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.

Homeostasis Homoios – “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 -b-body temperature -f-fluid balance -O-O 2 and CO 2 levels - blood pH

Homeostatic Control System Stimulus Deviation from set point Sensor Constantly monitors conditions Integrating Centre Compares conditions to a set point based on a desired value Effector Causes changes to compensate for deviation Response Move 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 compensate for 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.

Stimulus Local temperature changes from set point in mouth (palate) area Sensor Nerves in palate sense change in temperature and send signals to brain Integrator Set point (37 o C) Neurons in the brain (hypothalamus) compare input from sensory neurons with set point Effector blood vessels in palate briefly narrow (vasoconstrict) to limit blood flow to conserve body heat Effector blood vessels rebound by widening (vasodilate) to increase blood flow to restore temperature Response Blood 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 Mechanisms In 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. StressSensor Control Center Effector Intensifies Typical Positive Feedback Process monitorCoordinating 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 Blood Increasing strength of uterine contractions Intensifies STRESS monitor regulator Once event is accomplished, positive feedback mechanism stops

Hyperglycemia Pancreas-beta cells Sensor and Control center Insulin is released into 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