BDS General Physiology Syllabus

Describe the ABO blood group antigen and antibody pattern.

Type A has A antigen and anti-B antibodies; type B has B antigen and anti-A; type AB has both antigens and no antibodies (universal recipient); type O has neither antigen and both antibodies (universal donor).

What determines Rh (D) blood group status and why does it matter in pregnancy?

Presence of the D antigen makes a person Rh-positive; its absence Rh-negative. An Rh-negative mother carrying an Rh-positive fetus can be sensitized, causing hemolytic disease of the newborn in subsequent Rh-positive pregnancies.

Which blood type is the universal donor for packed red cells and which is the universal recipient?

Type O-negative is the universal red cell donor; type AB-positive is the universal recipient.

Name the four chambers and four valves of the heart.

Chambers: right atrium, right ventricle, left atrium, left ventricle. Valves: tricuspid (right AV), pulmonary (semilunar), mitral/bicuspid (left AV), and aortic (semilunar).

Trace the path of blood through the heart and lungs starting from the vena cavae.

Vena cavae → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary arteries → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta → body.

List the components of the cardiac conduction system in order.

Sinoatrial (SA) node → atrioventricular (AV) node → bundle of His → right and left bundle branches → Purkinje fibers.

What are the two main phases of the cardiac cycle and their meaning?

Systole (contraction and ejection of blood) and diastole (relaxation and filling of the chambers).

Define stroke volume and give the formula relating it to end-diastolic and end-systolic volumes.

Stroke volume is the blood ejected per beat: $$SV = EDV - ESV$$ Typical value is about $70$ mL.

State the formula for cardiac output and a typical resting value.

$$CO = HR \times SV$$ At rest, roughly $72\ \text{beats/min} \times 70\ \text{mL} \approx 5\ \text{L/min}$.

Define ejection fraction and its normal value.

Ejection fraction is the fraction of end-diastolic volume ejected per beat: $$EF = \frac{SV}{EDV} \times 100\%$$ Normal is about $55$–$70\%$.

What do the P wave, QRS complex, and T wave of the ECG represent?

The P wave is atrial depolarization, the QRS complex is ventricular depolarization (atrial repolarization is hidden within it), and the T wave is ventricular repolarization.

Describe the ionic basis of the ventricular myocyte action potential plateau (phase 2).

The plateau results from a balance between inward $\ce{Ca^{2+}}$ current through L-type calcium channels and outward $\ce{K+}$ current, prolonging depolarization and preventing tetany.

What generates the pacemaker (funny) current in SA node cells?

The slow inward $I_f$ current carried mainly by $\ce{Na+}$ (and some $\ce{K+}$) through HCN channels, causing spontaneous diastolic depolarization toward threshold.

State the fundamental hemodynamic equation relating flow, pressure, and resistance.

$$Q = \frac{\Delta P}{R}$$ where $Q$ is flow, $\Delta P$ is the pressure gradient, and $R$ is resistance (analogous to Ohm's law).

State Poiseuille's law and its most important implication for vascular resistance.

$$Q = \frac{\pi \Delta P r^{4}}{8 \eta L}$$ Flow is proportional to the fourth power of the radius, so small changes in vessel radius cause large changes in flow and resistance.

Define mean arterial pressure and give the estimating formula.

MAP is the average arterial pressure over one cardiac cycle: $$MAP \approx DBP + \frac{1}{3}(SBP - DBP)$$ or $MAP = CO \times TPR$.

Which blood vessels are the primary site of resistance and of gas/nutrient exchange?

Arterioles are the main resistance vessels (regulating blood pressure); capillaries are the site of exchange due to their thin walls and large total surface area.

Name the conducting and respiratory portions of the airway.

Conducting zone (no gas exchange): nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles. Respiratory zone (gas exchange): respiratory bronchioles, alveolar ducts, and alveoli.

What are pneumocytes type I and type II?

Type I pneumocytes are thin squamous cells forming the gas-exchange surface; type II pneumocytes secrete pulmonary surfactant and can regenerate the alveolar epithelium.

Explain how the diaphragm and intercostals produce quiet inspiration.

Contraction of the diaphragm (flattening downward) and external intercostals (raising the ribs) expands the thoracic cavity, lowering intrapleural and alveolar pressure below atmospheric so air flows in.

