

Vasopressin

(d) Parathyroid

Thyroxin — Parathyroid Hormone

Triiodothyronin

Calcitonin

(e) Adrenal

(f) Pancreas

Mineralocorticoids (mainly aldosterone) — Insulin Glucocorticoids (mainly cortisol) — Glucagon

Adrenaline

Nor-adrenaline

(g) Testis

(h) Ovary

Testosterone

Estrogen

Progesterone

(i) Thymus

(j) Atrium

Thymosins Atrial Natriuretic factor

k) Kidney

(l) G4 Tract

Erythropoietin — Gastrin

Secretin

Cholecystokinin (CCK)

Gastric inhibitory peptide (GIP)

4. Fill in the blanks:

Hormones Target gland

(a) Hypothalamic hormones

Pituitary

(b) Thyrotrophin (TSH)

Thyroid

Adernal

(d) Gonadotrophins (LH, FSH)

Ovary, Testis

(e) Melanotrophin (MSH)

Melanoycte

5. Write short notes on the functions of the following hormones,

(a) Parathyroid hormone (PTH)

(b) Thyroid hormones

(d) Androgens

(e) Estrogens

(f) Insulin and Glucagon

(a) Parathyroid hormone (PTH): It is secreted by Parathyroid gland. It increases

the Ca?* levels in the blood. PTH promotes the reabsorption of calcium from

nephrons and also, promotes the absorption of calcium from digested food. Thus, it

plays an important role in calcium balance in the body.

(b) Thyroid hormones: Thyroid hormones play an important role in the regulation

of the basal metabolic rate. These hormones also support the process of red blood

cell formation. Thyroid hormones control the metabolism of carbohydrates, proteins

and fats. Maintenance of water and electrolyte balance is also influenced by

thyroid hormones. Thyroid gland also secretes a protein hormone called

thyrocalcitonin (TCT) which regulates the blood calcium levels.

provide cell-mediated immunity. It also promotes production of antibodies to

provide humoral immunity.

(d) Androgens: It regulate the development, maturation and functions of the male

accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate

gland, urethra etc. Androgens mainly testosterone stimulate muscular growth,

growth of facial and axillary hair, aggressiveness, low pitch of voice etc. It

stimulates spermatogenesis and formation of mature sperms and also influences

male sexual behaviour. These hormones also produce synthetic effects on protein

and carbohydrate metabolism.

(e) Estrogens: It produce wide ranging actions such as stimulation of growth and

activities of female secondary sex organs, development of growing ovarian

follicles, appearance of female secondary sex characters (e.g., high pitch of voice,

etc.), development of mammary gland. Estrogens also regulate female sexual

behaviour.

(f) Insulin and Glucagon: These hormones are secreted by pancreas and helps in

regulation of glucose level in body.

INSULIN plays a major role in the regulation of glucose homeostasis. It acts mainly on hepatocytes and adipocytes (cells of adipose tissue), and enhances cellular

glucose uptake and utilization. It also stimulates conversion of glucose to glycogen(glycogenesis) in the target cells.

GLUCAGON plays an important role in maintaining the normal blood glucose levels. Glucagon acts mainly on the liver cells (hepatocytes) and stimulates glycogenolysis resulting in an increased blood sugar (hyperglycemia). It also stimulates the process of gluconeogenesis which also contributes to hyperglycemia.

6. Give example(s) of:

(a) Hyperglycemic hormone and hypoglycemic hormone

(b) Hypercalcemic hormone

(d) Progestational hormone

(e) Blood pressure lowering hormone

(f) Androgens and estrogens

(a) Hyperglycemic hormone — Glucagon

hypoglycemic hormone — Insulin

(b) Hypercalcemic hormone — Parathyroid hormone (PTH)

(d) Progestational hormone — Progesterone

(e) Blood pressure lowering hormone — Nor-adrenaline

(f) Androgens and estrogens — Testosterone

7. Which hormonal deficiency is responsible for the following:

(a) Diabetes mellitus (b) Goitre (c) Cretinism

(a) Diabetes mellitus — Insulin

(b) Goitre — Thyroxin hormone

8. Briefly mention the mechanism of action of FSH.FOLLICLE STIMULATING HORMONE (FSH) stimulates growth and development

of the ovarian follicles in females.

FSH produces its effect by binding to its specific receptors present on the ovarian

cell membrane. Binding of FSH hormone to its specific receptor present over the

cell surface activates an enzyme called Adenylate Cyclase. This enzyme converts

ATP into cyclic AMP. The cyclic AMP is called the second messenger and carries

out various biochemical responses in the cell by activating the existing enzyme

system in the cell. The biochemical responses then lead to physiological

responses like ovarian growth.

A220

RECAPTULATION:The human body has several organs. These organs cannot perform

their functions independently. So each organ depend on other organs.In order to maintain normal physiology functions of these organs must be coordinated so that they can work in proper manner. Coordination is the process through which two or more organs interact and

complement the functions of each other. Integration is a process which

makes two or more organs to work as a functional unit in harmony.In this assignment we are going to revise the important question answers and diagrams of chemical control and coordination.

