Homeostasis and Body Organization

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Homeostasis and Body Organization
What is homeostasis?
constancy or steady state maintained within
the organisms bodies.
Whereas the environment can be highly variable,
organisms incorporate internal control mechanisms
to oppose the forces that would change
their internal physiological equilibrium.
The organisms internal state can be described as
being in dynamic equilibrium, because the body
needs to be constantly adjusting to the Changes.
This regulation occurs in two basic ways
Negative feedback most important means of
maintaining homeostasis, negative feedback
creates a counter-effect to the outside
environmental change
Positive feedback a mechanism whereby the
effects from the original environmental changes
are intensified.
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Homeostasis and Body OrganizationPositive and
Negative Feedbacks
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Homeostasis and Body OrganizationPositive and
Negative Feedbacks
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Homeostasis and Body OrganizationPositive and
Negative Feedbacks
It should be noted though that there are many
systems involved in organisms Body, and that
they all need to interact with each other to
maintain homeostasis.
Different systems working independently could end
up working against each other, but since the body
has systems that move substances and signals from
one part of the body to the next, all the
different body parts remain connected.
This coordination is achieved via chemical
(hormones) and/or electrical (nervous)
communication between tissues that elicits
appropriate responses.
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Body Organization
The body is organized at different levels
Tissues includes structurally similar cells that
act together to perform a
particular function. (e.g. muscular, nervous,
epithelial, etc.)
Organs the next higher level of organization,
tissues come together to form
organs. (e.g. stomach, kidneys, liver, etc.)
Organ systems the different organs that work
together towards a particular function come
together to create organ systems. (e.g. digestive
system which is composed of the stomach, small
intestine, large intestine, and other organs.
You are responsible to read pages 526 533.
Learn the basic structure and function of the
major vertebrate organ systems outlined in table
26-2 on page 532.
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Circulation
Why do we even need a circulatory system?
Simple diffusion is too slow to serve the needs
of larger organisms.
Primary Functions?
1. Gas exchange
2. Distribution of nutrients
3. Waste removal
Other functions in vertebrates (and some
invertebrates)?
4. Distribution of hormones
5. Regulation of body temperature
6. Protection of body from bacteria and viruses
circulation of antibodies and white blood
cells.
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Circulation
All circulatory systems have 3 major components
1. A fluid blood that serves as a medium of
transport
2. A system of channels (blood vessels) that
transport the blood throughout the body.
3. A heart that acts as a pump and keeps the
blood circulating.
Animals have one of two types of circulatory
systems 1. Open 2. Closed
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Circulation
Note Vertebrates (including humans) have a
closed circulatory system
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Circulation the vertebrate heart
There is an increased level of complexity
associated with vertebrate evolution.
This increased complexity has created more
efficient circulatory systems that have
allowed for greater diversity of form and
function in different environments.
This is not of course the only solution, squids
for example have three hearts...
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Circulation the four chambered heart
The mammalian and avian hearts consist of two
pumps in one.
One pump is responsible for pulmonary circulation
consisting of the right atrium and ventricles,
this pump is responsible for sending blood to
the lungs.
The other pump is responsible for systemic
circulation consisting of the left atrium and
ventricles, this pump is responsible for sending
oxygenated blood to the body.
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Circulation the four chambered heart
Electric impulses coordinate the sequence of
contractions
Valves maintain directionality of blood flow. The
valves are one-way
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Circulation the four chambered heart
The atria and ventricles of the heart need to
pump in a coordinated fashion. The alternating
contraction and relaxation of the heart chambers
is called the cardiac cycle.
The contraction of the ventricles is called the
systole and the relaxation is called the diastole
The nervous system and hormones influence heart
rate...
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Circulation the four chambered heartMeasuring
blood pressure

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Circulation the four chambered
heartElectrocardiograms
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Circulation structure and function of blood
vessels
Arteries and Arterioles Thick-walled vessels
that carry blood away from
heart arterioles can control the distribution of
blood by muscular contractions they are
influenced by nerves, hormones, and chemicals
produced in nearby tissues.
Capillaries Microscopic vessels that allow
blood and body to exchange gas,
nutrients, and waste
Veins and Venules Carry blood back to the heart
Valves direct flow of blood in veins
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Circulation structure and function of blood
vessels
Change in blood velocity as a function of
circulatory cross section allows for more
efficient transport as well as gas, nutrient,
and waste exchange...
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Circulation blood
Blood components
Plasma the fluid part of the blood, it is
composed of 90 water along with proteins,
hormones, nutrients, gases, salts, and wastes...
Specialized cells these are cells suspended in
the plasma and include red blood cells, white
blood cells, and platelets.
Red blood cells are primarily involved in
transport of oxygen White blood cells are
primarily involved in the immune
system Platelets are primarily involved in blood
clotting
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Circulation blood
Red blood cells contain a large, iron-containing
protein called hemoglobin. Each hemoglobin can
bind to four oxygen molecules and is involved in
picking up oxygen in the lungs and transferring
it to the body...
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Circulation the lymphatic system
A network of lymph capilaries and large
vessels that empty into the circulatory system.
Function include
1. Removal of excess fluids and
dissolved substances that leak from capillaries.
2. Transport of fats from the small intestine to
the blood stream.
3. Defense of the body by exposing bacteria and
viruses to white blood cells.