Why do mammals dive?
- To find food, foraging
- To avoid predators (great white sharks)
- Energy efficent
What happens in response to diving?
- Apnea: stop breathing, no more O2 in and CO2 out
- Bradycardia: slowing HR to conserve CO2
- Peripheral Vasoconstriction: Send blood to vital organs (brain, heart, some muscles if moving)
What problems happen with diving
- Pressure: depressurizes too quickly = dissolve gases can form bubbles that lodge in critical organs.
- Nitrogen narcosis = Nitrogen gets toxic at higher pressures, intoxication - O2 storage: stored in Blood, Muscles, Lungs (covid fail). Gets pushed into blood/tissues, highly reactive, toxic at high pressures. CAUSES: Nausea, convulsion, death
- CO2 accumulates: leads to acidosis.
- Cold: must prevent hypothermia
- Buoyancy: most mammals float
- Decompression sickness: Increase solubility at depth, gasses saturated in tissues, form bubbles in tissues/joints on ascent
- High Pressure Nervous Syndrome (HPNS): Pressure causes changes in nerve function. CAUSES: tremors, seizures, and death
What is hydrostatic pressure? Effects?
Hydrostatic pressure: pressure at depth due to weight of water column. Pressure increases 1 atm with each 10m of depth.
- Effects of high pressure
- may change protein structure & function
- change enzyme kinetics
- influence viscosity of cell membrane
What is Henrys Law?
G = P [gas] x S [gas]
Increase pressure = Increase solubility of gas in blood & tissues
At depth, pressure is high & more gas is being pushed into blood/tissues
What adaptations do mammals have in order to dive
- Flexible chest
- Modified Lung Structure
- Bronchial Sphincters
- Large aortic bulb = allows blood flow regulate
- Enlarged spleen & Hepatic sinus = store RBC in spleen
- Vena caval sphincter
- HIgher brain capillary density
- Retia Mirabilia = increase surface area for gas exchange
What does a flexible chest do for mammals
Flexible Chest = lung and rib cage compresses and shint air into rigid upper airway
Reinforcement of distal airways, allow movement of air from alveoli to bronchi during lung compression = promotes lung collapse of alveoli and cessation of gas exchange at depth.
some mammals have transitional epithelium.
What does a aortic bulb do for mammals
Large Aortic Bulb = aortic bulb increases volume capacitance of aorta = helps maintain blood flow during bradycardia
Deeper dive mammals = bigger bulb
Engalrged spleen and hepatic sinus
Splenic Red Cell Storage = diving induced sympathetic vasoconstriction = spleen contracts. More RBC storage = use RBC during diving
Large venous reservoir = Hepatic sinus = dilation of the inferior vena cava at the site of entry.
Rentia mirabilia
High brain capillary density: lots of blood flow to the brain
Retia (high surface area) mirabilia = vascular network = primarily @ base of brain = function as “windkessel” for brain blood flow, or filter for arterial gas emboli = maintain blood flow during dive.
Windkessel = dapens arterial pressure pulses, protect brain against damage during diving
Prevent nitrogen bubbles form reaching brain.
What happens with O2
- Needs O2 to make ATP and carried by binding to hemoglobin. NO O2 = NO ATP
- If P50 INCREASES, Affinity DECREASES
- Myoglobin = holds onto O2 more strongly, usually in muscles
What happens with CO2
- CO2 produced in Citric Acid Cycle, carried away from tissues as HCO3-
- INCREASE H+ = DECREASE pH
- Decreases O2 affinity = Hb lets go of O2 sooner
What is the equation for cADL
Calculates how long to dive aerobically
cADL = O2 stores / Metabolic Rate
Calculated ADL = how much O2 is available & how much we are using
What’s Bradycardia?
Bradycardia: Decrease in HR
Regulation: Paraysmpathetic NS Decrease HR = Vacus CN = release ACH onto muscarinic receptors
- Increase permeability to K+, HR slows
What’s Peripheral Vasoconstriction?
Peripheral Vasoconstriction: Reduces blood blow to nonessential organs
- What causes Vasodilation? = INCREASES K+,
H+, CO2, Low O2
- What causes Vasoconstriction? = Cold temp,
SphinctersWhat is Hypometabolism?
Hypometabolic response: Slow down ATP usage, less O2 needed. Cold Temp helps.
- Helps prolong ADL
- Brain can be tolerant to cooler temps
- Diving mammals = adaptations to allow tolerance = more capillary density
Metabolic Rate is less during dive
Blood and O2 storage
Hypercoagulable Blood
Hypercoagulable Blood = hageman factor deficiency = Factor XII = Hageman factor = protein involved in blood clotting. Even @ higher viscosity
- may help improve microcirculation during dive. Higher hematocrit, blood flow still maintain bc of hypercoagulable abilities.
Free Radicals
Free Radicals: erosion of cell membranes, Damage of nuclear and mitochondrial DNA
Leads to: decrease protein synthesis, decrease tolerance to stress, impaired cellular physiology function (transport & communication)
Diving mammals have great immune system to counteract free radicals & they collapse lungs
Marine mammals have protective mechanisms against free radicals.
