2010 BIO 203 Lecture 5

2010 BIO 203 Lecture 5 - BIO 203: Lecture 5 - Water and Ion...

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1 BIO 203: Lecture 5 - Water and Ion Balance Prof. William Collins Office: 534 Life Sciences Building Office Hours: Tuesdays, 11:30 AM - 12:30 PM Thursdays, 4:00 - 5:00 PM Review Session - Monday, Feb. 22, 6:50-8:10 PM in Javits 102 T B 37 o C set point T B low Retain/Generate Heat e.g., vasoconstrict, change posture, increase MR Increase heat con- tent of body Increase T B T B high Reduce/Eliminate Heat e.g., vasodilate, change posture, sweat/pant Decrease heat con- tent of body Decrease T B T B 37 o C Monitor T B thermoreceptors
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2 Where is the Thermostat? Mammalian body temperature can vary widely between the core and the extremities. Extremities much more variable! Temperature is sensed by nerve endings (thermoreceptors) in brain, spinal cord, skin, and sites in the core that provide information to thermostatic centers in the brain. The brain coordinates a systemic response to temperature challenges. The Hypothalmus - The Mammal’s Thermostat • Henry G. Barbour (1912) Implanted a small temperature controlled probe into different parts of the rabbit brain. Evoked strong thermoresponses only when used to heat or cool the hypothalamus. • Cooling metabolic rate and T B • Heating panting and T B • Highly sensitive • Hypothalamus integrates all of the temperature-related information and orchestrates the systemic response. Temperature of hypothalamus most important
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3 PO/AH sensory input (thermal receptors) set point 37 o C Autonomic Nervous System • vasotone • metabolic rate • sweat Pituitary Gland / Endocrine System • vasotone • metabolic rate Higher Brain Centers • behavior The Integrator is in the Preoptic / Anterior Hypothalamus (PO/AH) Fever Hypothalamic thermoregulatory center is very sensitive to pyrogens (fever-producing substances). Pyrogens raise the set point in the hypothalamic thermoregulatory center. Exogenous pyrogens • Polysaccharides produced by gram negative bacteria • Very potent Endogenous pyrogens • Heat-labile proteins produced by the animal’s own leukocytes (white blood cells) • Released in response to circulating exogenous pyrogens Exogenous pyrogens raise body temperature both by: Acting directly on hypothalamic thermoregulatory center and Indirectly by stimulating the release of endogenous pyrogens.
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4 Thought Question #1 Fever is a biological response to an infection and, as long as it is not too high, it is actually good for you (our immune system functions better, relative to infecting bacteria/viruses, at higher temperatures). With a fever, the set-point in the above regulatory
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This note was uploaded on 03/28/2011 for the course BIO 203 taught by Professor Johncabot during the Spring '08 term at SUNY Stony Brook.

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2010 BIO 203 Lecture 5 - BIO 203: Lecture 5 - Water and Ion...

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