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 anatomy- diseased 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 °Fb.p.= ~ 120/80 mmHgglucose= ~ 90-130 mg/dlBlood pH= 7.4hydration= ~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