Test: Adrenal, Thymus & Pineal Gland - NEET MCQ

The triploblastic animals have three prominent germ layers known as ectoderm, endoderm and mesoderm. Thymus gland develops from two hollow elongations (third and fourth pharyngeal pouches) of endoderm which descends to the embryonic thorax by the end of eight weeks of gestation. The lymphoid cells of the gland originate from mesoderm. Thus, the correct answer is option B.

Addison's disease is caused due to hyposecretion of steroid hormones from adrenal glands. The steroid hormones are cortisol and aldosterone which are secreted from adrenal cortex.
Cretinism is the retarded mental and physical development due to hyposecretion of thyroid hormones.
Dwarfism is the retarded physical development due to hyposecretion of growth hormone during period of skeletal growth.
Sterility is the inability of an individual to produce offspring.
So, the correct answer is 'Addison's disease'.

Epinephrine is secreted from the adrenal medulla and increases heart rate.

- Adrenal medulla: Epinephrine is produced in the adrenal medulla, which is part of the adrenal glands located on top of the kidneys.
- Function: It acts as a hormone and a neurotransmitter, stimulating the "fight or flight" response in the body.
- Heart rate: Epinephrine increases heart rate by binding to beta-adrenergic receptors in the heart, leading to increased cardiac output.
- Overall impact: This physiological response prepares the body for physical activity or stress.

The correct answer is B: Immunology.

- The thymus is a crucial organ in the immune system of humans.
- It is primarily responsible for the maturation and differentiation of T-lymphocytes or T cells, which are essential for the immune response.
- T cells play a critical role in recognizing and attacking pathogens such as bacteria, viruses, and other harmful substances in the body.
- The thymus helps in training T cells to distinguish between self and non-self antigens, thus preventing autoimmune reactions.
- Overall, the thymus is vital for the development and regulation of the body's immune responses.

Addison’s disease is caused by the presence of ineffective ACTH which in turn leads to the deficiency of aldosterone and cortisol hormones of the adrenal cortex. Excessive ACTH secretion by anterior pituitary results in hyperproduction of cortisol causing Cushing’s disease. Gull's disease is caused by hypothyroidism in adults and is characterized by lethargy, hair loss and weight gain. Oversecretion of thyroid hormones causes Graves’s disease which is characterized by the formation of the exopthalamic goiter. 

- The correct answer is B: Steroids.
- Steroids are the hormones produced by the adrenal cortex and gonads (sex hormones).
- Steroids are a type of organic compound with a characteristic molecular structure containing four rings of carbon atoms.
- These hormones play crucial roles in various physiological processes in the body, including metabolism, immune response, and sexual characteristics.
- Examples of steroid hormones include cortisol, aldosterone, estrogen, and testosterone.
- Understanding the chemical nature of these hormones helps in grasping their functions in the body.

Melatonin is a hormone produced by the Pineal gland. Here's a detailed explanation:

- The Pineal gland, located in the brain, is responsible for producing and releasing melatonin.
- Melatonin plays a crucial role in regulating the sleep-wake cycle, also known as the circadian rhythm.
- This hormone helps to signal to the body when it's time to sleep and when to wake up.
- Production of melatonin is influenced by light exposure, with levels rising in the evening to promote sleepiness and dropping in the morning to encourage wakefulness.

• Pineal gland is the smallest gland in the human body with a length of about 5-8 mm.
• It is located in the epithalamus, near the center of the brain.
• The gland produces melatonin and serotonin and is, therefore, responsible for modulating sleep patterns.

Epinephrine and norepinephrine are very similar neurotransmitters and hormones. While epinephrine has slightly more of an effect on your heart, norepinephrine has more of an effect on your blood vessels. Both play a role in your body's natural fight-or-flight response to stress and have important medical uses as well.

Epinephrine and norepinephrine together known as Catecholamine.

Epinephrine and norepinephrine are two neurotransmitters that also serve as hormones , and they belong to a class of compounds known as Catecholamines. 

However, Epinephrines works on both alpha and beta receptors and norepinephrine only works on alpha receptors.

• The hypothalamus is the basal part of the diencephalon of the forebrain.
• It contains a hormone of stimulating and inhibiting the pituitary.
• The pituitary gland is also located at the base part of the brain region just below the hypothalamus and joined together whereas the pineal gland is present in the very deep region where two halves of the brain join together.
• This area is present in the middle of the brain known as the epithalamus.
• It secretes melatonin which functions during the darkness and sends information of night.

Mammals born without a thymus gland fail to manufacture T-Lymphocytes. Here's why:

- The thymus gland plays a crucial role in the development of T-lymphocytes.
- T-lymphocytes, also known as T cells, are a type of white blood cell critical for immune response.
- Without the thymus gland, T-lymphocytes cannot mature properly, leading to a compromised immune system.
- B-lymphocytes are produced in the bone marrow, so their production is not affected by the absence of the thymus gland.

Therefore, the correct answer is B: T-Lymphocytes.

The correct answer is A: Adrenal cortex.

- The adrenal cortex is responsible for the production of aldosterone, a hormone that regulates sodium retention in the body.
- Aldosterone acts on the kidneys to increase the reabsorption of sodium and water, helping to maintain blood pressure and electrolyte balance.
- Sodium retention is crucial for maintaining proper fluid balance and blood pressure regulation in the body.
- The adrenal medulla primarily produces adrenaline and noradrenaline, which are involved in the body's fight-or-flight response.
- Parathyroid hormones regulate calcium levels, while thyroid hormones control metabolism.

The correct answer is C: Glucocorticoids.

