System Physiology Animal MCQ Quiz in मल्याळम - Objective Question with Answer for System Physiology Animal - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is Option 3 i.e. The plasma oxygen tension reaches equilibrium with the oxygen tension of air.

Explanation:

The process of gas exchange in the lungs is governed by the principles of diffusion, where molecules move from an area of higher concentration to an area of lower concentration until equilibrium is reached. This principle explains why the air in our lungs never becomes fully deoxygenated and why the oxygen pressure doesn't drop much below 100 mmHg, despite oxygen being continuously absorbed into the blood and carbon dioxide being released from it.

The plasma oxygen tension reaches equilibrium with the oxygen tension of air," is the correct explanation because:

• Diffusion and Partial Pressure: In the alveoli (the tiny air sacs in the lungs where gas exchange occurs), oxygen diffuses from the air into the blood because the partial pressure of oxygen in the alveolar air is higher than the partial pressure of oxygen in the deoxygenated blood coming from the body. Similarly, carbon dioxide diffuses from the blood (where its partial pressure is higher) into the alveolar air (where its partial pressure is lower).
• Equilibrium: The process of oxygen entering the blood continues until the partial pressure of oxygen in the blood is roughly equal to the partial pressure of oxygen in the alveolar air. At this point, an equilibrium is reached, and the net diffusion of oxygen into the blood slows down significantly. This equilibrium prevents the complete deoxygenation of the air in the lungs, and it is established at a partial pressure of oxygen in the alveolar air that is around 100 mmHg.
• Hemoglobin Saturation: Additionally, the binding of oxygen to hemoglobin in red blood cells is not linear but follows a sigmoidal curve known as the oxygen-hemoglobin dissociation curve. At the high partial pressures of oxygen present in the lungs (around 100 mmHg), hemoglobin is nearly saturated with oxygen (about 97-98% saturation). This saturation level means that hemoglobin's ability to bind additional oxygen molecules is quite limited, further contributing to the difficulty of extracting all the oxygen from the alveolar air.
• Constant Renewal of Alveolar Air: The process of breathing continually replenishes the oxygen in the alveoli and removes carbon dioxide, helping to maintain the partial pressures of these gases in the alveolar air and preventing the air from becoming fully deoxygenated.

Therefore, the reason the blood cannot extract all the oxygen from the lungs, leading to an oxygen pressure that doesn't drop much below 100 mmHg, is due to the equilibrium reached between the oxygen tension in the plasma and the oxygen tension of the air in the alveoli. This equilibrium is fundamental to the efficient exchange of gases and the constant supply of oxygen needed for the body's metabolic processes.

The correct answer is Option 3 i.e. B and C only

Explanation:

B. Delay and Unidirectional Signal Propagation: The process of signal transmission at a chemical synapse is indeed characterized by a slight delay, which occurs because the neurotransmitter must be released from the presynaptic neuron, diffuse across the synaptic cleft, and bind to receptors on the postsynaptic neuron. Additionally, this process is unidirectional; the signal moves from the presynaptic neuron to the postsynaptic neuron and not in the reverse direction. This ensures precise control of neural signaling.

C. Efflux of Ca⁺⁺ ions leading to release of neurotransmitter at the pre-synaptic terminal: When an action potential arrives at the presynaptic terminal, it triggers the opening of voltage-gated calcium channels, allowing an influx of Ca²⁺ ions into the presynaptic neuron. This influx of calcium ions prompts the synaptic vesicles containing neurotransmitters to fuse with the presynaptic membrane and release their contents into the synaptic cleft. Note that the terminology should actually state "influx" of Ca²⁺ ions, not "efflux." 

• Option A (bidirectional signal propagation) is not characteristic of chemical synapses as they are inherently unidirectional.
• Option D is incorrect because it is the presynaptic neuron that experiences a significant influx of calcium ions leading to neurotransmitter release.
• The postsynaptic neuron receives the neurotransmitter, which may lead to changes in its membrane potential and possibly the generation of an action potential, but this does not involve the release of neurotransmitter by the postsynaptic neuron in response to calcium influx as part of the typical synaptic transmission process.

