Airgas template

1
if it takes 1 second for a given quantity of
glucose to diffuse 100 ?m, it will take 100 sec
for the same quantity to diffuse 1 mm, and almost
three hours to diffuse 1 cm.
A
2mm
1mm
A
1mm2 1 sec 2mm2 4 sec
B
B
2
So, diffusion is only effective when dealing with
a large surface area, minimal thickness, and a
relatively inactive tissue
Ficks Law of Diffusion Diffusion (C1
C2) SA thickness
3
More complex body plans Diffusion fails as a
sole means of distribution
Convective Exchange (constant) ?V (C1 C2)
Campbell Fig.32.4
4

• Flow (F) Pressure Gradient (?P)
• Resistance (R)

• What is this flow transporting?
• 1. Gases
• 2. Solutes
• 3. Nutrients
• 4. Hormones (chemical messages)
• 5. Wastes
• 6. Heat
• 7. Force

How do you get a good pressure gradient?
5
http//yakko.bme.virginia.edu/lab/images/beating_h
eart.gif
6
Gradual separation of the heart into two separate
pumps
7
Two Parts of the Circulatory System

• Pulmonary circulation
• Moves blood through the lungs and creates a link
  with the gas exchange function of the respiratory
  system
• Systemic circulation
• Supplies all the other tissues of the body

Body
Lungs
Right Heart
Left Heart
8
The Heart as a Pump

• The heart is an intermittent pump
• Blood flow in the arterial circulation is
  pulsatile

Porth Fig. 23.2
9
Moyes and Schulte Figure 9.31
10
GEOMETRY OF BLOOD VESSELS IN DOG MESENTERY
11

• Poiseuilles law

Porth Fig. 23.3
12
Usually the major determinant of TPR
http//www.oucom.ohiou.edu/CVPhysiology/H003.h
tm
13
Resistance varies inversely with the fourth power
of the vessel
R 1 r4
so, if the radius of a vessel is doubled, the
resistance drops to 1/16th of its original value
r4 1 x 1 x 1 x 1 1
r4 2 x 2 x 2 x 2 16
http//nobelprize.org/medicine/laureates/1998/meda
nim/images.html
14
Atherosclerotic plaque forming in a coronary
artery.
. decreasing radius (r), and increasing
resistance
. which is made even worse if a spasm develops
in the wall of this vessel
15
So, if a drug can be provided that relaxes the
spasm.
radius will be increased, and resistance will
be lessened
and flow will be increased

16
Velocity
Inversely proportional to cross-sectional area
Porth Fig. 23.4
17

• Blood pressure is highest in the left ventricle
• Blood pressure drops rapidly in arterioles due to
  high resistance
• Blood pressures decreases as the blood moves
  through the system
• The velocity of blood is highest in the arteries
  (high pressure), lowest in the capillaries (large
  cross-sectional area), and intermediate in the
  veins (lower pressure and cross-sectional area)

Moyes and Schulte Figure 9.33
18
Laminar vs. Turbulent Flow
Porth Fig. 23.5
19
Law of LaPlace (1) Pressure depends upon
surface tension and radius (a) P 2T/r
Porth Fig. 23.3
20
Compliance and elastance

• a) Compliance ( ? V / ? P)
• (1) ability to stretch
• b) Elastance
• (1) ability to return to original position

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22
Preload, afterload, and contractility
Porth Fig. 23.16

• Preload amount of tension on the muscle before
  it contracts
• Afterload load against which the muscle exerts
  its contraction
• c) Contractility changes in stroke volume not
  attributable to either preload or afterload
  (increase in the strength of contraction without
  an increase in length)

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SV EDV - ESV
EDV
Aortic pressure or mean arterial pressure
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Hct
Heart rate
a - v O2 difference
Arterial O2 saturation
O2 consumption
O2 supply

Contractility
Arterial pressure
Wall tension (systolic pressure, ventricular
volume, wall thickness)
Coronary blood flow
Resistance
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Regulation of Circulatory Systems

• CO MAP/TPR

27
Baroreceptors

• Baroreceptors are stretch-sensitive
  mechanoreceptors located in the walls of many
  major blood vessels
• Most important of these are located in the
  carotid artery and aorta
• Baroreceptor reflex regulates MAP

28
Superior cervical ganglia
Superior cervical cardiac n.
PNS vagal nuclei in medulla
Intermediolateral cell column of T1 to T4 or 5
postganglionic
Middle cervical ganglia
Middle cervical cardiac n.
postganglionic
via vagus n.
Stellate ganglia
Inferior cervical cardiac n.
postganglionic
Cardiac Plexus Anterior to the bifurcation of the
trachea Posterior to the arch of the
aorta Superior to the bifurcation of the
pulmonary trunk
Sympathetic afferents
preganglionic
Vagal afferents - primarily cardiac reflexes
Heart pain sensation
Remember - this is just a plexus!
Sympathetic output
Parasympathetic output
SA and AV nodes ? HR
SA and AV nodes ? HR
Myocardium ? contractility or strength of
contraction
INNERVATION OF THE HEART