General Physiology Practice Questions

Q: Why do eyebrows not grow beyond a certain length?

Anagen phase. **Anagen phase** - The **anagen phase**, or growing phase, is significantly shorter for eyebrow hairs (typically 30-45 days) compared to scalp hair (2-7 years), which limits their maximum length. - The duration of this active growth phase **determines the ultimate length** hair can reach before it transitions to resting and shedding. *Telogen phase* - The **telogen phase** is a **resting phase** where the hair follicle is completely inactive; it does not contribute to the hair's growth or final length. - During this phase, the old hair is shed to make way for new hair growth, but it is not the phase that dictates the maximum length. *Catagen phase* - The **catagen phase** is a **transitional phase** lasting about 2-3 weeks, during which hair growth stops and the hair follicle shrinks. - This phase prepares the hair for resting and shedding but does not directly limit how long the hair grows. *Exogen phase* - The **exogen phase** is when a hair is **shed from the follicle**, often aided by activities like washing or brushing. - This phase is responsible for hair shedding, not for limiting the maximum length hair can attain.

Q: Feed forward mechanism is seen in:

Salivation on smelling food. ***Salivation on smelling food*** - This is a classic example of a **feedforward mechanism** because the body anticipates a future event (eating) based on a sensory cue (smelling food) and initiates a preparatory physiological response (salivation). - The response occurs *before* the actual need for digestion arises, demonstrating proactive regulation. - Part of the **cephalic phase of digestion** mediated by parasympathetic nervous system activation. *Increase in heart rate on standing up* - This is an example of a **feedback mechanism** mediated by baroreceptors and the autonomic nervous system. - When standing, blood pools in lower extremities causing a transient drop in blood pressure, which is detected by baroreceptors. - The body responds by increasing heart rate and peripheral resistance to maintain adequate blood pressure - a reactive response to detected change. *Feeling thirsty while walking in hot temperature* - Thirst in response to hot temperatures is typically a **feedback mechanism** where the body detects increased dehydration (e.g., via osmoreceptors) and signals the need for fluid intake. - It is a reaction to an existing physiological imbalance rather than an anticipation of future needs. *Shivering on exposure to cold temperature* - Shivering is a **feedback mechanism** where the body responds to a drop in core body temperature by generating heat to restore thermal homeostasis. - The body reacts to the cold stimulus *after* the temperature change has occurred, rather than anticipating it.

Q: An athlete's heart rate and respiratory rate increase before the start of a race due to anticipatory responses. Which physiological mechanism explains this?

Feedforward control. ***Feedforward control*** - This mechanism involves the body making **preparatory adjustments** to physiological parameters in anticipation of a future demand or event. - The athlete's brain anticipates the physical exertion of the race, leading to a **pre-emptive increase in heart rate and respiratory rate** to meet expected metabolic demands. *Baroreceptor reflex* - The baroreceptor reflex primarily regulates **blood pressure** in response to changes detected by stretch receptors in the carotid sinus and aortic arch. - While it influences heart rate, its function is largely **reactive** to pressure changes, not anticipatory of future events. *Chemoreceptor activation* - Chemoreceptors detect changes in blood **pH, oxygen, and carbon dioxide levels**, primarily regulating respiration and heart rate in response to metabolic needs. - This mechanism is generally **reactive** to current metabolic states, not predictive of future ones, and wouldn't explain anticipatory responses before changes in blood chemistry. *Negative feedback* - Negative feedback is a regulatory mechanism that works to **maintain homeostasis** by counteracting deviations from a set point. - It involves a response that **reduces the initial stimulus** and brings the system back to equilibrium, which is not an anticipatory mechanism.

Q: What is the average survival time of a person without food and water under normal conditions?

3 to 5 days. ***3 to 5 days*** - When deprived of **both food and water**, the human body can typically survive for **3 to 5 days** under normal conditions. - **Water is the critical limiting factor** - while the body can tolerate food deprivation for weeks, lack of water becomes life-threatening within days. - Water is essential for cellular metabolism, temperature regulation, waste elimination, and cardiovascular function. *1 to 3 days* - This represents the **absolute minimum survival time** without water, particularly under harsh environmental conditions (heat, physical exertion, humidity). - However, under normal/average conditions, most individuals can survive slightly longer than this range. *10 to 12 days* - This duration is **not possible** without water, even with optimal conditions. - This timeframe is more consistent with survival **without food but WITH water**, which can extend to 3-4 weeks or more. *5 to 10 days* - While exceptional cases might approach 5-7 days without water in cool, resting conditions with low metabolic demands, **10 days is physiologically implausible**. - Severe dehydration typically causes death by day 5-7 maximum, with most succumbing earlier.

