Lecture 13

Question 1

General Adaptations of Flight (3):

Answer 1

1. Increasing muscle temperature
2. Skeletal adaptations
3. Mitochondrial modifications

Question 2

Flight muscles are either:

Answer 2

Synchronous
Asynchronous

Question 3

Synchronous Flight

Answer 3

• Excitation-contraction coupling
• limits wingbeat frequency (low frequency

Question 4

Asynchronous Flight

Answer 4

• Space and energy saving solutions allows for faster beats
• faster beat frequency

Question 5

Asynchronous Flight and APs

Answer 5

• Flight muscles initiates a series of contractions that are each triggered by stretch.
• The frequency of contractions is not synchronized with the frequency of APs

Question 6

Asynchronous Flight and Ca 2+

Answer 6

• Reduced Ca 2+ handling
• Less space is occupied by the sarcoplasmic reticulum and mitochondria
• More space is occupied by myofibrils

Question 7

Adaptations of Muscles for Heat:

Answer 7

• Aerobic swimming muscles (red muscles - fatty parts) are located laterally and heat is lost to environment.
• In lamnid sharks and tuna, red muscle is internalized to retain heat
• Produced as a by-product of aerobic metabolism

Question 8

Adaptations of Muscles for Heat - Rete mirabile:

Answer 8

• Rete mirabile retains heat in muscle and prevents loss of heat to gill.
• Specialized structure in the circulatory system.
• Composed of thousands of closely intermingled veins and arteries functioning as a countercurrent heat exchanger.
• Allows for cold O2 rich blood from gills to come in close contact with warm O2 depleted blood from the tissue.
• Blood from gill is warmed and heat loss from tissue minimized

Question 9

Adaptations of Muscles for Heat - Heater Organs:

Answer 9

• Are specialized eye muscles that keep brain/eye temperature stable and warmer than surrounding water.
• Brain heater organ is modified eye muscle (superior rectus) in all billfish
• Muscle cells have been modified to produce heat without contracting

Question 10

How Heater Organs Work:

Answer 10

• Increased mitochondrial content = increased ability to produce ATP
• Increased sarcoplasmic reticulum = increased ability to store and release Ca 2+
• Increased proliferation of T-tubules = Increased ability to release Ca 2+ into cell

Question 11

Heater Organs ATP:

Answer 11

= Futile Ca 2+ cycling
= moving Ca 2+ to burn ATP, increasing ATP demand
= heat produced as by-product of ATP synthesis