BIOLOGY – CLASS X THE ENDOCRINE SYSTEM Q1. Define the following termsa. Endocrine glands- are the ductless glands which secrete chemicals called hormones which are poured directly into the blood. b. Hormones – are the secretions of the endocrine glands, which are transported by the blood to the target cells. c. Homeostasis – is a state of equilibrium produced by a balance of functions and of chemical composition within the body of an organism. Q2. Why are hormones often referred to as ‘chemical messengers’? Hormones are produced in the body in response to changes in the environment within or outside the body and thus help maintain homeostasis in the body of the individual. Q3. List out the characteristics and functions of hormones
Hormones are secretions of the endocrine glands which are poured directly into the blood. They are produced in very small amounts. Chemically, hormones may be proteins, polypeptides, amino acid derivatives or steroids. Their action occurs in another part of the body far away from the source of production. They are specific in their action –certain organs respond only to certain hormones. Hormones help adjust and restore homeostatic balance. They help the body cope with infections, stress, trauma, starvation and extreme temperatures.
Q4. Differentiate between exocrine and endocrine glands.
Exocrine gland They are glands with ducts. Their secretions maybe enzymes, sweat, oil, or tears The dutcs transport these secretions to a region close to the source of production. Eg. Sweat gland, salivary gland
Endocrine gland They are ductless glands Their secrete chemicals called hormones They are transported by the blood to target cells far away from the source of production. Eg. Adrenal gland, thyroid gland
Q5. Differentiate between hormones and enzymes.
Hormones Secretions of endocrine glands Chemically maybe steroids, proteins or amino acid derivatives Transported by blood Reaction occurs away from the site of secretion in target cells or organs. They may accelerate or inhibit specific activity. Their action may be slow or quick
Enzymes Secretions of exocrine glands. Chemically always proteins
Transported by ducts. Reaction occurs close to the site of secretion Always accelerate chemical reactions
Their action is always quick.
Q6. Differentiate between nervous control and endocrine control
Nervous control Works by the conduction of nerve impulses. Works rapidly. Nerve impulse is conducted thorough nerve fibres. Effects of nerve impulses are shortlived Does not influence chemical changes and cannot regulate metabolism. Does not affect growth. THE ENDOCRINE SYSTEM
Endocrine control Works by release of hormones.
Works slowly. Hormones travel via the blood.
It has a prlonged effect. It brings about specific chemical changes and regulates metabolism. Affects growth
EXOCRINE GLAND – these cells produce pancreatic juice which is transported by the pancreatic duct to the duodenum ( target organ)
PANCREATIC GLAND
ENDOCRINE GLAND- these cells called the Islets of Langerhans produce hormones which are transported by the blood to the target cells
STRUCTURE – flattened leaf like. Three types of cells are differentiated in the Islets of Langerhans. They are the alpha, beta and the delta cells.
LOCATION –below the stomach, at the loop of the duodenum
FUNCTION
ALPHA CELLS secrete Glucagon. It converts the glycogen stored in the liver into glucose. It thus increases the glucose level in the blood. Secretion of glucagon is stimulated whenever there is a low level of glucose in the blood and while exercising.
BETA CELLS secrete Insulin. It converts the glucose in the blood into glycogen to be stored in the liver and muscles. It thus checks the level of glucose in the blood.
HYPERSECRETION – increased secretion of insulin leads to hypoglycemia or decreased levels of glucose in the blood. If the glucose level falls too low, a person may enter into a coma state or may become unconscious. An excess intake can also cause this. Symptoms –weakness, tremor, sweating Question - Insulin is administered to individuals suffering from diabetes mellitus in the form of injection and not in the form of tablets. Answer- Insulin is proteinaceous in nature and hence undergoes digestion, if taken orally as a tablet. When injected, it is directly transported by the blood to the target cells.
HYPOSECRETION- of insulin causes diabetes mellitus. In this disease the liver and muscle cells are unable to convert the glucose to glycogen, hence level of glucose in blood rises. This condition is also called Hyperglycemia. Symptoms- increased thirst , frequent urination, with presence of glucose in the urine (sweet or honey like).
LOCATION- fits like a cap above each kidney. OR Is found superior to each kidney.
ADRENAL ADRENALGLAND GLAND
STRUCTURE- is divided into an outer adrenal cortex and an inner adrenal medulla.
