Notes Endocrine System ICSE Class 10 Biology

Study Material

Students should refer to Endocrine System ICSE Class 10 Biology notes provided below designed based on the latest syllabus and examination pattern issued by ICSE. These revision notes are really useful and will help you to learn all the important and difficult topics. These notes will also be very useful if you use them to revise just before your Biology Exams. Refer to more ICSE Class 10 Biology Notes for better preparation.

ICSE Class 10 Biology Endocrine System Revision Notes

Students can refer to the quick revision notes prepared for Chapter Endocrine System in Class 10 ICSE. These notes will be really helpful for the students giving the Biology exam in ICSE Class 10. Our teachers have prepared these concept notes based on the latest ICSE syllabus and ICSE books issued for the current academic year. Please refer to Chapter wise notes for ICSE Class 10 Biology provided on our website.

Endocrine System ICSE Class 10 Biology

Quick Review
➢ Glands are differentiated into exocrine glands whose secretion are conducted by ducts and endocrine glands (or ductless glands) which do not have ducts and whose secretions are poured directly into the blood stream.
➢ The chemical substances produced by endocrine glands are termed hormones.
➢ The hormones act as chemical messengers or messenger molecules. Hormones are transported to target organs by blood.
➢ Hormones are produced in very small quantity. Their minute amount produce marked effect.
➢ Deficiency or excess of hormones may result in number of diseases.
➢ The main endocrine glands in human beings include adrenal glands, pancreas (only endocrine part), thyroid gland, pituitary gland etc.
➢ Adrenal glands are placed at the top of each kidney and have two regions, an outer yellow cortex and an inner reddish brown medulla.
➢ Cortex secrete corticoids. The important corticoids are – Mineralocorticoids, Glucocorticoids and sexcorticoids.
➢ Mineralocorticoids are concerned with water and electrolyte balance. Hyposecretion of it causes imbalance of Na+ and K+. As a result nervous disorder takes place, which leads to death while hypersecretion causes neuromuscular disturbance.
➢ Glucocorticoids are concerned with synthesis of glycogen in liver, protein break down, increased WBC etc. Hyposecretion causes Addison’s disease (Shock, reduced blood pressure, high urea in blood etc.). Hypersecretion causes Cushing’s disease .
➢ Medulla secrete adrenaline or epinephrine. It is called emergency hormone and fight, flight and fright (3F) hormone. It stimulate heart beat, blood glucose.
➢ Pancreas is a heterocrine gland because it is exo-endocrine in function.
➢ Endocrine part is formed by islets of Langerhans. Islets are of two types
(a) a – cells : secrete glucagon.
(b) b – cells : secrete insulin.
➢ Glucagon increases blood glucose levels by promoting glycogenolysis.
➢ Insulin make the cell membranes more permeable for uptake of blood glucose and as a result blood glucose level is lowered. Deficiency of insulin leads to diabetes mellitus and glucosuria (glucose in urine).
➢ Thyroid gland is the largest endocrine gland in the body. In mammals, it is bilobed gland, lie close to the trachea below the thyroid cartilage. The two lobes are connected by isthmus.
➢ It mainly secretes the hormone thyroxine and calcitonin (causes the deposition of ca²+ in bones).
➢ Thyroxine hormone is responsible for regulating the normal basal metabolism of the body. It also influences the general body growth, body temperature, mental development etc.
➢ Hypothyroidism causes cretinism (stunted physical and mental growth) in children and myxoedema or Gull’s disease (puffiness of skin) in adults.
➢ Hyperthyroidism causes increased metabolic rate, sweating, flushing etc.
➢ Pituitary gland is considered as the master gland of endocrine system because it performs many functions besides the control of other endocrine glands.
➢ It is present on the ventral side of diencephalon found attached to the infundibulum.
➢ Pituitary gland is a trilobed structure, having anterior lobe, intermediate lobe and posterior lobe. Hormones produced by these three lobes are as follows :
(i) Anterior lobe
(a) Growth hormone or Somatotropin : Primary function of this hormone is to stimulate growth of body and body parts proportionately. Hyposecretion of these glands causes dwarfism while hypersecretion in children causes gigantism. In adults causes acromegaly ( over growth of bones of hands, feet, jaws, cheeks etc.)
(b) Thyroid stimulating hormone : It stimulate the thyroid gland to secrete thyroxine.
(c) Adreno cortico tropic hormone : It stimulate the adrenal cortex.
(d) Gonadotropins: Stimulate primary organs i.e. ovaries and testes.

