Biology 12: Respiratory System

Name: ___________________

1

Biology 12: Respiratory System

Chapter: 22

Vocabulary:

alveoli, aortic bodies, bicarbonate ions, bronchi, bronchioles, carbaminohemoglobin, carbon dioxide, carbonic anhydrase, carotid bodies, cilia, diaphragm, exhalation, external respiration, hydrogen ions, inhalation, intercostal (rib) muscles, internal respiration, larynx, lungs, mucus, nasal cavity, oxygen, oxyhemoglobin, pH, pharynx, pleural membrane, reduced hemoglobin, respiratory centre in the medulla oblongata, respiratory tract, ribs, stretch receptors, thoracic cavity, trachea

Learning Outcomes:

-Analyse the functional inter-relationships of the structures of the respiratory system1. Identify and give functions for each of the following:– nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, diaphragm and ribs,

pleural membranes, thoracic cavity

2. Explain the roles of cilia and mucus in the respiratory tract

3. Explain the relationship between the structure and function of alveoli

-Analyse the processes of breathing

1. Describe the interactions of the following structures in the breathing process:-respiratory centre in the medulla oblongata, lungs, pleural membranes, diaphragm, intercostal

(rib) muscles, stretch receptors

2. Compare the processes of inhalation and exhalation

3. Explain the roles of carbon dioxide and hydrogen ions in stimulating the respiratory centre in the medulla oblongata

4. Explain the roles of oxygen, carbon dioxide, and hydrogen ions in stimulating carotid and aortic bodies

2

-Analyse internal and external respiration

1. Describe the exchange of carbon dioxide and oxygen during internal and external respiration, including– location of exchange, conditions that favour exchange (e.g., pH, temperature)

2. Explain the roles of oxyhemoglobin, carbaminohemoglobin, reduced hemoglobin, bicarbonate ions, and carbonic anhydrase in the transport of carbon dioxide and oxygen in the blood

3. Write the chemical equations for internal and external respiration

Part A: Introduction

3

-As with the other body systems discussed this year, the respiratory system has a large surface area to facilitate the diffusion of oxygen and carbon dioxide.

-The diagram below illustrates the difference between:

a) External Respiration: Exchange of gases between air in the alveoli of the lungs and blood capillaries.

-Gas exchange occurs across a moist, thin epithelium in the lungs. The water in the moist surface helps to transport O2 across the cell membrane.

-Remember, what blood vessel brings oxygenated blood to the body? And deoxygenated blood back to the lungs?

b) Internal Respiration: Exchange of gases between blood and interstitial fluid at the capillaries.

-What are some adaptations capillaries possess to facilitate the easy transfer of materials?

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Part B: Basic Structures in the Respiratory System

4

-Label the diagram below with the terms below:

a) Nasal Cavity: Receives air, filters foreign particles, warms air, contains olfactory sensory endings.

b) Pharynx: Common area for food and air to pass through.

c) Larynx: A cartilaginous organ containing vocal cords for sound production.

d) Trachea: Flexible tube of “c” shaped cartilage that allows air to reach the lungs.

-What role do cilia and mucous have in the respiratory tract?

_________________________________________

_________________________________________

_________________________________________

_________________________________________

_________________________________________

_________________________________________

e) Bronchi: Branches of the trachea to allow passage of air to the lungs.

5

f) Bronchioles: Tubes connecting bronchi to alveoli.

g) Alveoli: Simple squamous epithelium allows O2 and CO2 to diffuse down their concentration gradient. They are surrounded by blood capillaries to facilitate this exchange.

-Examine the images right. What features of alveoli allow them to perform their function efficiently?

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

_______________________________________

-Stretch receptors around the alveoli prevent them from over-inflating. When activated, the stretch receptors trigger the body to stop inhalation, allowing exhalation to occur (known as the Hering-Breuer inflation reflex).

6

Part C: Process of Inhalation and Exhalation

1. Volume and Pressure Changes

-Breathing depends on there being a continuous column of air from the nasal cavity to the alveoli of the lungs.

-The chest (thoracic) cavity is enclosed by the rib change and diaphragm.

-As you can see in the diagrams, the outer pleural membrane is attached to the rib cage and the inner pleural membrane is attached to the lung tissue.

-For inhalation to occur, the lung (pulmonary) cavity must increase in volume. How is this accomplished?

______________________________________________________________________________

______________________________________________________________________________

7

______________________________________________________________________________

-

Why is inhalation called “active” and exhalation “passive”?

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

-Changes in volume also alter the pressure found inside of the pulmonary cavity. These changes in pressure are extremely important in permitting normal breathing to occur.

-What do you imagine happens to the air pressure inside of the thoracic cavity when it expands? And relaxes?

______________________________________________________________________________

______________________________________________________________________________

-The diagrams right show the pressure changes in your thoracic cavity and intrapleural space when you inhale and exhale.

8

-Why do you imagine the intrapleural pressure (in the pleural space) is always lower than the intrapulmonary pressure?

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

-What is meant by the phrase “humans breathe by negative pressure?

