NVCC Bio 212

1
Martinis Visual Anatomy and Physiology First
Edition Martini w Ober
Chapter 20 - Respiratory System Lectures 12 13
2
Midterm Grades
Your midterm grades (due March 28) will be
calculated as follows Lec 1 Exam 100
pointsLec 2 Exam 100 pointsLab 1 Exam
100 pointsLaboratory Grade 25-35 points
(5-7 labs so far)Extra Credit 4 points Total
points possible so far...329-339 points Your
grade (Ex., Total points you have / 330)
100 Note No grades will be dropped for
calculation of midterm grade.
3
Mid-term Checkup
Based on the three (3) grades you have received
so far, you should do a mid-term checkup. To find
your average so far total the following points
Lec Exam 1 Lec Exam 2 Lab Exam 1 Lab points
(6 labs) Example (83 67 90 26) ? 330
0.80 (80) Dropping the low grade (83 90 26)
? 230 0.86 (86) To figure out what you need
to AVERAGE for the next lecture and/or lab exam
and the final COMBINED to get a particular grade
Points desired (see syllabus) Total points so
far
Average grade needed on remaining exams

350 (if no grade dropped) or 450 (if low grade
dropped)
This formula assumes you will have 50 pts for
lab and 6 XC pts at the end of the course
4
Points and Grades (from Syllabus) - Revised
Grade for Course Grade as Points (of a possible 700) Quality Points
A 92-100 644-700 4.0
A- 90-91 630-643 3.7
B 88-89 616-629 3.3
B 82-87 574-615 3.0
B- 80-81 560-573 2.7
C 78-79 546-559 2.3
C 70-77 490-545 2.0
D 68-69 476-489 1.0
D 60-67 420-475 0.7
F less than 60 less than 420 0.0
Example 1 To get a grade of B for the course,
using the example grades on previous slide, and
not dropping lowest grade (50), and assuming 50
pts for lab and 6 XC points
574 (83 67 90 50 6) x
x 0.79 (79) Average on upcoming exams
350
Example 2 To get a grade of B for the course,
using the example grades on previous slide, and
dropping lowest grade (67), and assuming 50 pts
for lab and 4 XC points
574 (83 90 50 6) x
x 0.76 (76) Average on upcoming exams
450
5
Lecture Overview

• Lectures 12 13
• The breathing mechanism (ventilation)
• Respiratory volumes and capacities
• Nonrespiratory air movements
• Alveolar gas exchange
• Transport of O2 and CO2 in the blood
• Control of breathing
• Factors affecting breathing

6
Gases and Pressure

• Our atmosphere is composed of several gases and
  exerts pressure
• 78 N2, 21 O2, 0.4 H2O, 0.04 CO2
• 760 mm Hg, 1 ATM, 29.92 Hg, 15 lbs/in2,1034 cm
  H2O
• Each gas within the atmosphere exerts a pressure
  of its own (partial) pressure, according to its
  concentration in the mixture (Daltons Law)
• Example Atmosphere is 21 O2, so O2 exerts a
  partial pressure of 760 mm Hg. x .21 160 mm
  Hg.
• Partial pressure of O2 is designated as PO2

7
Air Movements
If Volume increases, pressure decreases and vice
versa Stated mathematically P ? 1/V (Boyles Law)

• Moving the plunger of a syringe causes air to
  move in or out
• Air movements in and out of the lungs occur in
  much the same way

Figure from Saladin, Anatomy Physiology,
McGraw Hill, 2007
8
Lungs at Rest
When lungs are at rest, the pressure on the
inside of the lungs is equal to the pressure on
the outside of the thorax
Figure from Holes Human AP, 12th edition, 2010
Think of pressure differences as difference in
the concentration of gas molecules and use the
rules of diffusion. Higher pressure means higher
concentration (ignoring temperature difference)
9
Normal Inspiration

• Intra-alveolar (intrapulmonary) pressure
  decreases to about 758 mm Hg as the thoracic
  cavity enlarges
• Atmospheric pressure (now higher than that in
  lungs) forces air into the airways
• Compliance ease with which lungs can expand

An active process
Figure from Holes Human AP, 12th edition, 2010
Phrenic nerves of the cervical plexus stimulate
diphragm to contract and move downward and
external (inspiratory) intercostal muscles
contract, expanding the thoracic cavity and
reducing intrapulmonary pressure. Attachment of
parietal pleura to thoracic wall pulls visceral
pleura, and lungs follow.
10
Maximal (Forced) Inspiration
Thorax during normal inspiration