Follicle stimulating hormone (FSH) influence maturation of follicles of ovary to produce eggs in females and spermatogenesis in males.
Luteinizing hormone (LH) in female induces ovulation and secretion of progesterone from corpus luteum.
Interstitial cells stimulating hormone (ICSH) in male stimulates release of sperm and of testosterone hormone which controls secondary sexual characters.
Lactogenic hormone or Prolactin (PL) initiates milk production in pregnant female.
(ii) Posterior Lobe
The posterior lobe produces two hormones :
(a) Oxytocin stimulates smooth muscle contraction, specially of the uterus during child birth.
(b) Vasopressin or antidiuretic hormone (ADH) Regulate absorption of water from kidney tubules.
Hyposecretion causes diabetes insipidus in which loss of water through urine results.
Hypersecretion causes water retention in tissue.
(iii) Intermediate Lobe
It produces melanocyte stimulating hormone (MSH) controlling pigmentation of skin.
➢ Feedback Mechanism : It is the mechanism for maintaining the normal balanced state between the rise and fall of hormones i.e. to slow down the process if excess amount of hormone is secreted and speed up the process if very low amount of hormone is released.
➢ Glands are differentiated into exocrine glands whose secretion are conducted by ducts and endocrine glands (or ductless glands) which do not have ducts and whose secretions are poured directly into the blood stream.
➢ The chemical substances produced by endocrine glands are termed hormones.
➢ The hormones act as chemical messengers or messenger molecules. Hormones are transported to target organs by blood.
➢ Hormones are produced in very small quantity. Their minute amount produce marked effect.
➢ Deficiency or excess of hormones may result in number of diseases.
➢ The main endocrine glands in human beings include adrenal glands, pancreas (only endocrine part), thyroid gland, pituitary gland etc.
➢ Adrenal glands are placed at the top of each kidney and have two regions, an outer yellow cortex and an inner reddish brown medulla.
➢ Cortex secrete corticoids. The important corticoids are – Mineralocorticoids, Glucocorticoids and sexcorticoids.
➢ Mineralocorticoids are concerned with water and electrolyte balance. Hyposecretion of it causes imbalance of Na+ and K+. As a result nervous disorder takes place, which leads to death while hypersecretion causes neuromuscular disturbance.
➢ Glucocorticoids are concerned with synthesis of glycogen in liver, protein break down, increased WBC etc. Hyposecretion causes Addison’s disease (Shock, reduced blood pressure, high urea in blood etc.). Hypersecretion causes Cushing’s disease .
➢ Medulla secrete adrenaline or epinephrine. It is called emergency hormone and fight, flight and fright (3F) hormone. It stimulate heart beat, blood glucose.
➢ Pancreas is a heterocrine gland because it is exo-endocrine in function.
➢ Endocrine part is formed by islets of Langerhans. Islets are of two types
(a) a – cells : secrete glucagon.
(b) b – cells : secrete insulin.
➢ Glucagon increases blood glucose levels by promoting glycogenolysis.
➢ Insulin make the cell membranes more permeable for uptake of blood glucose and as a result blood glucose level is lowered. Deficiency of insulin leads to diabetes mellitus and glucosuria (glucose in urine).
➢ Thyroid gland is the largest endocrine gland in the body. In mammals, it is bilobed gland, lie close to the trachea below the thyroid cartilage. The two lobes are connected by isthmus.
➢ It mainly secretes the hormone thyroxine and calcitonin (causes the deposition of ca²+ in bones).
➢ Thyroxine hormone is responsible for regulating the normal basal metabolism of the body. It also influences the general body growth, body temperature, mental development etc.
➢ Hypothyroidism causes cretinism (stunted physical and mental growth) in children and myxoedema or Gull’s disease (puffiness of skin) in adults.
➢ Hyperthyroidism causes increased metabolic rate, sweating, flushing etc.
➢ Pituitary gland is considered as the master gland of endocrine system because it performs many functions besides the control of other endocrine glands.
➢ It is present on the ventral side of diencephalon found attached to the infundibulum.
➢ Pituitary gland is a trilobed structure, having anterior lobe, intermediate lobe and posterior lobe.

