System Physiology Animal MCQ Quiz - Objective Question with Answer for System Physiology Animal - Download Free PDF

The correct answer is Histamine

Explanation:

• Eosinophils are a type of white blood cell that play a key role in the immune response. They contain granules filled with various molecules that help them perform their functions.
• Eosinophilic granules contain a variety of proteins and enzymes, including ribonucleases, cytokines, and chemokines, which contribute to their immune functions.
  • Ribonucleases: These are enzymes found in eosinophilic granules that degrade RNA, playing a role in controlling viral infections and inflammatory responses.
  • Cytokines: These are signaling proteins that are found in eosinophilic granules and are important for cell signaling in the immune system. They help in the communication between cells to trigger the protective defenses of the immune system.
  • Chemokines: These are a subset of cytokines found in eosinophilic granules that induce chemotaxis in nearby responsive cells. They play a crucial role in guiding the movement of immune cells to the site of infection or inflammation.
• Histamine is not typically found in eosinophilic granules. It is primarily stored in and released by mast cells and basophils, other types of white blood cells involved in the immune response.

The correct answer is (B), (A), (D), (C)

Explanation:

• Adenoids (B): The adenoids, also known as pharyngeal tonsils, are located in the roof of the nasopharynx, which is in the upper part of the throat behind the nose. 
• Thymus (A): The thymus is located in the anterior part of the upper chest, just behind the sternum (breastbone) and in front of the heart.
• Spleen (D): The spleen is located in the left upper quadrant of the abdomen, behind the stomach and under the diaphragm.
• Peyer’s patches (C): Peyer's patches are found in the ileum of the small intestine, more posteriorly and inferiorly in the abdominal cavity.

Source:https://www.sciencedirect.com/topics/medicine-and-dentistry/organs-of-the-immune-system

Thus, the order of appearance of these organs from anterior to posterior direction is Adenoids (B) → Thymus (A) → Spleen (D) → Peyer's patches (C)

The correct answer is (A), (C), (D) and (E) only

Explanation:

Cortisol is a steroid hormone produced by the adrenal glands. It is often referred to as the "stress hormone" because it is released in response to stress and low blood-glucose concentration. Cortisol plays a crucial role in various bodily functions, including metabolism, immune response, and the body's response to stress.

• (A) It decreases the circulating lymphocytes: Cortisol has immunosuppressive effects and can decrease the number of circulating lymphocytes, which are a type of white blood cell involved in the immune response.
• (C) It decreases the production of prostaglandins: Cortisol inhibits the enzyme phospholipase A2, which is involved in the production of arachidonic acid. Arachidonic acid is a precursor for prostaglandins, which play a role in inflammation and pain. Therefore, cortisol reduces the production of prostaglandins.
• (D) It inhibits the production of fibroblasts: Cortisol can inhibit fibroblast proliferation and function. Fibroblasts are cells that produce collagen and other extracellular matrix components, which are essential for wound healing and tissue repair.
• (E) It alters immune system responses and suppresses the digestive and the reproductive systems: Cortisol can alter immune responses by suppressing inflammation and the activity of various immune cells. It also affects other systems in the body, including the digestive and reproductive systems, by diverting energy away from these functions during stress.
• (B) It increases the circulating eosinophils: Cortisol typically causes a decrease in the number of eosinophils, which are a type of white blood cell involved in allergic reactions and parasitic infections.

The correct answer is The endometrium shed by the uterus, during the estrous cycle, is reabsorbed, but the shed endometrium is excreted from the body, during the menstrual cycles.

Explanation:

Estrous and menstrual cycles are two types of reproductive cycles occurring in female mammals after they reach sexual maturity. Both cycles are induced by reproductive hormones and are designed to prepare the female body for potential pregnancy.

Endometrium Shedding: In the estrous cycle, which occurs in most non-primate mammals, the endometrium (the lining of the uterus) is reabsorbed by the body if pregnancy does not occur. In the menstrual cycle, which occurs in primates including humans, the endometrium is shed and expelled from the body through menstruation if pregnancy does not occur.

