Lecture 3: Diving 3

Question 1

How does blood redistribute during a dive?

Answer 1

1. Diving Apnea (breath hold)
2. Diving Bradycardia (slow HR) begins with a dive
3. Peripheral vasoconstriction (resistance) occurs
   (blood vessels in non-vital areas constrict down)
4. Dilatation in ascending aorta in cetaceans and
   pinnipeds (“Natural aneurysm”)
5. Helps circulate blood during prolonged diastole (relaxation of heart) due to slow heart rate , maintaining blood pressure and distributing oxygenated blood during a dive

Question 2

What is apnea?

Answer 2

breath hold

Question 3

What is Bradycardia?

Answer 3

slow HR

Question 4

What is peripheral vasoconstriction (general)?

Answer 4

blood vessels in non-vital areas constrict down

Question 5

Explain what happens during peripheral vasoconstriction?

Answer 5

• 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

Question 6

Explain some of the differences between an artery and a vein.

Answer 6

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.

Question 7

What are the different layers of skin going from inner to outer?

Answer 7

Muscle, subcutaneous tissue, dermis, epidermis

Question 8

True/False: Plasma takes up the most volume in blood?

Answer 8

True

Question 9

Explain how muscle myoglobin in marine mammals affects their metabolism.

Answer 9

• Normally muscle has O2 supply for aerobic metabolism
• Lack of O2 causes anaerobic metabolism

Question 10

Are the muscles during a dive aerobic or anaerobic?

Answer 10

Not entirely anaerobic

Question 11

What is an aerobic system?

Answer 11

Oxidation of foodstuffs in the mitochondria to provide energy; Glucose (sugar, carbs), Amino Acids (protein), Fatty Acids (fat) combine with oxygen to release ATP

Question 12

What is an anaerobic system?

Answer 12

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

Question 13

What are examples of aerobic excercise?

Answer 13

running, biking, swimming

Question 14

What are examples of anaerobic excercise?

Answer 14

sprints, weightlifting, and HIT workouts

Question 15

Explain what happens during the period of a dive (aerobic/anaerobic).

Answer 15

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

Question 16

Explain how the brain can operate anaerobically.

Answer 16

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)

Question 17

Why can diving mammals go longer anaerobically?

Answer 17

Healthy diving mammals have relatively high blood
glucose level and blood circulation is maintained
during latter part of dive, bringing glucose to brain

Question 18

Explains what happens during a “natural aneurysm”?

Answer 18

Dilatation in ascending aorta in cetaceans and pinnipeds

Question 19

What is diastole?

Answer 19

relaxation of heart

Question 20

What is the function of the large posterior vena cava and venous sinuses during a dive?

Answer 20

• 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

Question 21

What are the 4 methods of heat transfer between animal and environment?

Answer 21

Conduction, convection, evaporation, and thermal radiation

Question 22

What is conduction in terms of animals and the environment?

Answer 22

heat transfer through material that is macroscopically
motionless (e.g. ground)

Question 23

What is convection in terms of animals and the environment?

Answer 23

heat transfer through material by flow of the substance (e.g.
wind, water)

Question 24

What is evaporation in terms of animals and the environment?

Answer 24

lose heat/cool by evaporation
* Evaporation of sweat (if animal has sweat glands)
* Evaporation of water from respiratory tract (e.g. panting dog)

Question 25

What is thermal radiation in terms of animals and the environment?

Answer 25

receives heat from sun and surrounding objects * Animal also emits heat by thermal radiation to surrounding objects

Question 26

What is the pilomotor response?

Answer 26

contraction or relaxation of muscle at base of hair causes erection or compression of hairs to trap or release air, affecting heat transfer

Question 27

What is vasomotor response in blood vessels?

Answer 27

constriction of arterioles to preserve heat; vasodilation of superficial veins to release heat

Question 28

What are a few thermoregulation adaptations important for diving homeotherms?

Answer 28

- Integument modifications - Restriction of body surface area - Circulatory adjustments - Metabolism - Respiratory modifications

Question 29

Explain how cetaceans have improved insulation.

Answer 29

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

Question 29

Explain how pinnipeds have improved insulation.

Answer 29

fur and thick layer of subcutaneous fat - e.g. sea otter has thick fur coat that traps air

Question 30

Explain how cetaceans have improved body surface area.

Answer 30

- 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

Question 30

Explain the circulatory adaptations of cetaceans.

Answer 30

-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

Question 31

Why are circulatory adjustments important for cetaceans?

Answer 31

Important in heat conservation because most ocean water (even in tropics) is colder at depth

Question 32

How do mammals keep appendage tissues cool?

Answer 32

countercurrent heat exchange

Question 32

How do the arteries in dolphins react to heat?

Answer 32

Venous blood returns to heart via superficial veins which lose heat to environment

Question 33

How do the arteries in dolphins react to the cold?

Answer 33

Venous blood returns to heart via vessels that are wrapped around arteries, transferring heat from artery to vein, conserving body heat

Question 34

True/False: Cetaceans can also overheat during prolonged fast swimming, in warm water or if the animal is out of water

Answer 34

True

Question 35

What does overheating do to the body of cetaceans?

Answer 35

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

Question 36

True/False: A cetacean's metabolism decreases during dive

Answer 36

True

Question 37

True/False: In general, marine mammals have higher metabolic rates than land animals of similar size

Answer 37

True

Question 38

Why do marine mammals have higher metabolic rates than land animals of similar size?

Answer 38

- High protein diet (dolphins eat few carbs) - Thermoregulation  increased heat production

Question 39

Explain the respiratory modifications of marine mammals.

Answer 39

Marine mammals breathe less frequently which conserves considerable heat  Land animals lose 10-30% body heat in pulmonary ventilation