Hormones produced by these three lobes are as follows :
(i) Anterior lobe
(a) Growth hormone or Somatotropin : Primary function of this hormone is to stimulate growth of body and body parts proportionately. Hyposecretion of these glands causes dwarfism while hypersecretion in children causes gigantism. In adults causes acromegaly ( over growth of bones of hands, feet, jaws, cheeks etc.)
(b) Thyroid stimulating hormone : It stimulate the thyroid gland to secrete thyroxine.
(c) Adreno cortico tropic hormone : It stimulate the adrenal cortex.
(d) Gonadotropins: Stimulate primary organs i.e. ovaries and testes.
Follicle stimulating hormone (FSH) influence maturation of follicles of ovary to produce eggs in females and spermatogenesis in males.
Luteinizing hormone (LH) in female induces ovulation and secretion of progesterone from corpus luteum.
Interstitial cells stimulating hormone (ICSH) in male stimulates release of sperm and of testosterone hormone which controls secondary sexual characters.
Lactogenic hormone or Prolactin (PL) initiates milk production in pregnant female.
(ii) Posterior Lobe
The posterior lobe produces two hormones :
(a) Oxytocin stimulates smooth muscle contraction, specially of the uterus during child birth.
(b) Vasopressin or antidiuretic hormone (ADH) Regulate absorption of water from kidney tubules.
Hyposecretion causes diabetes insipidus in which loss of water through urine results.
Hypersecretion causes water retention in tissue.
(iii) Intermediate Lobe
It produces melanocyte stimulating hormone (MSH) controlling pigmentation of skin.
Feedback Mechanism : It is the mechanism for maintaining the normal balanced state between the rise and fall of hormones i.e. to slow down the process if excess amount of hormone is secreted and speed up the process if very low amount of hormone is released.
Negative feedback control : It is a closed loop in which synthesis of hormone stops and lowers when its blood level rises above normal. For example, If the level of glucose rises in the blood, it is detected by beta cells of the pancreas that produces more insulin. This promotes absorption of glucose by the cells and its level is brought back to normal.
Positive feedback control : In this feedback, the hormone further stimulate the production. For example, uterine contractions during child birth stimulates the release of oxytocin into the mother’s blood. This further intensifies uterine contractions, thus causing more oxytocin release.

Know the Terms
Acromegaly : Gorilla like appearance due to over secretion of STH (Somatotropin)of anterior lobe in adult.
Addison’s’ disease : A condition caused by deficiency of aldosterone hormone and characterized by skin discolouration, muscular weakness, low B.P etc.
Cretin : A dwarf and mentally backward person due to the deficiency of thyroxine hormone in childhood.
Cushing syndrome : Caused by hypersecretion of cortisol or glycocorticoid, characterized by high blood sugar level, swollen face, neck, hands.
Gigantism : Abnormal increase in height due to excessive secretion of STH from anterior pituitary lobe.
Grave’s disease : It is due to the excess of thyroxine.
Gynecomastia : Development of breasts in male.
Gluconeogenesis : Formation of glucose from non-sugars.
Glycogenesis : Formation of glycogen from glucose in liver and muscles.
Glycogenolysis : Breakdown of glycogen into glucose in liver and muscles.
Heterocrine gland : A gland with endocrine and exocrine parts.
Lag period : Period between secretion of hormone from endocrine gland and biological response to it.
Osteoporosis : Bones become soft and fragile.
Tetany : It is a condition which results due to the fall of calcium level in the blood.
Polydipsia : In this case there is a less insulin secretion and person fells thirsty. It leads to dehydration.
Pheromones : Pheromones are defined as chemical excreted or released by one animals to the exterior but evoke a physiological or behavioural response in another animals of the same species. This are secreted by exocrine gland.
Gull’s disease or Myxoedema : It is a disease caused by malfunctioning of thyroid.
Hypophysectomy : Removal of pituitary gland.
Endocrinology : Study of endocrine glands.
Glucagon : The hormone that brings about increase in blood sugar. It is also known as fasting hormone.

Introduction to Human Endocrine System

Hormones are the organic chemicals produced by the body, which are released into the blood.

The key feature of the hormones is that they are secreted by the ductless glands. The glands that secrete hormones do not have ducts. Hormones are released directly into the blood stream and reach the target organ.

Differences between Hormonal Control and Nervous Control

The endocrine system works in association with nervous system to control and coordinate our bodies. They contribute to the maintenance of homeostasis in our bodies.

Homeostasis is the capacity of an organism to adjust itself and cope up with external stress to maintain a steady state.

Glands

A cell, tissue, or an organ that secretes chemical messengers required for coordinating a specific function is called a gland. Glands are mainly divided into two broad categories – endocrine and exocrine.

Characteristics of Hormones

• Hormones are the organic chemicals that are secreted in response to environmental changes in or outside the body.
• Hormones are secreted by ductless glands and transported along with the blood stream to the site of their action. The site of their production and the organ of their influence are different.
• They can be amino-acid derivatives, proteins, or steroids.
• Being low molecular weight substances, they can easily diffuse through the cell membrane.
• They are produced in small quantities and are effective in extremely lower concentrations.
• Abnormal production of hormones (be it less or more) affects the body in a negative manner.

Some of the ductless glands that secrete hormones are thyroid gland, adrenal gland, pituitary gland, parathyroid gland, gonads, etc.

Human Endocrine System

• Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads are the organised endocrine glands in our body.
• In addition, GI tract, liver, kidney, heart also produce hormones.

