Pre-Clinical Physiology Flashcards

24 sample cards from the Physiology deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. State the relationship between pressure, flow, and resistance in the circulation (Ohm's law analog).

   $$Q = \frac{\Delta P}{R}$$ where $Q$ is blood flow, $\Delta P$ is the pressure gradient, and $R$ is vascular resistance.

2. How does vessel radius affect resistance according to Poiseuille's law?

   Resistance is inversely proportional to the fourth power of the radius: $$R = \frac{8\eta L}{\pi r^{4}}$$ so halving the radius increases resistance 16-fold.

3. Define mean arterial pressure and give its estimating formula.

   MAP is the average arterial pressure over a cardiac cycle: $$MAP \approx DBP + \frac{1}{3}(SBP - DBP)$$ where the term $(SBP-DBP)$ is the pulse pressure.

4. Name the paired respiratory muscles of quiet inspiration and the direction they move.

   The diaphragm (contracts and descends) and the external intercostals (elevate the ribs), both increasing thoracic volume.

5. Distinguish the conducting zone from the respiratory zone of the airways.

   The conducting zone (nose to terminal bronchioles) transports air and is anatomical dead space with no gas exchange; the respiratory zone (respiratory bronchioles, alveolar ducts, alveoli) is where gas exchange occurs.

6. What is pulmonary surfactant, which cells produce it, and its function?

   A phospholipid-protein mixture (mainly dipalmitoylphosphatidylcholine) produced by type II alveolar (pneumocyte) cells; it lowers alveolar surface tension, preventing collapse and reducing the work of breathing.

7. According to Boyle's law, how does lung volume change drive airflow during inspiration?

   Boyle's law states $P_1 V_1 = P_2 V_2$; increasing thoracic/lung volume lowers intra-alveolar pressure below atmospheric, so air flows inward down the pressure gradient.

8. Define tidal volume, and write the equation for minute ventilation.

   Tidal volume ($V_T$) is the air moved per normal breath (~500 mL). Minute ventilation: $$\dot{V}_E = V_T \times f$$ where $f$ is respiratory rate.

9. Differentiate vital capacity from residual volume.

   Vital capacity is the maximum air exhaled after a maximal inspiration ($VC = IRV + V_T + ERV$); residual volume is the air remaining in the lungs after maximal expiration and cannot be measured by spirometry.

10. State Fick's law of diffusion for gas exchange across the alveolar membrane.

    $$\dot{V}_{gas} \propto \frac{A \times D \times (P_1 - P_2)}{T}$$ Diffusion rate is proportional to surface area $A$, diffusion coefficient $D$, and partial-pressure gradient, and inversely proportional to membrane thickness $T$.

11. Give approximate partial pressures of $\ce{O2}$ and $\ce{CO2}$ in alveolar air and mixed venous blood.

    Alveolar: $P_{O_2}\approx 100\ \text{mmHg}$, $P_{CO_2}\approx 40\ \text{mmHg}$. Mixed venous blood: $P_{O_2}\approx 40\ \text{mmHg}$, $P_{CO_2}\approx 46\ \text{mmHg}$.

12. In what three forms is $\ce{CO2}$ transported in blood, and which predominates?

    As bicarbonate ($\ce{HCO3-}$, ~70%, the major form), bound to hemoglobin as carbaminohemoglobin (~23%), and dissolved in plasma (~7%).

13. What effect does the sigmoidal oxygen-hemoglobin dissociation curve's rightward shift represent (Bohr effect)?

    A rightward shift means decreased $\ce{O2}$ affinity, promoting unloading to tissues; it is caused by increased $\ce{CO2}$, decreased pH (increased $\ce{H+}$), increased temperature, and increased 2,3-BPG.

14. Where is the primary respiratory rhythm generator, and what chemical stimulus most strongly drives ventilation?

    The medullary respiratory centers (dorsal and ventral respiratory groups) generate the rhythm; arterial $P_{CO_2}$ (via central chemoreceptor sensing of CSF $\ce{H+}$) is the most powerful drive to ventilation.

15. Contrast central and peripheral chemoreceptors in respiratory control.

    Central chemoreceptors in the medulla respond to changes in CSF pH/$\ce{CO2}$; peripheral chemoreceptors in the carotid and aortic bodies respond mainly to low arterial $P_{O_2}$ (hypoxia), plus $\ce{CO2}$ and pH.

16. Name the three meningeal layers covering the CNS from outer to inner.

    Dura mater (outermost, tough), arachnoid mater (middle, web-like), and pia mater (innermost, adherent to the brain surface).

17. Where is cerebrospinal fluid produced and where is it absorbed?

    CSF is produced by the choroid plexus in the ventricles and absorbed into venous blood through the arachnoid granulations of the superior sagittal sinus.

18. Contrast the functional roles of the sympathetic and parasympathetic divisions of the autonomic nervous system.

    Sympathetic ('fight or flight') increases heart rate, dilates pupils, and mobilizes energy (thoracolumbar, noradrenergic); parasympathetic ('rest and digest') slows the heart and stimulates digestion (craniosacral, cholinergic).

19. Describe the sequence of events at a chemical synapse leading to neurotransmitter release.

    Action potential arrives → voltage-gated $\ce{Ca^2+}$ channels open → $\ce{Ca^2+}$ influx → synaptic vesicles fuse with the presynaptic membrane → neurotransmitter released into the cleft → binds postsynaptic receptors.

20. Differentiate an EPSP from an IPSP.

    An excitatory postsynaptic potential (EPSP) depolarizes the postsynaptic membrane (e.g., $\ce{Na+}$ influx), bringing it toward threshold; an inhibitory postsynaptic potential (IPSP) hyperpolarizes it (e.g., $\ce{Cl-}$ influx or $\ce{K+}$ efflux), moving it away from threshold.

21. What is the role of myelin, and how does saltatory conduction increase speed?

    Myelin insulates axons, so action potentials regenerate only at the nodes of Ranvier; the impulse 'jumps' node to node (saltatory conduction), greatly increasing conduction velocity while conserving energy.

22. Explain the labeled-line principle and sensory transduction in sensory systems.

    Sensory transduction converts a stimulus into receptor (generator) potentials and action potentials; the labeled-line principle holds that each receptor type and its dedicated pathway signal a specific modality regardless of how they are stimulated.

23. Contrast rods and cones in the retina.

    Rods are highly sensitive, function in dim light (scotopic), give monochromatic low-acuity vision, and dominate the periphery; cones need bright light (photopic), mediate color and high-acuity vision, and concentrate in the fovea.

24. How does the cochlea encode sound frequency (tonotopy)?

    By the place principle: the basilar membrane is stiff/narrow at the base (encoding high frequencies) and floppy/wide at the apex (low frequencies), so different frequencies maximally displace different locations, stimulating specific hair cells.

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