All Free Biology MCQs with Answers

• A. Secretin
• B. Testosterone
• C. Insulin
• D. Thyroxin

Explanation: Wm. M. Bayliss and Ernest H. Starling discovered secretin, the first hormone, in 1902. They discovered this hormone when they were studying pancreatic secretion. Secretin hormone stimulates the pancreas to secrete digestive fluid.

• A. Ovaries
• B. Testes
• C. Egg
• D. Kidneys

Explanation: The correct answer is ovaries. The ovaries are the female reproductive organs that produce eggs and secrete the hormones estrogen and progesterone. Estrogen is responsible for the development of female sex characteristics, such as breasts and hips. Progesterone is responsible for preparing the uterus for pregnancy.

• A. Cushing's disease
• B. Addison's disease
• C. Grave's disease
• D. Acromegaly

Explanation: The correct answer is Addison's disease. It is a condition where the adrenal glands are unable to produce sufficient steroid hormones due to autoimmune destruction of the adrenal cortex. This autoimmune process is the most common cause of Addison's disease. In contrast, Cushing's disease involves excessive cortisol due to a pituitary issue, Grave's disease is related to thyroid gland hyperactivity, and Acromegaly is associated with excessive growth hormone production, neither of which involve the adrenal cortex.

• A. Progesterone
• B. Parathormone
• C. Glucagon
• D. Tetraiodothyronine (T4)

Explanation: The correct answer is glucagon. Glucagon is produced by the pancreas and acts to increase blood glucose levels by promoting the conversion of glycogen to glucose in the liver, thereby antagonizing the action of insulin, which lowers blood glucose levels. Progesterone and parathormone are not involved in glucose regulation. T4 affects metabolism but does not directly counteract the effects of insulin.

• A. I only
• B. III only
• C. I and II
• D. II and III

Explanation: The correct answer is I and II. Luteinizing hormone (LH) plays a critical role in the reproductive systems of both males and females. In females, LH acts on the ovaries, triggering ovulation and stimulating the production of estrogen and progesterone. In males, LH acts on the testes, stimulating the production of testosterone. LH does not have a direct role in the functioning of mammary glands, which are primarily influenced by other hormones such as prolactin and estrogen. Therefore, options A and B are incorrect, as they exclude one of LH's primary targets, and option D is incorrect as it includes mammary glands, which are not a target of LH.

• A. A forest fire slowly expand outward, which provide it with even more fuel to burn
• B. During childbirth, oxytoxin creates a stimulus which causes the hypothalmus to release more oxytocin
• C. As more buffalo begin to run in a herd, the overall level of panic increases. This results in even more baffalo running
• D. As blood calcium level increase, parathyroid hormone (PTH) is reduced

Explanation: The release of parathyroid hormone (PTH) in response to decreased blood calcium levels helps increase calcium levels, and the subsequent reduction or cessation of PTH release occurs when calcium levels return to normal, creating a negative feedback loop.

• A. Glucagon
• B. Glucose
• C. Insulin
• D. All of these

Explanation: Glucagon is a hormone that your pancreas makes to help regulate your blood glucose (sugar) levels. Glucagon increases your blood sugar level and prevents it from dropping too low, whereas Insulin, another hormone, decreases blood sugar levels.

• A. Adrenaline
• B. Thyroid stimulating hormone
• C. FSH
• D. Antidiuretic hormone

Explanation: The posterior lobe of the pituitary gland produces two hormones, vasopressin (Antidiuretic hormone) and oxytocin. Adrenaline is released from the adrenal glands and its major action, together with noradrenaline, is to prepare the body for 'fight or flight'. Thyroid-stimulating hormone, also known as TSH, is a glycoprotein hormone produced by the anterior pituitary. Follicle-stimulating hormone (FSH) is released by the anterior lobe of the pituitary gland.

• A. Hypothalamus
• B. Midbrain
• C. Pons
• D. Cerebellum

Explanation: Neurosecretory muscles are present in the hypothalamus of the brain, where they function to produce hormones like ADH, which are then stored in the pituitary gland.

• A. Epinephrine and Nor-epinephrine
• B. GH and ADH
• C. Thyroxin and calcitonin
• D. Glucagon and insulin

Explanation: The main hormones secreted by the endocrine gland in the pancreas are insulin and glucagon, which regulate the level of glucose in the blood, and somatostatin, which prevents the release of insulin and glucagon.