Samacheer Class 11 Bio Zoology - Chemical Coordination and Integration

d) hypothalamic hypophyseal axis
Assertion and Reason:- Directions: In the following questions a statement of Assertion is followed by a statement of reason. Mark the correct choice as;
a) If both Assertion and reason are true and reason is the correct explanation of assertion
b) If both Assertion and reason and true but reason is not the correct explanation of Assertion.
c) If assertion is true but reason is false
d) If both Assertion and reason are false

The anterior lobe of the pituitary gland originates from the embryonic invagination of pharyngeal epithelium called Rathke’s pouch. The posterior lobe originates from the base of the brain as an outgrowth of the hypothalamus.

Growth hormone (GH):
It is also known as somatotropic hormone (STH) or Somatotropin. It is a peptide hormone Growth hormone promotes the growth of all the tissues and metabolic processes of the body. It influences the metabolism of carbohydrates, proteins, and lipids and increases the rate of protein biosynthesis in the cells.
It stimulates chondrogenesis (cartilage formation), osteogenesis (bone formation) and helps in the retention of minerals like nitrogen, potassium, phosphorus, sodium, etc., in the body. GH increases the release of fatty acid from adipose tissue and decreases the rate of glucose utilization for energy by the cells. Thus it conserves glucose for glucose-dependent tissues, such as the brain.

Follicle-stimulating hormone (FSH):
FSH is a glycoprotein hormone that regulates the functions of the gonads (ovary and testis). In males, FSH along with androgens acts on the germinal epithelium of seminiferous tubules and stimulates the production and release of sperms (spermatogenesis). In females, FSH acts on the ovaries and brings about the development and maturation of gratfran follicles.

• The hormones are released into the blood and circulated as chemical signals
• The target organs contain receptor molecules either on the surface or within the cell.
• The cells that contain the receptor molecules specific to the hormone are physiologically activated.
• Whereas other hormones that come in contact can not be activated.

Amines
Steroids
A. Small water-soluble
1. Mostly lipid-soluble
B. Derived from tyrosine or tryptophan
2. Derived from Cholesterol
C. Examples are Adrenalin Noradrenalin, Melatonin, and thyroid hormone
3. Examples are cortisol, aldosterone, testosterone, oestrogen, and progesterone

Exocrine glands
Endocrine glands
1. They have ducts to carry their substances to the membrane surfaces
1. These lack ducts and so release their hormone to the surrounding tissue fluid
2. They secrete enzymes, saliva, and sweat
2. Their secretions are collectively termed hormones.
3. Eg. Salivary gland, Sweat gland, and Gastric glands
3. Eg. Pituitary, Thyroid Pineal, Adrenal Parathyroid

• Exclusive endocrine glands, e.g. Pituitary thyroid, Parathyroid, Pineal, Adrenal
• Neuroendocrine gland – Hypothalamus
• Partial endocrine glands, e.g. Pancreas, gastrointestinal tract epithelium, kidney, heart gonads, and placenta – have endocrine tissues.

• The pituitary gland is known as the master endocrine gland, but it is in turn controlled by the hypothalamus and so the statement may not be totally applicable.
• The hypothalamus with its neurosecretory cells produces neurotransmitters which regulate the secretions of the pituitary.

• The pituitary gland is located in the bony cavity of the sphenoid bone the sella tunica at the base of the brain so is also called the hypothalamus cerebri.
• it is about one centimeter in diameter and 0.5gm in weight.

In humans, the pineal gland or epiphysis cerebri or conarium is located behind the third ventricle of the brain and is formed of parenchymal cells and interstitial cells.
It secretes the hormone, melatonin, which plays a central role in the regulation of the circadian rhythm of our body and maintains the normal sleep-wake cycle. It also regulates the timing of sexual maturation of gonads. In addition, melatonin also influences metabolism, pigmentation, menstrual cycle and defence mechanism of our body.

• Alcohol consumption has widespread effect on endocrine system.
• It impairs the regulation of blood glucose level.
• More over it reduces the testosterone level
• Increases the risk of osteoporosis.

• Humiline-N is administered to diabetic patients.
• Human insulin is administered as injection and not by oral consumption.
• The reason is if it is administered by oral consumption it may be digested by digestive enzymes.

It is the 24-hour cycle of biological activities associated with natural periods of light and darkness.
Eg. Sleep wake cycle, body temperature, appetite etc.
(3 Marks)
III. Short Answer

• Simple goitre is otherwise known as endemic goitre.
• It is due to the hypo secretion of thyroxine.
• The symptoms are Enlargement of thyroid gland, Fall in serum thyroxine level, Increased TSH secretion.

• The hyposecretion of parathyroid hormones leads to a decrease in calcium level and increase in phosphate level, it causes.
• convulsion in muscle, locking of jaws, increased heart beat rate increased body temperature muscular spasm lead to tetany.

The excess secretion of cortisol causes cushing’s syndrome. The symptoms are obesity of the face and trunk.
* Redness of face hand and feet.
* Thick skin.
* Excessive hair growth
* Loss of mineral from bone
* Systolic hypertension

It is due to the hypo-secretion of growth hormone in children in which skeletal growth and sexual maturity is arrested. They attain a maximum height of 4 feet only.

