Lab 4 Human Respiratory

internal cellular respiration (IR)

process by which O2 is consumed to produce ATP and CO2

Respiratory Quotient

CO2 produced / O2 consumed

What is the RQ for carbohydrates?

RQ = 1

External respiration

process by which O2 and CO2 are exchanged from the environment into the body

1. Ventilation of air from environment into lungs

2. Gas exchange between alveoli and capillaries

3. Transport of gases through bloodstream to tissues

4. Gas exchange between capillaries and tissues

Where does air travel down a pressure gradient during ventilation?

• entry through nose/mouth

• passage through nasopharynx and oropharynx, glottis, larynx

• entry into tracheobronchial tree

• exchange at alveoli

What are the secondary functions of the respiratory system?

• water and heat balance

• acid base balance

• respiratory pump

• immunity

• vocalization

• production of some enzymes & hormones

• olfaction (smell)

What are the two main airway zones and the general pathway?

1. Conducting Zone

2. Transitional and Respiratory Zones

Airways branch into bronchi and bronchioles, then respiratory bronchioles and alveolar ducts

In order from top to bottom, what are the parts of the conducting zone?

trachea → bronchi → bronchioles → terminal bronchioles

No alveoli, NO gas exchange

In order from top to bottom, what are the parts of the transitional and respiratory zones?

respiratory bronchioles → alveolar ducts → alveolar sacs

Gas exchange at alveolar ducts & sacs

Going down from trachea → bronchi → bronchioles → alveolar ducts, what happens to the diameter, length, number, and cross section?

Diameter: decreases

Length: decreases

Number: increases

Cross sectional area: increases

Type I Alveolar Cells

• flattened single layer of cells forming the wall of the alveoli & performing gas exchange with the capillary

• Total surface area of Type I to Capillary contact is about 75 square meters

Type II Alveolar Cells

About 5% of alveolar cells

secrete pulmonary surfactant (contains lipids and proteins)

facilitates lung expansion and decreases resistance.

*prevents collapsed lung

What is the role of surface tension in the lungs?

• liquid is more attracted to itself than to gas

• resist increase of surface area of gas-liquid interface, therefore decreases the size of alveoli (hollow space)

• Type II alveolar secrete pulmonary surfactant act to decrease surface tension by reducing the attraction of liquids to each other

What would happen if the lining of the air spaces were pure water (liquid)?

surface tension would make it hard to inflate the alveoli in the lung

Why is surfactant needed?

1. needed to lower the work of breathing and to prevent alveolar collapse at end-expiration

2. reduces H+ bonds below water molecular at the surface

3. reduces airway resistance and therefore increases the airflow

What happens to the diaphragm and the external intercoastal muscles during inspiration?

diaphragm contracts and pulls downward, expanding intrapleural space

external intercoastal muscles contract between ribs and pull upwards to enlarge the rib cage

During inspiration there is a ________ in the size of the thoracic cavity and a ______ in the intrapleural pressure. As a result, air rushes in and fills the lungs.

increase, decrease

What happens to the lung pressure during expiration?

lung pressure rises to force air out

What happens to the intercostal muscles during forced expiration?

can contract to force out additional air

ex: exericising, coughing, sneezing

What is the pO2 and pCO2 in venous blood?

pO2 < 40 mmHg

pCO2 > 46 mmHg

What is the pO2 and pCO2 in alveolar air?

pO2 ~100 mmHg

pCO2 ~40 mmHg

The change in pO2 and pH at the receiving tissue ______ Hb’s affinity for O2, delivering it to the tissue

reduces

Carbon dioxide diffuses from the cell into capillary blood and can react in 3 major ways:

• 8% slowly form bicarbonate

• 65% enter RBC and quickly make water and carbonix anhydrase to form bicarbonate

  • 27% will enter RBC and react with amine groups of blood proteins to make carbaminohemoglobin

Minute Ventilation (Ve)

volume of air moving IN and OUT of lungs PER minute

Ve = tidal volume (TV) - respiratory rate (RR)

Dead space ventilation (Vds)

volume of air NOT in gas exchange

leftover air that stays

Vds = dead space volume x RR

Alveolar Ventilation (Va)

part of tidal volume that enters or leaves the gas exchange area of the lung per breath per minute

Va = (TS - DS) x RR =. Ve - Vds

Tidal Volume (TV)

volume of air entering and leaving the lungs every NORMAL breath

Rest (12-15 breaths/min). TV = 500ml

Inspiratory Reserve Volume (IRV)

amount of air that can be forcefully inspired after normal TV inspiration

IRV = 1900-3100 ml

Expiratory reserve volume (ERV)

amount of air that can be forcefully expired after normal TV inspiration

ERV = 700-1200 ml

Residual Volume (RV)

residual volume of air in the lungs after a forced expiration

RV = 1100-1200 ml

What is the vital capacity?