Other Options (Incorrect):

• Behavioral Changes: Behavioral changes are usually more pronounced in the estrous cycle, where females exhibit clear signs of estrus (heat) to signal fertility.
• Season and Climate:  This is incorrect as many animals with estrous cycles are highly influenced by seasonal changes, which can determine their breeding periods.
• Cycle Duration: This is incorrect as the duration of estrous cycles can vary widely among different species, but they are not generally longer than menstrual cycles.

The correct answer is (E), (D), (C), (B), (A)

Explanation:

Blood clot formation, also known as coagulation, is a complex process that prevents excessive bleeding when a blood vessel is injured. It involves multiple steps that are initiated when a blood vessel is damaged, leading to the formation of a stable blood clot that seals the injury.

• Step (E) - Reduction of blood loss by initiation of a vascular system: When a blood vessel is injured, the first response is vasoconstriction, which reduces blood flow to the area and minimizes blood loss.
• Step (D) - Prothrombinase formed by extrinsic or intrinsic pathway: The damaged tissue exposes collagen and tissue factors that activate the extrinsic and intrinsic pathways, leading to the formation of prothrombinase.
• Step (C) - Adhesion and aggregation of platelets on damaged vessels: Platelets adhere to the exposed collagen and aggregate to form a temporary platelet plug at the site of injury.
• Step (B) - Conversion of prothrombin to thrombin: Prothrombinase converts prothrombin (a plasma protein) into thrombin, an enzyme that plays a critical role in the next step of coagulation.
• Step (A) - Conversion of fibrinogen to fibrin: Thrombin converts fibrinogen (a soluble plasma protein) into fibrin strands, which weave through the platelet plug to form a stable and insoluble clot.

The correct answer is B and C.

Explanation:

Thermoregulatory mechanisms are essential for maintaining body temperature within a narrow optimal range despite varying external conditions. Let's evaluate each statement about thermoregulation to determine their correctness.

A. Human voluntary activity is decreased in cold: Incorrect

• In cold environments, humans may reduce voluntary activity to conserve energy and minimize exposure to the cold. Movements and activities that generate heat might be reduced as part of an adaptive response to maintain core body temperature. However, sometimes shivering, an involuntary activity, increases which contributes to heat production.
• Voluntary activity might not decrease uniformly because shivering can be considered an involuntary response to generate heat.

B. There is a cutaneous vasodilation by heat: Correct

• When the body is exposed to heat, cutaneous (skin) blood vessels dilate (vasodilation) to increase blood flow to the skin. This helps release excess heat from the body through radiation, convection, and evaporation, thereby cooling the body.

C. There is an increased secretion of epinephrine and nor-epinephrine in cold: Correct

• In cold environments, the body increases the secretion of epinephrine and norepinephrine (catecholamines) which stimulate metabolic processes, increasing heat production. These hormones aid in thermogenesis by promoting glycogenolysis and lipolysis, which generate heat.

D. There is a decreased heat production in cold: Incorrect

• When exposed to cold, the body typically increases heat production through mechanisms such as shivering (which generates heat through muscle activity) and non-shivering thermogenesis (increased metabolic activity mediated by hormones like epinephrine and norepinephrine).

Conclusion: Combining the evaluations, the statements that are correct regarding thermoregulatory mechanisms are: B and C

The correct answer is 32.

Explanation:

Calcitonin is a polypeptide hormone produced by the C-cells (also known as parafollicular cells) of the thyroid gland. It plays a crucial role in regulating calcium levels in the blood by lowering them when they are elevated.

The primary structure of calcitonin in humans consists of 32 amino acids. This sequence includes several important functional residues that contribute to its biological activity, including its ability to inhibit osteoclast activity and reduce bone resorption, leading to a decrease in blood calcium levels.

Thus, calcitonin is composed of 32 amino acids, making 32 the correct answer.

The correct answer is Option 3 i.e.Their half-life is 20-24 days.

Key Points

• Blood is the connective tissue that is composed of an extracellular matrix called blood plasma.
• It consists of two main components: plasma and blood cells. 
• Following are different types of blood cells.

