Rapid Revision Reignite Physiology: Question-Answer Format
Sep 25, 2025
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Nerve Muscle Physiology
Detailed Questions
Detailed Questions
CVS Physiology
Detailed Questions
Detailed Questions
Nerve Muscle Physiology
Big Question 1: How are nerve fibers classified and what are their conduction properties?
Broad Answer: Nerve fibers are classified by myelination, diameter, conduction velocity, and function. Two major classification systems:
- Erlanger & Gasser for somatic fibers (A, B, C).
- Lloyd & Hunt for muscle afferents (I, II, III, IV).
| Fiber type | Numerical Classification (Lloyd & Hunt) | Function | Conduction velocity (m/sec) | Diameter (μm) | |
| A | Alpha | Ia Ib | Proprioception; somatic motor | 70-120 | 12-20 |
| Beta | II | Touch, pressure | 30-70 | ||
| Gamma | Efferent to muscle spindles | 15-30 | |||
| Delta | III | Pain, temperature (cold) | 12-30 | 2-5 | |
| B | Preganglionic autonomic | 3-12 | |||
| C | IV | Pain, temperature (warm), Postganglionic sympathetic | 0.5-2 | ||
Detailed Questions
Q1.1: Which fiber is fastest and largest in diameter?
Answer: Aα (Alpha) fiber — 70–120 m/s, 13–20 μm.
Q1.2: What is the classification and function of C fibers?
Answer:
- Type IV
- Unmyelinated
- Function: Slow pain, temperature, autonomic post-ganglionic
- Warm, burning pain, and freezing pain: Carried by C fiber.
- Cold sensation: Carried by Aδ fiber
Q1.3: Which fibers are affected first in hypoxia, pressure, and local anesthesia?
Answer:
| Condition | Order of Block |
| Pressure | Aα > B > C |
| Hypoxia | B > A > C |
| Local Anesthesia | Aγ and Aδ >> Aα and Aβ >> B >> C |
Q1.4: What is the significance of chronaxie and rheobase in nerve stimulation?
Answer:
- Rheobase: Minimum voltage required to trigger AP with long-duration stimulus.
- Chronaxie: Minimum time required to stimulate the neuron at 2× rheobase voltage.
- Utilization Time: It is the minimum duration of Rheobase voltage that is required to generate an action potential.
Q1.5: What is chronaxie?
Answer: Minimum duration of stimulation at 2× rheobase voltage needed to excite a neuron.
Q1.6: What is rheobase?
Answer: Minimum current intensity of long duration needed to excite a neuron.
Q1.7: What does a lower chronaxie indicate?
Answer: Greater neuronal excitability.
Q1.8: What are the typical spike (action potential) durations for A, B, and C nerve fibers?
Answer:
- C fiber - 2 ms
- B fiber - 1.2 ms
- A fiber - 0.4 to 0.5 ms
Big Question 2: What are the properties of different types of muscle twitch responses?
Broad Answer: Muscle twitch properties vary by muscle fiber type and stimulation frequency. A single AP causes a simple twitch, while repeated stimuli can produce incomplete or complete tetanus.
Detailed Questions
Q2.1: What are the properties of different muscle fiber types?
| Muscle Type | Property |
| Type I (Slow, Red) | High endurance, low power |
| Type II A (Fast, Red) | Moderate endurance, moderate power |
| Type II B (Fast, White) | Low endurance, high power |
Q2.2: What is a simple twitch?
Answer: A single AP leads to contraction-relaxation cycle ® one twitch response.
Q2.3: What is incomplete tetanus?
Answer: Repeated stimuli applied before complete relaxation, causing summation of contractions.
Q2.4: What is complete tetanus?
Answer: Stimuli applied at high frequency → no relaxation → sustained contraction.
Q2.5: What is the latent period and how long is it?
Answer: Time between stimulus and start of contraction: ~ 2 msec
Q2.6: A muscle contraction from a single stimulus is recorded in the diagram (tension vs time). Calculate the contraction time.
Answer: 2/3 × Total duration
Contraction time = ⅔ of the total duration (from start of contraction to peak tension)
Also Read : Nerve Muscle Physiology—Important Questions and Answers
CVS Physiology
Big Question 3: What are the phases, timing, and mechanical/electrical events of the cardiac cycle?
Broad Answer: The cardiac cycle lasts 0.8 seconds and consists of diastole (0.5 s) and systole (0.3 s). Diastole includes atrial and ventricular filling phases, while systole includes isovolumetric contraction and ejection. The cycle is tightly coordinated with heart sounds, ECG changes, and valve events.
