BIOLOGY 2 Marks Questions

Adrenal: The adrenal gland is divided into two parts, the outer adrenal cortex and the inner adrenal medulla. Hormones of adrenal cortex include the following:

1. Mineralocorticoids: The hormone secreted is known as aldosterone.
2. Glucocorticoids: The hormone secreted is cortisol.

Hormones of adrenal medulla are adrenaline and nor-adrenalin.

Hormones: Hormones are chemical messengers that regulate physiological processes in living organisms. They act upon specific cells/ tissues/ organs which are called target cells/ tissues/ organs.

Exocrine glands: Glands that discharge secretions into ducts are known as exocrine glands. Sebaceous gland in the skin, salivary gland in the buccal cavity, etc. are examples of exocrine glands.

Endocrine glands: Glands that do not discharge their secretions into ducts are known as endocrine glands. Instead, these glands discharge their secretions directly into the blood. Pituitary gland, thyroid gland, adrenal gland, etc. are examples of endocrine glands.

Thyroid hormones: Thyroid hormones play an important role in the regulation of the basal metabolic rate. These hormones also support the process of red blood cell formation. Thyroid hormones control the metabolism of carbohydrates, proteins and fats. Maintenance of water and electrolyte balance is also influenced by thyroid hormones. Thyroid gland also secretes a protein hormone called thyrocalcitonin (TCT) which regulates the blood calcium levels.

S. No	Diabetes Insipidus	Diabetes Mellitus
1.	It is a disorder caused by deficiency of vasopressin.	It is a disorder caused by deficiency of insulin.
2.	Urine does not show glucose.	Glucose appears in the urine.

Jet lag is caused by the disruption of the body clock as it is out of synchronisation with the unfamiliar time zone of the two different parts of the world. The body experte experiences different patterns of light and dark than it is normally used to which disrupts the natural sleep-wake cycle. Melatonin is a hormone that plays a key role in body rhythms and jet lag. After the Sun sets, the eyes perceive darkness and alert the hypothalamus to begin releasing melatonin, which promotes sleep. Conversely, when the eyes perceive sunlight, they tell the hypothalamus to with-hold melatonin production. However, the hypothalamus cannot read just its schedule instantly, it takes several days.

Glucagon and insulin.

Epinephrin and non-epinophrine.

Insulin, glucagon, follicle-stimulating hormone.

Differences between hyperglycaemia and hypoglycaemia are:

S. No.	Hyperglycaemia	Hypoglycaemia
1.	It results from hyposecretion of insulin.	It results from hypersecretion of insulin.
2.	Its symptoms include high blood glucose level, breakdown of muscles tissues, loss of weight and tiredness.	Its symptoms include low blood glucose level, hunger, sweating, irritability, double vision.

Although hormones are present in very small amounts, they effectively regulate many physiological processes. This is the result of signal amplification, an increase in signal strength. For example, a single hormone receptor complex can stimulate the production of many cAMP molecules. In turn, each cAMP can activate a protein kinase that phosphorylates many protein molecules. In this way, a single hormone molecule can activate many proteins.

Insulin will lowers blood glucose level by:

1. Stimulating transport of glucose from blood to muscle and adipose cells and indirectly causing the liver to take up glucose.
2. Promoting both oxidation of glucose and conversion of glucose into glycogen in muscles and liver cells.
3. Inhibiting metabolic breakdown of stored glycogen in liver and muscle cells.
4. Promoting synthesis of fats from glucose by adipose tissue and also inhibiting metabolic breakdown of fat.

1. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) are the gonadotropins.
2. Since they regulate the activity of gonads (testes in males and ovaries in females), they are called gonadotropins.
3. Since they regulate the activity of gonads (testes in males and ovaries in females), they are called gonadotropins.

Hormones of adrenal medulla, i.e., adrenaline and noradrenaline (belong to the category of compounds called catecholamines) are secreted in response to any kind of stress, danger and during emergency situations like fall in blood pressure or sugar, increase respiratory rate and heartbeat. CNS at the time of stress or danger stimulates adrenal medulla to release these hormones. All these conditions need more energy for their action. Thus, because these hormones prepare the body to face stress or danger hence, are called emergency hormones.

Following are the functions performed by progesterone:

1. Helps in maintaining pregnancy.
2. Stimulates the development of secretory alveoli in mammary glands and secretion of milk.
3. Its secretion is influenced by luteinising hormone of anterior pituitary.

Progesterone; it is secreted by the corpus luteum of the ovary.

Hypothalamic hormones are of two types:

1. The releasing hormones: They stimulate the secretion of pituitary hormone, e.g. gonadotropin releasing hormone.
2. The inhibiting hormones: They inhibit the secretion of pituitary hormones, e.g. somatostatin.

