BIO 203.11 Lecture 5s

BIO 203.11 Lecture 5s - BIO 203: Lecture 5 - Water and Ion...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
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 TA Office Hours in Life Sciences room 026 schedule posted on Blackboard Endotherms In The Cold Change Thermal Conduction (regulated process) Decrease Driving Force • Counter-current exchange mechanism in limbs • Pulsatile blood flow to limbs (e.g., artic fox) Decrease Surface Area (e.g., small ears, short limbs) • Less heat loss Increase Size • Smaller Surface Area / Volume ratio Increase Insulation • Fur, Feathers, Fat Avoidance • Hibernation, Torpor
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 MR versus size Log Body Mass (kg) small large MR Whole Animal MR per Unit Mass Small animal: low whole animal MR very high unit metabolic rate Large animal: high whole animal MR very low unit metabolic rate Larger animals use less energy per unit mass to stay warm! 1 kg Huddling - Another Example of Size Principle penguins Huddling decreased effective surface area reduced heat loss
Background image of page 2
3 Endotherms In The Cold (cont.) 3. Increase insulation Fur / hair - trapping of air • Piloerection (goose bumps!) Feathers - trapping of air • Birds--fluffing feathers in cold… Fat piloerection fluffing fat Endotherms - in the cold (effect of insulation) T amb MR BMR without insulation with insulation With insulation: • Expanded thermoneutral zone • Less increase in MR needed to maintain T B
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Endotherms —in the cold (cont.) 4. Avoidance—great savings cost in terms of energy hibernation : regulate T B but at lower value (e.g., bears, 25-30 o C) T amb MR torpor : suspend thermoregulation and allow T B to get get very low (e.g., small mammals, hummingbirds) T amb Endotherms In The Heat 1. Moderate heat stress (T B > T amb ) Vasodilation (facilitate heat transfer to external environment) Thermal windows (ostrich) Change posture Thermal Window: • Ostrich droops wings forward and downward to expose unfeathered thorax and thighs
Background image of page 4
5 Endotherms In The Heat 2. Extreme heat stress (T B < T amb ) or excessive heat production (e.g., exercise) Sweating/Panting (evaporative cooling) Water loss is a significant problem Allow T B to go high 3. Avoidance Desert animals…typically active at night Estivation (‘summer sleep’ equivalent to hibernation) 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 warm & cold thermoreceptors
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Where is the Thermostat? Mammalian body temperature can vary widely between the core and the extremities.
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 18

BIO 203.11 Lecture 5s - BIO 203: Lecture 5 - Water and Ion...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online