Download 14 - Circulation

PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
!Spring 2010!
Figure 24.1 The human heart
Figure 24.2 The heart as a pump: The dynamics of the left side of the human heart
Figure 24.3 Four systems evolved by animals to supply O2 to the myocardium (Part 1)
Figure 24.3 Four systems evolved by animals to supply O2 to the myocardium (Part 2)
Figure 24.4 The conducting system and the process of conduction in the mammalian heart
Figure 24.5 The neurogenic heart of a lobster and the cardiac ganglion that initiates and controls
its contractions
Topic 14 - 1!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
!Spring 2010!
Figure 24.6 Electrocardiography
Figure 24.7 Fluid-column effects on blood pressure in the arterial vascular system
Figure 24.8 Total fluid energy: The true driving force for blood flow
Figure 24.9 The physics of flow through tubes
Figure 24.10 The circulatory plan in mammals and birds
Figure 24.11 A microcirculatory bed
Topic 14 - 2!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
!Spring 2010!
Human Blood/Tissue Composition!
Figure 24.12 Blood flow in the human systemic vasculature (Part 1)
Figure 24.12 Blood flow in the human systemic vasculature (Part 2)
Figure 24.13 Fluid exchange across mammalian systemic capillary walls: The Starling-Landis
hypothesis
Figure 24.14 The circulatory plan in gill-breathing fish
Topic 14 - 3!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
!Spring 2010!
Dipnoi (lungfishes)!
Figure 24.15 The circulatory plans of some air-breathing fish
Six living species!
  Early forms also had lungs as well
as gills!
  South American and African
lungfishes can live out of water
for extended periods, and even
move overland!
 
• Aestivate in mud balls on land
during dry periods!
• Inside of ball is lined with slime,
which drys to a parchment-like
consistency and resists evaporation!
 
Australian lungfish relies on gills
for breathing (can t remain out of
water)!
Figure 24.16 The branchial vascular arches of a lungfish and their relation to heart, lungs, and
systemic tissues
Figure 24.18 The typical circulatory plans of the major vertebrate groups, plotted on a phylogenetic
tree of the groups (Part 1)
Figure 24.18 The typical circulatory plans of the major vertebrate groups, plotted on a phylogenetic
tree of the groups (Part 2)
Figure 24.19 Blood flow in the heart ventricles and the systemic and pulmonary arteries of
crocodilian reptiles
Topic 14 - 4!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
Annelid Circulation
!Spring 2010!
Figure 24.20 The circulatory plan of squids and octopuses
!Blood circulates in a closed"
system:!
•  Five main trunks run lengthwise"
through the body!
•  The dorsal vessel above the alimentary canal has valves and functions as a true
heart!
•  The dorsal vessel pumps blood anteriorly in to five pairs of aortic arches!
•  The aortic arches maintain steady pressure into the ventral vessels!
•  A ventral vessel serves as an aorta, delivering blood to body walls, nephridia
and digestive tract!
Figure 24.22 The heart of a decapod crustacean
Figure 24.23 Circulation through the body of a crayfish or lobster
Box 24.3 Blood flow through the tissues of an insect is principally through lacunae and sinuses
Figure 24.24 The microanatomy of blood flow in a lacunar system: Blood flows most vigorously
where it is needed most
Topic 14 - 5!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
Life at High Altitudes!
 
Effects of High Altitude on Humans!
Atmospheric pressure decreases by 50% with each 1.61 km
increase in altitude!
 
At top of Mount Whitney (4350 m, highest point in continental US), Patm
= 400 mm Hg, PO2 ≈ 75 mm Hg!
  At ≈ 5000 m (Patm ≈ 375 mm Hg, PO ≈ 68 mm Hg), most unacclimatized
2
persons lose consciousness from lack of oxygen!
  At ≈ 5500 m (Patm ≈ 350 mm Hg, PO ≈ 63 mm Hg is the highest
2
permanent human habitation (Andes)!
  At ≈ 8500 m (Patm ≈ 240 mm Hg, PO ≈ 43 mm Hg), human can survive on
2
atmospheric air for a few hours to couple of days!
  At top of Mount Everest (8882 m, highest point on Earth), Patm ≈ 220 mm
Hg, PO2 ≈ 33 mm Hg!
  At ≈ 13,500 m (Patm ≈ 125 mm Hg) is the highest point where humans can
live on pure oxygen!
 
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Migratory paths of some birds take them over the Himalayas!
Ballooning juvenile spiders go even higher!
Andes residents-live at very high altitudes ( highlanders vs.
lowlanders , with some transient sojourners from low to
high)!
 
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1° adaptation: increase in number of red blood cells (polycythemia)!
Result of chronic hypoxia: very long time before this response is
elicited!
Acute hypoxia (sojourners): response is reflex
hyperventilation!
Stimulation of peripheral chemoreceptors (carotid and aortic body) by
↑[CO2] in blood and ↓[O2] (not important at sea level at rest, but
becomes more important than ↑[CO2] for lowlanders!
  Stimulation of medulla oblongata chemoreceptors by [HCO3–] (≈ ΔpH)
in CSF and CO2•H+ (combined effects of CO2 and bicarbonate)!
 
 
Blunting of hypoxic response in highlanders!
 
CO2 response remains normal, but O2 response lost!
Diving!
Effects of High Altitude on Humans!
!Takes long term exposure to achieve maximum acclimatization
to high altitude. In addition to more RBCs, highlanders possess
several adaptations for high altitudes:!
 
Increase in capillary density !
Many air-breathing vertebrates can remain
submerged for long periods!
  Some can actually respire underwater at a low rate!
 
 
Decreases the distance from capillary to O2 source!
  Smaller O2 gradient from alveolar surface to capillaries due to
less O2 consumption by intervening tissues!
 
