Nakamura Human Physiology Lecture 8 Flashcards
(51 cards)
Respiration
.Ventilation: Physically moving volumes of air
•Gas exchange
–between air and blood in the lungs
–between blood and tissues
•02 consumption
–Cellular respirationConducting zone
-not for gas exchange
Anatomical structures air passes through before reaching the respiratory zone including:
–Mouth, nose, pharynx, larynx, trachea, primary bronchi, and bronchioles
-ends in terminal bronchioles
•Functions:
–Warms and humidifies inspired air
–Filters and cleans: Mucus traps airborne particles
Respiratory zone
.Region of gas exchange between air and blood
•Includes respiratory bronchioles and alveoli and alveolar sacs
-starts with respiratory bronchioles and ends in alveolus
•What is important for gas exchange?
–Moist environment
–Large surface area (60 – 80 m2) for diffusion
Properties of lung tissue
.Compliant (stretchable)
•Elastic
–Return to initial size after stretch
–High content of elastin proteins
•Elastic tension increases during inspiration and is reduced by recoil during expiration
Pleurae cavities
-thoracic cavity contains heart and lungs
-pleural cavity within thoracic, just lungs
-left and right pleural cavities sealed, air cannot pass through from one to the other
-Parietal pleura lines the inside of the thoracic wall
•Visceral pleura lines the surface of the lungs
•Pleural cavity is a fluid layer between the two coverings
•Visceral and parietal pleura stick together such that the lungs are suspended from the thoracic wall
Pressures
.Atmospheric pressure at sea level is 760 mMHg (micromercury)
-go deeper, higher pressure
-go higher, lower pressure
•Intrapulmonary (intra-alveolar) pressure
–Pressure in the alveoli
-higher than intrapleural
•Intrapleural pressure
–Constant pressure in the space between the pleurae
-is negative relative to the intrapulmonary pressure
•Transpulmonary pressure
-difference between the intrapulmonary and intrapleural pressures
–Slightly positive to keep the lungs pressed against the chest wall
Abnormal pressures
.Separation of the pleural membranes makes the intrapleural pressure less negative such that it equals the atmospheric pressure.
•If the intrapleural pressure equals the intrapulmonary pressure, the lung cannot expand.
•This condition is called a pneumothorax
Boyle’s law
.Changes in lung volume cause changes in intrapulmonary pressure
–Pressure of a gas is inversely proportional to its volume.
•Increase in lung volume decreases intrapulmonary (alveolar) pressure
–Air enters the lungs
•Decrease in lung volume, raises intrapulmonary pressure above atmospheric pressure
–Air exits the lung
4 processes/ types of respiration
Unforced and forced inspiration
Unforced and forced expiration
Unforced and forced inspiration
.Unforced (-3 mmHg)
•Diaphragm (vertical)
•Ext. intercostals, parasternal intercostals (lateral)
–Forced (-20 mmHg)
•Scalenes, pectoralis minor, sternocleidomastoid
Pressures indicate intrapulmonary pressure below atmospheric pressure
Unforced and forced expiration
Unforced (+3 mmHg)
•Passive process by recoil of lung, diaphragm, and thoracic muscles
–Forced (+30 mmHg)
•Int. intercostals (lateral)
•Abdominal muscles (vertical)
Pressures indicate intrapulmonary pressure whether below or above atmospheric pressure
Surface tension
-Force that causes alveoli to resist expansion
•H20 molecules on the alveolar surfaces are attracted to other H20 molecules
-similar to how water btwn glass cause the glass to stick together, occurs in the lungs as well
Law of Laplace
•Pressure in alveoli is directly proportional to surface tension and inversely proportional to radius of alveoli
- alveoli bigger, tension smaller
- because surfaces are farther apart
Surfactant
-Phospholipid produced by alveolar type II cells
•Lowers alveolar surface tension by separating H20 molecules
•As alveoli radius decreases, surfactant’s ability to lower surface tension increases
•Respiratory Distress Syndrome (RDS)
Carbon dioxide
transported from the body cells back to the lungs as:
1 - bicarbonate (HCO3) - 60% formed when CO2 (released by
cells making ATP) combines with H2O (due to the enzyme
in red blood cells called carbonic anhydrase)
2 - carbaminohemoglobin - 30% formed when CO2 combines
with hemoglobin (hemoglobin molecules that have given up
their oxygen)
3 - dissolved in the plasma - 10%
Respiratory center
-medulla and pons
-Stimulated by chemoreceptors (sense how much CO2 in body)
-Inspiration: more active
-Apneustic center (located in the pons) - stimulate I neurons
-I neurons (inspiratory centre) located in the medulla
Expiration: more passive
-Pneumotaxic center (pons) - inhibits apneustic center & inhibits I neuron
-goes to e neuron (expiratory centre) in the medulla
-inhibits inspiration
Rhythmicity center of medulla
.The rhythmicity center of the medulla:
1) controls automatic breathing
2) consists of interacting neurons that fire either during inspiration (I neurons) or expiration (E neurons)
a) I neurons - stimulate neurons that innervate respiratory muscles (to bring about inspiration)
b) E neurons - inhibit I neurons (to ‘shut down’ the I neurons & bring about expiration
Factors involved by increasing respiratory rate
.Chemoreceptors: located in aorta & carotid arteries (peripheral chemoreceptors) & in the medulla (central chemoreceptors)
2. Chemoreceptors (stimulated more by increased CO2 levels than by decreased O2 levels) > stimulate Rhythmicity Area > Result = increased rate of respiration
Give patients 95 oxygen 5 co2 otherwise shut down respiratory center
Why there is not increased CO2 in the blood during heavy exercise
Possible factors:
a) reflexes originating from body movements (proprioceptors)
b) increase in body temperature
c) epinephrine release (during exercise)
d) impulses from the cerebral cortex (may simultaneously stimulate rhythmicity
area & motor neurons)
Inspiration
.Contraction of external intercostal muscles
-elevation of ribs & sternum
-increased front- to-back dimension of thoracic cavity
-lowers air pressure in lungs
-air moves into lungs
Contraction of diaphragm
-diaphragm moves downward
-increases vertical dimension of thoracic cavity
-lowers air pressure in lungs
-air moves into lungs
Expiration
To exhale:
relaxation of external intercostal muscles & diaphragm
-return of diaphragm, ribs, & sternum to resting position
-restores thoracic cavity to preinspiratory volume
-increases pressure in lungs
-air is exhaled
FEV1
1 second forced expiratory volume test
-how much air forced out in 1 sec
Normal: expiratory: 3.2L/sec
Residual volume: 1.8L
5L-1.8L / 5L-1L * 100 = 80%Restrictive disorder
- vital capacity is reduced (tidal volume, inspiratory reserve volume, and expiratory reserve volume)
- FEV1 is normal
- pulmonary fibrosis (lung damage), more fibers in lung, less elastin protein in fiber
Obstructive disorder
- vital capacity is normal
- FEV1 is reduced
- residual volume: 2.5L
- expiratory: 2.5L/ sec
- 5L-1.8L / 5L-1L * 100= 62.5% - asthma
