To overcome surface/volume problem, place cells in thin layers very near to circulating fluid (blood vessels and capillaries)
Your Graduate Assistants:
On to the Syllabus!
Please get the following
info from your syllabus
Prerequisites:
BSCI 230 and CHEM 233
Textbook(s) with enclosed CD !!!!
Recitation/Lab Material on the Web site!
URL: www.life.umd.edu/classroom/
Recitations and Laboratories
Begin THIS Week!
You must print out and read the required
materials ahead of time!!!
A Few Suggestions for doing well in this course:
Come to Class (on time)! No, come early!
Recopy Your Notes
(see the Higgins Plan for Academic Success)
Use the Sample Problems
Answer the Recitation Questions
Study Groups
Slow me down??
Visit our Web site often: http://www.life.umd.edu/classroom/
ASK
ASK
ASK
ASK
ASK!
First Assignment:
Catch up on the assigned readings (mostly
review)
Begin working with the CD!
Review the materials from Chapters 2 through
4, and Chapter 11 before we begin. These pages discuss
cell structure, metabolism, membrane transport, and muscle. We assume
that you have a thorough understanding of these matters. You must
also begin with a review of the Muscle section of the CD.
Refer to the questions contained in the CD Exercises section of the Web
site to test your knowledge of this subject.
**Before
we begin, you must review the concepts found in Chapter 5 (Chemical
Messengers), Chapter 6 (Nerve Cells and Electrical Signaling), and Chapter
7 (Synaptic Transmission) to strengthen the understanding you obtained
in BSCI 230. You should also work with the Muscle, Nervous System
I and II modules of the CD. Do not
wait, do it immediately, before the semester begins. NOW! We
will briefly review this material in lecture very quickly. Stay tuned.**
See the Lecture Topics & Assigned Readings section of the Web site for detailed assignments
Why Multicellularity?
Specialization of function assigned to
different, specific cells
Size
Isolate Interior vs. Exterior
Problem: Diffusion Distances
As diffusion distance (X) increases, the
time required for diffusion increases
proportional to X2
If a solute molecule diffuses 1 mm in 1 sec,
how long would it take to diffuse 10 mm?
The distance increases by a factor of 10,
so time increases by 102 or 1 sec x 100 = 100 sec
Problem: Surface / Volume Ratio
As cell radius increases, the surface increases
by radius2
However the volume increases by radius3
Thus the surface area available to support
the increased volume is not adequate
To overcome diffusion distance, move
part of the extracellular fluid among the cells and the environment. Use
it as a shuttle. (hence, a circulatory system)
To overcome surface/volume problem, place
cells in thin layers very near to circulating fluid (blood vessels and
capillaries)
Internal Fluid Compartments
Extracellular
plasma
cerebrospinal fluid
interstitial fluid
Intracellular
Basic concepts:
Regulate the compostion of the fluid surrounding
the cells.
This fluid is isolated from the environment.
This requires tissues and organs to accomplish
this regulation,
but it eliminates the requirement
for each cell to react to drastic
changes in the composition of
its environment.
The internal fluids must all be at some constant
conditions compatible with life.
The composition of this fluid also reflects
the condition or state of the cells.
HOMEOSTASIS
maintenance of a constant, optimal internal
environment
Your organ systems function to maintain the
constant conditions
in the body fluids that surround the cells.
What are the factors regulated by each of
your organ systems?
Thus, you utilize energy to combat ENTROPY
in your body fluids
Your organ systems evolved and function to
maintain homeostasis
so you can survive and remain in the gene
pool!
Design a Control System
Sensor
Reference + Comparator
Effector for output
Homeostatic Loop
Closed loop - Output affects input
Negative feedback - Output offsets or negates
input
A demonstration of the concept
.