Homeostasis Notes
Homeostasis:
Maintaining Balance in the Body
Cell Specialization
· all cells start with the genes
needed to become any
cell in the body (liver cell,
heart cell, muscle cell, etc. )
· specialization occurs in two
main steps
determination - commit to
becoming 1 type of cell
ONLY
differentiation - acquiring
the structures and
functions needed to be
that cell
5 Levels of Organization
· cells
tissues
organs
organ systems
organisms
· complexity increases with each level
· each level relies on the structure and
function of the level below it
· example
cardiac muscle cells
cardiac
muscle tissue
heart
cardiovascular system
YOU!
Homeostasis
· homeostasis - stable internal environment
· to survive, humans must maintain homeostasis
blood pH = 7.35
body temp = 98.6 F
· relies on hormones (h) and enzymes (e)
gastrin, secretin, cholecystokinin (h) - digestion
estrogen, progesterone, testosterone (h) reproduction
DNA helicase, DNA polymerase (e) - DNA
protease, amylase, lipase (e) - digestion
· How?
homeostatic regulation
Homeostatic Regulation
· adjustments in physiological systems to maintain a
stable internal environment
· requires a receptor, control center, effector
receptor - sensitive to
specific stimuli
control center - receives
and processes info
effector - responds
(corrects or reinforces)
Negative Feedback
· negative feedback - when a stimulus rises or falls
outside normal, the receptor triggers an automatic
response that corrects the initial stimulus
negative feedback CORRECT the stimulus
· ex. thermostat
normal room temp
temp rises (stimulus)
registers with thermometer
(receptors)
sends info to thermostat
(control center)
turns on air conditioner
(effector)
room temp drops
normal room temp
Homeostasis Notes
Positive Feedback
· positive feedback - initial stimulus produces a
response that reinforces the stimulus
positive feedback REINFORCES the stimulus
accelerates processes that need to be completed
quickly (blood clotting or child birth)