BIOS 255 Week 7 Respiratory System-Physiology

Student Name

Chamberlain University

BIOS-252: Anatomy & Physiology II with Lab

Prof. Name

Date

Respiratory System – Physiology

Learning Objectives

• Explain the physiological adaptations of the cardiorespiratory system in seals that support extended deep dives.

• Identify the main differences between human and seal physiology in relation to diving capabilities.

• Evaluate both respiratory and cardiac function during dives.

• Measure oxygen consumption and calculate total oxygen needs for dives of varying durations, comparing these requirements with estimated oxygen stores in the lungs, blood, and tissues.

Introduction

Oxygen is essential for all metabolically active cells to generate energy through aerobic pathways. This process inevitably produces carbon dioxide (CO₂), a metabolic waste that must be exhaled to avoid cellular toxicity. The respiratory center located in the brainstem regulates the rate and depth of breathing, ensuring oxygen intake and CO₂ removal are appropriately matched with the body’s metabolic requirements.

In this lab exercise, the focus is on the Weddell seal, a marine mammal renowned for its extraordinary diving capacity. These seals can plunge to depths of approximately 600 meters and remain submerged for up to 30 minutes. Unlike humans, seals have evolved multiple physiological adaptations that allow them to store oxygen more efficiently and regulate aerobic and anaerobic metabolism during prolonged dives. By analyzing oxygen and lactate levels across three simulated dives, this activity explores oxygen stores, the aerobic dive limit (ADL), and critical differences between seal and human respiratory physiology.

Assignment

• Part 1: Complete the Labster simulation “Cardiorespiratory Physiology: How Can Seals Dive So Deep for So Long?”. Carefully record all data presented in the simulation and review the theory section for foundational knowledge.

• Part 2: Develop a comprehensive lab report that summarizes findings, interprets results, and highlights key physiological adaptations.

Respiratory Physiology Lab Report

Oxygen Stores in Seals vs Humans

Main Difference in Oxygen Stores

Unlike humans, who typically take a deep breath before submerging, seals exhale prior to diving. This adaptation reduces the risk of decompression sickness (the bends) that results from nitrogen bubble formation under increasing water pressure. Pressure increases significantly with depth, doubling every 10 meters, which makes this strategy vital for survival.

Greatest Proportion of Oxygen Stored in Humans

In humans, oxygen reserves are concentrated in the lungs and blood. However, seals have greater blood oxygen storage because of their larger red blood cells and higher hemoglobin concentrations. They also store substantial oxygen in muscle tissue via myoglobin, which supports sustained aerobic metabolism during submersion.

Factorial Increase in Oxygen Consumption

Do seals experience the same factorial increase in oxygen consumption as humans?

• Answer: No. Unlike humans, seals do not show a proportional increase in oxygen consumption with exertion. Their diving strategy includes metabolic suppression, which minimizes oxygen use and prolongs dive duration. This explains why Weddell seals can dive up to 16 times longer than humans.

Oxygen Consumption for 12-Minute vs. 30-Minute Dives

During a 12-minute dive, seals consumed about 4.88 mL/min of oxygen. In contrast, a 30-minute dive resulted in an oxygen use of 4.48 mL/min, showing that their oxygen consumption does not increase dramatically with dive duration. This stability reflects efficient physiological regulation, which conserves energy and prevents rapid depletion of oxygen stores.

Lactate Accumulation

During the 12-minute dive, no lactate accumulation was detected, suggesting energy production was entirely aerobic. However, in the 30-minute dive, lactate levels rose significantly—from 2 mmol/L at rest to 10 mmol/L. This indicates that prolonged dives surpass the aerobic dive limit (ADL), forcing the seal to rely partially on anaerobic metabolism to sustain energy demands.

Seal’s Heart Response to Diving

What happens to the seal’s heart during diving?

• Answer: Seals experience bradycardia (slowing of the heart rate) while submerged. This adaptation conserves oxygen by reducing cardiac output and redirecting oxygen-rich blood to vital organs, such as the brain and heart.

Heart Rate and Oxygen Consumption Patterns

In a 30-minute dive, heart rate slows considerably, while oxygen consumption remains steady or decreases slightly. This coordinated response highlights the seal’s energy conservation strategy, which ensures oxygen is distributed efficiently and prolongs underwater endurance.

Incorrect Statement About Seal Adaptations

Which statement is incorrect?

• Answer: The misconception is that seals have larger lungs than humans relative to body mass. In reality, seals have smaller lung capacity relative to body size, relying instead on their blood and muscle as primary oxygen storage sites.

How the Respiratory and Circulatory Systems Complement Each Other

The respiratory and circulatory systems in seals are highly integrated. The lungs compress under pressure, minimizing nitrogen absorption and avoiding decompression sickness. At the same time, the circulatory system contains a higher volume of blood with elevated hemoglobin content, which allows efficient oxygen storage and distribution. This synergy enables seals to maintain vital organ function while diving for extended durations.

References

• Castellini, M. A., & Kooyman, G. L. (2010). Diving physiology of marine mammals and birds. Physiological Reviews, 90(2), 367–409. https://doi.org/10.1152/physrev.00038.2008

• Ponganis, P. J. (2015). Diving physiology of marine mammals and seabirds. Cambridge University Press.

BIOS 255 Week 7 Respiratory System-Physiology

• Davis, R. W. (2014). Marine mammals: adaptations for an aquatic life. Springer.

• Scholander, P. F. (1940). Experimental investigations on the respiratory function in diving mammals and birds. Hvalrådets Skrifter, 22, 1–131.