• Due to the hyper-secretion of growth hormone in children there is a over growth of skeletal
• structure may occur up to 8 feet height. The visceral growth is not appropriate with that of limbs.

I will get bimple goose due to the Surge of vasodielation on the arector pili muscle and though, i am very much frightened, i will fight with that man. i will get that energy by the action of the hormone adrenalin.

During the period of emergency the gluco corticoids stimulate the synthesis of glucose from lipid and protein by lipolysis and proteolysis and releases energy to meet that emergency situation.

• Cortisone involved in maintaining cardio vascular and kidney functions. It produces anti inflammatory reactions and suppresses the immune response, it stimulates the RBC production.
• Hence it is known as stress combat hormone.

• The hormones are released into the blood and circulated as chemical signals and act on specific target organs.
• Hormones may speed up or slow down or alter the activity of the target organs.
• The hormones secreted do not remain permanently in the blood.
• They are converted by the liver into inactive compound and excreted by kidneys.

• It is a collection of special structures located in the middle of the brain.
• It is also known as paleo mammalian brain.
• It controls emotions, behavior, motivation of long term memory and olfaction.

• Hypothalamic hormones control anterior pituitary secretion through hypothalamic hypophyseal portal blood vessel.
• The nerve signal produced by the hypothalamic hypophyseal axis control the posterior pituitary secretion.
• Hypothalamus maintains homeostasis.
• Blood pressure
• Body temperature.
• Cardio and fluid electrolyte balance of the
• As the part of limbic system it influences various emotional responses.

• It is a glycoprotein hormone
• It is also known as Interstitial cell stimulating hormone (ICSH) in males.
• The ICSH hormones acts on the interstitial cells of testis to produce the male sex hormone testosterone.
• In females along with FSH matures the ovarian follicles.
• LH independently induces ovulation, maintains the corpus luteum and promotes synthesis and release of ovarian.
• FSH and LH secretion starts only during pre pubertal period.
• FSH and LH are collectively referred as gonadotropins.

Exocrine glands
Endocrine glands
1. Composed of a amino acids
1. Composed of a amino acids
2. Amino acid sequence is cysteine – tyrosine – Phenyl alanine – glutamine arspargine – cysteine – proline – argirune – glycine.
2. Amino acid sequence is – cysteine – tyrosine –
Isoleucine – Glutamine – aspargine – cysteine –
proline – leucine – glycine.

• ADH is a peptide hormone
• It promotes absorption of water and electrolytes by distal tubules of nephron and there by reduces loss of water through urine.
• Hence it is called as anti diuretic hormone.
• ADH deficiency causes Diabetes insipidus which induces the production of large amount of urine.
• This is how it helps in osmoregulation.
• ADH when released in large amount causes constriction of blood vessels and increases blood pressure.

• It is secreted by pineal gland.
• It plays a central role in the regulation of circadium rhythm of our body
• Maintains the normal sleep wake cycle.
• It also regulates the timing of sexual maturation of gonads.
• In addition it also influences metabolism, pigmentation, menstrual cycle and defence mechanism of our body.

• It regulates the Basal Metabolic Rate (BMR) and body heat production.
• It stimulates protein synthesis and promotes growth
• It is essential for the development of skeletal and nervous system.
• It plays an important role in maintaining blood pressure
• It reduces serum cholesterol levels.
• Optimum levels of thyroxine in the blood are necessary for gonadial functions.

• The parathyroid hormone (PTH) is the hypercalcemic hormone.
• It is a peptide hormone.
• It involves in controlling the calcium and phosphate homeostasis.
• The secretes or PTH is controlled by calcium level in the blood.
• It increases the blood calcium level by stimulating osteoclasts to dissolve the bone matrix.
• As a result calcium and phosphate are released into the blood.
• PTH enhances the re-absorption of calcium and exertion of phosphates by the renal tubules.
• It promotes activation of vitamin D to increase calcium absorption by intestinal mucosal cells.

1. In the heart, cardiocytes on the atrial walls secretes an important peptide hormone called Atrial Natriuretic Factor (ANF)
2. When blood pressure is increased ANF is secreted and causes dilation of the blood vessels to reduce the blood pressure.

* It is not good to take synthetic soft drinks.
* The branded soft drinks damage our endocrine system.
* While consuming soft drinks the sugar level increases in blood. Which leads to elevated insulin secretion
to reduce the blood glucose level.
* The elevated insulin level diminishes immunity.
* It causes obesity, cardio-vascular disorders etc.

The abuse of steroids can cause serious health problems such as.
* HighB.P.
* Heart diseases.
* Liver damage
* Cancer
* Stroke
* Blood clotsa
Side effects such as
* Nausea
* V omiting
* Ligament and tendon injuries
* Head ache
* JointPain
* Muscle cramps
* Diarrhoea
* Sleep problem

• Glycogenolysis is breakdown of glycogen to glucose
• This process is carried out in the liver by the Glucagon hormone.
• Glucagon thus releases glucose from the liver cells increasing Gluconeogenesis.
• it is the synthesis of glucose from lactic acid and from non-carbohvdrate molecules is called Gluconeogenesis. this increases the blood glucose levels.

