Download Lecture 7

Biology 103 - Main points/Questions
1. What was the answer to that question?
2. Remember muscles?
3. How do organisms keep cells supplied?
Keeping cells supplied
• All cells require supply of energy and “parts”
as well as removal of waste products.
– For example – muscle cells need sugars and
oxygen for ATP production
– They also generate waste carbon dioxide
• How do organisms keep cells supplied and
waste levels low?
Some organisms use diffusion as
primary means of moving material
around. This works well for single cells.
Remember diffusion?
• Movement from high concentration to low
– Doesn’t require any energy expenditure to make
happen
– Works very quickly over short distances
– Important transport mechanism of cellular
material
Factors controlling diffusion rate:
• Temperature
• Size of molecule:
• Concentration gradient:
• Surface area:
• Distance:
• Medium
What are some Materials in a cell
that need to diffuse
• Energy rich molecules (ATP, glucose...)
• Cellular products (proteins, tRNA...)
• Ions and cell nutrients (Na+, amino acids)
• Gasses (oxygen and carbon dioxide)
Diffusion is crucial for moving cellular
material over small distances but…
Some have very simplified circulatory
systems that simply move fluid into &
out of a gastro-vascular cavity.
More complex organisms
have more need for
specialization of
tissues/organs/organ systems
These
specialized
systems keep
cells bathed in
solutions full of
the materials
needed for life
and free from
waste products
Cells still use
diffusion over short
distance (the local
environment)
But these
organisms need a
circulatory system
to move fluids
throughout the
organism.
Some use an
internal pump to
circulate fluid inside
the body’s cavities.
(called an open
circulatory
system!)
Others use pumps
to circulate fluid
inside
interconnecting
tubes. (called a
closed circulatory
system!)
Goal is to move fluids quickly over
large distances so diffusion can do
its work over small distances.
Mammals use a 4-chambered heart
to circulate blood.
Blood movie
Blood = Connective tissue
Has cells (red, white) surrounded by
extracellular matrix (fluid = plasma)
Transports nutrients like glucose, amino acids,
oxygen…
Removes waste products like carbon dioxide
and urea
Type of cells
One pair of
chambers
collects
blood from
the body and
pushes it to
the lungs
(c) Mammals, birds
lung capillaries
The other
pair collects
blood from
the lungs
and pushes
it to the body
atria
ventricles
body capillaries
Each circuit of blood flows through a series of
tubes as it leaves and then returns to the heart.
Blood flows into
the heart from
the body and
enters into the
right atrium
From here it
flows into the
right ventricle
and out to the
lungs
Returning from
the lungs into
the left atrium
And then into
the left ventricle
where it is
pushed to the
body through
the aorta.
The energy for all of this fluid
movement comes from the
contraction of the heart - specifically
cardiac muscle tissue.
The chambers contract in a very
specific cycle that goes like this:
• Contraction of the two atria
• Contraction of the two ventricles
• Relaxation of the heart
The chambers contract in a very
specific cycle that goes like this:
• Contraction of the two atria
– This pre-pressurizes
1 Atria contract, forcing
blood into the ventricles.
The chambers contract in a very
specific cycle that goes like this:
• Contraction of the two atria
– This pre-pressurizes
• Contraction of the two ventricles
– Forces blood out of heart into arteries
This stage generates
peak blood pressure
called systolic pressure
2 Then the ventricles contract,
forcing blood through arteries to
the lungs and the rest of the body.
The chambers contract in a very
specific cycle that goes like this:
• Contraction of the two atria
– This pre-pressurizes
• Contraction of the two ventricles
– Forces blood out of heart into arteries
• Relaxation of the heart
– Blood flows into atria and ventricles
– Why not backwards?
This is where pressure is
at a minimum - called
diastolic pressure.
3 The cycle ends as
the heart relaxes.
1 Atria contract, forcing
blood into the ventricles.
2 Then the ventricles contract,
forcing blood through arteries to
the lungs and the rest of the body.
3 The cycle ends as
the heart relaxes.
systolic
pressure
diastolic
pressure
Path of blood flow in circuits and role of
capillaries
Arteries
• Blood leaving the heart
• Deal with high pressure
• Very little exchange with
surrounding tissue
Capillaries
• Lower pressure
• Major location of
exchange
• Very “leaky”
Veins
.
• Return blood to the heart
• Lowest pressure
Fig. 29.7
Low pressure in
veins means:
• Valves
• “muscle assist”
Why does exchange happen in capillaries?
Speed of blood in capillaries is much lower
• Like a wide spot in a river…
Capillary bed leaks fluid into interstitial fluid
• This “stirs” the interstitial fluid
• Makes diffusion even more efficient
• But more fluid leaves than returns…
Fig. 29.9
What type of tissue?