BIO3302 Circulatory Notes

Topics: Blood, Artery, Heart Pages: 21 (1267 words) Published: October 20, 2014
Circulatory physiology
 

Suggested reading
  Chapter

 

8

Topics to be covered
  Roles

of circulatory system
  Design of circulatory systems
  Elements of circulatory systems
Pumps
  Blood vessels
 

  Control
 

of blood pressure and flow

Adjustments for exercise

BIO 3302 – SLIDE #1

Roles of the circulatory system
Time to 95% equilibration of O2
by diffusion

What animals need a
circulatory system, and why?
  Once a circulatory system is
in place, what else can it be
used for?
 

0.1 mm ! 0.067 s

1 mm ! 6.7 s

1 cm ! 10.9 min

1 m ! 78 days

BIO 3302 – SLIDE #2

 

Diffusion vs. convection
 
 
 

Size (time α d2) and metabolic rate are limiting factors
Diffusion is always the final step in O2 transport
Convection is essential for
 
 
 

 

Complex organ systems
To support high metabolic rates
To achieve large body mass

Circulatory system functions in
 

Rapid mass transportation of:
 
 
 
 

 

respiratory gases (except insects)
nutrients
waste products
hormones

 
 

 

antibodies
salts/acid-base
equivalents
heat

Production of force:
 
 
 

Hydrostatic skeletons
Wing expansion in insects
Renal filtration and excretion in vertebrates (regulation of ECF volume)
BIO 3302 – SLIDE #3

Fig. 33.34 Campbell & Reece 2002

Design of circulatory systems
  Three

essential components:

(1) Pump (usually a heart):
 
 
 
 

Positive vs. negative forces
peristaltic pump
chamber pump with contractile walls
chamber pump driven by external forces

(2) Vascular system
 
 
 

arterial system
capillaries
venous system

Peripheral
circulation

(3) Circulating fluid

BIO 3302 – SLIDE #4

Fig. 8.2

 

Two broad trends (with increases in metabolic rate):
 

Open → closed systems
 

 

 

Undivided → divided systems
 

 

Open system = incomplete system of vessels (invertebrates)
- low blood pressure and blood flow
Closed system (vertebrates, some invertebrates)
- high blood pressure (resistance provided by vessels) and blood flow - exchange occurs across capillaries

Separation of systemic and respiratory circulations
(or oxygenated and deoxygenated blood)

Advantages
 

 

improved ability to control velocity and distribution of blood flow "  Allows increases in metabolic rate and body mass
higher pressures achieved
"  enabled evolution of glomerular kidney

BIO 3302 – SLIDE #5

 

Open systems
  Invertebrates
  Haemolymph

pumped by heart empties into sinuses or lacunae to bathe
tissues directly
  High haemolymph volume (~30% body weight)
  Low pressure (typically interstitial fluid → absorption force - Plasma proteins (albumin)
"  Net filtration pressure = (BP – PIF) – (OPblood – OPIF)   Starling-Landis hypothesis
"  Arterial vs venous end of capillary
"  net fluid loss and need for lymphatic
system
 

Hydrostatic
pressure (PIF)

Filtration

Osmotic
pressure (OPIF)

Absorption

Hydrostatic
Osmotic
pressure (BP) pressure (OPblood)

BIO 3302 – SLIDE #35

Fig. 12-38, Randall et al. 2002

 

Practise...
"  Net filtration pressure?
"  Assuming that interstitial fluid values and OPblood remain constant, what must BP fall to at venous end to prevent net loss of fluid?

OP = 3 mm Hg
OP = 28 mm Hg
BP = 35 mm Hg
Arterial end
PIF = 0 mm Hg

Venous end

BIO 3302 – SLIDE #36

  Lymphatic

system

Lymph capillaries
"  Highly permeable walls
"  Diffusion
  How does fluid move?
  Functions
"  Return plasma proteins to circulation
"  Drain extra fluid
  Failure, e.g. filariasis?
"  Oedema
"  Other causes of oedema
 

Fig. 8.41

BIO 3302 – SLIDE #37

Control of regional circulation
 

Capillary blood flow to an organ reflects metabolism
  Priority

 

system: brain, heart & lungs/gills vs. gut, liver, muscles

Definitions
 ...
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