Why do we need a respiratory system
* Need O2
* Aerobic cellular respiration
* Make ATP
* Need CO2 out
* Waste products from the Krebs cycle
Gas Exchange
* O2 and CO2 exchange between environment and cells
* Need moist membrane
* Need high surface area
Optimizing Gas Exchange
* High surface area
* Maximizing rate of gas exchange
* CO2 and O2 move across cell membrane by diffusion
* Rate of diffusion is proportional to surface area
* Moist Membranes
* Moisture maintains cell membrane structure
* Gases diffuse only dissolved in water
Evolution of Gas Exchange Structures
* Aquatic organisms
* External system with lots of surface area exposed to aquatic environment
* Terrestrial
* Moist internal respiratory tissues with lots of surface area
Counter Current Exchange System
* Water carrying gas flows in one direction, blood flows in the opposite direction
Gas Exchange on Land
* Advantages
* Air has many advantages over water
* Higher concentration of O2
* O2 and CO2 diffuse much faster through air
* Respiratory surfaces exposed to air do not have to be ventilates as thoroughly as gills
* Air is much lighter than water and therefore much easier to pump
* Expend less energy moving air in and out
* Disadvantages
* Keeping large respiratory surface moist causes high water loss
* Reduce water loss by keeping lungs internal
Terrestrial Adaptations
* Tracheae
* Air tubes branching throughout the body
* Gas exchanged by diffusion across moist cells lining terminal ends, not through open circulatory system
Alveoli
* Gas exchange across thin epithelium of millions of alveoli
Negative Pressure Breathing
* Breathing due to changing pressures in lungs
* Air flows from higher pressure to lower pressure
* Pulling air instead of pushing it
Mechanics of Breathing
* Air enters nostrils
* Filtered by hairs, warmed, and humidified
* Sampled for odors
* Pharynx → glottis → larynx (vocal cords) → tracheae (windpipe) → bronchi → bronchioles → air sacs (alveoli)
* Epithelial lining covered by cilia and thin film of mucus
* Mucus traps dust, pollen, and particulates
* Beating cilia moves mucus upward to pharynx, where it is swallowed
Autonomic Breathing Control
* Medulla sets rhythm and pons moderates it
* Coordinate respiratory, cardiovascular systems and metabolic demands
* Nerve sensors in walls of aorta and carotid arteries in the neck detect O2 and CO2 in blood
Medulla Monitors Blood
* Monitors CO2 level of blood
* Measures pH of blood and cerebrospinal fluid bathing the brain
* If pH decreases then increase depth and rate of breathing and excess CO2 is eliminated in exhaled air
Breathing and Homeostasis
* Homeostasis
* Keeping the internal environment of the body balance
* Need to balance O2 in and CO2 out
* Need to balance energy production
* Exercise
* Breathe faster
* Need more ATP
* Bring in more O2 and remove more CO2
* Disease
* Poor lung and heart function
* Breathe faster
* Need to work harder to bring in O2 and remove CO2
Hemoglobin
* Why use a carrier molecule
* O2 is not soluble enough in water for animal needs
* Blood alone could not provide enough O2 to animal cells
* Hemocyanin in incest
* Copper
* Hemoglobin in vertebrates
* Iron
* Reversibly binds O2
* Loading O2 at lungs or gills and unloading cells
Cooperatively in Hemoglobin
* Binding O2
* Binding O2 to first subunit causes shape change to other subunits
* Conformational change
* Increasing attraction to O2
* Releasing O2
* When first subunit release O2, causes shape change to other subunits
* Conformational change
* Lowers attraction to O2
O2 dissociation curve for hemoglobin
* Drop in pH lowers affinity of Hb for O2
* Active tissue lowers blood pH and induces Hb to release for O2
* Increase in temperature lowers affinity of Hb for O2
* Active muscle produces heat
Transporting CO2
* Dissolved in blood plasma as bicarbonate ion
Releasing CO2 from blood and lungs
* Lower CO2 pressure at lungs allow CO2 to diffuse out of blood into lungs
Adaptation for pregnancy
* Mother and fetus exchange O2 and CO2 across placenta tissue
Fetal Hemoglobin
* Fetal hemoglobin had greater attraction to O2 than hemoglobin
* Low % O2 by time blood reaches placenta
* Fetal hemoglobin must be able to bind O2 with greater attraction than maternal Hemoglobin