quiz 7 Flashcards
complex functions of single-celled organisms
- locomotion
- feeding
- decision making
- sensing (i.e. harpoons that detect nearby organisms and stab them)
common problems with the physiology of multicellular organisms (that are not problems for unicellular organisms)
- gas exchange
- nutrient/waste delivery
- water balance
- central control processing (internal homeostatic, motor control, external sensory stimuli)
materials needed to diffuse in/out of cells
- oxygen in
- CO2 out
- nutrients in
- waste out
*easy to diffuse with single cells, challenging with layers
rate of diffusion
about 100 micrometers every 2.5 seconds
diffusion in water vs air
- diffusion much slower in water/fluid
- explains why pneumonia or covid causes trouble getting enough oxygen, fluid in alveoli
how does diffusion impact metabolic rate
- metabolic rate can be stressed by a greater diffusion distance, as diffusion takes time (materials take longer to enter/exit cells)
basal and functional metabolic rates
- basal metabolic rate is consistent among organisms, both unicellular and multicellular
- functional metabolic rate changes depending on movement
how do capillaries solve diffusion problems
- diffusion works fine when cells are close to capillaries, but cells further back struggle with nutrition and waste (flux of materials)
- more capillaries = shorter diffusion distances, increasing plumbing is a solution
mouse capillary experiment
- mice put in low oxygen and grew more capillaries in thin ear tissue
- increasing amount of blood vessels allowed greater oxygen delivery to cells
***another possible solution to low O2 environment: increase amount of hemoglobin (protein that carries it)
connectivity of systems for metabolism
- multicellular organisms have a gas exchange surface (respiratory system) and a mechanism for delivering gas in/out of the system (cardiovascular system)
Highly connected!
diversity of respiratory surfaces
- we can use words like “more derived” or “less derived”, no system is better
examples
- transdermal: diffusion through skin
- spiracles on grasshoppers squeeze air in and out
- gills highly efficient at extracting oxygen from water (very little oxygen in water)
respiratory anatomy of mammals
large conducting airways
-cartilage (strong, prevents collapse), cilia (moves detritus up and cleans), smooth muscle
small airways (alveoli) - some smooth muscle (can cause asthma problems if too tight), no cartilage/cilia because gas exchange (needs to be thin)
how does airway diameter impact airflow?
- airway becomes narrower when smooth muscle contracts, asthma can cause this
- albuterol is smooth muscle relaxer
how does gas exchange work in the alveoli?
- capillary wall is one cell thick
- materials diffuse in and out at the same time, O2 going to blood and CO2 leaving blood move independently
CF complications with cilia
- cilia don’t function properly in people with CF, so the lungs can’t be cleaned out
what factors impact ability to oxygenate blood?
- amount of air moved in/out of lung
- size of conducting airways (asthma can shrink)
- number of alveoli (emphysema from smoking can decrease)
- number of functioning alveoli (pneumonia and illnesses cause non-functioning alveoli with fluid)
- alveoli blood flow (clots)
importance of lung surface area
- lung SA is huge which allows for fluctuations in our metabolic rate (more oxygen needed)
- tissue consumes 5L of oxygen per minute when exercising
- as SA increases moving down the lung (branching), velocity of oxygen decreases
what is partial pressure
- partial pressure = % gas in atmosphere x barometric pressure
- includes both a concentration component (oxygen is 21% of gas in atmosphere) and a pressure component (weight of atmosphere)
how does gas equilibration work?
- directional movement of gas based on partial pressure, not concentration!!
- takes 0.25 seconds to equilibrate in alveoli, so lungs are rarely limiting factor in ability to oxygenate
how does partial pressure change across locations?
% oxygen in atmosphere stays the same but barometric pressure changes, so partial pressure changes
oxygen cascade in the respiratory system
oxygen levels decrease as you approach the “end user” of the cell
ambient air - alveolar gas - arterial blood - capillaries - mitochondria
partial pressures of oxygen in air and within the body
- ambient air: 150-160 mmHg
- alveoli/arterial: 100 mmHg
- venous: 40 mmHg
partial pressures of carbon dioxide in atmosphere and in body
- ambient air: ~0.3 mmHg
- alveoli/arterial: 40 mmHg
- venous: 46 mmHg
why won’t alveolar gas levels match the ambient air?