• Thorax during maximal inspiration
• aided by contraction of sternocleidomastoid and
  pectoralis minor muscles

Compliance decreases as lung volume
increases Costal (shallow) breathing vs.
diaphragmatic (deep) breathing
Figure from Holes Human AP, 12th edition, 2010
11
Normal Expiration

• due to elastic recoil of the lung tissues and
  abdominal organs
• a PASSIVE process (no muscle contractions
  involved)

Normal expiration is caused by - elastic recoil
of the lungs (elastic rebound) and abdominal
organs - surface tension between walls of
alveoli (what keeps them from collapsing
completely?)
Figure from Holes Human AP, 12th edition, 2010
12
Maximal (Forced) Expiration
Figure from Holes Human AP, 12th edition, 2010

• contraction of abdominal wall muscles
• contraction of posterior (expiratory) internal
  intercostal muscles
• An active, NOT passive, process

13
Terms Describing Respiratory Rate

• Eupnea quiet (resting) breathing
• Apnea suspension of breathing
• Hyperpnea forced/deep breathing
• Dyspnea difficult/labored breathing
• Tachypnea rapid breathing
• Bradypnea slow breathing

Know these
14
Nonrespiratory Air Movements

• coughing sends blast of air through glottis
  and clears upper respiratory tract
• sneezing forcefully expels air through the
  nose and mouth
• laughing deep breath released in a series of
  short convulsive expirations
• crying physiologically same as laughing
• hiccupping spasmodic contraction of diaphragm
  against closed glottis
• yawning deep inspiration through open mouth
• valsalva maneuver expiration against a closed
  glottis

15
Alveoli and Respiratory Membrane

• consists of the walls of the alveolus and the
  capillary, and the basement membrane between
  them

Figure from Holes Human AP, 12th edition, 2010
Mechanisms that prevent alveoli from filling with
fluid
1) cells of alveolar wall are tightly joined
together 2) the relatively high osmotic pressure
of the interstitial fluid draws water out of
them 3) there is low pressure in the pulmonary
circuit
Surfactant resists the tendency of alveoli to
collapse on themselves.
16
Just a Quick Review!

• Atmosphere is composed of several gases, each
  exerting its own partial pressure, PO2
• P ? 1/V (Boyles Law)
• Inspiration
• Normal
• Forced or maximal
• Expiration
• Normal
• Forced or maximal
• The respiratory membrane for gas exchange

17
Blood Flow Through Alveoli
Mechanisms that prevent alveoli from filling with
fluid

• cells of alveolar wall are tightly joined
  together
• the relatively high osmotic pressure of the
  interstitial fluid draws water out of them
• there is low pressure in the pulmonary circuit

Low pressure circuit
Figure from Holes Human AP, 12th edition, 2010
18
Diffusion Across Respiratory Membrane
Figure from Holes Human AP, 12th edition, 2010
19
Diffusion Through Respiratory Membrane
The driving for the exchange of gases between
alveolar air and capillary blood is the
difference in partial pressure between the gases.
Figure from Holes Human AP, 12th edition, 2010
At a given temperature, the amount of a
particular gas in solution is directly
proportional to its partial pressure outside the
solution (Henrys Law)
20
Efficiency of Respiratory Membrane Diffusion

• Diffusion of gases across the RM of the lung is
  efficient due to
• Large partial pressure differences
• Small distances
• Lipid solubility of gases
• Large total surface area
• Blood flow and air flow are coordinated

21
Composition of Inspired and Alveolar Air
From Saladin, Anatomy Physiology, McGraw Hill,
2007
22
Factors Affecting O2 and CO2 Transport

• O2 and CO2 have limited solubility in plasma
• This problem is solved by RBCs
• Bind O2 to hemoglobin
• Use CO2 to make soluble compounds
• Reactions in RBCs are
• Temporary
• Completely reversible

23
Oxygen Transport

• Most oxygen binds to hemoglobin to form
  oxyhemoglobin (HbO2)
• Oxyhemoglobin releases oxygen in the regions of
  body cells
• Much oxygen is still bound to hemoglobin in the
  venous blood

Figure from Holes Human AP, 12th edition, 2010
Tissues
Lungs
But what special properties of the Hb molecule
allow it to reversibly bind O2?
24
Review of Hemoglobins Structure
Figure From Martini, Anatomy Physiology,
Prentice Hall, 2001
25
The O2-Hb Dissociation Curve
Recall that Hb can bind up to 4 molecules of O2
100 saturation At 75 saturation, Hb binds 3
molecules of O2 on average Sigmoidal (S) shape of
curve indicates that the binding of one O2 makes
it easier to bind the next O2
Figure from Holes Human AP, 12th edition, 2010
This curve tells us what the percent saturation
of Hb will be at various partial pressures of O2
26
Oxygen Release

