BIOL253 Exam 3 Questions

At the SRC, Jordan (they/them), 20, collapses after sprint intervals. “My legs felt like they were burning and then I got dizzy.” NP Bowen (she/her): “Let’s check your vitals. Your temperature is elevated from exertion.” Which physiological change MOST contributed to Jordan’s hemoglobin releasing more oxygen to their muscles during the sprints?

A rightward shift due to increased tissue temperature and CO2

Aanya (a graduate student, presents with long COVID symptoms.): “Walking from the bus stop to Wilson Library still wears me out.” PA Chen: “Damage to alveoli affects both oxygen diffusion and CO₂ removal.” Which physiological change BEST explains Aanya’s persistent shortness of breath?

Reduced diffusion area → decreased arterial PO₂ despite normal ventilation

Patient (Rina, she/her): “My legs have been really swollen since my doctor said my heart was getting weaker.” Provider (Jameson, he/him): “The swelling suggests your blood isn’t moving out of your veins very well.” Which mechanism explains her edema?

Increased venous hydrostatic pressure reducing reabsorption

A patient’s ventilation decreases, but their metabolism increases (e.g., fever + shallow breathing). What happens to alveolar gas pressures?

PO₂ ↓, PCO₂ ↑

In the cardiac cycle, most ventricular filling happens before the atria contract.

True

Patient (Mei Ling, she/they), a first year living in Hinton James Residence Hall, comes to UNC Campus Health after 4 days of fever and a productive cough. “Walking to class feels like climbing a mountain. I keep getting out of breath.”
PA (Nikhil, he/him): “Let’s see how your lungs are exchanging gases.”
At campus health, arterial blood gas (ABG) results show:
• PaO₂: 61 mmHg
• PaCO₂: 37 mmHg
• A chest X ray shows patchy infiltrates in the right lower lobe.
Pneumonia! This can cause some alveoli to fill with fluid and debris from infection. Which physiological change best explains her reduced oxygen levels?

Infection filled alveoli reduce the surface area available for oxygen to enter the blood

A mutation causes the α subunit of a GPCR in cardiac pacemaker cells to stay inactive (it stays bound to GDP) even after the ligand binds. Which ECG change would MOST likely appear?

Slower SA node firing → sinus bradycardia

A patient asks, “Why does the swelling go down when I put my feet up?” Which physiological mechanism best explains this?

Lower venous pressure reduces capillary hydrostatic pressure, shifting fluid movement toward reabsorption

UNC sophomore Kahlil Owens (he/him) with known sickle cell disease arrives at Campus Health after walking across campus in cold weather. Dialogue: Kahlil: “My chest feels tight and my hands are cramping.” RN Lovic: “Cold and low oxygen can worsen sickle cell symptoms. Let’s check your saturation.” Which change in hemoglobin physiology MOST contributes to worsening symptoms in cold environments?

Leftward shift increasing O₂ affinity and decreasing tissue delivery

In acute cardiogenic shock, stroke volume decreases even though EDV may increase.

True

Hyperventilation always means taking rapid, deep breaths.

False

A decrease in afterload, such as from vasodilation, will tend to increase ejection fraction.

True

Increasing CO₂ production without an increase in ventilation will increase hydrogen ion concentration and result in lower blood pH.

True

Beta and gamma subunits of the G protein do nothing after dissociating from the receptor; only the alpha subunit is functionally relevant.

False

A clinician reviewing pressure–volume loops notices significantly reduced end diastolic volume (EDV). Which situation could BEST explain this finding?

A ventricle that has become stiffer and cannot fill normally

A nurse is counseling a patient who asks, “Why does my body send more blood to my muscles when I exercise?” Which mechanism best explains the increased skeletal muscle blood flow?

Local metabolic changes in working muscle fibers cause arterioles to dilate and increase blood flow

Differences in epinephrine responses between adipose tissue and liver tissue occur because these tissues express different receptors.

True

A 21 year old NCAA swimmer comes in for a sports physical. Resting HR is 48 bpm, but stroke volume is significantly elevated. When asked if she feels dizzy with low HR, she laughs: “Not at all.” Which mechanism BEST explains her ability to maintain normal cardiac output at rest?

Increased contractility lowers ESV

At the end of a normal, unforced expiration, alveolar CO₂ rises slightly because blood continues delivering CO₂ even when airflow has paused.

True

Sara, a UNC lab TA, visits Campus Health complaining of calf cramps during her walk from South Campus to Phillips Hall. Sara (she/her): “It feels like my muscles need more oxygen when I’m going uphill.” RN Lovic (he/they): “That’s because your muscles are increasing ATP use. That changes how oxygen moves from the blood into your tissues.” What drives more O₂ into Sara’s muscle cells during increased metabolic activity?

A greater PO₂ gradient between blood and muscle

Patient (Keisha, she/her): “I lost a lot of blood after my bike accident. The paramedics said my body was ‘clamping down.’ What does that mean?” Provider (Jackson, (they/them): “Your vessels narrowed to maintain your blood pressure.” Which physiologic change is she describing?

Systemic arteriolar constriction increasing TPR

A sudden drop in blood volume (e.g., from hemorrhage) will initially reduce baroreceptor firing, which triggers an increase in sympathetic output.

True

Patient (Ezra, they/them): “Every time I take a deep breath, it feels like my ribs just won't expand. I had major spine surgery last year. Could that be affecting my breathing?” Provider: “Yes, limited chest wall movement can change how pressure inside the lungs shifts during inspiration.” Which physiological change is MOST likely occurring?

Intrapleural pressure does not become sufficiently negative during inspiration

A new nurse asks her instructor why a patient experiencing a panic attack has a heart rate of 132 bpm. The patient overhears and asks, “Is my heart going to explode?” Which explanation BEST describes the physiology?

Increased sympathetic signaling increases cAMP, speeding pacemaker depolarization

Patient (Tara, she/her): “My blood pressure has been high for years. Now that I’m being treated, will my body adapt?” Provider: “Your pressure sensors will adjust over time.” How do baroreceptors adapt after MAP is reduced for several weeks?

They reset and fire more frequently at the new, lower pressure

After being frightened, a person’s blood pressure is 190/130. The MAP of ___ is clearly ___ than average. The body might temporarily respond by systemic arteriole ____. MAP = DP + 1/3(SP-DP)

150 / higher / vasodilation

A 30 year old woman develops acute shortness of breath after a high speed motor vehicle collision Ultrasound reveals no chest wall injury, but air is noted within the pleural space on the right side. What will be the immediate effect on transpulmonary pressure (PTP)?

PTP becomes zero, causing loss of lung inflation

Sofia (who has mild asthma, becomes short of breath after climbing a long incline): “I can breathe in, but it feels tight and not enough air is getting through.” Her friend Rashad: “Use your inhaler. We can rest here.” Sofia (after using inhaler): “That helped fast. Why?” Which physiological mechanism best explains why Sofia improved after using her bronchodilator?

Bronchodilation increased airflow, improving alveolar PO₂

Increasing venous return in a healthy heart will automatically increase cardiac output because it increases EDV.

True

A patient develops a rapid heart rate after taking pseudoephedrine. Pseudoephedrine increases total peripheral resistance through α₁ adrenergic receptor-mediated vasoconstriction, which raises arterial pressure. This rise in pressure activates the baroreceptor reflex. However, the patient becomes tachycardic instead. Which mechanism BEST explains this finding?

α₁ receptor activation produces strong positive chronotropic effects

A defect reduces the heart’s ability to relax (lusitropy) quickly during sympathetic activation. What outcome is MOST likely during exercise?

Reduced EDV because filling cannot keep pace with increased HR