Respiratory systems

What is behavioral thermoregulation, and why is it more common in small animals?

Strategy used by small-bodied animals (due to high surface-area-to-volume ratio) involving seeking microhabitats, shade, burrows, or changing orientation to the sun to manage heat exchange.

How does vasodilation contribute to heat loss?

Widening of blood vessels to increase blood flow to the surface (e.g., fennec fox ears) and enhance heat loss, effective when body temperature is higher than environmental temperature.

What is evaporative cooling?

Heat loss mechanism through sweating (humans) or panting (dogs) which removes latent heat from the body as water evaporates from a surface.

What is shivering?

Involuntary muscle contractions that generate heat as a physiological adaptation for heat gain.

What is vasoconstriction and its role in thermoregulation?

Narrowing of blood vessels to reduce blood flow to the periphery, minimizing heat loss.

What is piloerection/feather fluffing?

Process of raising hair or feathers to trap a layer of air, providing insulation and minimizing heat loss.

Explain countercurrent heat exchange in limbs.

A physiological adaptation where arterial blood warms venous blood returning to the core in limbs, minimizing heat loss to extremities.

What is hibernation?

A deep, long-term state of metabolic depression common in small mammals, where core body temperature falls significantly and metabolic, heart, and respiration rates drastically decrease to conserve energy.

What is brumation?

A lighter state of dormancy primarily found in ectotherms (reptiles and amphibians), similar to hibernation but with animals more easily aroused and less drastic metabolic changes.

What is torpor?

A short-term, daily metabolic depression, often a response to food scarcity or cold, allowing animals to conserve energy for a few hours before rapid arousal.

What is homeostasis?

The process of maintaining physiological variables within a narrow range around a set point in biological systems.

Define negative feedback in biological systems, and give an example.

A regulatory mechanism where a deviation from a set-point triggers responses that reverse or counteract the change, stabilizing the system (e.g., in thermoregulation and blood glucose).

What is positive feedback, and provide an example?

A regulatory mechanism that amplifies an initial change, moving the system further from the set-point until an external event or endpoint stops the loop (e.g., childbirth, blood clotting).

What is oxygen's vital role in the electron transport chain?

The role of oxygen as the acceptor of electrons in the electron transport chain (ETC), enabling ATP synthesis through oxidative phosphorylation.

What is the electron transport chain (ETC)?

A series of protein complexes in the inner mitochondrial membrane where electrons are passed down to pump protons, creating a gradient used for ATP synthesis.

How is ATP synthesized through oxidative phosphorylation?

The process facilitated by ATP synthase, which uses the energy from the proton gradient (created by the ETC) to synthesize the majority of cellular ATP.

What is bulk flow (convection) in gas exchange?

The mass movement of a fluid (air or blood) down a total pressure gradient, responsible for rapid transport of gases over long distances, such as ventilation and circulation.

What is diffusion?

The passive movement of individual gas molecules from higher to lower partial pressure, occurring over short distances at respiratory surfaces and between capillaries and tissues.

State Fick’s Law of Diffusion and its key components.

A law describing the rate of gas diffusion, stating it is proportional to the partial pressure gradient and surface area and inversely proportional to the diffusion distance.

What is Boyle’s Law?

States that for a fixed amount of an ideal gas at a constant temperature, pressure and volume are inversely proportional (P \times V = \text{constant}), explaining how changes in thoracic volume drive air movement.

Describe tidal ventilation in mammalian lungs.

A respiratory pattern in mammalian lungs where air flows in and out through the same pathway, leading to mixing of fresh and residual air and reduced gas exchange efficiency.

Which muscles are responsible for breathing in mammals, and how do they function during inhalation?

The primary muscles responsible for breathing in mammals; the diaphragm contracts (flattens) and external intercostals contract during inhalation to increase thoracic volume.

Describe the alveolus in mammalian lungs.

The primary site of gas exchange in mammalian lungs, composed of a single layer of Type I pneumocytes and lined with water film and surfactant to prevent collapse.

What is surfactant and its function in the lungs?

A substance produced by Type II pneumocytes in alveoli that reduces surface tension, preventing alveolar collapse during exhalation.

Explain countercurrent exchange in fish gills, and why is it efficient?

A highly efficient mechanism in fish gills where blood flows in the opposite direction to water flow over the gill surface, maintaining a continuous and steep partial pressure gradient for maximizing O2 diffusion.

What is the buccal/opercular pump?

A ventilation method used by most fish involving synchronized movements of the mouth and gill cover to actively pump water over the gills.

What is ram ventilation?

A ventilation method used by highly active swimming fish (e.g., sharks, tuna) where they keep their mouths open to force water continuously over their gills.

What makes the bird respiratory system highly efficient?

A highly efficient respiratory mechanism in birds where air flows continuously in one direction through fixed lungs and air sacs, minimizing mixing of fresh and stale air.

What are air sacs in birds and their role?

A system of compliant (flexible, non-gaseous exchange) sacs (anterior and posterior) in birds that facilitate unidirectional airflow through the rigid lungs in a two-breath cycle.

What are parabronchi in the bird respiratory system?

The actual gas exchange surfaces within the rigid lungs of birds, over which fresh, oxygen-rich air flows continuously.

Describe the insect tracheal system.

A unique respiratory system in insects that delivers O2 directly to almost every cell without involving the circulatory system, via a network of spiracles, tracheae, and tracheoles.

What are spiracles?

External openings along insect body segments that regulate gas exchange and minimize water loss in the tracheal system.

What are tracheoles and their function?

Minute, fluid-filled tubes that are the finest branches of the insect tracheal system, directly invading individual cells for direct oxygen diffusion.

What is cutaneous respiration?

Gas exchange that occurs directly across the skin or outer body surface, which is minor in most vertebrates but major in amphibians with moist, thin, and highly vascularized skin.

What is hemoglobin?

A protein in red blood cells that primarily transports oxygen, whose affinity for oxygen changes based on local conditions like partial pressure of oxygen, CO2, and pH.

Explain the Bohr Effect.

The phenomenon where metabolically active tissues (with higher CO2 and lower pH) cause hemoglobin to decrease its affinity for O2, promoting O2 release from hemoglobin.

What is carbonic anhydrase (CA) and its role in CO2 transport?

A highly efficient enzyme inside red blood cells that rapidly catalyzes the conversion of CO2 and water into carbonic acid, which then dissociates into H+ and bicarbonate ions.

How is carbon dioxide primarily transported in the blood?

The most significant form of CO2 transport in blood (around 70 \text{ percent}), formed inside red blood cells and then transported into the plasma.

Describe the Chloride Shift.

The exchange of a bicarbonate ion ( \text{HCO}_3^-) out of the red blood cell into the plasma for a chloride ion ( \text{Cl}^-) to maintain electrical neutrality during CO2 transport.

What is the Haldane Effect?

The phenomenon where the binding of O2 to hemoglobin decreases its affinity for CO2 and H+, facilitating CO2 release at the lungs.

What is the bicarbonate buffer system, and why is it critical?

Crucial system ( \text{HCO}_3^-/\text{H}_2\text{CO}_3) for maintaining blood pH within a narrow physiological range ( \text{approximately } 7.35-7.45), linking respiration directly to acid-base homeostasis.