Human Endocrine System and Adrenal, Pancreas and Gonads

Adrenal Gland

Location: 1 pair − 1 gland at the anterior part of each kidney

• Catecholamine:

• Emergency hormones or hormones of fight or flight
• Increases alertness, pupilary dilation, piloerection (raising of hair)
• Increases heart beat, respiration rate
• Stimulates the breakdown of glucose, lipids and proteins

• Glucocorticoid:

• Stimulates gluconeogenesis, lipolysis and proteolysis
• Inhibits uptake and utilisation of amino acids
• Suppresses immune response by producing anti-inflammatory reaction (Example − Cortisol)
• Stimulates RBC production (Example − Cortisol)
• Mineralocorticoid: Example − Aldosterone
• Acts on renal tubule and stimulates re-absorption of Na+ and water
• Stimulates excretion of K+
• Maintains electrolysis, osmotic pressure and blood pressure
• Androgenic steroids plays a role in the growth of axial, facial and pubic hair during puberty

Hyposecretion of hormones from adrenal cortex results in Addison’s disease. Symptoms:

• Loss of energy and weight
• Skin pigmentation
• Hypoglycemia
• Sensitivity to cold
• Increased susceptibility to infections, etc

Hypersecretion of hormones from adrenal cortex causes Cushing’s Syndrome. Symptoms:

• Obesity
• Hyperglycemia
• Osteoporosis
• Weakness, etc

Pancreas

• Glucagon: Hyperglycemic hormone

• A peptide hormone
• Maintains the normal blood glucose level
• Acts on liver cells and stimulates glycogenolysis, resulting in hyperglycemia
• Stimulates gluconeogenesis (synthesis of glucose from sources like fats)

• Insulin: Hypoglycemic hormone

• A peptide hormone
• Stimulates liver cells to enhance the cellular glucose uptake and utilisation
• Moves the glucose from the blood to hepatocytes and adipocytes
• Converts glucose into glycogen
• Glucagon + Insulin = Maintain glucose homeostasis

Insufficient secretion of insulin causes Diabetes mellitus Symptoms:

• High sugar concentration in blood
• Excretion of glucose with urine
• Increased thirst
• Loss of weight

Over secretion of insulin causes hypoglycemia. It results in low glucose level in blood. Under extreme cases, brain may enter in a state of of coma.

An overdose of insulin to a diabetic patient may also result in hypoglycemic conditions. As a result, the patient may become unconscious. This phenomena is called insulin shock. It can be reversed by instant intake of sweet biscuits or candies.

Testis

• Location: scrotal sac, in males
• Testis is composed of seminiferous tubules, and stromal or interstitial tissues.
• In the intertubular spaces, Leydig cells (interstitial cells) are present that secrete androgens, mainly testosterone.

• Functions of androgens:

• Development, maturation and functioning of the male accessory sex organs like vas deferens and seminal vesicles
• Stimulate muscular growth, growth of facial hair, low pitch voice, etc.
• Stimulatory role in spermatogenesis
• Act on the CNS and influence male sexual behaviour (libido)
• Anabolism of proteins and carbohydrates

Ovary

• Location: inside abdomen, in females
• Hormones produced: Oestrogen and progesterone
• Ovary is composed of ovarian follicles and stromal tissues
• Ovarian follicles: Secrete oestrogen

• Functions of oestrogen:

• Growth and functioning of the female secondary sex organs
• Development of growing follicles and mammary glands
• Regulates female secondary sex characters (Examples − high pitch voice)

• Functions of progesterone:

• Acts on mammary glands and stimulates formation of alveoli-like structures storing milk
• Milk secretion

Human Endocrine System and Hypothalamus, Pineal, Thyroid, Parathyroid

Hypothalamus
• Basal part of diencephalon in forebrain
• It has several groups of neurosecretory cells (known as nuclei) that produce hormones. The synthesis and secretion of pituitary hormones is regulated by these hormones.
• Hormones originate from hypothalamic neurons, pass through axons, and are released from their nerve endings.
• Reach pituitary gland through a portal circulatory system and regulate the functioning of anterior pituitary
• Hormones from hypothalamus are of two types:

Pineal Gland

• Location − Dorsal side of forebrain
• Secretes melatonin that regulates 24-hour (diurnal) rhythm of the body such as sleep-wake cycle, body temperature, etc.
• Melatonin also regulates metabolism, pigmentation, and menstrual cycle.

Thyroid Gland

• Location − Two lobes of thyroid gland are located on either side of trachea.
• Isthmus − Thin flap of connective tissue interconnecting the thyroid glands
• Composition − Follicles + Stromal tissues • Follicular cells synthesize two hormones:
• Tetraiodothyronine or thyroxine (T4) • Triiodothyronine (T3)
• Importance of thyroid hormones:
• Regulates BMR (Basal Metabolism Rate)
• Supports the process of RBC synthesis
• Maintains water-electrolyte balance
• Insufficient secretion of thyroxine results in
• goitre (enlargement of thyroid gland due to deficiency of iodine)
• cretinism (dwarfism and mental retardation in children)
• myxoedema (swelling in hands and face of an adult)
• Excessive secretion of thyroid hormone leads to hyperthyroidism. This may occur due to cancer of thyroid gland or development of nodules of thyroid glands. A person suffering from hyperthyroidism show following symptoms:
• Goitre in neck (exophthalmic goitre)
• Protruded eyes
• Increased heart beat
• Increased metabolic rate

