Lecture 17 - Respiration

Question 1

What are the Features of Animals without Respiratory Organs?

Answer 1

• Small
• Thin
• Porous

Question 2

Name the Steps of Gill Ventilation:

Answer 2

1. Mouth cavity expands, operculum is closed, opercular cavity expands, water is pulled into the mouth and across the gills.
2. Mouth closed, mouth cavity is compressed, operculum opens, water is pushed across gills.

Question 3

What is Countercurrent Flow?

Answer 3

• Essential component of opercular and ram ventilation
• Maintains concentration gradient
• Feature of many biological exchange systems

Question 4

What are Trachea and what Purpose Does it Serve?

Answer 4

Trachea allow respiration for insects in air. They have limited transport capacity and rely on body compression. Underwater, insects create air bubbles with their trachea.

Question 5

What are the Features of Vertebrate Respiration in Their Lungs?

Answer 5

• Positive pressure breathing
• Negative pressure breathing (change in volume of thoracic cavity and lungs in double walled sac)
• Synchronisation of breathing and locomotion

Question 6

The Main Disadvantage of Breathing Water is:

Answer 6

Its density. As water is much more dense and viscous than air, it is harder to ventilate in and out of tracheal tubes in marine organisms.

Question 7

Define Positive and Negative Pressure Breathing:

Answer 7

Positive Pressure Breathing:
Actively pushing air into the lungs in the absence of a diaphragm or rib structure (e.g. - frogs)

Negative Pressure Breathing:
By breathing in, mammals create a negative pressure inside their chest cavity. The diaphragm and muscles between a mammal’s ribs contract thus the negative pressure draws air that is breathed into their lungs.

Question 8

How does Avian Respiration Work?

Answer 8

• Increased efficiency with air sacs
• Parabronchi
• Volume of air changes in air sacs, not in lungs
• Aerodynamic valving (directional resistance)

Question 9

Closing Spiracles Prevents Water Loss by Insects Because?

Answer 9

When water evaporates, closing spiracles prevents gas exchange however, the water is also prevented from exiting the insect’s system.

Question 10

Where Does Gas Exchange Take Place in Mammals?

Answer 10

• Gas exchange takes place ONLY in the alveoli
• The rest is dead space (non respiratory)
• Oxygen dissolves in surfactant
• Diffuses across epithelium into blood
• Carbon dioxide exits in opposite direction

Question 11

How do Breath-Holding Dives Work?

Answer 11

• When diving, blood CO2 increases until urgent breathing stimulus is reached.
• Hyperventilation decreases pre-dive blood CO2
• Breathing stimulus not reached before black-out occurs.

Question 12

Why is it Not Possible for a Human to Completely Empty the Lungs?

Answer 12

There is always some air left in the lungs after a maximal exhalation. If this residual volume did not exist and the lungs emptied completely, the lung tissues would stick together and the energy necessary to re-inflate the lung could be too great to overcome.

Question 13

Describe how a Countercurrent Arrangement Increases the Efficiency of Oxygen Uptake in the Fish Gill:

Answer 13

As a countercurrent arrangement has water flowing one way and blood flowing the other, it allows for maximum oxygen for the blood to receive during oxygen exchange as the blood is constantly exposed to the water with higher oxygen levels.