Conclusion:

Therefore, the answer that includes both B (delay and unidirectional signal propagation) and C (influx of Ca++ ions leading to neurotransmitter release at the presynaptic terminal) is the correct response, despite the minor miswording in C.

The correct answer is Option 3 i.e.A - ii; B - iii; C - i

Explanation-

• Aldosterone is a steroid hormone that plays a crucial role in the regulation of electrolyte and fluid balance in the body. It is synthesized in the adrenal glands, specifically in the outermost layer of the adrenal cortex called the zona glomerulosa.
• The synthesis of aldosterone involves several enzymatic steps within the adrenal cortex. The key steps in aldosterone synthesis include the conversion of cholesterol to aldosterone through a series of enzymatic reactions.
• Cholesterol Uptake: Cholesterol is taken up by the zona glomerulosa cells.
• Conversion to Pregnenolone: Cholesterol is converted to pregnenolone through a series of enzymatic reactions, with the rate-limiting step often involving the enzyme CYP11A1 (also known as P450scc).
• Conversion to Aldosterone: Pregnenolone is further metabolized to aldosterone through several intermediate steps, involving enzymes such as 3-beta-hydroxysteroid dehydrogenase (3β-HSD), 21-hydroxylase (CYP21A2), and aldosterone synthase (CYP11B2).
• The intracellular locations of these enzymatic reactions take place within the mitochondria and endoplasmic reticulum of the zona glomerulosa cells. These organelles provide the necessary machinery for the synthesis of steroid hormones.

Concept:

• The adrenal glands are small, triangular-shaped glands located on top of each kidney.
• Each adrenal gland is structurally and functionally divided into two main parts: the adrenal cortex (outer part) and the adrenal medulla (inner part).
• The adrenal cortex itself is organized into three distinct zones, each responsible for the production of different hormones:

• This is the outermost layer, which produces mineralocorticoids like aldosterone. It regulates electrolyte balance and blood volume.

Zona fasciculata:

• The zona fasciculata is in the middle and is the thickest of the three zones.
• This is the region of the adrenal cortex that secretes glucocorticoids, such as cortisol. Glucocorticoids are steroid hormones that regulate a wide array of functions in the body, including metabolism, inflammatory response, immune function, and the body's response to stress.
• In response to stress, the hypothalamic-pituitary-adrenal axis regulates the secretion of glucocorticoids.

• The innermost layer which secretes adrenal androgens.
• These hormones serve as precursors that are converted to other sex hormones in different tissues.

• This is the inner region of the adrenal gland, but it is not part of the adrenal cortex.
• The adrenal medulla secretes catecholamines like epinephrine (also known as adrenaline) and norepinephrine, which are stress-responsive hormones that help prepare the body for "fight or flight" reactions.

• This middle layer of the adrenal cortex is primarily responsible for producing and secreting glucocorticoids, including cortisol, which is the main glucocorticoid in humans.
• These hormones have numerous effects on the body, including the regulation of metabolism and immune response, as well as helping the body respond to stress.

Hence the correct answer is option 2

Concept:

• The leads in an ECG system are used to provide different views or perspectives of the electrical activity of the heart.
• Each lead represents a specific pathway between two or more electrodes, which are the conductive pads attached to the skin.
• They help in observing and recording the electrical signals of the heart to generate an ECG graph.
• A standard 12-lead ECG contains ten physical electrodes that create twelve distinct views or leads.
• There are basically three types of leads:

1. Limb Leads:
   • Also known as bipolar leads, limb leads consist of Leads I, II, and III.
   • They measure the electrical activity in the heart in a frontal plane, providing a vertical view.
2. Augmented Limb Leads:
   • ​Also known as unipolar leads, these include aVR, aVL, and aVF.
   • They are called 'augmented' because their electrical activity is magnified in order to create readable ECG tracings.
3. Chest (Precordial) Leads:
   • The chest leads are also unipolar and are denoted by V1 through V6.
   • They provide a horizontal view of the heart, specifically of the activity in the anterior and lateral sections of the heart.