 
Cascade of from inspired atmospheric O2 to venous O2!
 
 
Less precipitous for highlanders!
  Both highlanders and lowlanders have same venous O2 levels!
 
 
Some amphibians can respire through the skin!
Some turtles can perform buccal-pharyngeal and/or cloacal
respiration!
However, the majority of diving vertebrates (reptiles,
birds, and mammals):!
Stop breathing (apnea)!
Rely on oxygen stores in blood!
  Regulate cardiovascular system to provide oxygen to body
parts (brain, heart, and some endocrine glands) that can
least withstand anoxia!
 
Highlanders have easier dissociation of O2 from Hb!
  Highlanders have higher DPG levels!
 
 
 
!Spring 2010!
Decreases Hb affinity slightly!
Increases O2 loading, decreases O2 unloading!
Diving Patterns!
Figure 25.6 A comparison of the total O2 stores of five species of marine mammals and humans
 
Extremely variable!
Some species (e.g., Weddell seal) dive deeply and repetitively, others
(e.g., fur seal) dive less deeply and more variably!
  Some dive aerobically, others anaerobically!
  Some animals hyperventilate before diving!
  Animals may dive on inspiration, expiration or both!
 
 
When varying diving time, animals know what they are going
to do, and adjust their physiology accordingly!
 
 
 
Change their store of O2 that they take down with them!
O2 stores in blood depend on affinity, blood volume, initial quantity
of dissolved O2 !
Some animals show a big increase in blood O2, others stay
about the same!
 
 
Topic 14 - 6!
In seals, there is a large increase in myoglobin-stored O2!
Also, more O2 stored in lungs, but may not be available during dive!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
!Spring 2010!
Some Physiological Characteristics of Divers!
Figure 25.1 Durations of dives by wild Weddell seals
 
High resting tidal volumes!
Restore O2 to tissues after surfacing, rather than acting as a reservoir
of O2 during the dive!
  This allows a decrease in the interval between dives!
 
Low resting ventilation rate!
Lower chemoreceptor sensitivity to CO2 !
  Lungs collapse and alveoli close during dives!
 
 
 
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Restriction of peripheral blood flow via vasoconstriction!
 
 
No gas exchange means no gas pressure increase in lungs: decreases
possibility of the bends!
Decreases O2 consumption in tissues by isolating muscle mass from
perfused blood!
Bradycardia (slower heart rate)!
 
 
May be stress response or experimental artifact!
Weddell seals have very variable bradycardia: heart rate slows as
length of dive increases!
Figure 25.5 The thorax is highly compressible in marine mammals
Figure 25.14 The hypothesis of preferential collapse of the alveoli and alveolar sacs at depth
Figure 25.10 Metabolic subdivision of the body in seals during forced submergence
Figure 25.9 Diving heart rate varies with dive duration in a graded manner in freely diving seals
Topic 14 - 7!
PSLY 4210/5210
!Comparative Animal Physiology
!Circulation!
Physiological Responses Accompanying
Resumption of Breathing!
Physiological Responses During Diving!
 
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In mammals (but not other vertebrates) stimulation of the facial receptors that
inhibit breathing induces bradycardia.!
As animal undergoes apnea and the lungs are compressed during the dive,
lung stretch-receptor activity decreases.!
Initial pressurization of the lungs can produce a transient increase in blood O2
and CO2. Continued diving reduces O2 and increases CO2. Lactic acid washout
occurs only on long dives (little buildup during short dives because no
bradycardia and hence on anoxia in tissues).!
Decreased O2 stimulates arterial chemoreceptors and, in the absence of lung
stretch-receptor activity, causes increase in sympathetic nerve output and
consequent peripheral vasoconstriction and reduction in heart rate and cardiac
output. Blood flow to major organs such as the kidneys is greatly reduced. In
some cases, blood flow to muscles is also reduced (depending on exercise
during the dive).!
In some animals, increase in arterial pressure is sensed by baroreceptors and
bradycardia is maintained by a rise in both chemoreceptor and baroreceptor
discharge frequency. Bradycardia is caused by an increase in parasympathetic
activity and decrease in sympathetic activity of nerve fibers innervating the
heart. In birds, decreased O2, increased CO2, and ΔpH stimulate
chemoreceptors in carotid body, inducing bradycardia.!
Diving in a Seal!
!Spring 2010!
In absence of breathing, lung inflation tends to suppress reflex
cardiac inhibition and peripheral vasoconstriction caused by
stimulation of arterial chemoreceptors. As animal rises in the
water column, the lung becomes inflated, possibly activating
lung stretch-receptors and causing cardiac acceleration!
  Once animal resumes breathing, stimulation of arterial
chemoreceptors results in a marked increase in lung
ventilation!
 
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 
 
Low blood O2 and/or high blood CO2 levels cause peripheral
vasodilation!
Leads to increased cardiac output to maintain blood pressure in the
face of this increased peripheral blood flow!
Thus, hypoxia caused by a cessation in breathing during
diving is associated with a decrease in heart rate and cardiac
output. In contrast, hypoxia that occurs during breathing (e.g.,
at high altitudes) is associated with an increase in heart rate
and cardiac output.!
Figure 25.11 The aftermath of a prolonged dive: Lactic acid in muscles and blood
When a seal dives,
heart rate, cardiac
output, and blood
O2 content decrease,
and blood CO2
increases. During
the post-dive
recovery period,
blood lactate
increases greatly,
while the other
parameters first
overshoot and then
return to their predive levels. !
Figure 25.12 Peak concentration of lactic acid in arterial blood of freely diving, adult Weddell seals
following dives of various durations
Figure 25.13 Energy-sparing behaviors of freely diving Weddell seals
Topic 14 - 8!