Download A) HUMAN ORGANIZATION - Kevan Kruger

HUMAN BIOLOGY
A) HUMAN ORGANIZATION: We are classified in the following
way:
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Primata
Family Hominidia
Genus Homo
Species sapiens.
We are vertebrates with a bony endoskeleton. We have a vertebral column
that supports us and also encloses and protects the spinal cord. The spinal
cord extends from the brain, which is protected by the skull.
We contain a true body cavity called a coelom, which is divided in to two
regions by our diaphragm.
1) Thoracic cavity (chest) contains the heart, lungs, and upper
digestive tract.
2) Abdominal cavity contains all other internal, ‘visceral’ organs.
We are also mammals, so we have the following characteristics:
1) Homeotherms: we are able to regulate our internal body
temperature and we keep it elevated. This is a high-energy cost
(lots of food and oxygen is required to do this), and therefore, it must
be efficient.
2) We have skin that is covered with hair. This provides us with
insulation, protection, and sensation.
3) We have well-developed brains and senses.
4) We have internal fertilization and development. This allows us a
long gestation period.
5) We have mammary glands to feed our young. This allows us to
have a long post natal care period.
B) LEVELS OF ORGANIZATION
Cells
tissues
organs
organ systems
organism
Tissues: groups of similar cells working co-operatively together to do a
common function. (ie: muscle tissues, nerve tissues, glandular tissues)
a) Epithelial tissues: covering (in sheets) and protection of body
surfaces and cavities. There are three types:
i)
Squamous (thin, flat cells line capillaries & make up
alveoli). Used to cover, protect & exchange materials.
ii)
Cuboidal (cube shaped cells, form glands and
kidneys. Make hormones and involved in urine
formation).
iii)
Columnar (column shaped cells line digestive tract
beyong eosphagus, synthesize enzymes). Some are
ciliated
a. cilia (movement) – respiratory tract and oviducts.
b. villi (increase surface area) – intestines
c. may be secretory (glands)
endocrine (ductless)
exocrine (ducted)
b) Connective tissues: binding and support. Insulates, stores fat, and
produces blood cells. Connective tissue cells are separated by a
‘matrix’.
i.
adipose (fat storage – support)
ii.
cartilage (flexible)
iii.
fibrous (support)
iv.
bone (rigid)
v.
blood (transport)
vi.
areolar (‘saran wrap’ of the body)
c) Muscular tissues: These cells have the remarkable ability to shorten
or contract; thus giving them the ability to move. Muscles move the
skeleton, things within the body, and help hold things together.
i)
Smooth (involuntary); digestive tract.
ii)
Skeletal (attached to skeleton and moves it)
iii)
Cardiac (found in heart only); strong and reacts quickly
d) Nervous tissues: this tissue is adapted for transmitting chemicalelectrial impulses throughout the body. There is a lot of variation in
what nervous tissue look like. The basic cell is the neuron. They are
designed for communication, and allow for rapid response.
Organs: a group of related tissues that work co-operatively together to do a
job (ie: heart, stomach, liver)
Organ systems: a group of related organs working co-operatively together
to do a job (ie: digestive system, circulatory system, respiratory system..)
Organism: a group of organ systems working co-operatively together to
produce an independent free living entity.
HOMEOSTASIS
This is the concept that organisms must maintain a fairly constant internal
environment, regardless of external environment.
Much of our body activity and energy is directed to doing this. We can
survive within only a very narrow range of variation of things, such as pH,
tonicity, temperature, etc…
In humans, the blood and tissue fluids have a primary responsibility for
homeostasis. Homeostasis is maintained by feedback loops (like a
thermostat in a house).
There are two types of feedback loops:
1) Negative Feedback loops: When a substance (like a hormone)
reaches a certain blood level, it triggers the shutdown of the pathway
that makes it. The pathway resumes when the hormone level drops
to a low level
Examples:
1. Blood Glucose Concentration remains about
0.01%
2. pH of blood is always near 7.4 (slightly basic)
3. Blood pressure in the brachial artery averages
near 120 mm Hg over 80 mm Hg.
4. Body temperature averages ~ 37C
5. Pancreatic Juice (pH 8.5) neutralizes stomach
acids so that food entering the small intestine is
basic.
6. CO2 concentration in our blood stimulates our
breathing.
2) Positive Feedback loops: This type of loop stimulates a
production pathway when a level of another chemical triggers it.
SUMMARY
Negative Feedback tends to stabilize a system.
Positive Feedback leads to instability.