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

______________________________

-If the pressure in the intrapleural space is higher than the intrapulmonary pressure, the lung can collapse.

-Collapsed lungs are caused by a chest injury or lung disease that permits air to leak into the intrapleural space. Treatment involves inserting a tube or needle to remove the excess air.

9

-Below is a small summary of inhalation and exhalation:

2. Changes in Oxygen, Carbon Dioxide and Hydrogen Concentrations

-The respiratory centre in the brain (Medulla Oblongata) triggers autonomic (involuntary) nerve impulses, which stimulate the diaphragm and intercostal muscles to contract. This causes inhalation (10-14 breaths per minute at rest).

-When the level of CO2 increases in the blood, its pH goes down. This is a result of CO2 reacting with water to produce carbonic acid:

10

CO2 + H2O (in blood) ↔ H2CO3 (Carbonic Acid) ↔ H+ + HCO3

-Chemoreceptors in the medulla oblongata moniter the acidity of the blood. pH changes are also detected by receptors in the aortic and carotid arteries, which send nerve impulses to the medulla oblongata.

-The medulla oblongata changes the rate and depth of breathing in response to CO2 and H+ concentrations in the blood.

-What do you think will happen to the breathing rate is there is too much CO2 and H+?

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

-Carotid and aortic bodies also monitor changes in O2 concentration and signal the medulla to increase the breathing rate when O2 levels become low. However, this response is not as great as the high CO2 response.

Part D: O2 and CO2 Transport by Hemoglobin

-Oxygen is carried around the body by haemoglobin.

-How many molecules of O2 does one hemoglobin molecule hold when it is saturated?

______________________________________________________________________________

11

-The level of hemoglobin saturation changes depending on several environmental conditions:

Hemoglobin (Hb) can have a high or low affinity for O2 depending on a few environmental cues:

1. Partial Pressure

-Air pressure is a measurement of the pressure exerted by air. The portion of this total pressure that O2 exerts is called Oxygen’s Partial Pressure.

-Gases always flow down their partial pressure gradient, from [high] to [low]

-As O2 is always being used in cellular respiration our bodies have a lower O2 partial pressure than the atmosphere. This makes it easy for O2 to flow into our bodies.

-Inside our bodies, tissues will always have a lower partial pressure than Hb, allowing O2 to flow into them.

2. Heat

-Remember, Hb is a protein and alterations to its shape will affect its ability to carry O2.

-Muscles that are working hard produce heat, which can affect the shape of passing Hb. This additional heat will make Hb less able to hold onto O2, ensuring that it reaches cells with a high rate of cellular respiration.

-The effect of heat can cause Hb to release O2 at a rate 20% greater than it would under normal conditions.

3. CO2

12

-CO2 is also carried by Hb and its bonding causes red blood cells to release their remaining O2. This is useful, as it ensures areas undergoing a high rate of respiration obtain a lot of O2.

4. pH

-Again, as Hb is a protein its shape and effectiveness are affected by changes in pH.

-Active muscle tissues produce more CO2, which will ultimately result in H+ being produced. Hb will bind with the H+, causing it to change shape and have a lower affinity for O2.

5. Summary of Hb Affinity for O2

13

Part E: Summary of Chemical Reactions in External and Internal Respiration

1. Oxygen Transport

a) In the Lungs

-Oxygen attaches to Hb in red blood cells. When oxygen attaches to Hb, it is called oxyhemoglobin (HbO2).

O2 + Hb HbO2 (in the lungs)

b) In the Tissues

-Oxyhemoglobin releases the oxygen in the tissue capillaries to become Hb again. The oxygen is used in cellular respiration.

HbO2 O2 + Hb

2. Carbon Dioxide Transport

a) In the Tissues

14

-When carbon dioxide is produced by cellular respiration most of it reacts with water to produce carbonic acid. The carbonic acid dissociates into H+ and HCO3

-. The hydrogen ions create an acidic condition in the tissues and tissue capillaries.

CO2 + H2O H2CO3 H+ + HCO3-

i) Hb acts like a buffer in the blood by picking up much of the H+, producing reduced haemoglobin (HHb). The hydrogen ions travel to the lungs attached to the Hb.

ii) The bicarbonate ion (HCO3-) travels to the lungs dissolved in plasma.

iii) Some carbon dioxide attaches directly to the hemoglobin and travels to the lungs as carbaminohemoglobin (HbCO2).

b) In the Lungs

-When the blood reaches the lungs, the reactions that occurred in the tissues reverse themselves and the carbon dioxide leaves the blood and enters the alveoli.

i) Reduced hemoglobin gives up its H+ to become Hb again. It can now pick up O2 to take back to the tissues.

ii) The H+ reacts with bicarbonate ions in the plasma to produce carbonic acid, which breaks down into carbon dioxide and water. The carbon dioxide diffuses into the alveoli and is exhaled.

H+ + HCO3- H2CO3 CO2 + H2O

iii) Carbaminohemoglobin releases its carbon dioxide to become Hb. The carbon dioxide diffuses into the alveoli and the Hb can pick up oxygen again.

Complete this concept map, which summarizes some of the main concepts in this unit:

15

16