• Poly urea – Excessive urination
• Polyphagia – Excessive intake of food
• Polydipsia – Excessive consumption of liquids due to thirst.
• Ketosis – Breakdown of fat into glucose results in accumulation of ketone bodies.

• Hypothalamus is a small cone shaped structure that projects downward from the brain ending into the pituitary stalk.
• It interlinks both the nervous system and endocrine system.
• Pituitary gland is controlled by the hypothalamus.
• It produces neuro transmitters which act either as a releasing hormone or as an inhibitory hormone.
• Hypothalamus contains groups of neuro secretory cells which produces neuro transmitters which regulate the secretions of the pituitary gland.

• It is located behind the third ventricle of brain.
• In human it is called epiphysis cerebri conarium.
• It is formed of parenchymal cells and interstitial cells.
• It secretes the hormone melatonin.
• It plays a central role in the regulation of circadian rhythm of our body and maintains the normal sleep wake cycle.

• In man, four tiny parathyroid glands are found in the posterior wall of the thyroid glands.
• It composed of two types of cells. The chief cells and oxyphil cells.
• The chief cells secrete parathyroid hormone.
• The functions of oxyphil cells are not known.

• Thymus gland is partially an endocrine and partially a lymphoid gland.
• It is a bi-lobed structure located just above the heart and aorta behind the sternum.
• It is covered by a fibrous capsule.
• Anatomically it is divisible into an outer cortex and an inner medulla.
• It secretes four hormones such as thymulin, thymosin, thymopoietin and thymic humoral factor (THF).
• The primary function is the production of immuno competent T lymphocytes which provides cell mediated immunity.

Acromegaly is due to excessive secretion of growth hormone in adults.
Symptoms:-
* Over growth of hand bones, feet bones, jaw bones
* Malfunctioning of gonads
* Enlargement of viscera, tongue, lungs, heart, liver, spleen and endocrine gland like thyroid adrenal.

1. Hyperparathyroidism is caused due to excess parathyroid hormone in blood.
Symptoms:-
* Demineralisation of bones
* Cyst formation, softening of bone.
* Loss of muscle tone
* General weakness
* Renal disorders.

Addison’s disease is caused due to hyposecretion of glucocorticoids and mineralocorticoids from the adrenal cortex.
Symptoms:-
* Muscular weakness, Low BP
* Loss of appetite, vomiting
* Hyper pigmentation of the skin
* Low metabolic rate, subnormal temperature.
* Weight loss reduced blood volume.
* Low aldosterone level increases urinary excretion of NaCl and water and decreases potassium excretion leading to dehydration.

Function:- The general function of nor adrenalin is to mobilize the brain and body for action. Nature of secretion: Its secretion is less during sleep, more during wakefulness and reaches much higher levels during stress situations. This response is known as ‘fight or flight’ response.

* In mammals the role of pass intermedia is insignificant.
* In other vertebrates it secretes melanocyte stimulating hormone (MSH)
* It induces pigmentation in skin.
(5 Marks)
IV. Brief Answers

• Peptide hormones cannot cross the phospholipid cell membrane and bind to the receptors on the exterior cell surface.
• They are transported to the golgi which is the site of modification.
• It acts as a first messenger in the cell.
• Hormones generate a second messenger like cyclic AMP (cAMP) that regulates cellular metabolism. This cAMP is catalyzed by the adenylate cyclase ezyme.
• The interaction between the hormone surface and the effect of cAMP within the cell is known as a signaling cascade. There may be amplication at each step.
• One hormone molecule may bind to multiple receptor molecules before it is degraded.
• Each receptor activates to form more cAMP and produces more signals.

• Steroid hormones can easily cross the cell membrane and bind their receptors which may be intracellular or intercellular.
• Then they pair up with another receptor and form a receptor-hormone complex. This can bind to DNA and alter its transcription.
• As it changes the mRNA and protein the effect will be with stand for a long time. Eg. Estrogen

• There is a hyper pigmentation of the skin. It is caused due to hypo secretion of glucocorticoids from the adrenal cortex.
• Muscular weakness low BP, loss of appetite vomiting, low metabolic rate subnormal temperature reduced blood volume and weight are the other symptoms of Addison’s disease.

• Hypothyroidism is the cause of cretinism in infants. There is a retarded skeletal growth absence of sexual maturity, retarded mental ability, thick wrinkled skin protruded enlarged tongue bloated face thick and short limbs.
• There is low BMR, slow pulse rate subnormal body temperature and elevated blood cholesterol levels.

Insulin and glucagon are the hormones secreted by Islets of Langerhans of the pancreas:-
Insulin:
Insulin is a peptide hormone and plays an important role in glucose homeostasis. Its main effect is to lower blood glucose levels by increasing the uptake of glucose into the body cells, especially muscle and fat cells. Insulin also inhibits the breakdown of glycogen to glucose, the conversion of amino acids or fats to glucose, so insulin is rightly called a hypoglycemic hormone.
Glucagon:
Glucagon is a polypeptide hormone. It is a potent hyperglycaemic hormone that acts on the liver and promotes the breakdown of glycogen to glucose (Glycogenolysis), synthesis of glucose from lactic acid and from non-carbohydrate molecules (gluconeogenesis).
Releases glucose from the liver cells, increasing the blood glucose levels. Since glucagon reduces the cellular uptake and utilisation of glucose it is called a hyperglycemic hormone. Prolonged hyperglycemia leads to the disorder called diabetes mellitus.