Detailed Questions
Q3.1: What is the total duration of the cardiac cycle?
Answer: 0.8 seconds
Q3.2: What is the duration of diastole and systole?
Answer:
|
Diastole |
Systole |
|
Duration: 0.5 seconds |
Duration: 0.3 seconds |
|
Diastolic duration of Atrium: 0.7 seconds |
Systolic duration of Atrium: 0.1 seconds |
|
Ventricular diastole consists of:
contraction/systole.
|
Consists of:
|
Q3.3: What are the phases of diastole and their features?
Answer:
| Diastolic Phase | Description |
| 1. Protodiastole (0.04 sec) | Begins with closure of semilunar valves |
| 2. Isovolumetric relaxation | Closure of semilunar valves; ends with opening of AV valves |
| 3. First rapid filling phase | Passive filling of ventricles |
| 4. Diastasis (0.2 sec) | Reduced filling |
| 5. Last rapid filling phase | Due to atrial contraction; contributes 25–30% of ventricular filling |
Q3.4: What are the passive filling phases of the cardiac cycle?
Answer:
- First rapid filling phase
- Diastasis
Together they contribute about 70% of total ventricular filling.
Q3.5: What is the importance of the last rapid filling phase?
Answer:
- Occurs due to atrial contraction
- Contributes 25–30% of ventricular filling
- Also known as active/atrial kick
Q3.6: What are the phases of systole and their timing?
Answer:
| Systolic Phase | Description |
| 1. Isovolumetric contraction | AV valves close, pressure rises, all valves closed |
| 2. Rapid ejection | 66% of total stroke volume is ejected |
| 3. Slow ejection | 33% of total stroke volume ejected |
Q3.7: What are the characteristics of first and second heart sounds?
Answer:
| First heart sound | Second heart sound | |
| Phase of Cardiac cycle | At the start of isovolumic contraction. | At the start of isovolumic relaxation. |
| Duration | Long - 0.15 sec | Shorter - 0.12 sec |
| Frequency | Low frequency - 25 to 45 Hz | Sharp/high frequency - 50 Hz |
| Amplitude | Loud/high amplitude | Soft/low amplitude |
| ECG | Corresponds with R wave peak | Corresponds with End of the T wave |
Big Question 4: What are the features and clinical implications of Jugular Venous Pulse, Cardiac Output, and ventricular loading conditions?
Broad Answer: The Jugular Venous Pulse (JVP) reflects right atrial pressure and has positive and negative deflections related to atrial and ventricular activity. Cardiac Output depends on stroke volume and heart rate, influenced by preload, afterload, and contractility. Preload and afterload are defined by the timing of ventricular loading relative to contraction and are influenced by venous return and aortic pressure respectively.
Detailed Questions
Q4.1: What does Jugular Venous Pulse (JVP) represent?
Answer: JVP is a surface recording of the right atrial pressure.
Q4.2: What are the positive waves seen in JVP and their causes?
Answer:
| Wave | Cause |
| a wave | Atrial contraction (last rapid filling phase) |
| c wave | Bulging of tricuspid valve cusp into atrium |
| v wave | Venous return during ventricular systole |
Q4.3: What are the negative descents seen in JVP and their causes?
Answer:
| Wave/Descent | Cause |
| x descent | Atrial relaxation |
| x′ descent | Downward pulling of tricuspid valve during systole |
| y descent | Opening of tricuspid valve; rapid ventricular filling |
Q4.4: What is the pressure event summary table?
Answer:
| Phase | Waves Involved |
| Late Rapid Filling Phase | a |
| Isovolumic Contraction | c |
| First Rapid Filling + Diastasis | v,y |
| Ejection Phase | x,x” |
Q4.5: What are the effects described by Starling, Bowditch, and Anrep laws?
Answer:
| Law | Description |
| Frank-Starling | Contractility will increase when the end-diastolic volume is high. ↑EDV - ↑Stretch- ↑Contractility |
| Bowditch Effect | When the heart rate increases, the contractility will also increase. ↑ Heart Rate - ↑ Contractility (Force-frequency relationship) |
| Anrep Effect | When afterload increases, the contractility will also increase. ↑ Afterload- Reflex↑ in Contractility (intrinsic myocardial response) |
Also Read : Important Topics in Physiology for NEET-PG 2026
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