Q: All of the following physiological processes occur during growth at the epiphyseal plate except:

Replacement of red bone marrow with yellow marrow. ***Replacement of red bone marrow with yellow marrow*** - The replacement of **red bone marrow** with **yellow marrow** is a process that occurs in the **diaphysis (shaft)** of long bones with aging, not directly within the **epiphyseal plate** during growth. - While it's a normal physiological change in bone, it's distinct from the primary mechanisms of **longitudinal bone growth** occurring at the growth plate. *Proliferation and hypertrophy* - **Chondrocytes** in the **proliferative zone** of the epiphyseal plate divide rapidly, increasing in number. - In the **hypertrophic zone**, these chondrocytes enlarge significantly, contributing to the lengthening of the bone. *Calcification and ossification* - The hypertrophied chondrocytes in the **calcification zone** undergo apoptosis, and their extracellular matrix becomes calcified. - In the **ossification zone**, osteoblasts invade the calcified cartilage and lay down new bone matrix, replacing the cartilage with bone. *Angiogenesis and remodeling* - **Angiogenesis** (formation of new blood vessels) is essential for delivering osteoblasts and nutrients to the epiphyseal plate and removing chondrocytes. - **Bone remodeling**, involving both bone formation and resorption, occurs as part of the ossification process to shape the new bone and maintain its structural integrity.

Q: What is the primary force that enables medical tapes and bandages to remain attached to the skin during emergency medical procedures?

Adhesion. ***Adhesion*** - **Adhesion** refers to the attractive forces between two *different* surfaces or substances, such as the adhesive on tape and the skin. - Medical tapes and bandages are designed with adhesives that create a strong bond to the skin's surface, preventing them from falling off. *Surface tension* - **Surface tension** is the contractive force exerted by the surface of a liquid, causing it to minimize its surface area. - While present in bodily fluids, it is not the primary force responsible for the adherence of solid materials like medical tape to skin. *Cohesion* - **Cohesion** is the attractive force between *identical* molecules or substances. - It describes the internal strength of the adhesive material itself, not its ability to stick to another surface. *Atmospheric pressure* - **Atmospheric pressure** is the force exerted by the weight of the air above a surface. - While it plays a role in phenomena like suction cups, it is not the primary mechanism by which medical tapes, which rely on a sticky substance, adhere to the skin.

Q: Positive feedback mechanisms are observed in all of the following except:

Moderate hemorrhage. ***Moderate hemorrhage*** - Moderate hemorrhage typically triggers **negative feedback mechanisms** to restore homeostasis, such as increased heart rate and vasoconstriction, rather than escalating the initial disturbance. - In cases of **severe hemorrhage**, positive feedback (e.g., cardiac depression leading to further decreased blood pressure) can occur, but moderate hemorrhage is generally contained by compensatory responses. *Blood coagulation* - **Blood coagulation** is a classic example of positive feedback; the activation of one clotting factor triggers the activation of many more, rapidly forming a clot to stop bleeding. - For instance, thrombin activates more thrombin and other clotting factors, amplifying the response. *Parturition* - During **childbirth (parturition)**, uterine contractions stimulate the release of oxytocin, which in turn enhances uterine contractions. - This positive feedback loop continues until the baby is delivered. *Generation of nerve action potential* - The **depolarization phase of an action potential** involves positive feedback, where a small influx of sodium ions causes further membrane depolarization. - This depolarization opens more voltage-gated sodium channels, leading to a rapid and massive influx of sodium, creating the rising phase of the action potential.