This disease is caused due to hyper secretion of the thyroid.
Symptoms:
* Enlargement of the thyroid gland
* Increased BMR.
* Elevated respiratory and excretory rates
* Increased heart beat
* High blood pressure
* Increased body temperature
* Protection of eye ball (Exophthalmic)
* The weakness of eye muscles
* Weight loss.

When the thyroxine level in the blood decreases it is sensed by the hypothalamus to release the thyroid releasing factor that induces the pituitary to secrete thyroid stimulating hormone that stimulates the thyroid to release thyroxine – when the thyroxine level in the blood increases TTH acts on both the pituitary and hypothalamus to inhibit TSH secretion. This is meant by negative feedback mechanism.

• It increases the blood calcium level by stimulating osteo clasts to dissolve the bone matrix.
• It enhances the reabsorption of calcium and also increases calcium adsorption by intestinal mucosal cells.
• By all these action it increases the blood calcium level. Hence it is known as hypercalcemic hormone.

In infants, hypothyroidism causes cretinism. A cretin shows retarded skeletal growth, absence of sexual maturity, retarded mental ability, thick wrinkled skin, protruded enlarged tongue, bloated face, thick and short limbs occurs. The other symptoms are low BMR, slow pulse rate, subnormal body temperature and elevated blood cholesterol level.
Hyposecretion of the thyroid in adults causes myxoedema. It is otherwise called Gull’s disease. This disease is characterised by decreased mental activity, memory loss, slowness of movement, speech, and general weakness of body, dry coarse skin, scarce hair, puffy appearance, disturbed sexual function, low BMR, poor appetite, and subnormal body temperature.
Grave’s disease also called thyrotoxicosis or exophthalmic goiter. This disease is caused due to hypersecretion of the thyroid. It is characterised by enlargement of the thyroid gland, increases BMR (50% -100%), elevated respiratory and excretory rates, increased heartbeat, high BP, increases body temperature, protrusion of eyeball, and weakness of eye muscles and weight loss.
Simple goitre is also known as Endemic goitre. It is caused due to hyposecretion of thyroxine. The symptoms include enlargement of thyroid gland, fall in serum thyroxine level, increases TSH secretion.

• Insulin lowers the blood glucose level by increasing the uptake of glucose into the body cells.
• It inhibits the conversion of amino acids or fat to glucose.
• Insulin is called a hypoglycemic hormone.

Tetany is caused due to the hyposecretion of parathyroid hormone (PTH). Due to hyposecretion of PTH serum calcium level decreases (Hypocalcemia), as a result serum phosphate level increases. Calcium and phosphate excretion level decreses. Generalized convulsion, locking of jaws increased heart beat rate, increases body temperature, muscular spasm are the major symptoms of tetany. Hyperparathyroidism is caused due to excess PTH in blood. Demineralisation of bone, loss of muscle tone, general weakness, renal disorders are the symptoms of hyperparathyroidism.

a) The systems that regulate and co-ordinate the physiological functions of our body are
* Nervous or neural system
* Endocrine system
b) The meaning of the word “Hormone”is “to excite”
c) General characters of hormones:
* The endocrine system influences the metabolic activities through the hormones
* These are chemical messengers released in to the blood and acts specifically on certain target organs or target tissues.
* Hormones may speed up or slow down or alter the activity of the target organs.
* Hormones secreted do not remain permanently in the blood.
* After their function they are converted by the liver into inactive compounds and excreted by the kidneys.

Hyperglycaemia is otherwise known as Diabetes mellitus. Is caused due to reduced secretion of insulin. As the result, the blood glucose level is elevated. Diabetes mellitus is of two types, Type! Diabetes and Type II Diabetes. Type I diabetes is also known as Insulin-dependent diabetes, caused by the lack of insulin secretion due to illness or viral infections. Type II diabetes is also known as Non-Insulin dependent diabetes, caused due to reduced sensitivity to insulin, often called insulin resistance.
Symptoms of diabetes include polyuria (excessive urination), polyphagia (excessive intake of food), polydipsia (excessive consumption of liquids due to thirst), ketosis (the breakdown of fat into glucose results in accumulation of ketone bodies) in blood. Gluconeogenesis (Conversion of non-carbohydrate) also occurs in diabetes.

