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

Popsicle gone to your head?

But How?

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

Wood frog

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