Parathyroid Gland

• Location − Four parathyroid glands are present on back side of thyroid glands.
• Secretes − Parathyroid hormone (PTH)
• Secretion of PTH is regulated by circulating level of calcium ions.
• PTH is a hypercalcemic hormone. It increases blood calcium levels by
• dissolution/demineralization from bones
• reabsorption of Ca2+ by renal tubules
• Ca2+ absorption from digested food

Human Endocrine System & Pituitary Gland and Thymus Gland Pituitary Gland

• Location: In the bony cavity called sella tursica; attached to the hypothalamus via a stalk

Thymus

• Location: Dorsal side of the heart and the aorta
• Importance: Development of the immune system
• Secretion: Peptide hormone called thymosins
• Role of thymosins: • Differentiation of T-lymphocytes (Cell Mediated Immunity)
• Promotes production of antibodies (Humoral Immunity)
• Thymus is degenerated in old people. Hence, their immune response becomes weak.

Functions and Regulation of Hormone

Feedback mechanism regulates the action of the hormones

The glucose present in blood is broken down to produce energy required for the body. If it is present in an excess amount in the blood, then it is converted into glycogen.

How does the body know when to convert glucose into glycogen or to breakdown glycogen into glucose?

Hormones control most physiological reactions.

How is the timing and the quantity of hormones released regulated? Is there any mechanism to control the system?

The endocrine glands secrete hormones depending upon the need of the organism. The amount of hormones secreted should be in an accurate amount. The regulation of the quantity of the hormones and the timing of its release are controlled by feedback mechanisms.

There are two types of feedback mechanisms—positive and negative feedback Positive feedback: In this mechanism, the response accelerates after the feedback. The effect is further intensified in the same direction. It helps in speeding up the process occurring in various body systems. It is the opposite of negative feedback.

Negative feedback: In this mechanism, the information given by the feedback causes a reverse response. It occurs when the system needs to slow down or completely stop a process.

Illustrations to understand the two types of mechanisms

1. Child birth
Uterine contractions occur during the onset of labour pain. These contractions stimulate the release of a specific hormone called oxytocin (from the pituitary gland), which intensifies the contractions. The contractions further stimulate the production of oxytocin and this cycle stops only after the birth of the baby.

This is an example of positive feedback.

2. Insulin

When you consume a carbohydrate-rich diet, it is digested into glucose. The glucose is then absorbed by the blood. This results in the increase of blood-sugar level and leads to the stimulation of the pancreas to secrete insulin. Insulin stimulates the target cells to take up the extra glucose from the blood.

This glucose is either used during respiration or stored as glycogen. Thus, the level of glucose in the blood is maintained. This is an example of negative feedback.

3 Thyroid Stimulating Hormone (TSH)

The negative feedback loop can also be observed in case of regulation of thyroid hormones. In this particular regulation, the hypothalamus secrete Thyroid Releasing Hormone (TRH) which stimulates anterior pituitary to produce TSH. TSH further activates the cells of thyroid glands and consequently, thyroid hormones are released in the blood.

A gradual rise in the concentration of thyroid hormones serves as an inhibitory signal for hypothalamus and it stops producing TRH. In response to inhibition of TRH, TSH production is also lowered and eventually, the secretion of thyroid hormones is lowered.

Some Interesting Facts:
• Do you know that insulin was first extracted from dog pancreas in 1921 in the University of Toronto?
• Human insulin (Humulin) is produced by using human genes in the bacterium called E.coli.

Functions of Hormones
• To regulate the metabolic activities
• To regulate the morphogenic activities such as growth, development, etc.
• To regulate mental activities, growth maturation, reproductive activities, etc.
• To control the activities of other endocrine glands
• To maintain homeostasis

Glands are modified epithelium which produces certain secretions.
TYPES OF GLANDS:

Notes Endocrine System ICSE Class 10 Biology

Secretions of Endocrine Glands-HORMONES
HORMONES: Special chemicals secreted by Endocrine Glands, which are directly poured into the BLOOD and are carried to the site of action, called Target Organ.

CHARECTERISTICS OF HORMONES:

• They are Proteins, specific in function and specific in target
• Secreted in LOW concentration, if in excess it is excreted through urine
• Hypo or Hyper secretion causes diseases
o Hormones act as chemical messengers.
o They are secreted by living cells/tissues or organs called glands.
o They are secreted in very small quantities by glands.
o They act upon specific cells, tissues, or organs called the target sites.
o They are generally slow in action, but have long lasting effects.
o They either accelerate or inhibit a reaction.