Hormones
Functions
1. Thyrotropin-releasing hormone (TRH)
Stimulates the secretion of TSH
2. Gonadotropin-releasing hormone(GnJRH)
Stimulates the secretion of FSH
3. Corticotropin-releasing hormone (CRH)
Stimulates the secretion of ACTH
4. Growth hormone-releasing hormone (GHRH)
Stimulates the secretion of GH
5. Prolactin releasing hormone (PRH)
Stimulates the secretion of Prolactin
6. Luteinizing hormone-releasing hormone (LHRH)
Stimulates the secretion of LH
7. MSH releasing hormone
Stimulates the secretion of MSH
8.Growth hormone-inhibiting hormone(GHIH)
Inhibits the secretion of GH
9. Prolactin inhibiting hormone (PIEI)
Inhibits the secretion of Prolactin
10. MSH inhibiting hormone
Inhibits the secretion of MSH

• Hypothalamus is a small cone-shaped structure that projects downward from the brain ending into the pituitary stalk.
• It interlinks both the nervous system and endocrine system.
• Hypothalamus contains a group of neuro secretary cells and it produces neuro transmitters which regulate the secretions of the pituitary.
• The hormones produced by the hypothalamus act either as a releasing hormone or as an inhibitory hormone.
• Though the pituitary gland is known as the master endocrine glands really it is in turn controlled by the hypothalamus.
• The hypothalamus and pituitary gland are anatomically different they are interlinked and functioning as a co-ordinated unit in maintaining the physiological process. They can not functions as a separated unit.
• The hypothalamic hypophyseal portal blood vessel allows hypothalamic hormones to control the anterior pituitary.
• The nerve signal produced by the hypothalamic hypophyseal axis (nerve bundle) controls the posterior pituitary secretion.
• Hypothalamus maintains homeostasis.
• Maintains blood pressure, body temperature cardio, and fluid-electrolyte balance of the body it influences emotional responses.
• The pituitary gland through its hormones performs various functions.

Class
Chemical properties
Example
Amines
Small, water-soluble derived from tyrosine or tryptophan
Adrenalin, nor adrenalin, melatonin, and thyroid hormone
Protein/ Peptides
Water-soluble
Insulin, glucagon, and pituitary hormones
Steroids
Derived from cholesterol mostly lipid-soluble
Cortisol, aldosterone, testosterone, oestrogen, progesterone.

* A pair of the testis is present in the scrotal sac of males.
* The testis functions as a sex organ and also as an endocrine gland.
* Testis composed of seminiferous tubules and Ley dig cells.
* Lay dig cells secrete several male sex hormones collectively called Androgens.
* The main male sex hormone is Testosterone.
Functions of Testosterone:
* Under the influence of FSH and LH, testosterone initiates the maturation of the male reproductive organ.
* The appearance of secondary sexual characters. Eg. Muscular growth, growth of facial and axillary hair, masculine voice, and male sexual behaviour.
* It enhances the total bone matrix and stimulating the process of spermatogenesis.

* Females have a pair of ovaries located in the pelvic region of the abdomen.
* It is composed of ovarian follicles and stromal tissue.
* It produces the egg or ova.
* It secretes the steroid hormones oestrogen and progesterone.
Functions:
* Oestrogen is responsible for the maturation of reproductive organs and the development of secondary sexual characters at puberty.
* Along with progesterone, oestrogen promotes breast development and initiates the menstrual cycle.
* Progesterone prepares the uterus for implantation of the fertilized ovum.
* It decreases the uterine contraction during pregnancy and stimulates the development of mammary glands and milk secretion.
* It is responsible for premenstrual changes in the uterus and for the formation of the placenta.

Heart: The cardiocytes on the atrial walls secrete an important peptide hormone called atrial natriuretic factor (ANF)
Function: When blood pressure is increased ANF is secreted and causes dilation of the blood vessels to reduce the blood pressure.
Kidney: Three hormones are secreted by the kidneys. They are Renin, erythropoietin, and calcitriol.
Renin:
* It is secreted by Juxta glomerular Cells (JGA).
* It increases blood pressure when angiotensin is formed in the blood.
Erythropoietin:
* It is also secreted by JGA.
* Stimulates erythropoiesis ie formation of RBC in bone mawow.
Calcitriol:
* It is secreted by proximal tubules of the nephron.
* It is an active form of vitamin D3.
* It promotes calcium and phosphorus absorption from the intestine and accelerates bone formation.

The person may be suffering from either cretinism or Dwarfism.
The following symptoms may be observed in cretinism. It is due to the hypo-secretion of Thyroxine.
* A cretin shows retarded skeletal growth.
* Absence of sexual maturity.
* Retarded mental ability.
* Thick wrinkled skin.
* Protruded enlarged tongue.
* Bloated face.
* Thick and short limb occur
* Low BMR
* Slow pulse rate.
* Subnormal body temperature
* Elevated blood cholesterol levels.
If the person shows the following symptom, he may have Dwarfism, it is due to hyposecretion of growth hormone.
* Skeletal growth and sexual maturity is arrested.
* They attain a maximum height of 4 feet only.