- Glucocorticoids, produced by the adrenal cortex, regulate carbohydrate metabolism.
- These hormones, like cortisol, help in maintaining blood sugar levels by promoting gluconeogenesis (formation of glucose from non-carbohydrate sources) and inhibiting glucose uptake in peripheral tissues.
- They also play a role in suppressing the immune system and reducing inflammation.
- Glucocorticoids are essential for the body's response to stress and help in adapting to changing metabolic demands.

The cells of the Zona Fasciculata secrete the glucocorticoids Cortisol and Corticosterone. These hormones regulate carbohydrate metabolism, particularly when an individual is in a time of stress (as part of the “fight-or-flight” response).

• The thymus is an endocrine gland that is located beneath the sternum and between the lungs.
• Thymosin is secreted from there, and T lymphocyte differentiation occurs there.
• Production of antibodies is encouraged.
• However, in elderly people, the thymus degenerates.

Hyperaldosteronism is a disease in which the adrenal gland(s) make too much aldosterone which leads to hypertension (high blood pressure) and low blood potassium levels.

• Just above the kidneys are the adrenal glands. It is shaped like a pyramid.
• The thymus is situated between the lungs, the pituitary gland is situated at the base of the hypothalamus, and the thyroid gland is situated surrounding the trachea.

To explain why the correct answer is C (Both):

- Adrenaline, also known as epinephrine, affects the body in various ways.
- It stimulates the release of glucose from energy stores, providing a quick energy boost.
- Adrenaline also increases heart rate (A) by acting on the heart's pacemaker cells.
- Moreover, it causes blood vessels to constrict, leading to increased blood pressure (B).
- Therefore, the correct answer is C as adrenaline elevates both heart rate and blood pressure simultaneously.

When the renal blood flow is reduced, juxtaglomerular cells in the kidneys convert the prorenin in the blood into renin and secrete into circulation. Plasma renin performs the conversion of angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II by the enzyme angiotensin-converting enzyme. Angiotensin II causes blood vessels to constrict, resulting in increased blood pressure. Angiotensin II also stimulates the secretion of the hormone aldosterone from the zona glomerulosa of adrenal cortex. Aldosterone causes the tubules of the kidneys to increase the reabsorption of sodium and water into the blood. This increases the volume of fluid in the body, which also increases blood pressure.

Thus, the correct answer is option A.

Adrenaline is produced in the medulla of the adrenal gland. The overall effect of adrenaline is to prepare the body for the fight or flight response in times of stress, i.e., for vigorous sudden action. 

Key actions of adrenaline include increasing the heart rate, increasing blood pressure, expanding the air passages of the lungs, enlarging the pupil in the eye, redistributing blood to the muscles and altering the body's metabolism, so as to maximise blood glucose levels (primarily for the brain).
Progesterone allows the blastocyst for implanting and develop and protects against the expulsion of the developing pregnancy. Progesterone declines towards the time of delivery, leaving oestrogen to increase the uterine contractility.

So, the correct answer is option C.C.W

A T cell is a type of lymphocyte, which develops in the medulla region of the thymus gland (hence the name) and plays a central role in the immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor on the cell surface. T cell differentiation continues even after they have left the thymus.

• The thymus gland is lobe-shaped. It functions as an essential lymphatic organ.
• Between the lungs and behind the sternum is where the thymus is situated. Thymosin, a peptide hormone, is released by it.
• The thymus gland supports the development of T-lymphocytes, sometimes referred to as T-cells, which are specialized white blood cells.
• The thymus gland receives lymphocytes from the bone marrow, which are white blood cells.
• The lymphocytes in the thymus mature into particular T-cells.
• Before entering circulation, T-cells are in the process of development.
• They travel to the lymph nodes, which are cellular collections, and other organs of the lymphatic system, where they support the immune system’s defense against disease and infection.

During normal human sexual development the adrenal gland undergoes a maturational process, termed adrenarche, which results in increased adrenal secretion of androgens and estrogens. Adrenarche begins several years before the onset of gonadal maturation and correlates with the appearance of the adrenal reticular zone. In normal puberty, adrenarche and gonadarche (gonadal maturation) are closely linked, but in pathological situations adrenarche can occur without gonadarche, and gonadarche without adrenarche.

Melatonin is secreted by the Pineal body. Here's why:

- The Pineal gland, also known as the Pineal body, is a small endocrine gland in the brain.
- Melatonin is a hormone produced by the Pineal gland, primarily at night, helping regulate sleep-wake cycles.
- It plays a crucial role in maintaining the body's circadian rhythm, influencing when you feel sleepy and when you wake up.
- Melatonin production is stimulated by darkness and inhibited by light, hence its association with sleep regulation.

Therefore, the correct answer is A: Pineal body.

Middle lobe of pituitary secretes MSH(melanocyte stimulating hormone) that controls the synthesis of melanin granules in the chromatophores.

Thymosin stimulates T-lymphocytes. Here's why:

- Thymosin is a hormone that plays a crucial role in the development and maturation of T-lymphocytes, which are a type of white blood cell essential for the immune system.
- T-lymphocytes are produced in the thymus gland, and thymosin aids in their differentiation and maturation process.
- This hormone helps in the regulation of the immune response by ensuring the proper functioning of T-lymphocytes in recognizing and fighting off pathogens.

Correct Answer: A. Option A is correct.

Explanation: Adrenal cortical hormones are indeed known as corticosteroids. Cortisol is a glucocorticoid, aldosterone is a mineralocorticoid, and the adrenal cortex does produce small amounts of androgenic steroids.