FMGE 2018 — Physiology
17 Previous Year Questions with Answers & Explanations
From which part of the gastrointestinal tract is glucose absorbed?
Cardiac event at the end of isometric relaxation phase:
Which of the following receptors mediate stretch reflex?
Cold water is not used for ear cleaning because
Inhibin is secreted by:
In which of the following conditions there is an increase in lung diffusion capacity?
Enteropeptidase enzyme is secreted by:
Resting membrane potential of nerve fibre is close to isoelectric potential of:
Cell that can form all cell types in the body is called?
What is the best stimulus for release of vasopressin?
FMGE 2018 - Physiology FMGE Practice Questions and MCQs
Question 1: From which part of the gastrointestinal tract is glucose absorbed?
- A. Stomach
- B. Colon
- C. Duodenum and jejunum (Correct Answer)
- D. Ileum
Explanation: ***Duodenum and jejunum*** - The **duodenum** and **jejunum** are the primary sites for nutrient absorption in the small intestine, including the majority of **glucose**. - Their large surface area, due to **villi** and **microvilli**, and abundant transport mechanisms facilitate efficient glucose uptake. *Stomach* - The stomach's primary role is **digestion**, particularly of proteins, with very little absorption of nutrients. - While some small, lipid-soluble substances like alcohol can be absorbed, significant **glucose absorption does not occur** here. *Ileum* - The **ileum** is mainly responsible for the absorption of **vitamin B12** and **bile salts**. - Although some remaining nutrients might be absorbed, the bulk of **glucose absorption** is completed in the upstream **duodenum and jejunum**. *Colon* - The **colon's** main functions are **water and electrolyte absorption** and the formation of feces. - It does not play a significant role in the absorption of **glucose** or other macro-nutrients.
Question 2: Cardiac event at the end of isometric relaxation phase:
- A. Atrioventricular valves open (Correct Answer)
- B. Corresponds to T wave in ECG
- C. Atrioventricular valves close
- D. Corresponds to peak of C wave in JVP
Explanation: ***Atrioventricular valves open*** - This event marks the end of isometric relaxation, where ventricular pressure has dropped below atrial pressure, allowing the **mitral and tricuspid valves** to open and ventricular filling to begin. - During **isometric relaxation**, the ventricles relax without changing volume, causing a rapid drop in intraventricular pressure until it is overcome by atrial pressure. *Corresponds to T wave in ECG* - The **T wave** on an ECG represents **ventricular repolarization**, which occurs during the early part of ventricular diastole, *before* the end of isometric relaxation when the AV valves open. - The opening of AV valves occurs a bit later, as ventricular filling phase commences. *Atrioventricular valves close* - The closing of the **atrioventricular valves** (mitral and tricuspid) occurs at the beginning of **isovolumetric contraction (systole)**, not at the end of isometric relaxation (diastole). - This event marks the start of ventricular systole and is associated with the **first heart sound (S1)**. *Corresponds to peak of C wave in JVP* - The **C wave** in the jugular venous pressure (JVP) tracing corresponds to the bulging of the **tricuspid valve** into the right atrium during early ventricular systole, immediately after the AV valves close. - This event is distinct from the end of isometric relaxation, which occurs later in diastole, *before* atrial filling.
Question 3: Which of the following receptors mediate stretch reflex?
- A. Golgi tendon organ
- B. Muscle spindle (Correct Answer)
- C. Meissner's corpuscles
- D. Merkel's disc
Explanation: ***Muscle spindle*** - Muscle spindles are **stretch-sensitive receptors** located within the muscle belly that detect changes in muscle length and the rate of change in length. - When a muscle is stretched, the muscle spindles are activated, sending signals via **afferent neurons** to the spinal cord, which then initiates a reflex contraction of the same muscle to counteract the stretch—this is the basis of the stretch reflex. *Golgi tendon organ* - **Golgi tendon organs** are located in the tendons and respond to changes in **muscle tension**, not muscle length. Its primary role is to prevent excessive muscle contraction. - When activated by high tension, Golgi tendon organs inhibit the muscle, leading to relaxation (inverse stretch reflex), which is opposite to the stretch reflex. *Meissner's corpuscles* - **Meissner's corpuscles** are **mechanoreceptors** located in the superficial layers of the skin, primarily responsible for detecting **light touch** and **vibrations**. - They are not involved in the regulation of muscle length or tension and therefore do not mediate the stretch reflex. *Merkel's disc* - **Merkel's discs** are **mechanoreceptors** found in the basal layer of the epidermis, specialized for detecting **sustained pressure** and **texture**. - These receptors contribute to fine tactile discrimination but are unrelated to the proprioceptive mechanisms of the stretch reflex.
