Transcript Animal Physiology, Chapter 5

The burden of food
Figure 5.2 The uses of energy by an animal
Effect of body size on weekly food requirement
• Meadow- 30-g and 1900-Kg white rhino
• Eat similar food
– Vole eats about 6X its body weight to meet its
energy needs
– Rhino eats 1/3 of its body weight to meet its
energy needs
• Energy needs not proportional to their
respective body size
Figure 5.6 The effect of body size on weekly food requirements
Figure 5.8 Weight-specific BMR as a function of body weight in various species
Figure 5.10 Metabolic rate and body weight are related linearly on log–log coordinates (Part 1)
Metabolic rate and body weight are related linearly on log-log coordinates
• Metabolic rate and body weight are related
alloemtrically among individuals of a single
species
MR-body weight relation- physiological and ecological implications
• Smaller animals breath more rapidly
• Hearts of small animals beat faster for
oxygen to be delivered at a greater rater
per unit of body weight
• Small-bodied species required food at a
greater rate per unit of body weight
MR-body weight relation- physiological and ecological implications 2
• Population biomass per Km2- regular
function of body size
• Smaller animals eat food and breathe air
at a greater rate
• Small and large species process foreign
chemicals differently
• Smaller species more likely to accumulate
environmental pollutants
Fundamentals of animal energetics cont’d
• Animals use their absorbed chemical
energy for 3 functions
– Biosynthesis
• Growth
• Synthesis of organic materials that are exported
from the body
– Maintenance
– Generation of external work
Fundamentals of animal energetics cont’d
• Some energy is degraded to heat
whenever one high-grade form of energy
is transformed to another
• Energy is not recycled
• Animal takes in chemical-bond energy and
put out heat, and external work
• Units of measurement for energy and
metabolic rates– calorie (cal)
• Amount of heat needed to raise the
temperature of 1 g of water by 1degree
centigrade
• Fundamental unit of measurement for
energy in the SI system of units is the
joule (J)
• Summary: Metabolic rate
– An animal’s MR is the rate at which it converts
chemical energy into heat and external work
– MR determines the amount of food an animal
needs, and measures an animal’s intensity of
existence
– Rate of oxygen consumption is the most
common measure of MR
– MR can also be measured by direct
calorimetery
• Two themes in exercise physiology
– Fatigue
• Lessening of a muscle’s ability to generate peak forces and
maintain power output
• Depends on type and duration of exercise
• Lactic acid accumulates
• Acid-base disturbance
• Inadequate muscle glucose
• Accumulation of critical ions– Ca ++
• Overheating
– Muscle fiber types
Figure 6.6 The fueling of intense but sustained muscular work in humans
Figure 6.9 The mechanisms of meeting the ATP costs of world-class competitive running
Metabolic depression in 2 invertebrates experiencing anoxia
• Hypoxia or anoxia- low level of oxygen or
an absence of oxygen
• Respond to lack of oxygen by a drop in
MR
• Reduction in ATP needs
• Metabolic depression depends on pH
Figure 6.11 Metabolic depression in two invertebrates experiencing anoxia (Part 1)
Figure 6.11 Metabolic depression in two invertebrates experiencing anoxia (Part 2)
Figure 6.12 Oxygen regulation and conformity (Part 1)
Figure 6.12 Oxygen regulation and conformity (Part 2)
Figure 6.12 Oxygen regulation and conformity (Part 3)
Oxygen regulation and conformity
• Red circles mark ambient oxygen levels at which
deaths occurred
• Oxygen regulation- maintaining steady rate of
aerobic catabolism regardless of oxygen level
– Increase in breathing rate
• Oxygen conformity- rate of oxygen consumption
fall as environmental oxygen drops
• Correlate with the types of habitats in which they
live
• Fish in slow-flowing water exhibits a much
broader range of oxygen regulation
Oxygen consumption and physical performance at high altitudes
• Human peak oxygen consumption and
physical performance at high altitude
– Decrease concentrations of oxygen
– Cost of exercise remains the same
– At 8000 meter minimal rates of climbing
requires maximal O2 consumption
Box 6.3 The maximal rates of O2 consumption of human mountaineers at increasing altitudes
• The interplay of aerobic and anaerobic
catabolism during exercise
– Cruising fish– steady-state aerobic catabolism
• Can sustain for long periods
• Use red swimming msucles
– Sudden intense exertion
• Use white swimming muscles
• Accumulates lactic acid
– Short period performance
– Exception– insect flight muscle– always aerobic
Summary: Responses to impaired oxygen flux from the environment
• Animals adapted to living without oxygen
undergo metabolic depression when
deprived of O2– lower MR
• Reduce the rate the ATP must be supplied
by catabolic mechanisms
Summary: Responses to impaired oxygen flux from the environment
• Invertebrate anaerobes produce ATP by
means of complex catabolic pathways
• Organic products during anoxia are
excreted as a way of avoiding end-product
accumulation in their bodies
– All vertebrates use anaerobic glycolysis to
produce ATP in tissues deprived of O2
– Anoxia– strictly regional
– CNS must retain adequate O2 supply
Summary: Responses to impaired oxygen flux from the environment
• Turtles capable of total-body anoxia
– Metabolic depression of the CNS
– Become comatose
• Goldfish and Crucian carp also can undergo
total-body anoxia
– Convert lactic acid to ethanol
– Excrete ethanol to avoid end-product accumulation in
their bodies
– Maintain brain activity during anoxia to remain aware
of their environment