• Amount of oxygen released from oxyhemoglobin
  increases as
• partial pressure of carbon dioxide increases
• the blood pH decreases and H increases (Bohr
  Effect shown below)
• blood temperature increases (not shown)
• concentration of 2,3 bisphosphoglycerate (BPG)
  increases (not shown)

Figure from Holes Human AP, 12th edition, 2010
27
Carbon Dioxide Transport in Tissues

• dissolved in plasma (7)
• combined with hemoglobin as carbaminohemoglobin(1
  5-25)
• in the form of bicarbonate ions (68-78)

CO2 H2O ? H2CO3 H2CO3 ? H HCO3-
Figure from Holes Human AP, 12th edition, 2010
CO2 exchange in TISSUES
28
Chloride Shift

• bicarbonate ions diffuse out RBCs
• chloride ions from plasma diffuse into RBCs
• electrical balance is maintained

Figure from Holes Human AP, 12th edition, 2010
29
Carbon Dioxide Transport in Lungs
Figure from Holes Human AP, 12th edition, 2010
CO2 exchange in LUNGS
30
Control of Respiration

• Homeostatic mechanisms intervene so that cellular
  gas exchange needs are met
• Control occurs at two levels
• Local regulation
• Lung perfusion (blood flow 5.5 L/min)
• Alveolar ventilation (4.2 L/min)
• Ventilation/perfusion coupling (matching)
• Respiratory center of the brain

31
Local Control of Respiration

• Local Control regulates
• Efficiency of O2 pickup in the lungs
• Lung perfusion (blood flow)
• Alveolar capillaries constrict when local PO2 is
  low
• Tends to shunt blood to lobules with high PO2
• Alveolar ventilation (air flow)
• High PCO2 (hypercapnia) causes bronchodilation
• Low PCO2 (hypocapnia) causes bronchoconstriction
• Directs airflow to lobules with higher PCO2
• Rate of O2 delivery in each tissue
• Changes in partial pressures
• Local vasodilation in peripheral tissues

32
Factors Affecting Resistance to Airflow

• Diameter of bronchioles
• Bronchodilation (epinephrine, sympathetic
  stimulation)
• Bronchoconstriction (parasympathetic stimulation,
  histamine, cold air, chemical irritants)
• Pulmonary compliance
• Surface tension of alveoli and distal bronchioles.

33
Neural Control of Respiration
Figure from Holes Human AP, 12th edition, 2010
Neural control of respiration has an autonomic as
well as a voluntary component
34
Respiratory Center Autonomic Control
Figure from Holes Human AP, 12th edition, 2010
-
2 sec / 3 sec
-

Apneustic area
Respiratory centers can be facilitated (caffeine,
amphetamines) or depressed (opioids, barbiturates)
35
Factors Affecting Breathing
Central chemoreceptors Respond to PCO2 and pH of
the CSF Effect is actually due to H as
follows CO2 H2O ? H2CO3 H2CO3 ? H HCO3-
Bicarbonate
Carbonic acid
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
36
Factors Affecting Breathing
Both central and peripheral chemoreceptors are
subject to adaptation
Decreased blood PO2 or pH (or increased CO2)
stimulates peripheral chemoreceptors in the
carotid and aortic bodies Stimulation leads to
anincrease in the rate and depth of
respiration
Figure from Holes Human AP, 12th edition, 2010
CO2 is the most powerful respiratory stimulant
37
Factors Affecting Breathing

• motor impulses travel from the respiratory
  center to the diaphragm and external intercostal
  muscles
• contraction of these muscles causes lungs to
  expand
• expansion stimulates stretch receptors in the
  lungs
• inhibitory impulses from receptors to
  respiratory center prevent overinflation of lungs
  (Hering-Breuer reflex)

Figure from Holes Human AP, 12th edition, 2010
CO2 is the most powerful respiratory stimulant
38
Control of Respiration

• Control of respiration is accomplished by
• 1) Local regulation
• 2) Nervous system regulation
• Local regulation
• ? alveolar ventilation (O2), ? Blood flow to
  alveoli
• ? alveolar ventilation (O2), ? Blood flow to
  alveoli
• ? alveolar CO2, bronchodilation
• ? alveolar CO2, bronchoconstriction