• The role of these leads is to help diagnose various cardiac conditions by recognizing abnormal patterns of electrical conduction, which might, for instance, hint at heart disease or electrolyte imbalances.
• Different leads provide different angles of view, and examining them all collectively provides a comprehensive picture of the heart's electrical activity.

Hence the correct answer is option 2

Key PointsNeural regulation of the cardiac cycle 

• Neural regulation of the cardiac cycle primarily involves two arms of the autonomic nervous system—the parasympathetic nervous system and the sympathetic nervous system.
• Both these systems help regulate the heart's rate and rhythm, its contractility, and the diameter of coronary vessels, thereby playing a key role in the heart's functional response to changing physiological conditions.

• The sympathetic nervous system typically increases heart rate, strengthens the force of contraction, and dilates coronary vessels to enhance blood flow through the coronary circulation.
• This can occur as a reflex response to peripheral stimuli or due to input from higher centers of the brain, an aspect referred to as "central command".

• The parasympathetic division largely via the vagus nerve, sends signals to decrease the heart rate, with negligible effects on contractility and vessel diameter.
• Specific neural structures are implicated in the direct control of cardiac function.
• Neurons of the anterior insula, anterior cingulate cortex, amygdala, hypothalamus, periaqueductal gray matter, parabrachial nucleus, and several regions of the medulla influence the heart's function on a beat-to-beat basis.
• These are key regions involved in emotional responses, stress responses, and homeostatic reflexes.
• Additionally, the heart possesses its intrinsic nervous system comprising intracardiac neurons, which play a critical role in modulating the pacemaker activity of the sinoatrial and atrioventricular nodes thus further contributing to the fine-tuning of cardiac rhythm.

Explanation:

• Neural regulation of the cardiac cycle primarily involves two arms of the autonomic nervous system—the parasympathetic nervous system and the sympathetic nervous system.
• Both these systems help regulate the heart's rate and rhythm, its contractility, and the diameter of coronary vessels, thereby playing a key role in the heart's functional response to changing physiological conditions.

Hence the correct answer is option 3

Key Points

• The blood clotting process, also known as coagulation, involves a variety of proteins known as clotting factors.
• There are 13 known clotting factors, each playing a critical role in the coagulation cascade.
• This is a series of events where the different clotting factors interact with each other to stop bleeding [0].

Clotting factors:

• Factor I (Fibrinogen): A protein produced by the liver that helps in clot formation by transforming into fibrin, a sticky protein that forms the meshwork for the clot.
• Factor II (Prothrombin): It is converted into thrombin, an enzyme that turns fibrinogen into fibrin.
• Factor III (Tissue Factor/ Thromboplastin): It's produced by the body's tissues. If blood comes into contact with tissue factor, it helps initiate the process of clotting.
• Factor IV (Calcium Ions): Calcium is needed in several steps of the coagulation cascade.
• Factor V (Proaccelerin): Acts as a cofactor to enhance the conversion of prothrombin (II) into thrombin.
• Factor VII (Proconvertin): It also helps convert prothrombin into thrombin. It becomes activated by coming into contact with tissue factor (III).
• Factor VIII (Antihemophilic Factor): It is part of a larger protein complex that includes factor IX, and aids in activating factor X.
• Factor IX (Christmas Factor): Works closely with factor VIII to activate factor X.
• Factor X (Stuart-Prower Factor): It plays a role in converting prothrombin into thrombin.
• Factor XI (Plasma Thromboplastin Antecedent): It activates factor IX.
• Factor XII (Hageman Factor): It's involved in the initiation of the coagulation cascade.
• Factor XIII (Fibrin-Stabilizing Factor): It helps stabilize the fibrin clot.