i) Structure of pancreas:
* Pancreas is a composite gland which performs both endocrine and exocrine functions.
* It is located just below the stomach as a leaf-like structure.
* It is composed of two major tissues such as acme and islets of Langerhans
* Acme secretes digestive enzymes and the islets of Langerhans secretes hormones like insulin and glucagon.
* Human pancreas has 1 -2 million islets of Langerhans.
* In each islet about 60% cells are beta cells 25% cells are alpha cells and 10% are delta cells.
* The alpha cells secrete glucagon the beta cells secrete insulin and delta cells secrete somatostatin.
ii) Structure of Islets of Langerhans (pancreas)
iii) Insulin control-blood sugar:-
* Insulin is a peptide hormone and plays an important role in glucose homeostasis.
* Its main effect is to lower blood glucose levels by increasing the uptake of glucose into the body cells
* especially muscle and fat cells.
* Insulin also inhibits the breakdown of glycogen to glucose, the conversion of amino acids or fats to glucose.
* So insulin is rightly called a hypoglycemic hormone.
* Reduced secretion of insulin leads to diabetes mellitus. As a result glucose level is elevated.
* It is of two types. Type I. Diabetes and Type II Diabetes. Type I Diabetes is caused by lack of secretion of insulin due to illness or viral infection. Type II or Non-insulin-dependent diabetes caused due to reduced sensitivity to insulin.
iv) Role of Glucagon:
* Glucagon is a polypeptide hormone.
* It is a potent hyper glycemic hormone.
* It acts on the liver and promotes the break down of glycogen to glucose (glycogenolysis)
* It also promotes synthesis of glucose from lactic acid and from non-carbohydrate molecules is called Gluconeogenesis.
* Glucogon releases glucose from the liver cell increasing the blood glucose levels.
* Since glucagon reduces the cellular uptake and utilisation of glucose it is called a hyperglycemic hormone. Prolonged hyperglycemia leads to the disorder called diabetes mellitus.

• Polyurea – excessive urination
• Polyphagia – excessive intake of food
• Poly dispsia – excessive consumption of liquids due to thirst.
• Ketosis – breakdown of fat into glucose results in accumulation of ketone bodies in blood.
• Gluconeogenesis also occur ie conversion of the non-carbohydrate form like amino acids and fat into glucose.

a. Location of pituitary gland:-
* It is located in a depression called sella tursica a bony cavity of the sphenoid bone below the brain.
* The pituitary gland means “to grow under”.
* It is connected to the brain by a stalk called the infundibulum
* Dimension:- It is about 1cm in diameter and 0. 5gm in weight.
b. Internal structure:-
* The pituitary consists of two lobes, anterior glandular adenohypophysis and posterior neural neuro hypophysis.
* Anatomically the anterior lobe or adenohypophysis has three lebesor zones namely pass intermedia, pass distalis and pass tuberalis.
* The neurohypophysis is otherwise known as pars nervosa.
* Embryonic origin:- The anterior lobe originates from the Embryonic invagination of pharyngeal epithelia called Rathke’s pouch.
* The posterior lobe originates from the base of the brain as an outgrowth of the hypothalamus.
c. Hypothalamus and pituitary gland

It secretes six hormones.
1. Growth Hormone:-
* It is also known as somatotropic hormone (STH) or somatotropin
* It is a peptide hormone.
* It promotes the growth of all the tissues and metabolic processes of the body.
* It influences the metabolism of carbohydrates, proteins, and lipids and increases the rate of biosynthesis in the cells.
* It stimulates chondrogenesis (cartilage formation), osteogenesis (bone formation).
* It helps in the retention of minerals like nitrogen and potassium, phosphorous, sodium, etc. in the body.
2. Thyroid Stimulating Hormone TSH or Thyrotropin:-
* It is a glycoprotein.
* It stimulates the thyroid gland to secrete Tri-iodothyronine (T3) and Thyroxine (T4).
* TSH secretion is regulated by a negative feedback mechanism.
* Its release from the anterior pituitary is induced by the thyrotropin-releasing hormone (TRH).
* When thyroxine level in the blood increases TRH acts on both the pituitary and hypothalamus to inhibit TSH secretion.
3. Adreno Corticotropic Hormone (ACTH):-
* It is a peptide hormone.
* It stimulates the adrenal cortex to secrete glucocorticoids and mineral corticoids.
* It stimulates melanin synthesis in melanocytes induces the release of fatty acids from adipose tissues and stimulates insulin secretion.
* its secretion is regulated by a negative feedback mechanism.
4. Follicle Stimulating Hormone (FSH):-
* It is a glycoprotein hormone.
* It regulates the functions of the gonads.
* In males, FSH along with androgens act on the germinal epithelium of seminiferous tubules and stimulates the production and release of sperms (Spermatogenesis).
* In females, it acts on the ovaries and brings about the development and maturation of graffian follicles.
5. Luteinizing hormone (LH):-
* It is a glycoprotein hormone.
* It is also known as interstitial cell-stimulating hormone.
* In females LH, along with FSH matures the ovarian follicles.
* LH independently induces ovulation, maintains the corpus luteum and promotes synthesis and release of ovarian hormones.
* In males, ICSH acts on interstitial cells of testes to produce the male sex hormone testosterone.
6. Luteo Tropic Hormone (LTH):-
* It is a protein hormone.
* It is also called luteotropin or lactogenic hormone or prolactin or mammotropin.
* It stimulates milk secretion after childbirth.
* Since it induces the corpus luteum hence named as a luteotropic hormone.

