The Cardiovascular System
Respiration
___________________of the Respiratory System
Exchange of Gas (at the alveoli)
Exhaled air used in vocalization
Heat dissipation of Heat and Water
______________ Balance
________________ in Respiratory Zones
Movement of Air (Conducting zone):
–mouth/nose --> trachea --> bronchioles
–Conducts air to the respiratory zone
–Also serve to warm, humidify and filter inspired air
Gas Exchange (_________________ zone):
–Alveoli
–Site of gas exchange
Steps in Respiration:
Ventilation: breathing Movement of Air
Gas exchange: Movement of Molecules
air --> blood --> tissue
__________ utilization: Use of Oxygen
Cell Respiration Production of CO2
The Respiratory Cycle
___________ (Active negative pressure)
–Diaphragm Contracts (flattens)
–Muscles Pull the ribcage up and out
_______________ (Passive positive pressure)
–Muscles relax
–Elastic Lung tissue recoils
Gases diffuse down their pressure concentration gradients
_____ Phases of Respiration
Pulmonary ventilation – moving air into and out of the lungs
External respiration – gas exchange between the lungs and the blood
_________ – transport of oxygen and carbon dioxide between the lungs and tissues
Internal respiration – gas exchange between systemic blood vessels and tissues
Mechanisms of Breathing
Inspiration and expiration are accomplished by contraction and relaxation of striated muscle
Quiet __________________
–contraction of the diaphragm and external intercostal muscles increase thoracic volume --> increased lung volume
–intrapulmonary pressure becomes subatmospheric and air comes into t the lungs
Mechanisms of Breathing
Quiet _______________
–muscles relax --> elastic recoil of lungs and thorax decreases thoracic volume --> raise intrapulmonary pressure
–air is forced out
Forced inspiration and expiration
–contraction of accessory respiratory muscles leads to larger changes in intrapulmonary pressure
Muscles of Breathing
Pulmonary Respiration -
Lung Volumes and Capacities
Lung volumes:
–__________ (TV)
–inspiratory reserve volume (IRV)
–expiratory reserve volume (ERV)
–residual volume (RV)
Lung capacities:
–total lung capacity
–_______________ (VC)
–inspiratory capacity
–functional residual capacity
_____________________ = tidal volume x breaths/minute
Accommodation in Exercise
Increase Total Minute Volume
ν Increase the Volume in the Lungs
ν Increase the Number of Breaths per Minute
Unforced Respiratory Cycle
Forced Expiration
Forced Inspiration
____________ of Breathing
Breathing must occur in a continuous cyclical pattern to sustain life
Cyclical neural activity to the respiratory muscles
The motor neurons that stimulate the respiratory muscles are controlled by two major descending pathways:
–voluntary breathing
–involuntary breathing
Regulation of Breathing
Brainstem respiratory centers:
–a diffuse neuronal system in the medulla forms the rhythmicity center that controls automatic breathing
–respiratory areas in the pons influence breathing
Regulation of Breathing
Nuclei in the medulla control the cycle of inspiration and expiration
Dorsal respiratory group neurons (DRG neurons):
–control the diaphragm and external intercostal muscles (I neurons)
CNS Regulation of Ventilation
Negative Feedback Control of Ventilation
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Oxygen Transport
Hemoglobin
–Heme: organic pigment molecule; contains ferrous iron (Fe++)
–Globin: four polypeptide chains
Anemia
–Hemoglobin concentration is below normal
Polycythemia
–Hemoglobin concentration is above normal
Erythropoietin
–Secreted by kidneys; controls production of hemoglobin & RBCs in bone marrow
Loading/unloading reactions
Lungs: deoxyhemoglobin + O2 --> oxyhemoglobin (loading)
Tissues: oxyhemoglobin --> deoxyhemoglobin + O2 (unloading)
Factors influencing reactions
–PO2 of the environment
•High PO2 favors loading
–Affinity between hemoglobin and oxygen
•Weak bond favors unloading
Oxyhemoglobin dissociation
Blood entering the tissues contains 20 ml O2 per 100 ml blood
Blood leaving the tissues contains 15.5 ml O2 per 100 ml blood
–22%, or 4.5 ml of O2 out of the original 20 ml O2 per 100 ml blood, is unloaded to the tissues
- Oxyhemoglobin dissociation curve
–Oxyhemoglobin in the venous blood at rest functions as an oxygen reserve
Effects of pH and temperature
Bohr effect: affinity between hemoglobin and oxygen is decreased when pH is lowered and increased when pH rises
Reduced affinity = greater unloading of O2
Effect of pH on oxyhemoglobin dissociation curve (See figure 23.1)
–A shift to the right of the curve indicates a greater unloading of oxygen
Affinity between hemoglobin and oxygen is decreased when temperature increases
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