Download Chapter 42 – Circulation and Gas Exchange

The circulatory system is great because
we don’t have to rely on diffusion. Why is
this a good thing?
 The circulatory system rapidly transports
fluid in great quantities to the body
allowing exchange of gasses, absorption
of nutrients, and disposal of waste
products by the cells with much greater
efficiency.
 Math problem?
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Chapter 42 – Circulation and Gas
Exchange
If it takes 3 hours for a given quantity of glucose
to diffuse 1 cm, how long would it take (in years)
for that same quantity to move 2 meters (the
approximate distance from your liver to your big
toe)?
 The time it takes for a substance to diffuse form
one place to another is proportional to the
square of the distance. Multiply the square of
the increase in distance (square the factor that
the distance increased by and multiply that by
the amount of time given for the previous
diffusion distance).
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Math Problem – really it’s
diffusion with the problem!
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Why again are they necessary?
Gastrovascular Cavities – we know them
well!
Open circulatory system? It’s like a
bellows!
Bring on the hemolymph!
Closed circulatory system
That’s what you have – blood and tissues
are separate.
Which one is less costly in terms of
energy?
Types of Circulatory Systems
Open and closed cardiovascular
systems
Different types of closed systems
have been shaped by environmental
factors
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The heart – mechanical pump consisting of
two atria (receive blood) and two ventricles
(pump blood to body).
The vessels – arteries, veins, and capillaries
(100,000Km is how many miles?). You also
have arterioles and venules.
We needed that four chambered heart and
double circulation to deliver the energy
needed for homeostasis – endotherms
require a great deal of energy to sustain
themselves.
Vertebrate (and specifically
mammal) cardiovascular systems
Let’s follow Ms. RBC through the circulatory
system.
Below the sternum, the heart is about the
size of your fist and is made mostly of
cardiac muscle.
 The atria are thin walled and function
mainly to collect blood returning to the
heart (from where?).
 Ventricles are thicker and pump blood out
to the pulmonary and systemic
circulation.
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The Heart
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Thoughts about the pig heart dissection:
Anterior and Posterior view of heart
Different Chambers
Find where the heart was cut by the
butcher (anything missing?)
ID Vessels – pulmonary artery, aorta,
coronary arteries
Semilunar and AV valves
Muscle fibers
Trace the path of blood flow
Contraction (called systole) is the
pumping of blood.
 Relaxation (called diastole) is the heart
filling with blood.
 One complete contraction and relaxation
is called the cardiac cycle.
 The volume of blood/minute that left
ventricle pumps to the systemic
circulation is the cardiac output.
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The heart is rhythmic. If not,
you’re in trouble…
The rate of contraction, or heart rate
(heart beats/min and measured by taking
your pulse) and stroke volume (amount
of blood pumped by each ventricular
contraction – averages 75mL).
 What is your cardiac output if your heart
rate is 80 beats/min and your stroke
volume equals the average?
 Many things can affect heart rate and
stroke volume for better or worse.
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Cardiac output depends on two
factors.
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How does your stamina (ability to sustain physical activity)
increase with exercise?
It has to do with an increased ability to get oxygen to your
tissues.
It turns out, the more you exercise, the thicker and
stronger the muscle making up your ventricle becomes (as
with any muscle – the myofibrils increase to increase
muscle mass, not the number of cells).
This increases the volume of blood the ventricles can pump
with each contraction (called _______)
Increased stroke volume means you body can decrease the
other factor (called ______) that contributes to cardiac
output.
So Carmen asked me a question and my
answer was lackluster. So I gave it some
thought…
We need the heart to maintain its rhythm
or our tissues go without _______ and
_________. We would also build up
________.
 Certain cardiac muscle cells are selfexcitable and have their own rhythm.
 When things function normally, the
pacemaker of the heart excites all other
cardiac cells.
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How the heart maintains it’s
beat…
Let’s see how impulses are
conducted through the heart.
 Nervous
system
 Hormones
 Temperature
 Exercise
 What’s are ECGs and AEDs?
What affects heart rate?
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Arteries, Veins, and capillaries (arterioles
and venules, too).
Arteries are thicker because they move
blood rapidly under higher pressures.
Veins have valves and take advantage of
muscle movement.
Capillaries are thin.
All are lined with endothelium.
Which ones carry oxygenated blood?
http://www.biosbcc.net/doohan/sample/h
tm/vessels.htm
Da pipes…
When you build up muscle, do you make new
capillaries to accommodate the increase muscle
size.
 The answer is yes, which is surprising, because
in most instances we don’t.