1. RBC: 
   • They are circular and biconcave-shaped cells. 
   • It has a diameter of about 7-8μ 
   • The total number of RBCs in females is about 4.8 million RBCs per microliter of blood and about 5.4 million RBCs per microliter of blood in males.
   • It contains a red respiratory pigment called hemoglobin. 
   • The life span of RBCs is about 120 days.
2. WBC:
   • Eosinophils - It is granulocyte, that contains larger granules in the cytoplasm, these granules contain histamine. It has a diameter of about 10-15μ. The nucleus is bilobed. 
   • Basophils - It is granulocytes, that contain smaller granules in larger number. It has a diameter of about 8-10μ. It has an S-shaped nucleus. 
   • Neutrophils - It is granulocytes, that contain the finest granules in the cytoplasm. It is about 10-12μ in diameter. It has a multilobed nucleus. 
   • Lymphocytes - It is the smallest WBCs. It has a diameter of about 8-12μ. It has large, spherical and surrounded by a thin layer of cytoplasm. It has a lifespan of about 24 hours in lymph and about 00 days in the bloodstream.
   • Monocytes - It is the largest WBCs. It has about 15-22μ diameter. It has a kidney-shaped nucleus that is surrounded by abundant cytoplasm. It has a lifespan of about 3 days. 
3. Platelets:
   • They are small and non-nucleated. It has a diameter of about 2-4μ.
   • They are formed by the fragmentation of large cells called megakaryocytes of bone marrow. 
   • Their life span is about 12 days in the bloodstream.

Explanation:

• Hemopoietic stem cells also differentiate into platelets. 
• Platelets' main function is to prevent blood loss from damaged blood vessels by the formation of platelet plugs. 
• Platelets have a short life span, normally it is just 5-9 days. 

Hence, the correct answer is Option 3.

The correct answer is Option 3 i.e. Opening of Na+ channels in the outer segment of photoreceptors

Concept:

• Vertebrate rod and cone photoreceptors use graded, hyperpolarizing responses to indicate the rate of photons absorbed. 
•  In darkness the photoreceptor's membrane potential is around -40 mV, significantly more depolarized than that of most neurons.
• When light reduces the level of cGMP, thus closing cGMP-gated channels, the inward current that flows through these channels is reduced and the cell becomes hyperpolarized.

Explanation:

• In darkness the cytoplasmic concentration of cGMP is high, thus maintaining the cGMP-gated channels in an open state and allowing a steady inward current, called the dark current. 

• In complete darkness, a photoreceptor has two dominant currents.
• While an outward K⁺ current travels through non-gated K⁺-selective channels and is restricted to the inner segment of the photoreceptor, while an inward current travels through cGMP-gated channels, which are restricted to the photoreceptor's outer segment.
• The K⁺ channels' outward current tends to hyperpolarize the photoreceptor in the direction of the K+ equilibrium potential (around -70 mV).
• The photoreceptor is often depolarized by the inward current.
• The inner segment of the photoreceptor possesses a high density of Na⁺-K⁺ pumps, which pump out Na⁺ and pump in K⁺, allowing the photoreceptor to maintain stable intracellular concentrations of Na⁺ and K⁺ in the face of these massive fluxes.

​
Explanation:

Option 1: Closing of Na+ channels in the outer segment of photoreceptors.

• Consider the explanation above thus this option is not true, as in darkness cGMP is generated which causes opening of Na⁺ channels ​​

• Consider the explanation above thus this option is not true

• Consider the explanation above thus this option is true,  in darkness cGMP is generated which causes the opening of Na⁺ channels.                     

The correct answer is Option 2 i.e. A - iii; B - iv; C - ii; D - i

Concept:

• Hormones are organic substances that are produced in small amounts by particular tissues, secreted in the blood and control the metabolic and biological activities of the target tissue or organs.
• Hormones are also called chemical messengers.
• In some cases, the endocrine gland can produce more than one hormone.
• One physiological effect can be regulated by more than one hormone.  For example, glucose concentration in the blood is regulated by insulin as well as glucagon hormone. 
• According to their chemical nature, hormones are classified as follows:

1. Steroid hormone - 
   • They are mainly derived from cholesterol.
   • It includes two classes corticosteroids and sex steroids.
   • It includes glucocorticoids and mineralocorticoids, androgens, etc. 
2. Amine hormones - 
   • They are made of amines and they are derivatives of amino acid tyrosine. 
   • They are secreted by the adrenal medulla and thyroid.
   • Before being released into the bloodstream they are stored in the respective organs.
   • Some of these hormones are polar while others are protein bound.
3. Peptide hormone - 
   • They are hormones which contain peptide chains.
   • They are unable to pass the plasma membrane due to their hydrophilic and lipophobic property. 
   • Oxytocin, vasopressin, insulin, etc are examples of peptide hormones.
4. Glycoprotein hormone - 
   • They are glycoproteins in nature where protein is conjugated with carbohydrate group
   • Examples, are FSH, LH, TSH, etc.
5. Eicasanoid hormones - 
   • They are fatty acid derivatives of arachidonic acid. 
   • They include prostaglandins, thromboxane, etc.