Concept:

• The process of urination, or micturition, is a complex physiological process that involves the coordination of multiple nerve centers in the nervous system.
• These nerve centers are responsible for regulating the contraction and relaxation of the muscles in the bladder and urethra, as well as the opening and closing of the internal and external urethral sphincters.
• The micturition reflex center is located in the spinal cord and is responsible for coordinating the reflexive process of urination.
• When the bladder fills with urine, sensory nerves in the bladder wall send signals to the micturition reflex center in the spinal cord.
• This center then coordinates the contraction of the detrusor muscle, which is responsible for emptying the bladder, and the relaxation of the internal urethral sphincter, which allows urine to flow from the bladder into the urethra.
• The pontine micturition center, located in the brain stem, receives information from the bladder and coordinates
• The relaxation of the internal urethral sphincter and the contraction of the detrusor muscle to empty the bladder. It also coordinates with other regions of the brain to regulate voluntary control over urination.
• The cerebral cortex is involved in voluntary control over micturition, which is important for bladder control in humans.
• For example, a person can consciously delay urination until an appropriate time or location or can initiate urination when it is socially acceptable to do so.
• This voluntary control involves the communication between the cerebral cortex and the pontine micturition center, as well as the internal and external urethral sphincters.

Explanation:

• The dura mater is a tough membrane that surrounds and protects the brain and spinal cord, but it is not directly involved in the regulation of micturition.
• The other options are all involved in the regulation of micturition:
• Spinal cord: The spinal cord contains the micturition reflex center, which coordinates the process of urination.
• Brain stem: The brain stem contains the pontine micturition center, which receives information from the bladder and coordinates the relaxation of the internal urethral sphincter and the contraction of the detrusor muscle to empty the bladder.
• Cerebral cortex: The cerebral cortex can inhibit or facilitate micturition through voluntary control, which is important for bladder control in humans.

Concept:

• The development of mammary glands, their synthesis of milk, and the ejection of milk to the suckling offspring are all regulated by hormones.
• These glands are apparently modified sweat glands, glands that are also unique to mammals.
• The internal structure is rather uniform and includes supporting stromal cells and a glandular epithelium that is organized into clusters of minute, sac-like structures called alveoli.
• It is this glandular epithelium that is responsible for the synthesis of milk.
• The alveoli are continuous with ducts and various duct-derived enlargements for storing milk.

Explanation:

Fig 1: Mechanism of milk ejection mammals

• Mechanical stimulation of the nipple generates impulses to the spinal cord via the fourth to sixth intercostal nerves.
• These neural pathways terminate in the supraoptic and paraventricular nuclei of the hypothalamus.
• Oxytocin synthesized in neurons with cell bodies in these nuclei is secreted in response to suckling and it stimulates the myoepithelial cells to contract, expelling milk.

 hence the correct answer is option 1

The correct answer is not show peak D and may not show C, but would show A and B.

Concept:

• Electrical stimulation of a region of the nervous system generates nerve impulses in centers receiving input from the site of stimulation.
• This method, using microelectrodes, has been widely used in animal studies; however, the precise path followed by the artificially generated impulse may be difficult to establish.
• Electrical and optical measurements of the nerve impulse for different stimulation voltages.
• The optical measurements were done in the pulsed mode using 1000 averages.
• The figures show the signals in time, the square-root of the power spectral density PSD and the 400 Hz frequency component.

​Fig 1: Optical measurement of nerve impulse

Fig 2: Action potential

• In addition to changes in the frequency of activity, nerve terminal impulse shape also changed with heating and cooling.
• At the same ambient temperature, nerve terminal impulses were larger in amplitude and faster in time course during heating than those recorded during cooling.
• Since the ion channels take time to open to allow the ions to travel across the membrane, cooling a neuron causes the ion channels to open more slowly, causing a reduction in the speed of the action potential as it travels down the axon.

Explanation:

• Lower temperatures generally slow down physiological processes, including the propagation of action potentials along nerve fibers.
• The peaks A, B, C, and D in the diagram likely represent action potentials or similar electrical activities arriving at the recording site at different times, which could be due to different conduction velocities in different fibers within the nerve bundle.
• At a lower temperature, the conduction velocity would decrease, particularly affecting the fibers that transmit signals for peaks C and D, which are later peaks and might represent fibers with inherently slower conduction velocities or longer pathways.
• Peaks A and B, arriving earlier, likely represent faster-conducting fibers that would still be able to transmit their signals at a reduced temperature, although possibly with some delay or reduction in amplitude.

​Hence the correct answer is Option 3