Chemical control and coordination is performed by hormones which are released by endocrine glands.

SHORT ANSWER TYPE QUESTIONS-

1. Which hormone regulate calcium balance in body?

Ans. Parathormone

2. Which hormone is known as birth hormone?

Ans. Oxytocin

3. Name the amino acid from which thyroxine is synthesized.

Ans. Tyrosine

4. Which endocrine gland is considered the throne of immunity?

Ans. Thymus

5. Name the hormones of the posterior pituitary?

Ans. Adrenaline and noradrenaline

6. Name the disease characterized by the high plasma sodium low plasma potassium rise in blood volume and high blood pressure.

Ans. Aldosteronin

7. Which gland act as biological clock of the body?

Ans. Pineal gland

8. Name the cells of pancreas which secrete insulin?

Ans. Beta cells

9. Name the hormone which regulate the blood pressure under normal conditions.

Ans. Nor epinephrine

10. Which hormone is also known as as Collip’s hormone?

Ans. Parathormone

LONG ANSWER TYPE QUESTIONS-

11. What is meant by the synergistic effect of hormone? Give an example.

Answer-Synergistic effect of hormones:

1) it is a type of hormonal interaction where two or more hormones complement each others action and both of them are needed for the full expression of their effects.

ll) Production, secretion and ejection of milk from the mammary gland require synergistic effect of progesterone, prolactin and oxytocin.

12. Name the hormones secreted by the follicles of thyroid. Give two symptoms of hyperthyroidism and name the diseases.

Ans- The hormones secreted by the follicles of thyroid is Thyroxine and less secretion of thyroxine from thyroid results in reduced oxidation of food and less tissue metabolism. This disease is known as myxoedema.

13. Why is posterior pituitary known as a storage releaser centre?

Ans- Posterior pituitary does not manufacture any hormone but only store

two hormones VASOPRESSIN and OXYTOCIN which are synthesized in the hypothalamus and transported to posterior pituitary. These hormones remain stored in the axon terminals until released into the blood on

stimulation. These are then carried in the body via blood as hormones of posterior pituitary. Hence posterior pituitary is known as a Storage Releases Centre.

14. What is feedback control? Give its types.

Ans- When the secretion of hormones is under the control of factors or other hormones is called feedback control. The regulation of secretion of thyroxine from the thyroid gland is an example of such feedback controlmechanism.

Feedback control is of two types:

1) Positive feedback control- If the level of thyroxine is less than normal

limits in the blood, thyroxine levels stimulate the hypothalamus to secrete

more of TRH (Thyroid Releasing Hormone) which result in increased secretion of TSH (Thyroid Stimulating Hormone) which in turn stimulate increased secretion of THYROXINE. Such regulatory factor is called

positive feedback control.

Il) Negative feedback control-The THYROTROPIN Releasing Hormone from

the hypothalamus stimulates the anterior lobe of pituitary gland to secreted

by Thyroid Stimulating Hormone. The Thyroid Stimulating Hormone in turn stimulates the thyroid gland to secrete thyroxine. High amount of oxygen in the blood exerts and inhibitory effect on hypothalamus in such a way that less of TRH and TSH is produced respectively. This eventually Result in

decrease in thyroxine. This is called negative feedback control.

15. What are pheromones?

Ans- Pheromones are secreted by exocrine glands of the skin and are poured on the surface of the skin and they were also called Ectohormones.The smell of these substances affect the mutual behaviour of members of a species. Certain insects secrete pheromones to transmit the information of food sources or danger to their fellow insects. Certain insects secrete pheromones to attract their meeting partners.

16. Write a note on pituitary disorders.

Ans- 1) Pituitary dwarfism- It is caused by the deficiency of growth hormone from childhood. It is characterized by a small but well proportioned body and sexual immaturity.

2) Gignatism- It is caused by excess of growth hormone from early age. It is

characterized by large and well proportioned body.

3) Acromegaly-It is caused by excess of growth hormone after adult size is

reached. It is characterized by disproportionate increase in size of bones of face hand and feet.

4) Diabetes insipidus- It is caused by deficiency of ADH. It is characterized

by excessive dilute urine.

17. How the function of epinephrine is different from nor- epinephrine?

Ans- 1) Epinephrine has a greater effect on cardiac activity then nor epinephrine.

2) Epinephrine causes only weak constrictions of the blood vessels of the

muscles in comparison with a much stronger constrictions that results from

the nor epinephrine.

3) The action of epinephrine and norepinephrine relates to their effect on

tissue metabolism. Epinephrine probably has several times as great metabolic effect as nor- epinephrine.

18. Discuss the role of antidiuretic hormone.

Answer-this hormone has two main functions-

A) Antidiuretic effect - It increase the reabsorption of water in the distal

convoluted tubule and collecting ducts of the nephrons of the kidneys. As a

result the reabsorption of water from the glomerular filtrate is increased.

B) Pressure effect - Involuntary muscles in the walls of the intestine, gall bladder, urinary bladder and blood vessels are stimulated to contract by ADH. Contraction of the walls of the blood vessel raises the blood pressure and this may be it to its most important pressure effect.