39
Control of Respiration

• Nervous System Control
• Normal rhythmic breathing -gt DRG in medulla
• Forced breathing -gt VRG in medulla
• Changes in breathing
• CO2 is most powerful respiratory stimulant
• Recall H2O CO2 ? H2CO3 ? H HCO3-
• Peripheral chemoreceptors (aortic/carotid bodies)
• ? PCO2, ? pH , ? PO2 stimulate breathing
• Central chemoreceptors (medulla)
• ? PCO2, ? pH stimulate breathing

40
Breathing Reflexes

• Protective Reflexes
• Sneezing - Triggered by an irritation of the
  nasal cavity
• Coughing Triggered by an irritation of the
  larynx, trachea, or bronchi
• Both sneezing and coughing involve
• A period of apnea
• Forceful expulsion of air from lungs opening the
  glottis (up to 100 mph or more!!)
• Laryngeal spasms chemical irritants, foreign
  objects, or fluids into the area around glottis
• Temporarily closes the airway
• Some stimuli, e.g., toxic gas, can close the
  glottis so powerfully that it doesnt open again!

41
Life-Span Changes

• reflect accumulation of environmental influences
• reflect the effects of aging in other organ
  systems
• cilia less active
• mucous thickens
• swallowing, gagging, and coughing reflexes slow
• macrophages in lungs lose efficiency
• increased susceptibility to respiratory
  infections
• barrel chest may develop
• bronchial walls thin and collapse
• dead space increases

42
Clinical Application
The Effects of Cigarette Smoking on the
Respiratory System
Figure from Holes Human AP, 12th edition, 2010

• cilia disappear
• excess mucus produced
• lung congestion increases lung infections
• lining of bronchioles thicken
• bronchioles lose elasticity
• emphysema fifteen times more common
• lung cancer more common
• much damage repaired when smoking stops

43
Clinical Application
Figure from Martini, Fundamentals of Anatomy
Physiology, Pearson Education, 2006
44
Review

• The atmosphere is composed of a mixture of gases
• Each gas exerts a partial pressure (Pg)
• Sum of all partial pressures atmospheric
  pressure (14.7 lbs/in2,760 mm Hg., )
• Gases move from a higher concentration (pressure)
  to a lower concentration (pressure)
• Function of the diaphragm is to create a lower
  intrpulmonary pressure so that atmospheric gases
  flow into the lungs

45
Review

• Normal inspiration
• An active process
• Phrenic nerve and diaphragm
• External (inspiratory) intercostal muscles
• Role of the lung pleura
• Normal expiration
• A PASSIVE process
• Due to elasticity of lung/abdominal organs and
  alveolar surface tension
• Forced inspiration
• Forced expiration

46
Review

• Oxygen travels in the blood bound to Hb
• Four O2 molecules can be bound to 1 Hb
• O2 bound to Hb - oxyhemoglobin
• Uptake and release of O2 is dependent upon PO2 in
  alveoli and tissues
• Several factors can increase the release of O2
  from Hb
• Increased PCO2
• Increased H (decreased pH)
• Increased temperature of blood

47
Review

• Carbon dioxide can travel in several ways
• Dissolved in plasma (7)
• As carbaminohemoglobin (15-25)
• As HCO3- ion (70)
• Recall H2O CO2 ? H2CO3 ? H HCO3-
• Carbonic anhydrase in RBCs accelerates
  interconversion between CO2 and HCO3-
• H combines with or dissociates from Hb
• HCO3- diffuses into plasma or into RBCs
• Cl- diffuses into RBC (chloride shift) as HCO3-
  exits
• Diffusion of CO2 is related to PCO2 in alveoli
  and tissues

48
Review

• The respiratory membrane
• Simple squamous epithelium of the alveoli and
  capillaries
• Basement membrane between them
• Terms used to describe breathing (know these)

49
Control of Respiration

• Control of respiration is accomplished by
• 1) Local regulation
• 2) Nervous system regulation
• Local regulation
• ? alveolar ventilation (O2), ? Blood flow to
  alveoli
• ? alveolar ventilation (O2), ? Blood flow to
  alveoli
• ? alveolar CO2, bronchodilation
• ? alveolar CO2, bronchoconstriction

50
Control of Respiration

• Nervous System Control
• Normal rhythmic breathing -gt DRG in medulla
• Forced breathing -gt VRG in medulla
• Changes in breathing
• CO2 is most powerful respiratory stimulant
• Recall H2O CO2 ? H2CO3 ? H HCO3-
• Peripheral chemoreceptors (aortic/carotid bodies)
• ? PCO2, ? pH , ? PO2 stimulate breathing
• Central chemoreceptors (medulla)
• ? PCO2, ? pH stimulate breathing