a. Neuro hypophysis secretes two hormones.
* Vasopressin or anti-diuretic hormone
* Oxytocin.
Vasopressin or Anti diuretic Hormone (ADH):-
* It is a peptide hormone.
* it promotes reabsorption of water and electrolytes by distal tubules of the nephron and thereby reduces the loss of water through urine.
* Hence it is called an anti-diuretic hormone.
* When released in large amounts it causes constriction of blood vessels and increases blood pressure.
* ADH deficiency causes Diabetes insipidus which induces the production of a large amount of urine.
Oxytocin:-
* It means quick birth.
* It is a peptide hormone.
3. It stimulates vigorous contraction of the smooth muscles of the uterus during childbirth.
4. And it also stimulates the ejection of milk from the mammary glands.
b. Chemical nature:
* The insulin hormone is a peptide hormone with 51 amino acids.
* The molecular weight of insulin hormone is 5734 Dalton.
* It consists of two chains A and B which are linked together by disulphide bridges formed between cystine residues.
Role of Insulin:
* It increases uptake of glucose into body cells especially muscle and fat cells.
* It inhibits the breakdown of glycogen to glucose, the conversion of amino acids or fats to glucose.
Thus it decreases the blood glucose level and so insulin is rightly called as a hypoglycemic hormone.
c. How can this condition be reversed?
* maintenance of normal body weight through adoption of nutritional habits ie. balanced diet and physical exercise.
* Correction of over nutrition and obesity may reduce the risk of diabetes and its complications.
* Alcohol and smoking should be avoided.
* Control of high blood pressure elevated cholesterol and high triglyceride levels.

a) Hormones are chemical messengers because they act as organic catalysts and co-enzymes to perform specific functions in the target organs.
b) Special features of target organs:
* The target organs contain receptor molecules either on the surface or within the cell.
* Although different hormones come in contact, only the cells that contain receptor molecules specific to the hormone are physiologically activated.
* A single hormone may have multiple effects on a single target tissue or on different target tissues.
* Many hormones exhibit long-term changes like growth, puberty, and pregnancy.
* Serious deficiency or excess secretion of hormones leads to disorders.
* Hormones coordinate different physiological mental activities and maintain homeostasis.

* Four tiny parathyroid glands are found in the posterior wall of the thyroid gland.
* It is composed of Chief cells and oxyphil cell.
* The chief cells secrete parathyroid hormone and the function of oxyphill cell are not known
Functions
* It involves in calcium and phosphate.
* It promotes the activation of vitamin D to increase calcium absorption by intestine.
Hyper secretion
* Hyper parathyroidism causes demineral isation of calcium in bones.
* Thus increasing the calcium and phosphate level in the blood.
* PTH enhances the reabsorption of calcium and excretion of phosphate by the renal tubules.
Hypo secretion
* Due to the hyposecretion of PTH serum calcium level decreases and the serum phosphate level increases.
* Generalised convulsion occurs.

a) Position
A pair of adrenal glands are located at the anterior end of the kidney. Hence called supra renal glands.
b) Structure
The adrenal gland is composed of the outer cortex and an inner medulla.
The cortex consists of
* zona glomerulosa
* zona fasciculata
* zona reticularis.
1. zona glomerulosa
– secretes minerals corticoids
2. zona fasciculata
– secretes gluco corticoids
3. zona reticularis.
– secretes androgen and oestrogen.
b) Functions
* Gluco corticoids stimulate gluco neogenesis.
* Cortisolies involved in maintaining cardio vascular and kidney functions.
* Cortisol stimulates RBC production.
* Mineralocorticoids regulated the water and electrolyte balance of our body.
* Androgen plays a role in hair growth in the axial region pubis and face during Puberty.

* Maintenance of constant internal environment of the body by the different co-ordinating system.
* The maintenance of the constant internal environment of the body is due to the functioning of the endocrine system and nervous system.
Endocrine gland.
1. a) If the calcium level in the blood decreases the parathyroid gland secretes parathyroid hormones and increases the calcium level in the blood.
b) If there is more calcium in the blood the other hormone secreted by the parathyroid gland called calcitonin acts against the parathormone and reduces calcium level.
2. a) The adrenalin secreted by the adrenal gland in emergency increases heartbeat rate and blood pressure.
b) The other hormone secreted by the adrenal is nor-adrenalin which reduces heartbeat rate and blood pressure.
Nervous system:
1. a) The sympathetic nervous system at the time of shock induces tear glands to secrete tears,
b) The parasympathetic nerve at the time of shock and emotion reduces the tear secretion.

Hormones are released into the blood stream and circulated as chemical signals. These act specifically on certain organs or tissues called target organs or tissues. These speed up or slow down or alter the activity of target tissues or organs. Hence they are known as chemaical messengers.

• Oestrogen hormones promote the growth of the ovarian follicle
• While the follicles are growing it secretes the hormone oestrogen which in turn promotes the ovum to develop.
• The shedding up of ovum at the Luteal phase takes place by the influence of the Luteinizing hormone.

The thyroid gland is a bilobed endocrine gland. Each lobe is made up of many lobules. The lobules consist of follicles called acini. Each acinus is lined with glandular, cuboidal, or squamous epithelial cells. The lumen of acinus is filled with colloid, a thick glycoprotein mixture consisting of thyroglobulin molecules.

• Diabetes emeritus: If the insulin is not secreted sufficiently the liver and muscles are unable to convert the glucose into glycogen. As a result, more glucose enters into the bloodstream raising the blood sugar level leads to diabetes mellitus.
• Diabetes Insipidus: The hormone antidiuretic hormone is secreted by the neurohypophysis, which promotes reabsorption of water and thus reduces the loss of water through urine ADH deficiency induces the production of large amounts of urine leads to diabetes insipidus.

