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Lecture 1: Homeostasis
No t e b o o k:
C re at e d :
U RL :

Physiology
8/15/2012 10:20 PM
8/15/2012 10:20 PM
U p d at e d :
http://www
...
com/workshop/human-animal-physiology-university-level-mcat-da…

Homeostasis: process of maintaining a constant internal environment
for all cells in the body

Ex: body temperature, it is maintained at 98
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the salt water is hypertonic
Water moves out of the cell (From low concentration of solutes to high
concentration of solutes aka Osmosis)

More simply put water moves from less salt (inside the cell) to more
salt (outside the cell)
Fresh Water

Has a lower [ions] than the
single cell
Water moves into the cell (the cell bulges or may even "lyse," which means
burst)
...
They maintain
gradients of ions via diffusion (and other modes of transport covered later)

Diffusion: a substance moves from an area of high concentration to
an area of low concentration
Stuff (ions, etc
...


Feedback Loops (mentioned here
because they are important to homeostasis, but are important to basically
everything)

Negative Feedback Loops: disturbance
occurs --->
action takes place --->
DECREASE disturbance
When something changes:

Disturbance can be balanced out
by an equal and opposite disturbance (less common)
Disturbance can be removed (more
common)
Negative feedback uses "set
points" : there is a normal range of conditions allowed, any deviation from
this range is out of the set point range

Analogous to a thermostat
Insulin secretion is controlled
by negative feedback
Positive Feed Back: disturbance occurs ---> action takes place ---> INCREASE
disturbance

This may seem bad, but there is
normally a point in which the increasing stops
Ex: Child birth (increase stops
once baby is out), Blood Clotting
Feed Forward: body anticipates a disturbance ---> faster response

Ex: going into the cold when
knowing it is cold outside, body anticipates the lower temperature and
increases body temp before going out in the cold



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