Explanation:

• Cortisol is a steroid hormone that is produced by two adrenal glands located on the top of each kidney. It plays an important role in stress response. 
• Adrenaline is also known as flight or fight hormone, it helps our body to deal with emergency situations. it acts on various organs to its effect include, increases in heart rate, dilation of pupils, increased in blood pressure, etc. 
• Melatonin hormone is produced in response to darkness, it helps to maintain the circadian rhythms or internal clock of the body. Nocturnal secretion of melatonin is important for initiating and maintaining sleep. 
• Dopamine is an amine hormone and also a neurotransmitter. It plays an important role in many various body functions, including movement, memory, motivation, etc.

Corrected table:

Hence, the correct answer is Option 2.

The correct answer is Option 3 i.e.Oxidized iodine

Concept:

• The "organification of tyrosine residues in thyroglobulin" refers to a crucial step in the biosynthesis of thyroid hormones, which is an important physiological process for maintaining metabolism and growth in humans.
• Thyroglobulin is a glycoprotein that serves as the precursor for the production of the thyroid hormones triiodothyronine (T3) and thyroxine (T4).
• This protein is synthesized by the follicular cells within the thyroid gland and stored within its structures awaiting iodination and further processing.
• The process begins with the active uptake of iodide by the thyroid cells.
• This iodide is then oxidized to iodine, typically in the presence of an enzyme known as thyroid peroxidase.
• Thyroglobulin has several tyrosine residues within its structure, which provide a site for the attachment of iodine.
• This process is known as "organification" and it results in the formation of monoiodotyrosine (MIT) and diiodotyrosine (DIT) residues on thyroglobulin.
• When the need for thyroid hormones arises, the MIT and DIT residues combine to form T3 (formed by one DIT and one MIT) and T4 (formed by two DIT residues), which are then released into the blood.
• This iodination and subsequent combination of iodinated tyrosine residues is critical for thyroid hormone production.
• Importantly, it is the "oxidized iodine" that participates in the organification process, iodinating the tyrosine residues on thyroglobulin

Explanation

Iodide ions (I^-) are transported into the thyroid gland and subsequently oxidized to form iodine (I₂), which is then able to iodinate tyrosine residues on thyroglobulin for the synthesis of thyroid hormones. Thus, it is the oxidized form of iodine that participates directly in the organification process.

The correct answer is A and D.

Explanation: 

P₅₀ is the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen. An increase in P₅₀ means hemoglobin has a lower affinity for oxygen, which facilitates oxygen unloading to tissues like active muscles during exercise. Several physiological factors influence P₅₀, such as temperature, pH (Bohr effect), CO₂ levels, and 2,3-DPG levels.

Statement A: "P₅₀ is increased during exercise as the temperature rises in active muscles."

• True. During exercise, active muscles produce heat, raising the temperature. Increased temperature shifts the oxygen-hemoglobin dissociation curve to the right, increasing P₅₀. This helps release more oxygen to the tissues.

Statement B: "During exercise, metabolites accumulate in the active muscles resulting in higher pH that increases P₅₀."

• False. During exercise, lactic acid and CO₂ accumulate, leading to a decrease in pH (i.e., muscles become more acidic, not alkaline). Lower pH reduces hemoglobin's affinity for oxygen (Bohr effect), increasing P₅₀. Thus, it's not a higher pH but a lower pH that increases P₅₀ during exercise.

Statement C: "P₅₀ is increased during exercise as CO₂ is decreased in active muscles."