Q: The net diffusion of water from one solution to another through a semipermeable membrane, where the concentration of water is lower in the receiving solution, is termed?

osmosis. ***osmosis*** - **Osmosis** specifically describes the **net movement of water** across a **selectively permeable membrane** from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). - The driving force for osmosis is the difference in **water potential** between the two solutions. *filtration* - **Filtration** is a process by which fluid and small solutes are forced through a membrane by **hydrostatic pressure**, often from a higher pressure to a lower pressure area. - This process typically involves the separation of particles based on size, as seen in the **kidneys' glomeruli**, rather than water concentration gradients. *diffusion* - **Diffusion** refers to the general movement of any substance (solutes or solvent) from an area of **higher concentration to a lower concentration**, down its concentration gradient. - While osmosis is a type of diffusion, it is specific to **water movement** across a **semipermeable membrane**, which is a more precise description for the scenario presented. *brownian motion* - **Brownian motion** is the random movement of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving atoms or molecules in the fluid. - It describes the **random jiggling** of molecules, which contributes to diffusion, but it is not the term for the net diffusion of water across a membrane.

Q: Which of the following techniques is used to study current flow across a single ion channel?

Patch clamp. ***Patch clamp*** - The **patch clamp** technique allows for the direct measurement of **ion current flow** through a single ion channel or a small group of channels. - It involves isolating a small patch of cell membrane with a micropipette to record the electrical activity. *Voltage clamp* - The **voltage clamp** technique is used to maintain a constant membrane potential while measuring the **total ionic current** across the entire cell membrane. - It is not typically used for studying current across a *single* ion channel, but rather for analyzing whole-cell currents. *Iontophoresis* - **Iontophoresis** is a method used to introduce ionized substances, such as drugs or neurotransmitters, into tissues using a small electric current. - It is a technique for drug delivery or localized stimulation, not for directly measuring ion channel current. *Galvanometry* - **Galvanometry** is a general term for the measurement of small electric currents using a galvanometer. - While ion channel activity involves electric currents, galvanometry is not a specific technique for isolating and studying single ion channels.

Question 1

Why do eyebrows not grow beyond a certain length?

Accepted Answer

Anagen phase

Answer

Telogen phase

Answer

Catagen phase

Answer

Exogen phase

Question 2

Feed forward mechanism is seen in:

Accepted Answer

Salivation on smelling food

Answer

Increase in heart rate on standing up

Answer

Feeling thirsty while walking in hot temperature

Answer

Shivering on exposure to cold temperature

Question 3

An athlete's heart rate and respiratory rate increase before the start of a race due to anticipatory responses. Which physiological mechanism explains this?

Accepted Answer

Feedforward control

Answer

Baroreceptor reflex

Answer

Chemoreceptor activation

Answer

Negative feedback

Question 4

What is the average survival time of a person without food and water under normal conditions?

Accepted Answer

3 to 5 days

Answer

10 to 12 days

Answer

1 to 3 days

Answer

5 to 10 days

Question 5

What is the primary function of the 'patch-clamp' technique in electrophysiology?

Accepted Answer

To record ionic currents through single or multiple ion channels

Answer

To record facilitated diffusion

Answer

To record osmotic pressure around semipermeable membrane

Answer

To record RMP

Question 6

All of the following physiological processes occur during growth at the epiphyseal plate except:

Accepted Answer

Replacement of red bone marrow with yellow marrow

Answer

Proliferation and hypertrophy

Answer

Calcification and ossification

Answer

Angiogenesis and remodeling

Question 7

What is the primary force that enables medical tapes and bandages to remain attached to the skin during emergency medical procedures?

Accepted Answer

Adhesion

Answer

Surface tension

Answer

Cohesion

Answer

Atmospheric pressure

Question 8

Positive feedback mechanisms are observed in all of the following except:

Accepted Answer

Moderate hemorrhage

Answer

Parturition

Answer

Generation of nerve action potential

Answer

Blood coagulation

Question 9

The net diffusion of water from one solution to another through a semipermeable membrane, where the concentration of water is lower in the receiving solution, is termed?

Accepted Answer

osmosis

Answer

filtration

Answer

diffusion

Answer

brownian motion

Question 10

Which of the following techniques is used to study current flow across a single ion channel?

Accepted Answer

Patch clamp

Answer

Galvanometry

Answer

Voltage clamp

Answer

Iontophoresis

General Physiology — MCQs

General Physiology — MCQs

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