FUNCTION
ADRENAL MEDUL LA – Secretes a hormone called Adrenalin or Epinephrine
ADRENAL CORTEXsecretes 3 hormones 1. Mineralocorticoids 2. Glucocorticoids 3. Sex corticoids Eg. Aldosterone Regulates metabolism of K+ and Na+ ions. Stimulates kidneys to retain Na+and excrete K + ions
Eg. Cortisones Regulates carbohydrate and protein metabolism Eg. Androgens Stimulates the development of external secondary sexual characteristics in males and females
HYPOSECRETION ADDISON’S DISEASE Skin pigmentation Hypoglycemia Low energy levels
HYPERSECRETION CUSHING’S SYNDROME Moon face Buffalo hump Spindly legs Hyperglycemia
ROLE OF ADRENALIN 1. Stimulates the breakdown of glycogen in muscles and hence increases glucose level in the blood. 2. Increases the contractility of muscles. 3. Helps body to adapt to various situations such as stress, trauma, fasting, starvation, etc 4. Is often called the “emergency hormone” or the “flight and fight hormone”. Hypersecretion of adrenalin puts an individual through a prolonged version of “fight or flight response” which in the long run wears out the body.
Question: What is “Adrenal virilism”? Androgens are male sex hormones produced in the testes and in the adrenal cortex. It regulates secondary sexual characteristics in the male. Appearance of some male characters in the female is called virilism. Excess secretion of adrenal androgen in female produce male secondary sexual characteristics such as appearance of beard, low pitched voice and under developed breasts.
STRUCTUREButterfly shaped , bilobed structure. The two lobes are joined by a narrow piece of tissue called isthmus.
THYROID GLAND
LOCATION – situated on the lateral and ventral sides of the trachea, just below the larynx
FUNCTION- secretes an hormone called thyroxin. Iodine is an important constituent of thyroxin. 1. This regulates the basal metabolism,(BMR) which is the rate of cellular oxidation ,resulting in heat production and energy formation when the body is at rest. 2. It regulates general physical and mental growth and development esp. in children. 3. It controls body weight.
HYPOSECRETION
CRETINISM- caused due to under secretion of thyroxin in the growth years. This is characterized by low metabolic rate, retarded physical, mental and sexual development.
HYPERSECRETION
MYXOEDEMA-caused due to the under secretion of thyroxin in an adult. Symptoms include puffiness and swelling(edema) of facial muscles due to fluid retention. Low metabolic rate, low body temp. and general lethargy.
EXOPHTHALMIC GOITRE- Its symptoms include protrusion of the eyeballs due to fluid retention behind the eyes. Metabolic rate becomes high, high body temp. sweating, high blood pressure.
SIMPLE GOITRE- caused due to iodine deficiency in one’s diet. It leads to an enlargement of the thyroid gland to step up production of thyroxin. Hence it manifests as a swelling in the neck.
Note- In ageing thyroid, body activities slow down and heat production reduced. So, old tend to feel cold faster.
LOCATION –ATTACHED TO THE HYPOTHALAMUS OR BELOW THE HYPOTHALAMUS.
PITUITARY GLAND
STRUCTURE - pea sized gland. Divided into a larger anterior lobe and a smaller posterior lobe. In between is an intermediate lobe which is more developed in animals.
FUNCTION
ANTERIOR LOBE
Hgh or the human growth or Somatotropin regulates normal body growth
TSH- thyroid stimulating hormonestimulates thyroid gland to produce thyroxin
Hyposecretion in the growing years results in dwarfism .
POSTERIOR LOBE
Tropic hormones – stimulate other endocrine glands to secrete their hormones
ACTH- Adreno cortico tropic hormonestimulates the adrenal cortex to produce its hormones
Hypersecretion in growing years causes gigantism. In an adult, it results in Acromegaly – disproportionate growth of bones.
FSH -follicle stimulating hormone – stimulates testes to produce sperms and ovaries to produce ova.
Oxytocin –stimulates the contraction of the uterine muscles at child birth
LH- Luteinizing hormone – stimulates the testes to produce testosterone and the ovaries to produce progesterone and oestrogen
Vassopressin or ADH-Anti Diuretic Hormone-regulates the reabsorption of water in kidney tubules
Prolactin – stimulates the breasts to produce milk at child birth.
Hyposecretion causes Diabetes insipidus or excessive urine formation which leads to dehydration and extreme thirst.
