Introduction to Anatomy and
Physiology
anatomy = “a cutting open”
o Study of internal and external
structures of the body and the
physical relationship between
body parts
o Ex – a particular bone attached
to a muscle
physiology
o Study of the function of
anatomical structures; considers
both physical and chemical
processes
o Ex. how a muscle contracts to
move the bone
cell: basic unit of life
o Cytology
o Histology
Levels of Organization
Homeostasis
Objectives:
1. Significance of homeostasis
2. Positive and negative feedback
Start
here
Lots of examples of negative feedback
loops, few positive loops
For test be able to analyze:
o Calcium homeostasis (page 132)
o Body temperature (page 7)
o Water regulation (refer to notes)
o Control center for sympathetic and
parasympathetic divisions of PNS
o Effectors and response after sympathetic
disruption of homeostasis occurs
Two ways to maintain
homeostasis
o Negative feedback
o Positive feedback
Negative Feedback: example body
temperature
Q1: compare response to
original stimulus
o Answer:
o The response by the effectors is
antagonistic (opposite) of the
stimulus
Stimulus = body temp ↑
Response = body temp ↓
Q2: homeostasis restored? How do you know?
o Answer
o Yes, because the response
counteracts the stimulus
o Brings back balance
Positive Feedback: example
labor contractions
Q3: compare response and stimulus in positive
feedback
o Answer
o The response acts to heighten or
increase the stimulus
Stimulus = ↑ distortion of uterus
Response= ↑ distortion and
contraction of
uterus
Q4: Is homeostasis restored in
this example? How do you
know?
o Answer:
o No, homeostasis is continually disrupted
o This is a good thing in this case b/c returning
to homeostasis would cause the birthing
process to stop.
o The positive feedback loop will continue until
birth is complete.
Positive feedback examples
o Childbirth
o Blood clotting
o Sexual orgasm
o Milk production from mammary
glands
Cellular homeostasis
Every level of organization within
the body must maintain
homeostasis
Phospholipid
Bilayer
Diffusion
o Diffusion is the movement of
molecules from a higher
concentration to a lower
concentration.
o The difference in concentration of
two solutions is called the
concentration gradient
o Demonstration: food coloring in
water
ttp://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.h
tml
Diffusion: Anatomy example
o Oxygen gas enter body and
blood stream
o Carbon dioxide leave blood and
body
Diffusion across membranes
o Molecules that
dissolve in lipids
can cross the lipid
bilayer through
diffusion.
Example: O2
CO2 H2O
Osmosis
o Think back to solutions:
solutes and solvents
o Osmosis is the process by which water
molecules diffuse across a cell
membrane from an area of lower solute
concentration to an area of higher solute
concentration.
o Direction of movement depends on
relative concentrations of solutions.
Osmosis: anatomy connection
o Excess water versus dehydration
o Kidneys help to rid excess water
as urine = osmosis of water out of
blood (high) into kidneys (low)
Direction of movement into cells
o Hypotonic to the cytosol
o solution outside the cell is less concentrated than inside the
cell
o water moves into the cell
o Hypertonic to the cytosol
o solution outside the cell is more concentrated than inside the
cell
o water moves out of the cell
o Isotonic
o concentrations are equal
o
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osm
osis.htm
What about the molecules that can’t pass
through the membrane freely?
o Glucose, Na+, Ca+, K+ and lots
of other molecules need to get
into and out of the cell but can’t
get through the lipid bilayer
o They must use the proteins
embedded in the lipid bilayer
Facilitated transport
o Protein channels embedded in
the cell membrane allow ions
and other molecules to diffuse
into and out of a cell
o Where have we seen facilitate
diffusion in action?
o Neuron’s gated Na+ and K+
channels
o Ca+ channels in nerve and muscle
cells
Active transport
o Requires energy to transport
molecules across a cell’s
membrane
Ex. 1 Membrane proteins may
serve as pumps to push ions
across the cell against the
concentration gradient
o Examples of pumps?
o Na+/K+ pump in neurons
Active Transport (con’t)
Ex. 2 Exocyotosis – the cell
excretes wastes, chemicals or
other products by releasing them
from vesicles
o Where have we seen this?
o Release of neurotransmitters
Ex 3 Endocytosis – the cell takes in
molecules or food by engulfing it
o We will see this with immune system
and WBCs