 Blood vessels grow to line the uterus each month
and new vessels grow in the process of repairing
a wound.
 Turns out exercise causes chemicals to be
released that stimulate vessel growth when
muscle mass increases.
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Then Anthony asked me a
question…
The majority of the 100,000km of vessels
in your body are capillaries.
 If volume per minute is constant, velocity
of fluid will increase when diameter
decreases
 If total diameter of the pipe determines
velocity, why does blood slow down in the
capillaries? Why is this good?
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Blood velocity and pressure in
the cardiovascular system.
Force exerted by blood on walls of vessels
Blood pressure is pressure on arteries
during contraction – systolic pressure and
relaxation – diastolic pressure).
 Blood enters arteries faster than it can
leave and the arteries stretch.
 You can feel your pulse and take your
blood pressure because of arterioles.
 Arterioles cause peripheral resistance.
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Pressure, coming down on
me…
Peripheral resistance and cardiac output
play off each other to maintain
appropriate pressure.
 As blood pressure decreases, cardiac
output (pulse x stroke volume) increase
and vice versa.
 Position, exercise, hormones, nerve
signals, and other factors affect blood
pressure.
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Blood pressure is a team effort.
What’s up with this?
Lymphatic system has capillaries
intertwined with blood capillaries to catch
excess fluid and protein that would
otherwise be lost after leaving the blood
capillaries.
 Dumps back into circulatory system into
the vena cava near the right atrium.
 Lymph capillaries to lymphatic vessels
passing lymph nodes along the way.
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Lymph
Several cell types are suspended in a
liquid matrix called plasma. Mostly water,
but also contains ions for osmotic balance
and to help buffer the blood.
 Cells in the blood include erythrocytes
(RBCs), leukocytes (WBCs – several
different kinds) and platelets (chunks of
cells that help with clotting).
 Cellular elements don’t last forever. Thank
the Good Russo for pluripotent stem cells
in red marrow of bones.
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Blood
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Negative Feedback involves a set point.
In the case of RBC production, the set
point is for _____ in the blood.
Low O2 getting to tissues, kidneys release
_____, stimulating production of
_________.
What happens if the tissues get more
than they need.
What does this get us back to?
Naughty, naughty!
Homeostasis!
 Fibrinogen
to fibrin…thanks
_______!
 It’s positive feedback because
there’s no _____________.
 What’s hemophilia?
Positive feedback – we are so
lucky to have an example of each
in the same chapter!
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Heart attack
Stroke
Atherosclerosis (plaque builds up)
Arteriosclerosis (hardening of the arteries)
Hypertension
LDLs (bad) and HDLs (good)
What lifestyle choices will you make (are
you heart smart or heart stupid?).
It feels like an elephant is
sitting on my chest.
Exchange gas with what?
How do we exchange gas or perform
respiration (don’t confuse with cellular
respiration)?
 What are the two respiratory mediums?
 What happens at an animal’s respiratory
surface? How does water play a role
regardless of the terrestrial or aquatic
nature of the animal?
 Why do endotherms have a larger surface
area for gas exchange?
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How do you expel…oh, oh, I mean
exchange…gas?
The majority of cells that make up an
animal usually don’t have direct access to
a respiratory medium.
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Fish use gills
Insects use tracheal systems – tubes that
deliver air directly to body cells.
We (mammals, birds, reptiles, and
amphibians, spiders, and snails) use
lungs.
Some also exchange through skin – these
animals must live in moist environments.
What is ventilation?
Where it starts!
Let’s follow an O2 molecule through the
respiratory system.
Here’s a real larynx!
Here’s the alveoli!
Positive and negative pressure
breathing
Lung volume increase when intercostal
(rib) muscles and the diaphragm contract.
 Other muscles help when you are really
working.
 The volume of air that goes in and out is
your tidal volume and the max is your
vital capacity.
 Don’t smoke unless you want more
residual air lurking in your lungs.
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Again, what creates the
negative pressure?
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What influences the
breathing centers?
CO2 levels. But
how?
Once CO2 dissolves
into the CSF, what
happens? How is
the pH of CSF
affected by CO2?
Jim Newman, you
fool!
Why you shouldn’t chase the dragon…
A gas always diffuses from a region of
higher partial pressure to a region of
lower partial pressure…oh wait, what’s
partial pressure?
 CO2 has a higher partial pressure in lungs
than atmosphere and its just the opposite
for O2…oh goody!
 Know your hemoglobin…and who cares if
elephant seal can dive down over a mile
and hold their breath for two hours!
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Thank goodness for partial
pressure