Acromegaly is caused due to excessive secretion of growth hormone in adults. The symptoms of acromegaly are an overgrowth of hand bones, feet bones, jawbones malfunctioning of gonads. enlargement of viscera, tongue, lungs, heart, liver, spleen, and endocrine glands like thyroid, or adrenal glands.

Cretinism is caused due to hypothyroidism in infants. A cretin child shows the following symptoms:-
* Retarded skeletal growth.
* Absence of sexual maturity
* Retarded mental ability
* Thick and short limbs
* Thick wrinkled skin
* Bloated face
* Protruded enlarged tongue
* Low BMR, slow pulse rate, subnormal body temperature, and elevated blood cholesterol levels

The thyroid gland is butterfly-shaped, bilobed situated below the larynx on each side of the upper trachea. The two lobes are connected by a median tissue mass called isthmus. Each lobe is made up of many lobules. The lobules consist of follicles called acini. Each acinus is lined with glandular, cuboidal, or squamous epithelial cells.
The lumen of acini is filled with colloid, a thick glycoprotein mixture consisting of thyroglobulin molecules. The thyroid gland secretes Tri-iodothyronine (T,) and tetra-iodothyronine (T4) or thyroxine hormones. These are concerned with metabolism.

A pair of adrenal glands are located at the anterior end of the kidneys. Elence, they are called suprarenal glands. The outer region is called cortex and the inner region is medulla. The adrenal cortex has three distinct zones,
* Zona Glomerulosa
* Zona fasciculata
* Zona reticularis
1. Zona Glomerulosa:
* It is the outer thin layer. It constitutes about 15% of the cortex.
* It secretes mineralocorticoids.
2. Zona fasciculata:
* It is the middle wide layer constituting about 15% of the adrenal cortex.
* It secretes glucocorticoids such as cortisol, corticosterone and trace amounts of adrenal androgen and oestrogen.
3. Zona reticularis:
* It is the inner zone of adrenal cortex.
* It constitutes about 10% of adrenal cortex.
* It constitutes about 10% of adrenal cortex.
* It secretes the adrenal androgen, trace amount of oestrogen and glucocorticoids.

Hyper glycemia:
Hyperglycemia is a condition in which there is increased blood glucose level, it may be due to the reduced secretion of insulin.
Hypo glycemia:
Hypoglycemia is a condition in which the blood glucose level decreases. It may be due to increased secretion of insulin thereby reducing blood glucose level.

CholecystokininCholecystokinin is secreted by duodenum in response to the presence of fat and acid in the diet. It acts on the gall bladder to release bile into duodenum and stimulates the secretion of pancreatic enzymes and its discharge.

Growth hormone promotes growth of all the tissues and metabolic process of the cell. The growth hormone stimulates the growth in the following ways
* It influences the metabolism of carbohydrate proteins and lipids.
* It increases the rate of protein biosynthesis.
* It stimulates cartilage formation of chondrogenesis.
* It stimulates bone formation osteogenesis.
* It helps in the retention of minerals like nitrogen, potassium, phosphorous sodium in the body.
* It increases the release of fatty acid from adipose tissue.
* It decreases the rate of glucose utilization for energy by the cell, by which it conserves glucose for glucose-dependent tissues such as the brain.

The pineal gland or epiphysis cerebri or conarium is located behind the third ventricle of the brain. It is formed of parenchymal cells and interstitial cells. It secretes the hormone, melatonin.
It plays a central role in the regulation of the circadian rhythm of our body and maintains a normal sleep-wake cycle. It also regulates the timing of the sexual maturation of gonads. It also influences metabolism, pigmentation, menstrual cycle and defence mechanism of our body.

• Adrenalin increases liver glycogen breakdown into glucose and increases the release of fatty acids from fat cells.
• During emergency, it increases heartbeat rate and blood pressure.
• It stimulates the smooth muscles of cutaneous and visceral arteries to decrease blood flow.
• It increases blood flow to the skeletal muscles thereby increases the metabolic rate of skeletal muscles cardiac muscles and nervous tissues.

Pancreas is both exocrine and endocrine gland. It is located just below the stomach as a leaf-like structure. It secretes digestive enzymes and hormones like insulin and glucogon.
The digestive enzymes digest carbohydrates, proteins, and fats. Insulin and glucose regulate blood sugar levels. If pancreas is removed from the body, digestion and maintenance of blood sugar level get affected.

Kidney has endocrine tissues which act as a partial endocrine gland. It secretes renin, erythropoietin, and calcitriol. Renin is secreted by juxtaglomerular cells. It increases blood pressure when angiotensin is formed in the blood.
Erythropoietin is also secreted by the juxtaglomerular cells of the kidney and stimulates erythropoiesis in the bone marrow. Calcitriol is secreted by proximal tubes of nephrons. It is an active form of vitamin D3 which promotes calcium and phosphorus absorption from the intestine and accelerates bone formation.
Part – II.
11th Bio Zoology Guide Chemical Coordination and Integration Additional Important Questions and Answers
I. Choose The Correct Answer