State Boyle's law and its relevance to breathing.

$$P_1 V_1 = P_2 V_2$$ At constant temperature, pressure varies inversely with volume; increasing thoracic volume lowers alveolar pressure to draw air in during inspiration.

What is pulmonary surfactant and why is it important?

A phospholipid–protein mixture (rich in dipalmitoylphosphatidylcholine) secreted by type II pneumocytes that reduces alveolar surface tension, preventing alveolar collapse and reducing the work of breathing.

Define tidal volume, vital capacity, and residual volume.

Tidal volume is air moved per normal breath (~500 mL); vital capacity is the maximum air expelled after maximal inspiration (IRV + TV + ERV); residual volume is air remaining after maximal expiration (cannot be exhaled).

State Fick's law of diffusion as it applies to alveolar gas exchange.

$$V_{gas} \propto \frac{A \cdot D \cdot (P_1 - P_2)}{T}$$ Diffusion rate is proportional to surface area $A$, the diffusion coefficient $D$, and partial pressure difference, and inversely proportional to membrane thickness $T$.

How is oxygen primarily transported in the blood?

About 98% is bound to hemoglobin as oxyhemoglobin ($\ce{Hb} + \ce{O2} \rightarrow \ce{HbO2}$); only about 2% is dissolved in plasma.

What is the Bohr effect?

An increase in $\ce{CO2}$ or $\ce{H+}$ (lower pH) shifts the oxygen–hemoglobin dissociation curve to the right, decreasing hemoglobin's affinity for $\ce{O2}$ and promoting $\ce{O2}$ unloading in active tissues.

In what forms is carbon dioxide transported in the blood, and which is dominant?

As bicarbonate ($\ce{HCO3-}$, ~70%, formed via $\ce{CO2 + H2O <=> H2CO3 <=> H+ + HCO3-}$), bound to hemoglobin as carbaminohemoglobin (~23%), and dissolved in plasma (~7%).

Which brainstem centers control the basic rhythm of breathing?

The medullary respiratory center (dorsal and ventral respiratory groups) sets the basic rhythm, modulated by the pontine centers (pneumotaxic and apneustic areas).

Which chemoreceptors most powerfully regulate ventilation and to what stimulus?

Central chemoreceptors in the medulla respond mainly to increased $\ce{CO2}$ (via increased $\ce{H+}$ in CSF); peripheral chemoreceptors (carotid and aortic bodies) respond to low $\ce{O2}$, high $\ce{CO2}$, and low pH.

Name the divisions of the nervous system anatomically and functionally.

Anatomically: central nervous system (brain and spinal cord) and peripheral nervous system (nerves/ganglia). Functionally the PNS divides into somatic (voluntary) and autonomic (sympathetic and parasympathetic) systems.

Compare the actions of the sympathetic and parasympathetic nervous systems.

Sympathetic (thoracolumbar) mediates 'fight or flight': increases heart rate, dilates pupils, dilates airways, inhibits digestion. Parasympathetic (craniosacral) mediates 'rest and digest': slows heart rate, constricts pupils, stimulates digestion.

Describe the sequence of events in chemical synaptic transmission.

An action potential opens voltage-gated $\ce{Ca^{2+}}$ channels at the presynaptic terminal; $\ce{Ca^{2+}}$ influx triggers vesicle fusion and neurotransmitter release; the transmitter binds postsynaptic receptors, altering membrane potential (EPSP or IPSP).

What is the difference between an EPSP and an IPSP?

An excitatory postsynaptic potential (EPSP) is a depolarization that brings the neuron toward threshold; an inhibitory postsynaptic potential (IPSP) is a hyperpolarization that moves it away from threshold.

Define a sensory receptor and list the main functional classes.

A structure that transduces a stimulus into electrical signals. Classes include mechanoreceptors (touch/pressure), thermoreceptors (temperature), photoreceptors (light), chemoreceptors (chemicals), and nociceptors (pain).

What is sensory transduction and receptor (generator) potential?

Transduction is conversion of a stimulus into a change in membrane potential; the resulting graded depolarization is the receptor or generator potential, which, if it reaches threshold, triggers action potentials in the afferent neuron.

Name the photoreceptors of the retina and their functional roles.

Rods provide high-sensitivity, monochromatic vision in dim light (scotopic); cones provide color vision and high acuity in bright light (photopic) and come in three types tuned to different wavelengths.