Question 4: Cold water is not used for ear cleaning because
- A. Damage to tympanic membrane
- B. It will cause infection
- C. Caloric stimulation caused by cold water (Correct Answer)
- D. It will make the wax hard
Explanation: ***Caloric stimulation caused by cold water*** - Irrigating the ear canal with **cold water** causes significant **caloric stimulation** of the vestibular system. - This can induce **vertigo**, **nausea**, and **vomiting** due to the temperature difference stimulating the semicircular canals. *Damage to tympanic membrane* - While excessive pressure from irrigation can potentially damage the **tympanic membrane**, the temperature of the water itself is not the primary factor for this risk. - Damage is more related to the **force of irrigation** and pre-existing membrane integrity, not cold temperature. *It will cause infection* - The temperature of the water used for irrigation does not directly determine the risk of infection. - **Infection risk** is primarily associated with using unsterile water or introducing bacteria into a compromised ear canal, regardless of water temperature. *It will make the wax hard* - Earwax, or **cerumen**, is softened by water irrigation, not hardened. - **Warm water** is typically preferred because it aids in softening the wax more effectively and comfortably than cold water.
Question 5: Inhibin is secreted by:
- A. Peg cells
- B. Leydig cells
- C. Sertoli cells (Correct Answer)
- D. Interstitial cells
Explanation: ***Sertoli cells*** - **Sertoli cells** are located in the seminiferous tubules of the testes and play a crucial role in spermatogenesis. - They secrete **inhibin**, a hormone that selectively inhibits the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland. *Peg cells* - **Peg cells** (non-ciliated secretory cells) are found in the lining of the fallopian tubes, not the testes. - They produce **tubal fluid** which nourishes the ovum and spermatozoa, and aids in sperm capacitation. *Leydig cells* - **Leydig cells** are found in the interstitial tissue between the seminiferous tubules of the testes. - Their primary function is to produce and secrete **androgens**, such as testosterone, in response to luteinizing hormone (LH). *Interstitial cells* - This term is a general descriptor for cells located in the spaces between functional tissues or organs. - In the context of the testes, **Leydig cells** are the primary interstitial cells responsible for hormone production, while **Sertoli cells** are part of the seminiferous tubules.
Question 6: In which of the following conditions there is an increase in lung diffusion capacity?
- A. Alveolar haemorrhage (Correct Answer)
- B. Pulmonary oedema
- C. Idiopathic pulmonary fibrosis
- D. Emphysema
Explanation: ***Alveolar haemorrhage*** - The presence of **red blood cells within the alveoli** provides an additional source of **hemoglobin**, which can bind to carbon monoxide (CO) and therefore **increase the measured CO diffusion capacity (DLCO)**. - This is often seen in conditions like **Goodpasture's syndrome** or **pulmonary capillaritis**. *Pulmonary oedema* - Characterized by an **accumulation of fluid in the interstitial and alveolar spaces**, which **increases the diffusion barrier** for gases. - This fluid buildup **impairs gas exchange**, leading to a **decrease in DLCO**. *Idiopathic pulmonary fibrosis* - This condition involves **thickening and scarring of the alveolar-capillary membrane**, which significantly **increases the diffusion distance** for gases. - The resultant **fibrosis and destruction of capillaries** lead to a **marked decrease in DLCO**. *Emphysema* - Emphysema causes **destruction of alveolar walls** and the **pulmonary capillary bed**, leading to a **reduction in the surface area available for gas exchange**. - This loss of functional alveolar-capillary units results in a **decreased DLCO**.
