Q1: Differentiate between the mechanism of action of protein hormones and steroid hormones.
Answer: Protein hormones and steroid hormones act in different ways because their chemical nature is different.
Protein hormones are water-soluble, so they cannot pass through the cell membrane. They bind to membrane-bound receptors present on the surface of the target cell. After binding, they activate second messengers such as cAMP, IP3, or Ca²⁺, which bring about changes in cellular activity.
Steroid hormones are lipid-soluble, so they can easily enter the target cell. They bind to intracellular receptors, usually present in the cytoplasm or nucleus. The hormone-receptor complex then acts on DNA and regulates gene expression.
Key points:
- Protein hormones → membrane receptor → second messenger
- Steroid hormones → intracellular receptor → gene expression
- Protein hormones act faster, steroid hormones are slower but long-lasting
Q2: Explain the antagonistic role of insulin and glucagon in glucose homeostasis.
Answer: Insulin and glucagon work in opposite ways to keep blood glucose level normal.
Insulin is a hypoglycemic hormone, which means it lowers blood glucose. It helps body cells take up glucose and also stimulates glycogenesis, where glucose is converted into glycogen for storage.
Glucagon is a hyperglycemic hormone, which means it raises blood glucose. It stimulates glycogenolysis and gluconeogenesis, which increase glucose availability in blood.
Because one lowers blood sugar and the other raises it, they act antagonistically and together maintain glucose homeostasis.
Key points:
- Insulin lowers blood glucose
- Glucagon raises blood glucose
- Both together maintain normal sugar level
Q3: What is the significance of the Hypophyseal Portal System?
Answer: The Hypophyseal Portal System is a special blood vessel connection between the hypothalamus and the anterior pituitary.
Its importance is that it carries releasing hormones and inhibiting hormones produced by the hypothalamus directly to the anterior pituitary. In this way, the hypothalamus can control the secretion of anterior pituitary hormones in an efficient and direct manner.
Key points:
- Connects hypothalamus and anterior pituitary
- Carries releasing and inhibiting hormones
- Helps in control of anterior pituitary function
Q4: List the hormones secreted by the adrenal medulla and their primary functions during stress.
Answer: The adrenal medulla secretes two hormones:
- Adrenaline (Epinephrine)
- Noradrenaline (Norepinephrine)
These are together called catecholamines and are known as emergency hormones or fight-or-flight hormones.
During stress, they:
- Increase heart rate and force of heartbeat
- Increase breathing rate
- Cause pupillary dilation
- Cause piloerection and sweating
- Stimulate breakdown of glycogen, lipids, and proteins to provide more energy
Key points:
- Hormones: Adrenaline and Noradrenaline
- Main role: fight or flight response
- Increase energy availability during stress
Q5: Describe the physiological effects of hypothyroidism during pregnancy.
Answer: If hypothyroidism occurs during pregnancy, it can affect the normal development of the baby and may lead to cretinism.
The affected child may show:
- stunted growth
- mental retardation
- low IQ
- deaf-mutism
- delayed physical and mental development
This happens because thyroid hormones are very important for normal growth and brain development.
Key points:
- Hypothyroidism during pregnancy can cause cretinism
- It affects both physical and mental development of the baby
Q6: Define 'Second Messenger' with examples.
Answer: A second messenger is a substance formed inside the target cell after a hormone binds to a membrane receptor.
It carries the signal from the cell membrane to the inside of the cell and helps produce the final response.
Common examples of second messengers are:
- cAMP
- IP3
- Ca²⁺
Key points:
- Second messenger works inside the cell
- It is formed after hormone-receptor binding
- Examples: cAMP, IP3, Ca²⁺
Q7: What are the functions of Parathyroid Hormone (PTH)?
Answer: Parathyroid Hormone (PTH) is a hypercalcemic hormone, which means it increases the level of calcium in the blood.