1. Four parathyroid glands.
2. They are present on the back of thyroid gland, one pair each in the two lobes of the thyroid.
3. It secretes parathyroid hormone (PTH).

1. Thymus gland is located between the lungs behind the sternum on the ventral side of aorta.
2. This gland plays a major role in the development of immune system of of the body in the following ways.

• The thymosins secreted by the thymus has a role in the differentiation of T-lymphocytes, which provide cell-mediated immunity.
• It also stimulates the production of antibodies, which provide humoral immunity.

The posterior pituitary releases vasopressin and oxytocin.Vasopressin:

• It acts on the kidney tubules and stimulates the reabsorption of water and electrolytes by the distal tubules and reduces the loss of water in the urine, i.e. it prevents diuresis.

Oxytocin:

• It stimulates the vigorous contractions of smooth muscles of uterus to effect childbirth.
• It also stimulates milk ejection from the mammary glands.

S. No	Glycogenesis	Glycogenolysis
1.	It is the process of formation of glycogen from glucose.	It is the process of breakdown of glycogen.
2.	It is stimulated by by insulin.	It is stimulated glucagon, cortisol and adrenaline.
3.	It results in hypoglycemia.	It results in hyperglycemia.

1. The neurosecretory cells of hypothalamus secrete vasopressin.
2. It is stored in the posterior pituitary.
3. It acts on the kidney tubules.
4. It stimulates reabsorption of water and electrolytes from the distal part of the tubules and reduces the loss of water through urine, i.e., it prevents diuresis.

Adrenocorticotropin is secreted when adrenocorticotropin Releasing Hormone (ACRH) stimulates the corticotroph cells of the anterior lobe of pituitary gland. It is released because its stimulation is responsible for the synthesis and secretion of glucocorticoid steroid hormone from the adrenal cortex of adrenal gland.

Differences between endocrine and exocrine glands are:

S. No	Endocrine Glands	Exocrine Glands
1.	They do not have ducts.	They have ducts.
2.	They secrete hormones directly into the blood.	They secrete their secretions into the ducts.
3.	e.g., thyroid, hypothalamus, pituitary, etc.	e.g., sweat and oil glands (of skin) liver and salivary glands.

Adrenaline and noradrenaline are rapidly secreted in response to stress of any kind and during emergency situations and are called emergency hormones or hormones of Fight or Flight. These hormones increase alertness, pupilary dilation, piloerection (raising of hairs), sweating etc. Both the hormones increase the heart beat, the strength of heart contraction and the rate of respiration. Finally the body is ready to counter the emergency situations.

1. Aldosterone is the main mineralocorticoid in our body.
2. Its function is to maintain.

• Volume of body fluids
• Osmotic pressure of body fluids.
• Electrolyte balance.
• Blood pressure.

Endocrine glands are tubeless glands and their secretion is directly released on the target site. Because of the absence of tubes the hormone is secreted in the gland itself hence the name endocrine gland is given for them.

1. In adult women, it causes irregularities in the menstrual cycle.
2. In pregnant women, it causes defective development and maturation of the foetus, leading to the birth of a child with cretinism.

Hormones are known as informational molecules because their synthesis takes place in one part of the body, i.e., the endocrine cells and are carried by the blood to another part of the body, i.e., target organ or tissues where they stimulate or inhibit the specific physiological processes according to the need of the body.

Characters which do not play direct role in sexual reproduction but are basically means of sexual differentiation are called secondary sexual characters. For example, facial hair and deep voice in males and thin voice in females are secondary sexual characters.

1. Estrogens and progesterone are the steroid hormones produced by the ovaries.

1. Estrogens stimulate the growth, and activities of secondary sex organs, ovarian follicles and female sexual features.
2. Progesterone is necessary to maintain pregnancy and it stimulates the growth of secretory alveoli and secretion of milk by the mammary glands.

2.  

1. Thyroid stimulating hormone.
2. Anti-diuretic hormone.

• Leydig cells/ Interstitial cells.
• They are located in the intertubular spaces or interstitial tissue.

1. Gastrin controls the secretion of gastric juice by the gastric glands.
2. Secretin acts on the exocrine region of pancreas and stimulates the secretion of water and bicarbonate ions.
3. Cholecystokinin (CCK) acts on pancreas to secrete pancreatic enzymes; it also acts on gall bladder to release bile juice into duodenum.
4. Gastric Inhibitory Peptide (GIP) inhibits gastric secretion and motility.

In the absence of iodine, neither thyroxine nor triiodothyronine hormone is produced, due to which their concentration in the blood decreases. To compensate this, the anterior pituitary secretes large amounts of TSH, which stimulate the growth of the thyroid gland, sometimes to gigantic proportions, leading to formation of goitre. However, enlargement of the gland cannot increase production of the hormones, because of the deficiency of the of main ingredient, i.e., thyroxine hormone.

