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Chapter 1

Chapter 1


Department
Biological Sciences
Course Code
BIOD27H3
Professor
A.Elia
Chapter
1

Page:
of 5
-Physiology: study of normal functioning in living organisms
PHYSIOLOGICAL SYSTEMS
-Cell: smallest unit of structure capable of carrying out all life processes; collection of molecules
separated from external environment by barrier called cell membrane
-Tissues: collection of cells that carry out related function
-Organs: collection of tissues
-Organ systems: group of organs with integrated function
ORGAN SYSTEM
-Integumentary system: composes the skin; forms protective boundary separating internal environment
from external environment
-Musculoskeletal system: provides support and body movement
*4 systems that exchange materials between internal and external environment:
-Respiratory system: exchanges gas
-Digestive system: takes up nutrients & water and eliminates wastes
-Urinary system: removes excess water and waste materials
-Reproductive system: produces egg or sperm
*4 systems that extend throughout the body:
-Circulatory system: distributes material by pumping blood through vessels
-Nervous system/endocrine system: coordinate body function
-Immune system: immune cells positioned to intercept materials that may enter through exchange
surfaces or break in skin; protect internal environment from foreign invaders. Closely related to
circulatory system.
*refer to pg 4 table 1.1 for details
FUNCTION AND PROCESSES
Q: Why do red blood cells transport oxygen?
-Teleological approach (function of physiological system or event)
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A: because cells need oxygen and red blood cells brings it to them
why the system exists or why event happened
example explains why red blood cell transport oxygen but not how
-Mechanistic approach
 A: Oxygen binds to haemoglobin molecules in the red blood cells
examine physiological processes (or mechanism): the β€œhow” of a system
explains exactly how oxygen transport occurs but nothing about the significance of oxygen
transport to intact animal
HOMEOSTASIS
ability to cope with external variability by keeping internal environment relatively stable
-Extracellular fluid (ECF):
watery internal environment of multi-cellular organisms
 a β€œsea within” the body that surrounds the cell
serves as transition between organism’s external environment and intracellular fluid
buffer zone between outside world and most cell of the body therefore elaborate physiological
processes have evolved to keep ECF stable
 when composition varies outside normal range -> compensatory mechanisms activate and returns
fluid to normal range
ex: drinking a large volume of water-> dilution of ECF triggers a mechanism that causes
kidneys to remove excess water to protect cells from dilution
most cells of multi-cellular organisms don’t tolerate change & depend on consistency of ECF
to maintain normal function
-Claude Bernard (French physician)
 developed concept of relative stable internal environment in mid 1800s
noted stability of various physiological functions (eg. Body temperature, heart rate, blood pressure)
during studies of experimental medicine
wrote of β€œla fixite du milieu interior” (the constancy of the internal environment)
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-Walter B. Cannon (American physiologist)
came up with the word homeostasis to describe regulation of internal environment
selected the prefix homeo- (like or similar) instead of homo- (same) because internal environment
is maintained within a range of values (not exact fixed value)
suffix –stasis (condition), not meant a stat that is static and unchanging in this instance
Cannon’s homeostasis: a β€œsimilar condition”, also a β€œrelative constant internal environment”
body monitors its internal state & takes up action to correct disruption that threatens
normal functioning
 proposed a list of variables that are under homeostasis control divided into
external factors (osmolarity, temperature, and pH)
ξ€‚β€œmaterials for cell needs” (nutrients, water, sodium, calcium and other inorganic ions
ξ€‚β€œInternal secretion(hormones & other chemical that cells used to communicate with each
other) having general and continuous effects”
-if body fails to maintain homeostasis of those variable-> normal functioning disrupted & diseases (or
pathological condition) may result
-disease separated into 2 groups based on origin; those in which problem:
1.arises from internal failure
causes include: abnormal growth of cell (may lead to cancer or tumours), production of
antibodies by the body against its own tissue (autoimmune disease), premature death of
cells or the failure of cell processes
2.originates from outside sources
causes include: toxic chemical, physical trauma & foreign invaders (e.g. bacteria + viruses)
-when homeostasis disturbed-> body ties to compensate
if compensation successful-> homeostasis restored
if compensation fails-> illness or disease may occur
-Pathophysiology: study of body function in a disease state
PHYSIOLOGY: MOVING BEYOND THE GENOME
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