PITUITARY GLAND (A.K.A MASTER GLAND)

Notes Endocrine System ICSE Class 10 Biology

• Location: Below Hypothalamus in the Forebrain.
• Pituitary Gland id divided into 3 lobes:
o Anterior Lobe
o Inter-mediate Lobe
o Posterior Lobe

ANTERIOR PITUITARY LOBE:
o Some of the Hormones of Anterior Pituitary Lobe are called Tropic Hormones
o Tropic Hormones: Hormones which stimulates other Endocrine Glands to produce their secretions.

E.g.: TSH, ACTH, FSH, and LH
o Thyroid Stimulating Hormone (LHT):
Stimulates Thyroid Gland to produce its secretions.
o Adreno-Cortico Tropic Hormone (ACTH):
♦ Stimulates Adrenal Cortex to secrete its hormones

o Follicle Stimulating Hormone (FSH):
♦ Stimulated in both MALES & FEMALES
♦ It maintains the growth and development of GRAAFIAN follicle.
♦ In Males- Spermatogenesis (Production of Sperms)
♦ In Females- Maturation of Follicle (Production of Ovum)

♦ Testis
• Leydig cells (Interstitial cells) – Secrete androgens, mainly testosterone
• Testosterone plays a role in spermatogenesis and development of male secondary sexual characters.

♦ Ovary
• It secretes two hormones.
• Estrogen – Secreted by Graafian follicle, it regulates the development of female secondary sexual characters.
• Progesterone – Secreted by corpus luteum, it acts on mammary glands and helps in milk secretion.

o Luteinizing Hormone (LH):
♦ It helps in secretion of Androgens from Testis. It also induces Ovulation from GRAAFIAN follicle.
♦ In Males, it stimulates secretion of male hormone Testosterone.
♦ In Males, it also called INTESTITIAL CELL STIMULATING HORMONE.
♦ In Females, it stimulates secretion of female hormone Progesterone.
♦ Progesterone – Secreted by corpus luteum, it acts on mammary glands and
♦ helps in milk secretion.

GROWTH HORMONE/SOMATOTROPIN

Functions

Notes Endocrine System ICSE Class 10 Biology

♦ Hypo-secretion:
a. Dwarfism in children-
1. Stunted physical growth
♦ Hyper-secretion:
a. Gigantism in children-
1. Abnormal growth in height
b. ACROMEGALY in adults-
1. Elongation of Bones of Limbs
2. Bones of Jaw protrude

PROLACTIN
♦ Stimulates MAMMARY glands to produce the secretions after the birth of a child.
♦ ONLY in FEMALES

POSTERIOR PITUITARY LOBE:
ANTI-DIURETIC HORMONE [ADH]/VASOPRESSIN]

Notes Endocrine System ICSE Class 10 Biology

♦ Hypo-secretion:
a. Diabetes insipidus-
1. Watery urine without Glucose
2. Person feels thirsty & tired
OXYTOCIN (The “Feel Good” Hormone)
♦ Simulates forceful contraction of Uterine wall (wall of the Uterus) during child birth.
♦ It also helps in Milk ejection.

THYROID GLAND
♦ Location: Below larynx on either sides of trachea
♦ Function: Secretes two Hormones,
1. Thyroxin
2. Calcitonin

Notes Endocrine System ICSE Class 10 Biology

1. Thyroxin:
♦ Functions (of Thyroxin):
✔ Controls Cell Division & its differentiations
✔ Controls BMR (Basal Metabolism Rate)
✔ Controls Metabolism of Carbohydrates, Proteins & Fat
✔ Decides the onset of puberty in young Males and Females

♦ Hypo-secretion:
a. Cretinism in children-
1. Stunted physical and mental growth
b. Myxoedema in adults-
1. BMR falls
2. Swelling in the Neck
3. Swelling in different parts of the body
4. Tiredness

♦ Hyper-secretion:
a. Exophthalmic Goitre-
1. Rate of Heart Beat, Breathing increases
2. Eyeballs seem to bulge out
3. Rate of Oxidation of food increases
4. Person becomes irritable

♦ Simple Goitre:
→ Caused due to the deficiency of Iodine in diet. Hence, Thyroxin secretion isn’t normal.
→ Symptoms:
1. BMR falls
2. Weakness
3. Exhaustion
4. Swelling in the neck due to enlargement of Thyroid Gland
5. Lower Thyroxin levels may also lead to Infertility

2. Calcitonin:
♦ Functions:
1. Regulates Calcium Metabolism in the body
2. Regulates Mobilization of Calcium ion from BONES to BLOOD

ADRENAL GLAND
♦ Location: A pair of Adrenal Glands one above each Kidney (Like CAP)

Notes Endocrine System ICSE Class 10 Biology

♦ Internally, Adrenal Gland is divided into two parts:
(a) Outer Cortex – It secretes hormone called corticoids.
• Corticoid such as glucocorticoid regulates carbohydrate metabolism. Example includes cortisol.
• Corticoid such as mineralocorticoid maintains the sodium potassium level in blood and tissue. Example includes
Aldosterone.
(b) Inner Medulla – It secretes ADRENALINE (epinephrine) and NORADRENALINE (norepinephrine). These are collectively called as
CATECHOLAMINES. These hormones are also called “EMERGENCY” hormones.

