Your mission, should you choose to accept it
(because you never back down from a challenge)…..
• On my mark…
Eat your popsicle FASTER than everyone else
What happened? Nerve bundle in palate
(sphenopalatine nerve) sensitive to abrupt changes in temperature. Sends signal to brain to prepare itself. Blood vessels in palate shrink (to avoid heat loss) in response to the stimuli (overreact).
• Warm the palate, nerves no longer stimulated.
HomeostasisHomoios – “similar” or “like”
stasis – “standing still”
- the ability to maintain a constant internal environment (steady state), allowing the
organism to adapt to external environmental changes.
Adjusting to changing External Environment….
Requires help of body’s regulatory systems.
Your body must maintain :
- blood pressure
- blood sugar- body temperature- fluid balance
- O2 and CO2 levels
- blood pH
Homeostatic Control SystemStimulus
Deviation from set point
SensorConstantly monitors
conditions
Integrating Centre
Compares conditions to a set point based on a
desired value
EffectorCauses changes to
compensate for deviation
ResponseMove system towards set
point
Negative feedback (-)
Functional Components of Homeostatic Control Systems
Monitor – detects changes
Coordinating centre – compares condition to a set point
Regulator – causes changes to compensatefor deviation
Stimulus – deviation from set point
An example of a negative feedback system – mechanisms that make adjustments to restore conditions to their original state. Negative feedback mechanisms prevent small changes from becoming too large.
StimulusLocal temperature changes from set point in mouth (palate) area
SensorNerves in palate sense change in temperature and send signals to
brain
IntegratorSet point (37oC)
Neurons in the brain (hypothalamus) compare input from sensory neurons with set
point
Effectorblood vessels in palate briefly narrow (vasoconstrict) to limit
blood flow to conserve body heat
Effectorblood vessels rebound by
widening (vasodilate) to increase blood flow to restore temperature
ResponseBlood vessels return to normal
circumference and local temperature rises back to set point
Negative feedback (-)
Thermoregulation
Mechanism of temperature
regulation varies between
endotherms and ectotherms
- fevers
Hypothermia• Body core temperature falls below normal
range
• Can be deadly
• How do some people survive frigid temperatures? (ex: falling into cold water)
• Called mammalian diving reflex
Feb 2001
A Famous Hitter is Frozen in Time
Since his death in 2002, baseball legend Ted Williams has been stored in a 10
foot-tall, stainless steel container at Alcor Life Extension Foundation in Arizona,
the world's largest cryonics facility. His head is reportedly being stored in a
separate container. But the story doesn't end there. After his death, the famous
slugger became embroiled in a rather bizarre custody battle. His daughter,
Bobby-Jo Williams Ferrell, fought in court to get her father's body back so that
she could have him cremated and his ashes sprinkled over the Florida Keys,
which she claims was his wish. She accused her half-brother John-Henry
Williams of wanting to preserve their father's body so that he could cash in on his
famous DNA. But John Henry and his sister Claudia said they had signed a pact
with their father in 2000 promising to have all of their remains frozen. The three
siblings finally reached a settlement: Ted Williams was allowed to stay where he
was, and John-Henry promised not to sell any of his father's DNA.
• latest kook
Positive Feedback MechanismsIn positive feedback systems, the initial imbalance or stress
is intensified rather than reduced as it is negative feedback.
Value?
Allows a specific physiological event to be accomplished
rapidly. Once event is accomplished, feedback system stops.
Stress Sensor Control Center
EffectorIntensifies
Typical Positive Feedback Process
monitor Coordinating centre
regulator
Homeostatic Regulation of Child Birth through Positive Feedback
Pressure of Fetus on the Uterine Wall
Nerve endings in the uterine wall carry afferent messages
to the Hypothalamus
Production and Release of Oxytocin into the
BloodIncreasing strength of uterine contractions
Intensifies
STRESSmonitor
regulator
Once event is accomplished, positive feedback mechanism stops
Hyperglycemia Pancreas-beta cells
Sensor and Control center
Insulin is releasedinto blood
Liver and Muscle cells take up glucose from
the blood
Effectors
Blood glucose is reduced
Stress is reduced shutting down
mechanism
Stress
Homeostatic Regulation of Blood Sugar through Negative Feedback