Ch. 1 – Characteristics
of Life & Organization
of the Human Body
What is the difference between Anatomy
and Physiology?
A. Anatomy- study of the
structures of an organism
-Examples of 4 subcategories:
1. Gross anatomy- large, what you can
see
2. Microscopic anatomy - tiny
Cytology= study
of cells
Histology=
tissues
3. Developmental Anatomy
-structure of an embryo (embryology)
4. Pathological anatomydiseased structures
B. Physiology- study of the functions
of an organism
What are the levels of organization
in the human body?
-chemical (subatomic, atomic,
molecules, macromolecules)
-organelles
-cells (differentiated to perform
unique functions) 100 Trillion!
-tissues
-organs
-organ system (see below)
-organism (human)
Virtually all processes in the body
occur in order to maintain
Homeostasis
• What is Homeostasis?
Homeostasis- an organism’s
maintenance of a relatively constant
internal state within set ranges.
Examples:
Temp.= ~ 98.6 °F
b.p.=
~ 120/80 mmHg
glucose= ~ 90-130 mg/dl
Blood pH= 7.4
hydration= ~60% H2O
MANY, MANY more!
Homeostatic control mechanisms-known as a feedback control loop
-virtually all of the body’s organ systems can be involved
-there are three basic components:
-Sensor – senses a change (a “stimulus”)
-Integrator, (control center) – interpret the change
-Effector – responds to the change
Example:
SENSOR: pressure sensor in the walls of
the heart and major arteries senses low
blood pressure and sends a signal to the
brain.
INTEGRATOR: Medulla oblongata in the
brain determines degree in which b.p.
must be corrected and send a signal back
to the heart.
EFFECTOR: the heart begins to beat faster
thereby increasing pressure.
NEGATIVE feedback mechanism-creates a response that opposes the initial
disturbance. (reverses the change)
-work to stabilize physiological variables
-are responsible for maintaining homeostasis
POSITIVE feedback mechanism-amplifies or reinforces the change that is
occurring
-can be harmful or disasterous
CANCER! 
-very few normal positive feedback mechanisms
-childbirth, bloodclotting, a sneeze