Download Lock and Key Model

HUMAN PHYSIOLOGY
Objectives:
1. Define homeostasis
2. Describe mechanisms used by the
human body to maintain balance
3. Identify how the body uses these
mechanisms
HOMEOSTASIS
• Tendency towards a relatively stable state or
equilibrium (balance)
• Examples:
• Body Temperature 98.6 F
• Blood has a neutral pH = 7
Mechanisms Use to Maintain
Homeostasis
1. Electro-chemical signals  quick messages
transferred by the nervous system
2. Negative feedback mechanisms  long term
responses often carried out by hormones
3. Lock and Key  controls transmission of
messages based on a shape configuration at
the cellular level
Negative Feedback
Mechanisms
• Any change from the normal range of function
is opposed or resisted
• Two responses that work in opposition
• Examples:
• Blood pressure
• Temperature
• Respiration rate
• Blood glucose levels
Negative
Feedback
and Blood
Sugar
Lock and Key Model
• Molecules have a shape that only fits specific
receptors
• Ex. Square peg only fits into square hole
• Enzymes  chemical proteins in the body that
assist or speed up chemical reactions (catalyst)
http://highered.mcgrawhill.com/sites/0072495855/
student_view0/chapter2/an
imation__how_enzymes_w
ork.html
Communication
• Cells communicate with one another by releasing
chemicals.
• Chemicals bind to receptors on the surface of
other cells
• The blood stream carries the chemicals to where
they are needed
• When the lock and key is formed, the message
has been sent
http://www.youtube.com/watch?v=U6uHotlXvPo
Determining “Self”
from Invaders
• Your bodies immune (defense) system needs to be
able to determine what is “self” and what is an
invader
• It uses the lock and key method to determine
invaders from self
http://www.youtube.com/watch?v=cL9KY_ECzfo
Using Lock and Key
Model in Therapies
• Scientists create drugs that mimic (look like)
messenger molecules
• These messenger molecules may activate
the response
• Or the molecule may fit, but not
perfectly, so the hole is blocked and the
message CANNOT be sent