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Respiration
and Breathing
Anatomy
Know the pathway for inhaled and exhaled air in the respiratory system
Know terms such as nasal cavity, oral cavity, pharynx, epiglottis, larynx, trachea, lung, bronchi, bronchioles, intercostal muscles, diaphragm, alveoli
Breathing Movements
Know what happens to the diaphragm and the internal and external intercostal muscles when inhaling and exhaling– Understand the pressure of the chest
cavity and how it facilitates the moving of air in and out
Regulation of Breathing Breathing movements are
controlled by the medulla oblongata in the brain
information about the amount of CO2 and O2 is directed by chemoreceptors which send a message to the medulla – there are separate receptors
for CO2 (more sensitive) and O2
What Happens when CO2 levels increase? chemoreceptors sense increase in CO2
the diaphragm and intercostal muscles’ activity increases (stimulated by medulla oblongata)
this increases breathing movements and therefore increases the amount of CO2 being exhaled
when CO2 levels fall, the chemoreceptors become inactive and breathing rates return to normal
What Happens when CO2 levels increase? Drugs like morphine and barbiturates (aka.
Downers/depressants) can make the medulla less sensitive to CO2 levels and as a result, breathing rate decreases which could eventually cause death
Why can’t you hold your breath forever? Why do people breathe into paper bags when
having an anxiety attack?
Feedback LoopHigh CO2
Chemoreceptors
Medulla
Diaphragm Intercostals
Breathing Rate Increases
Less CO2 absorbed in
blood inactivates chemoreceptors
What Happens When O2 Levels Are Low?
oxygen chemoreceptors called the carotid and aortic bodies detect when oxygen levels are low and become stimulated
a message is sent to the medulla the medulla sends nerve impulses to the diaphragm
and the ribs begin breathing movements this will increase the amount of oxygen in the blood the O2 receptors are only called into action
when O2 levels fall and CO2 levels remain in the normal range
What Happens When O2 Levels Are Low?
Some examples– when you hold your breath, your O2 levels drop while the
CO2 levels increase and the high CO2 levels will initiate breathing movements
– in high altitudes where there is less O2 present, the opposite will happen. Low levels of O2 is not accompanied by high CO2 levels, the oxygen chemoreceptors initiate breathing movements
– when carbon monoxide poisoning occurs, CO (carbon monoxide) competes with O2 on the binding sites of the hemoglobin molecules in the blood. This reduces the O2 levels in the blood, stimulating the oxygen chemoreceptors to initiate breathing movements
Feedback LoopLow Blood O2
Chemoreceptors
Medulla
Diaphragm Intercostals
Breathing Rate Increases
Breathing Graphs
Breathing Graphs Tidal Volume (TV) – volume of air being inhaled and exhaled
during normal breathing. Inspiratory Reserve (IR) – maximum amount of air that is
inhaled above tidal volume. Expiratory Reserve (ER) – amount of air that can be exhaled
after normal exhalation/ Residual Volume – volume of air that always stays in the lungs Vital Capacity (VC) – total volume of air that the lungs can
inhale and exhale. Vital Capacity = Tidal Volume + Inspiratory Reserve +
Expiratory Reserve VC = TV + IR + ER Total capacity = vital capacity + residual volume
Respiration and Blood
Respiration and Blood
Oxygen Transport– O2 in the alveoli diffuses into the fluid
around the cells surrounding the capillary bed
– O2 then diffuses through the capillary walls
and into the blood plasma and the oxygen binds on the hemoglobin molecules in the red blood cell
Respiration and Blood
Carbon Dioxide Transport– 23% of CO2 is carried on hemoglobin– 7% is carried in plasma– 70% of CO2 (from cellular respiration) enters the
red blood cells and in order to maintain blood pH, is chemically converted to carbonic acid (H2CO3) in a reaction that is catalyzed by carbonic anhydrase (an enzyme)
• carbonic acid molecules dissociate forming bicarbonate ions and hydrogen ions
• bicarbonate diffuses out of RBC into the plasma
Respiration and Blood
Carbon Dioxide Transport– when blood rich in CO2 reaches the lungs,
bicarbonate ions combine with hydrogen ions, reforming carbonic acid
• carbonic acid dissociates, forming water and CO2 which diffuses out of the blood and into the alveoli
• when present in normal amounts, the ratio of carbonic acid to bicarbonate creates an acid-base balance in the blood, helping to keep the pH at a level where the body's cellular functions are most efficient
Respiration and Blood
Carbon Dioxide Transport– CO2 travels from the capillaries to the
alveoli, this is driven by concentration differences (the concentration of CO2 in the capillaries is slightly higher than in the alveoli)
– CO2 is then expelled out of the lungs in exhalation
Respiration and Blood Reaction Summary
CO2 + H2O H2CO3 (carbonic acid) In RBC
carbonic anhydrase
Respiration and Blood Reaction Summary
CO2 + H2O H2CO3 (carbonic acid) In RBC
carbonic anhydrase
H2CO3 HCO3- + H+ In RBC then to
plasma
(bicarbonate)
Respiration and Blood Reaction Summary
CO2 + H2O H2CO3 (carbonic acid) In RBC
carbonic anhydrase
H2CO3 HCO3- + H+ In RBC then to
plasma
(bicarbonate)
HCO3- + H+ H2CO3 In
RBC
Respiration and Blood Reaction Summary
CO2 + H2O H2CO3 (carbonic acid) In RBC
carbonic anhydrase
H2CO3 HCO3- + H+ In RBC then to plasma
(bicarbonate)
HCO3- + H+ H2CO3 In RBC
H2CO3 CO2 In RBC
H2O
The Function of the Hydrogen Ions the H+ ions help to dislodge O2 from the hemoglobin
causing O2 to diffuse into the tissues by removing H+ ions from the plasma, the hemoglobin
acts as a buffer when the deoxygenated blood from the veins reaches
the lungs, O2 dislodges the H+ from the hemoglobin the free H+ combines with bicarbonate to eventually
form CO2 and H2O this is called blood buffering, it helps to maintain
blood pH
Respiratory System Disorders Laryngitis – swelling of the larynx which leads to
temporary voice loss Respiratory Distress Syndrome – newborn
babies lack the lipoprotein coating the alveoli. Extreme force is required by the baby to breathe. May result in death
Pleuracy – inflammation of the pleural membranes (a thin membrane that covers the outer surface of the lung) caused by rubbing together. This results in a fluid buildup in the chest. Exhaling becomes more difficult.
Respiratory System Disorders Bronchitis – caused by a bacterial or viral infection.
It causes mucus cells of the respiratory pathway to secrete more mucus. Tissue swelling occurs and air passages narrow, restricting breathing in and out
Asthma – sufferers require extreme force to exhale, as a result, more air comes in than goes out. Caused by allergies (causing tissues to swell), or muscle spasms on the surface of the bronchioles
Sinusitis – inflammation of the sinuses, mucus discharge and blockage of the nasal passages. Leads to headaches.
Respiratory System Disorders Emphysema – inhalation is easier than exhalation.
The buildup of pressure on the alveoli causes them to rupture, thus reducing the surface area for gas exchange. Breathing rate will increase
Pneumonia – inflammation of the lungs caused by bacteria, viruses, or inhalation of irritating gases. Leads to cough and fever, shortness of breath, chills, sweating, blood in mucus
Lung Cancer – cancer cells destroy healthy lung tissue Cystic Fibrosis – the mucus coating on the insides of
the lungs becomes very sticky leading to breathing problems (genetic condition)