It does this by:
- Stimulating bone resorption, so calcium is released from bones into blood
- Increasing reabsorption of calcium in kidney tubules
- Helping increase calcium absorption from digested food
Thus, PTH is very important for maintaining calcium balance in the body.
Key points:
- PTH increases blood calcium
- Acts on bones, kidneys, and calcium absorption
Q8: Differentiate between Diabetes Mellitus and Diabetes Insipidus.
Answer: These two diseases have different causes and symptoms.
Diabetes Mellitus is caused by deficiency of insulin or reduced response to insulin. It leads to high blood glucose, glycosuria, and formation of ketone bodies.
Diabetes Insipidus is caused by deficiency of ADH (Vasopressin). In this condition, the kidneys cannot conserve water properly, so the person passes a large amount of dilute urine and feels excessive thirst.
Key points:
- Diabetes Mellitus → insulin problem → sugar in urine
- Diabetes Insipidus → ADH problem → excessive dilute urine
Q9: Name the hormones involved in the regulation of the menstrual cycle.
Answer: The major hormones involved in regulation of the menstrual cycle are:
- FSH – stimulates growth of ovarian follicles
- LH – triggers ovulation and helps maintain corpus luteum
- Estrogen – supports follicular growth and female reproductive functions
- Progesterone – prepares and maintains the uterus for pregnancy
These hormones work in coordination to control the different phases of the menstrual cycle.
Key points:
- FSH and LH control ovarian events
- Estrogen and Progesterone regulate female reproductive cycle
Q10: What is the function of Thymosins?
Answer: Thymosins are hormones secreted by the thymus gland. Their main function is to help in the differentiation and maturation of T-lymphocytes.
Because of this, thymosins play an important role in the development of immunity, especially cell-mediated immunity.
Key points:
- Thymosins → T-lymphocyte maturation
- Important for immunity
Q11: Explain the role of the Juxtaglomerular apparatus (JGA) in erythropoiesis.
Answer: The Juxtaglomerular apparatus (JGA) of the kidney secretes a hormone called erythropoietin.
This hormone acts on the bone marrow and stimulates erythropoiesis, which means formation of red blood cells.
So, the kidney helps in maintaining normal RBC count through erythropoietin.
Key points:
- JGA secretes erythropoietin
- Erythropoietin stimulates RBC formation
Q12: Why is iodine essential for the body?
Answer: Iodine is essential because it is required for the synthesis of thyroid hormones T3 and T4.
These hormones regulate:
- Basal Metabolic Rate (BMR)
- growth and development
- metabolism of carbohydrates, proteins, and fats
- normal mental development
If iodine is deficient, thyroid hormone production falls and disorders like goitre may occur.
Key points:
- Iodine is needed for T3 and T4 synthesis
- Important for metabolism and growth
Q13: What is Acromegaly?
Answer: Acromegaly is a disorder caused by excess secretion of Growth Hormone (GH) in adults.
Since adult bones cannot grow in length, excess GH causes abnormal enlargement of parts such as:
- face
- hands
- feet
It leads to severe body disfigurement and may also cause serious health complications.
Key points:
- Acromegaly = excess GH in adults
- Causes enlargement of face, hands, and feet
Q14: Describe the role of Melatonin.
Answer: Melatonin is secreted by the pineal gland. It mainly helps in regulating the 24-hour biological rhythm of the body.
Its important roles include control of:
- sleep–wake cycle
- body temperature rhythm
- metabolism
- menstrual cycle
So, melatonin helps the body maintain its natural daily rhythm.
Key points:
- Melatonin = pineal hormone
- Regulates sleep–wake cycle and biological rhythm
Q15: Which hormones are called 'Gonadotrophins' and why?
Answer: LH (Luteinizing Hormone) and FSH (Follicle Stimulating Hormone) are called gonadotrophins.
They are called gonadotrophins because they act on the gonads, that is:
- testis in males
- ovary in females
They regulate reproductive functions such as spermatogenesis, follicular growth, and ovulation.
Key points:
- LH + FSH = Gonadotrophins
- They act on the gonads