Question 7: Enteropeptidase enzyme is secreted by:
- A. Ileum
- B. Duodenum (Correct Answer)
- C. Stomach
- D. Jejunum
Explanation: ***Duodenum*** - **Enteropeptidase** (also known as enterokinase) is a key enzyme primarily secreted by the mucosal cells of the **duodenum**. - Its main function is to activate **trypsinogen** (from the pancreas) into **trypsin**, initiating a cascade of protein digestion. *Ileum* - The ileum is primarily involved in the absorption of **vitamin B12** and **bile salts**. - It does not significantly contribute to the secretion of digestive enzymes like enteropeptidase. *Stomach* - The stomach secretes **pepsin** (to digest proteins) and **hydrochloric acid**, and is involved in initial protein digestion. - It does not produce enteropeptidase, which acts much later in the digestive process. *Jejunum* - The jejunum is a major site for the absorption of **nutrients** like carbohydrates, fats, and proteins. - While it has some brush border enzymes, the primary secretion of enteropeptidase occurs in the duodenum.
Question 8: Resting membrane potential of nerve fibre is close to isoelectric potential of:
- A. Sodium ions
- B. Potassium ions (Correct Answer)
- C. Chloride ions
- D. Magnesium ions
Explanation: ***Potassium ions*** - The **resting membrane potential** is primarily determined by the **equilibrium potential of potassium ions** because the membrane is far more permeable to potassium than to other ions at rest. - Due to the high **permeability to K+**, a significant outward flow of potassium ions occurs, making the inside of the cell negative relative to the outside, approaching the **Nernst potential for K+**. *Sodium ions* - The membrane has very low permeability to **sodium ions** at rest, so **Na+ influx** only slightly affects the resting potential. - The **Nernst potential for Na+** is positive, which is opposite to the negative resting membrane potential. *Chloride ions* - While chloride ions contribute to the **resting membrane potential**, their contribution is typically less significant than potassium due to varying membrane permeability in different neurons. - In many cells, chloride ions follow the electrical gradient set by other ions and do not actively determine the resting potential. *Magnesium ions* - **Magnesium ions** play crucial roles as cofactors for enzymes and in neurotransmission but have minimal direct influence on establishing the **resting membrane potential**. - The membrane is largely **impermeable to Mg2+** at rest, and their concentration gradients do not establish the baseline voltage.
Question 9: Cell that can form all cell types in the body is called?
- A. Lineage stem cells
- B. Multipotent
- C. Totipotent (Correct Answer)
- D. Pluripotent
Explanation: ***Totipotent*** - **Totipotent** cells have the ability to differentiate into **all cell types** of the organism, including the **extraembryonic tissues** (like the placenta). - The **zygote** immediately after fertilization is the most well-known example of a totipotent cell, as it can form an entire organism. *Lineage stem cells* - **Lineage stem cells** (or **multipotent** stem cells) are restricted to differentiating into cells within a specific **cell lineage** or germ layer. - For example, **hematopoietic stem cells** can form all types of blood cells but no other tissue types. *Multipotent* - **Multipotent** stem cells can differentiate into a limited number of cell types within a specific tissue or organ, but not all cell types of the body. - Examples include **mesenchymal stem cells** which can form bone, cartilage, and fat cells, or **neural stem cells** which can form neurons and glia. *Pluripotent* - **Pluripotent** cells can differentiate into **all cell types** of the three germ layers (ectoderm, mesoderm, and endoderm) that make up the embryo, but not the extraembryonic tissues. - **Embryonic stem cells** are a prime example of pluripotent cells, as they can form any cell type in the body but cannot form a complete organism on their own.
Question 10: What is the best stimulus for release of vasopressin?
- A. Hypotension
- B. Hypertension
- C. Hyperosmolality of extracellular fluid (Correct Answer)
- D. Decreased plasma volume
Explanation: ***Hyperosmolality of extracellular fluid*** - **Hyperosmolality** is sensed by **osmoreceptors** in the hypothalamus, which then stimulate the release of vasopressin (ADH). - This response is crucial for **water conservation** to dilute the extracellular fluid and restore normal osmolality. *Hypotension* - While hypotension does stimulate vasopressin release, its effect is less potent than that of hyperosmolality in terms of triggering release. - Baroreceptors sense a decrease in blood pressure, leading to an increase in **ADH** to help maintain blood volume and pressure. *Hypertension* - **Hypertension** would typically inhibit vasopressin release, as the body would attempt to excrete more water to lower blood volume and pressure. - Increased blood pressure signals stretch receptors, leading to a decrease in **ADH** secretion. *Decreased plasma volume* - A decrease in **plasma volume** (hypovolemia) also stimulates ADH release, but this is often accompanied by changes in osmolality. - The primary stimulus for ADH is usually the resulting **increase in plasma osmolality** due to water loss, or significant drops in blood pressure detected by baroreceptors.