- alveoli are mixing chambers; we never fully expel the air
- impossible to reach PO2 as high as in the atmosphere with this left over air
how do muscles aid in ventilation?
inspiration is an active process
- diaphragm is a dome that flattens when contracted, generating a suction pressure
- external intercostals between ribs help
expiration is a passive process
- muscles relax
impact of high altitude on partial pressure of oxygen
- Mt Everest partial pressure at 40 mmHg, equal to venous partial pressure
- most people can’t survive extreme high altitude
- people will act drunk, be unable to do simple tasks, and take risks
impact of low altitude on partial pressure of nitrogen
- symptoms of high nitrogen levels can begin at 70 ft underwater (triple the ambient pressure of sea level)
- Nitrogen narcosis also called “rapture of the deep”
- solution: lower nitrogen content in gas tank (helium is replacement)
danger of fast pressure changes while diving
- as pressure decreases, nitrogen leaves tissues and forms bubbles
- can bubble in joints causing “the bends” or bubble in a blood vessel which can block flow and cause death
- to avoid this, divers must slowly ascend to lower pressure–like bubbling on a soda can, the pressure must change gradually
how do oxygen-binding proteins aid in delivery to tissues?
- oxygen not very soluble in water, binding pigments increase delivery
- most iron or copper based
* hemoglobin is iron-based, carries 4 O2, found in red blood cells
* hemocyanin is copper-based, carries 1 O2, found in plasma
importance of myoglobin in animals
- oxygen-binding protein found in muscle
- oxygen transferred from hemoglobin to form reserves in highly metabolic tissue (like neurons)
hemoglobin subunits and oxygen binding
- hemoglobin has 4 subunits; 2 alpha chains and 2 beta chains
- first 2 added easily even with lower PO2 (steep curve with high affinity)
- last 2 added less easily and require higher PO2 (flatter curve with lower affinity)
- full oxygen saturation at 60 PO2, even though alveoli PO2 is normally 100
what does the shape of graph of hemoglobin saturation for PO2 levels indicate?
- sigmoid shape indicates that there’s cooperativity between multiple subunits of hemoglobin
- affinity very high for first 2 oxygens, then lowers for last 2
affinity
oxygen saturation per change in PO2
shape of myoglobin saturation graph for PO2 levels
- myoglobin found in muscles, oxygen transferred from hemoglobin
- not sigmoid (single polypeptide chain)
- left shifted curve indicates higher affinity for oxygen than hemoglobin
why does myoglobin have a higher oxygen affinity than hemoglobin?
- in muscles; must receive oxygen from hemoglobin (must bind at PO2 that hemoglobin releases)
- only one polypeptide; easier to saturate with no sigmoid curve
roles of hemoglobin and myoglobin
- hemoglobin delivers oxygen
- myoglobin is a depot for oxygen, allowing for rapid changes in metabolism
hematocrit and its percentages in people
hematocrit: % whole blood packed with RBCs
- 42-45% in women
- 45-48% in men
- endurance training increases 2-3%, body needs to produce more RBCs to sustain exercise
where and why are RBCs formed?
- to increase oxygen delivery, body must increase RBC number
- RBCs formed in bone marrow, surrounded by lots of fat
what signals synthesis of more RBCs?
Erythropoietin (EPO) released from kidneys when tissues are hypoxic (caused by various kinds of anemia)
results of PulseOx experiment
- infrared light in PulseOx measures arterial O2 levels
- Megan had high air hunger but barely any O2 change
results of breath holding experiments in divers
- oxygen saturation will remain normal over 2 minutes into breath holding
- although normal alveoli PO2 is 100 mmHg, hemoglobin will remain saturated until PO2 is at 60 mmHg
- blood can remain fully saturated even with decreasing partial pressures of oxygen!
at what point does low oxygen affect breathing?
- ventilation rates increase when PO2 gets to 60 mmHg (hemoglobin not fully saturated)
- this requites high elevation (breathing shouldn’t be impacted until at least 10,000 feet)
*oxygen is not the main driver of breathing!
how does our body sense oxygen levels?
- peripheral chemoreceptors: aortic and carotid bodies
- humans mainly use carotid bodies, located at bifurcation of carotid arteries
what is the main determinant of breathing rate? why?
carbon dioxide–ventilation rates will increase with very small PCO2 increases; most people can only tolerate 9% CO2 inspired
- CO2 forms carbonic acid with water
- enzymes that drive our body’s reactions have a narrow pH range, causing “air hunger” when carbonic acid levels are higher