♦ CORTEX- Stimulated by ACTH to secrete its hormones.
• Cortex is divided into 3 layers:
→ Outer Layer
→ Middle Layer
→ Inner Layer

• Outer Layer-
→ Secretes a group of hormones called MINERALORTICOIDS E.g.- Aldosterone
→ Maintains ionic concentration of Blood, i.e., concentration of Na (Sodium) ion, K (Potassium) ion and Ca (Calcium) ion.
→ Hypo-secretiona.

a. Addison’s Disease
1. Low Na level in blood
2. Low BP
3. Low Blood Sugar level
4. Weakness
5. Nausea
6. Vomiting
7. Bronze Pigmentation
→ Hyper-secretiona.

a. Conn’s Syndrome/Aldosteronism
1. Kidney failure
2. High Blood Sugar level
3. High Na level in blood

• Middle Layer-
→ Secretes a group of hormones called GLUCOCORTICOIDS E.g.’: Cortisol & Cortisone
→ Function: Regulates Carbohydrates, Protein & Fat metabolism in the body.
→ These hormones are also called “Anti-Stress Hormone”
→ Hypo-secretion- Stress
→ Hyper-secretiona.

a. Cushing’s Syndrome
1. Rise in Blood volume
2. Rise in BP
3. Rise in Blood Sugar level
4. Obesity

• Inner Layer-
♦ Secrete a group of hormones called SEX-CORTICOIDS E.g.: Androstenedione
♦ Secrete both in males & females
♦ Function: Requires for maintaining secondary sexual characters in males and females.

[Facial Hair (boys) |Breasts (Girls)]
♦ Hyper-secretiona.
Adrenal Virilism –
1. In males-Enlargement of Breasts
In females- Hoarse voice & appearance of Facial hair
♦ MEDULLA- Secretes Adrenaline (epinephrine) also called “EMERGENCY” hormones.

Prepares the body for emergencies like,
✔ Increased rate of Heart beat
✔ Increased rate of Breathing
✔ Increased Blood Sugar level
✔ Decreased Blood Supply to skin

PANCREAS
♦ Location: Below the stomach in the loop of duodenum
♦ It is a Heterocrine Gland, the Pancreas have bothEndocrine and Heterocrine Gland
♦ Endocrine part of Pancreas- “Islets of Langerhans”
♦ Islets of Langerhans has three types of cells:

Notes Endocrine System ICSE Class 10 Biology

ALPHA cells
BETA cells
DELTA cells
♦ ALPHA cells- secrete Glucagon.
♦ Hyperglycemia – Increased blood glucose level
♦ Glucagon is a hyperglycaemic hormone.
♦ Function of Glucagon: Converts Glycogen to Glucose
♦ BETA cells- secrete Insulin
Hypoglycaemia – Decreased blood glucose level
Insulin is a hypoglycaemic hormone.
Functions of Insulin: Converts Glucose to Glycogen. Helps the cells in the uptake of Glucose and its utilization.
• Hypo-secretion of Insulina.

a. Diabetes mellitus
1. Frequent urination
2. Person feels thirsty
3. Person feels hungry
4. Muscle wasting
5. Overtime this condition affects Kidney, Eyes, Nervous System, Heart
• Hyper –secretion of Insulin- COMA, due to nerve cell starvation.
♦ DELTA cells- secretes Somatostatin
• Function of Somatostatin: Regulates the functioning of Glucagon & Insulin

INSULIN SHOCK- If a diabetic person has taken the insulin injection but has not eaten his food properly, it results in INSULIN SHOCK.
→ Symptoms:
1. Dizziness/Blackout
2. Sweating
3. Disorientation due to nerve cell starvation
→ Reason: Person’s glucose level falls below normal
→ Treatment: The person has to be administered orally.

HYPOTHALAMUS: Contains NEUROSECRETORY cells that produce hormones
♦ Hormones regulate the synthesis and secretion of pituitary glands.
♦ Two types of hormones are released.
♦ Releasing hormones – Stimulate pituitary gland to release hormones
♦ Inhibiting hormones – Inhibit pituitary gland from releasing hormones

PINEAL GLAND
♦ It secretes a hormone called melatonin.
♦ It also regulates the rhythm of body.

FEEDBACK MECHANISM
* Hypothalamus is considered to be a link between Nervous System &
Endocrine System, as it controls the functioning of Pituitary Gland.
* Between Hypothalamus and Pituitary Gland is present a Portal System called Hypophyseal Portal System.
* Hypothalamus produces two secretions which pass via the portal system to reach Pituitary Gland. These secretions are:
a. RELEASING factor
b. INHIBITING factor
* E.g.- If the level of Thyroxin in blood is more than normal

Notes Endocrine System ICSE Class 10 Biology

“The Producers of Chemical Messengers”

Multicellular organisms communicate with and control their various activities by means of two major systems—the nervous system and the endocrine system.