• False. During exercise, CO₂ levels increase due to increased metabolic activity in muscles. Higher CO₂ levels lead to increased P₅₀ by promoting oxygen unloading (Bohr effect). A decrease in CO₂ would actually decrease P₅₀ (increase oxygen affinity), so this statement is incorrect.

Statement D: "An increase in 2,3-DPG has been reported in non-trained persons within 60 min of exercise resulting in higher P₅₀."

• True. 2,3-DPG (2,3-diphosphoglycerate) is a byproduct of glycolysis that binds to hemoglobin and decreases its affinity for oxygen, increasing P_50. During prolonged or intense exercise, especially in untrained individuals, 2,3-DPG levels can rise, aiding in oxygen release to tissues.​

The correct answer is 'A' is a ligand secreted from the brain and 'B' is a receptor in ovaries.

Explanation:

Key Observations from the Experiment

1. Overexpression of 'A' in the brain causes ovary degradation: This suggests that protein 'A' has an effect that originates in the brain but impacts the ovaries. The degradation implies a negative influence on ovary development.
2. Overexpression of a secretion-incompetent allele of 'A' does not cause ovary degradation: This indicates that protein 'A' must be secreted from the brain to affect the ovaries.
3. Downregulation of protein 'B' in the ovaries, along with overexpression of 'A' in the brain, prevents ovary degradation: This suggests that protein 'B' is required in the ovaries for the degradation effect to occur. In other words, 'B' might be acting in concert with 'A' to cause ovary degradation.
4. Physical interaction of 'A' and 'B' in ovary lysates: This means that when both proteins are present in the ovaries, they physically interact, implying a direct or indirect functional relationship.

Evaluation of the Inferences:

1. The protein 'A' cell autonomously influences ovary development while 'B' is secreted to influence brain function:  This is inconsistent with the observations. 'A' needs to be secreted from the brain to affect the ovaries, and there's no indication from the experiments that 'B' influences brain function.
2. A' is a ligand secreted from the brain and 'B' is a receptor in ovaries: This matches the observation that 'A' needs to be secreted from the brain to have an effect. The prevention of ovary degradation by downregulating 'B' suggests 'B' might be responding to 'A', fitting the ligand-receptor model. The physical interaction in the ovary lysates also supports this inference.
3. A' is a neurotransmitter secreted from the brain and 'B' is a signal transducer in the ovaries:This is incorrect because Neurotransmitters typically function at synapses between neurons or between neurons and other cell types, generally having a very short-range action due to the small synaptic gap.
   • Neurotransmitters are not usually described as having long-distance effects on organs (like the ovaries) because they primarily mediate communication between adjacent or closely situated cells within the nervous system.
4. A' is a receptor secreted from the ovaries and 'B' is a ligand in the ovary cell membrane:  This contradicts the requirement for 'A' to be secreted from the brain and the described interaction within the ovaries.

Conclusion: Based on the described evidence the correct answer is  'A' is a ligand secreted from the brain and 'B' is a receptor in ovaries.

The correct answer is a - iii, b - iv, c - i, d - ii

Explanation:

Types of Mammalian Nerve Fibers and Their Conduction Velocities:
1. Aa (Alpha) fibers:

• These are large-diameter, myelinated fibers. They are the fastest conducting fibers.
• Conduction Velocity: Typically in the range of 70-120 m/s.

2. B fibers:

• These are smaller diameter, myelinated fibers than Aa fibers. They belong primarily to the autonomic nervous system.
• Conduction Velocity: Generally in the range of 3-15 m/s.

3. Aδ (Delta) fibers:

• These medium-diameter, myelinated fibers are responsible for transmitting quick, sharp pain sensations.
• Conduction Velocity: Usually between 12-30 m/s.

4. Aβ (Beta) fibers:

•  These are medium to large-diameter, myelinated fibers involved in touch and pressure sensation.
• Conduction Velocity: Typically in the range of 30-70 m/s.

Therefore,

• Aa fibers should match with iii (70-120 m/s), as they are the fastest conducting fibers.
• B fibers should match with iv (3-15 m/s), which fits their slower conduction compared to other myelinated fibers.
• Aδ fibers should match with i (12-30 m/s), corresponding to their moderate conduction speed.
• Aβ fibers should match with ii (30-70 m/s), as they have a faster conduction velocity than Aδ fibers but slower than Aa fibers.