1. Thymus gland is responsible for this.
2. It secretes hormone thymosin.
3. Thymosins play a major role in the differentiation of T-lymphocytes that provide cell-mediated immunity.
4. They also stimulate the formation of antibodies that provide humoral immunity.

1. It is a form of hyperthyroidism, also known as Grave's disease.
2. Its symptoms are:

• Enlargement of thyroid gland.
• Protrusion of eyeball.
• Increased basal metabolic rate.
• Weight loss.

Estrogen, progesterone, epinephrine, testosterone.

1. Deficiency of insulin:

• Loss of glucose in urine.

2. Deficiency of thyroid hormones (thyroxine) during pregnancy in the mother:

• Mental retardation.
• Stunted growth.

1. MSH.
2. Glucagon.
3. Relaxin.
4. Interstitial cells.

The thymus gland secretes the hormone thymosin which plays a major role in differentiation of T-lymphocytes. T-lymphocytes are responsible for cell mediated immune response. In old age, the thymus gland gets degenerated resulting in reduced production of thymosin. Hence, old people have weak immune system.

LH stimulates the synthesis and secretion of androgens called male hormones. In females, LH is essential for ovulation. In females, LH induces ovulation of fully mature follicles (graafian follicles) and maintains the corpus luteum formed from the remnants of the graafian follicles after ovulation.

1. Juxtaglomerular cells.
2. Growth factors.

Melanin controls the circadian variations of the body. During 24 hours different organ system of our body works at different pace. During sleep certain body functions slow down. All of this is known as circadian rhythm. Additionally, melanin influences metabolism, pigmentation, menstruation and defence capability.

S. No	Hypothyroidism	Hyperthyroidism
1.	It refers to the deficient production of thyroid hormones.	It refers to the excess production of thyroid hormones.
2.	The basal metabolic rate is decreased.	The basal metabolic rate increases.
3.	It is caused by deficiency of iodine.	It is caused by tumor or cancer of thyroid glands.

It is a type of hormonal interaction, where two or more hormones complement each other's actions and both are needed for full expression of the hormone effects. e.g., the production, secretion and ejection of milk by mammary glands require the synergistic effects of oestrogens, progesterone, prolactin and oxytocin.

The hypothalamic hormones secreted by the neurosecretory cells called nuclei, transport through their axons and released from their nerve endings and mixed with blood of hypophyseal portal vein. These are then transported to anterior pituitary. The posterior pituitary hormones pass through the axons that reach the posterior pituitary and remain stored in the axon terminals, till they are stimulated for release.

1. Cortisols stimulate gluconeogenesis, lipolysis and glycogenolysis, to increase the blood glucose level.
2. They control cardiovascular system and blood pressure.
3. They inhibit inflammatory reactions by suppressing immune system.
4. They stimulate RBC production (erythropoiesis).

It refers to the effect of a hormone that are countered by an antagonistic (opposing) signal, often another hormone. For example, the sympathetic and parasympathetic nervous systems achieve antagonistic effect on heartbeat. This mechanism involves the use of more than one second messenger. In heart cells cyclic form of adenosine monophosphate (CAMP) serves as a second messenger, speeding up muscle cell contraction in response to adrenaline, while cyclic guanosine monophosphate (CGMP) serves as another second messenger, slowing muscle contraction in response to acetylcholine.

Excess secretion of growth hormone in adults, especially in middle age can result in severe disfigurement (especially of the face). This is called acromegaly. This can lead to serious complications and even death; if unchecked. The disease is hard to diagnose in the early stages and is frequently missed for many years, until changes in external features become noticeable.

Acromegaly refers to the severe disfigurement, especially of the face, due to excess secretion of growth hormone in adults. It may lead to death, if not treated.

S. No	Neural system	Endocrine system
1.	This provides point-to-point coordination in the form of electrical impulses through nerves.	This provides co-ordination through hormones, which are secreted by the endocrine glands into the blood.
2.	It is fast, but short lived.	It is slow, but effects prevail for sometime.

Functions of thymus are as follows:

1. It secretes thymosin, a peptide hormone that plays an important role in differentiation of T-lymphocytes.
2. Release of thymosin provides cell-mediated immunity.
3. It is also responsible for creating antibodies for the immune system during childhood.
4. It gets degenerated with age due to which production of thymosin gets decreased.

Zona glomerulosa, Zona fasciculata and Zona reticularis.

1. The hormones are corticoids.
2. Glucocorticoids, mineralocorticoids and androgenic steroids.

1. It is a disease caused by defeciency of mineralo corticoids.
2. Adrenal cortex.
3. Disturbance in level of electrolytes, body fluid volume osmotic pressure and blood pressure of the body.
4. Akash's father is protective, caring and concerned for his son's health.