Inspiratory reserve volume + tidal volume + expiratory reserve volume

OR
Total lung capacity - Residual volume (RV) = vital capacity

Total Lung Capacity (TLC)

maximum amount of air in the lungs after a forced maximal inspiration

TLC= 4200 - 6000 ml

TLC = TV + IRV + ERV + RV

Forced vital capacity (FVC)

amount of air that can be expelled when a forced inspiration is taken, then forcefully expired as much as possible

Forced expiratory volume (FEV1)

amount of VC that is expire during the 1ST second of FVC test

Normall 75-85% of VC

What happens to the alveolar ventilation during deep, slow breathing?

increases, higher than quiet breathing at rest

What is the intrapleural pressure?

pressure at the interface of the lung and chest wall

about 756 mmHg at rest

What is the transmural pressure?

difference in pressure across lung wall or across thoracic wall

(P alv - P ip) or (P atm - Pip)

Intra-alveolar pressure (Palv)

pressure of alveoli, which changes with the phases of breathing

Palv always _________ with Patm

equalizes

Interpleural pressure (Pip)

pressure inside the pleural cavity (space between the lungs and chest wall)

• also changes with phases of breathing

INterpleural pressure is always _______ to Palv ( and therefore Patm)

negative

What causes negative interpleural pressure?

• elastic properties of the lungs pulls lungs inward away from thoracic wall

• surface tension in pleural cavity pulls lungs out

Outward pull is ________ than the inward pull, which creates the ____ mmHg intrapleural pressure

slightly greater

Pneumothorax

abnormal collection of air in the intrapleural space and equilibration with Patm

• pleura becomes equalized with atmospheric pressure

• can cause the lung to collapse, called Atelectasis due to low or absent gas exchange

What happens to ventilation during exercise?

increase metabolic demand, increases the demand for oxygen and produced more CO2

Exercise hypernea

increase in ventilation (RR and TV) to match an increase in metabolic activity

What are factors that affect ventilation?

• arterial pO2 and pCO2

• temperature

• blood pH

• exercise activity

• voluntary control of breathing

Dorsal Respiratory Group (DRG)

mostly inspiratory neurons (phrenic nerve)

Ventral Respiratory Group (VRG)

both inspiratory and expiratory neurons, but more important in pacing (exercise)

Pre-Botzinger Complex

contains pacemakers

Pneumotaxic Center

stopping inspiration

Apneustic Center

involved in initiating inspiration

Hypoventilation

decrease in ventilation, INCREASE in arterial pCO2 (hypercapnia)

the increase in pCO2 will cause a decrease in pH (respiratory acidosis)

activates chemoreceptors to increase respiratory rate

Hyperventilation

increase in ventilation achieved by increasing respiratory rate and or tidal volume

rate of ventilation is HIGHER than what is needed to remove CO2 from blood

• decrease in pCO2 hypocapnia

  • decreased pCO2 causes decreased inspiratory drive

Prolonged hyperventilation will lead to…

respiratory alkalosis (increase in pH)

• leads to vasoconstriction in brain arterioles

• decreases blood flow in brain → dizziness

Peripheral Chemoreceptors

• found in aortic arch and carotid bodies

• sensitive to decreases in arterial pO2 (hypoxia) and to a lesser extent increases in pCO2, decreases in pH

Central Chemoreceptors

• found in medullary respiratory center

  • sense increases in pCO2 and decreases in pH by sensing [H+] in cerebrospinal fluid

Hering-Breuer Reflex

high levels of inflation = increased stretch = decreased respiratory drive

low levels of inflation = decreased stretch = increased respiratory drive