Lecture 3: Diving 3 Flashcards
How does blood redistribute during a dive?
- Diving Apnea (breath hold)
- Diving Bradycardia (slow HR) begins with a dive
- Peripheral vasoconstriction (resistance) occurs
(blood vessels in non-vital areas constrict down) - Dilatation in ascending aorta in cetaceans and
pinnipeds (“Natural aneurysm”) - Helps circulate blood during prolonged diastole (relaxation of heart) due to slow heart rate , maintaining blood pressure and distributing oxygenated blood during a dive
What is apnea?
breath hold
What is Bradycardia?
slow HR
What is peripheral vasoconstriction (general)?
blood vessels in non-vital areas constrict down
Explain what happens during peripheral vasoconstriction?
- Appendages will have less blood circulation, while
blood shunts to vital organs (e.g. brain, heart) - Decreased blood flow to muscles
- Increased blood flow to brain and heart (vital organs)
- Brain needs certain amount of glucose (sugar) and
blood flow to survive
Explain some of the differences between an artery and a vein.
An artery has a thick outer wall, small lumen (tube), and thick media (smooth muscle).
A vein has a thin outer wall, large lumen, and thin media.
What are the different layers of skin going from inner to outer?
Muscle, subcutaneous tissue, dermis, epidermis
True/False: Plasma takes up the most volume in blood?
True
Explain how muscle myoglobin in marine mammals affects their metabolism.
- Normally muscle has O2 supply for aerobic metabolism
- Lack of O2 causes anaerobic metabolism
Are the muscles during a dive aerobic or anaerobic?
Not entirely anaerobic
What is an aerobic system?
Oxidation of foodstuffs in the mitochondria to provide energy; Glucose (sugar, carbs), Amino Acids (protein), Fatty Acids (fat) combine with oxygen to release ATP
What is an anaerobic system?
Energy from food without utilization of oxygen; Carbs are metabolized (stored glycogen in cells breaks down into pyruvic acid and ATP (E) ->lactic acid which diffuses out of cells – makes muscles burn – stay hydrated, good cool down
What are examples of aerobic excercise?
running, biking, swimming
What are examples of anaerobic excercise?
sprints, weightlifting, and HIT workouts
Explain what happens during the period of a dive (aerobic/anaerobic).
Most dives are aerobic, but throughout the latter
part (e.g. >20 minutes) of a prolonged dive, the
animal is in an almost completely anaerobic state
Explain how the brain can operate anaerobically.
Brain must operate with at least a partial decrease in
O2 consumption (brain can function anaerobically
for a period of time if enough glucose is available)
Why can diving mammals go longer anaerobically?
Healthy diving mammals have relatively high blood
glucose level and blood circulation is maintained
during latter part of dive, bringing glucose to brain
Explains what happens during a “natural aneurysm”?
Dilatation in ascending aorta in cetaceans and pinnipeds
What is diastole?
relaxation of heart
What is the function of the large posterior vena cava and venous sinuses during a dive?
- Fill with blood, offering a large blood reservoir
- May prevent fluid overload of heart during diving
- Caval sphincter in vena cava at diaphragm interrupts
blood flow through vena cava - May open periodically to allow bolus of blood to travel to
heart
What are the 4 methods of heat transfer between animal and environment?
Conduction, convection, evaporation, and thermal radiation
What is conduction in terms of animals and the environment?
heat transfer through material that is macroscopically
motionless (e.g. ground)
What is convection in terms of animals and the environment?
heat transfer through material by flow of the substance (e.g.
wind, water)
What is evaporation in terms of animals and the environment?
lose heat/cool by evaporation
* Evaporation of sweat (if animal has sweat glands)
* Evaporation of water from respiratory tract (e.g. panting dog)
What is thermal radiation in terms of animals and the environment?
receives heat from sun and surrounding objects
* Animal also emits heat by thermal radiation to surrounding objects
What is the pilomotor response?
contraction or relaxation of muscle at base of hair causes erection or compression of hairs to trap or release air, affecting heat transfer
What is vasomotor response in blood vessels?
constriction of arterioles to preserve heat; vasodilation of superficial veins to release heat
What are a few thermoregulation adaptations important for diving homeotherms?
- Integument modifications
- Restriction of body surface area
- Circulatory adjustments
- Metabolism
- Respiratory modifications
Explain how cetaceans have improved insulation.
Thick blubber layer (hypodermis) with fibrous tissue interspersed with a lot of fat
- Reduces heat loss which saves energy
- An energy reservoir during long
periods without food
Explain how pinnipeds have improved insulation.
fur and thick layer of
subcutaneous fat
- e.g. sea otter has thick fur coat that traps air
Explain how cetaceans have improved body surface area.
- Decreased appendages and
spindle-shaped body - Reduce total surface area to
mass ratio - Decrease amount of exterior
area to which blood is exposed - Therefore, both reduce heat
radiation
Explain the circulatory adaptations of cetaceans.
-Countercurrent heat exchange in flipper, dorsal fin and flukes of cetaceans
-Peripheral artery surrounded by many veins which returns heat to body core
- Restriction of peripheral circulation keeps blood away from surface and conserves heat
Why are circulatory adjustments important for cetaceans?
Important in heat conservation because most
ocean water (even in tropics) is colder at depth
How do mammals keep appendage tissues cool?
countercurrent heat exchange
How do the arteries in dolphins react to heat?
Venous blood returns to heart via superficial veins which lose heat to environment
How do the arteries in dolphins react to the cold?
Venous blood returns to heart via vessels that are wrapped around arteries, transferring heat from artery to vein, conserving body heat
True/False: Cetaceans can also overheat during prolonged
fast swimming, in warm water or if the animal is
out of water
True
What does overheating do to the body of cetaceans?
Overheating increases blood pressure and size of central artery in countercurrent heat
exchange, closing peripheral veins, forcing blood to flow to superficial veins and dissipates heat
- Example: for a beached marine mammal, apply water and sunscreen
True/False: A cetacean’s metabolism decreases during dive
True
True/False: In general, marine mammals have higher
metabolic rates than land animals of similar size
True
Why do marine mammals have higher metabolic rates than land animals of similar size?
- High protein diet (dolphins eat few carbs)
- Thermoregulation increased heat production
Explain the respiratory modifications of marine mammals.
Marine mammals breathe less frequently which
conserves considerable heat
Land animals lose 10-30% body heat in pulmonary
ventilation