Notes Endocrine System ICSE Class 10 Biology

Hormones

A hormone is a secretion from some glandular part of the body, which is poured into the blood and which acts on the target organs or cells of the same individual.

Most hormones are secreted by special glands called endocrine glands.

General Properties of Hormones

1. Hormones are secreted by the endocrine glands directly into the blood.
2. Produced in very small quantities.
3. Biologically very active.
4. Act on target organs or cells usually away from the source.

Endocrine System

The endocrine system is made of endocrine glands and tissues.

Notes Endocrine System ICSE Class 10 Biology

Adrenal Glands
The human body has two adrenal glands located on top of the kidneys; hence, they are also known as suprarenal glands.

Notes Endocrine System ICSE Class 10 Biology
Notes Endocrine System ICSE Class 10 Biology

Abnormal Secretions of Adrenal Glands
Hyposecretion of the adrenal cortex causes Addison’s Disease.
Hypersecretion of the adrenal cortex causes Cushing Syndrome.

Pancreas

Notes Endocrine System ICSE Class 10 Biology

The pancreas is exocrine as well as an endocrine gland.
The exocrine part pours its secretion—pancreatic juice—into the duodenum through the pancreatic duct.
The endocrine part is made up of a special group of cells known as islets of Langerhans.

Three kinds of cells found in the islets of Langerhans and their secretions are

Notes Endocrine System ICSE Class 10 Biology

Abnormal Secretions of Insulin

Notes Endocrine System ICSE Class 10 Biology

Thyroid Gland
The thyroid gland is a bilobed, butterfly-shaped gland.
The two lobes are joined by a narrow mass of tissues called isthmus.

Notes Endocrine System ICSE Class 10 Biology
Notes Endocrine System ICSE Class 10 Biology
Notes Endocrine System ICSE Class 10 Biology

Pituitary Gland
It is a small gland about the size of a pea. The pituitary controls the secretions of all the other endocrine glands; therefore, it is also called the master gland.

The pituitary gland is divided into three lobes. The secretions from these lobes are as follows:

Notes Endocrine System ICSE Class 10 Biology

Anterior Pituitary
• Growth Hormone:
o Essential for normal growth.
o Deficiency of growth hormone causes dwarfism.
o Oversecretion causes gigantism and acromegaly.
• Thyroid Stimulating Hormone (TSH):
o Controls the activities of the thyroid gland.
• Gonadotropins (FSH/LH):
o Regulate the activities of testes and ovaries.
• Adrenocorticotropic Hormone (ACTH):
o Regulates the activity of the adrenal cortex.
Intermediate Lobe of the Pituitary Gland: Regulates the activity of the adrenal cortex.

Posterior Pituitary
• Anti-diuretic Hormone (Vasopressin):
o Regulates the amount of water excreted in the urine.
o Deficiency of ADH causes diabetes insipidus.
 Oxytocin:
o Stimulates contraction of uterine muscles during childbirth.

Feedback Mechanism
Negative Feedback Mechanism
• The body has mechanisms to maintain a normal state.
• Whenever there is a change in the normal state, the messages are sent to ‘increase’ secretions if there is a fall below normal or to ‘decrease’ secretions if there is a rise above normal to restore the normal body state. Such a mechanism is called a Negative Feedback Mechanism.

Notes Endocrine System ICSE Class 10 Biology

Gonads
1. Testes

Notes Endocrine System ICSE Class 10 Biology

• Found in males.
• Lie in scrotum.
• Interstitial cells of testes secrete testosterone.
• Testosterone is responsible for the maturation of sperms.
• Stimulates the growth and development of the male reproductive system.

2. Ovaries

Notes Endocrine System ICSE Class 10 Biology

• They are the female gonads.
• Found in females.
• They secrete oestrogen, progesterone and relaxin.
• Oestrogen is responsible for the development of ovarian follicles.
• Progesterone is responsible for the development of corpus luteum and placenta.
• Relaxin dilates the cervix towards the end of pregnancy.

Parathyroid Glands

Notes Endocrine System ICSE Class 10 Biology

• Two pairs of parathyroid glands are located on the posterior surface of the thyroid gland.
• These glands secrete parathormone (PTH).
• PTH controls calcium metabolism and maintains blood calcium at a constant level.
• Its hyposecretion causes tetany, while its hypersecretion results in demineralisation of bones.

Thymus Gland

Notes Endocrine System ICSE Class 10 Biology

• It is a bilobed gland which is present between the lungs.
• This gland produces different hormones such as thymic protein, thymosin etc.
• Functions:
o Controls the maturation and distribution of lymphocytes.
o Stimulates antibody production.

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