John Stein Office Hours (SFH 354) -Thursdays 5-6 pm -Friday 12-1:00pm (lunch) -Friday 1-3pm (SFH 354) -or by appointment - After class on Wed and Fridays

Tips for success… Look at the readings before class. Pay careful attention to the content and questioning that occurs in class, lab and homework assignments. Go back to readings to reinforce what was covered in class. (Lectures Slides will be posted) Some exam questions will cover content while others will involve analysis, critical thinking skills and application of knowledge; the kind of stuff we do in class, lab and homework assignments. (Freeman often does this as well!)

Physiology – the study of body functions Anatomy - the study of body structure “Function follows Form” – if it looks interesting there must be a reason. Much more meaning when we study physiology in light of what we know about evolution and molecular and cellular biology Comparative Physiology Relate to Adaptation, Natural Selection

Major Recurring Themes Constrained by laws of chemistry and physics Diffusion and Surface area to volume ratio Homeostasis Evolutions role in developing diverse physiological systems.

Today’s Goals Layout of organisms Issues encountered as body size increases Internal environment and maintaining homeostasis Role of negative feedback in maintaining homeostasis Analytical skills and asking good scientific questions with body temp/torpor example Cell communication via Endocrine and Nervous Systems – Introduction…maybe.

To Maintain HOMEOSTASIS! literally means “alike-standing.” does NOT always mean “keeping oneself the same”. (chemical & physical states kept within a tolerable range) can be seen at many levels throughout an organism…from whole organism (temperature) to cellular/molecular level (enzymes, transcription factors).

Multicellular Organisms What does this cell need? Hospitable Environment What defines hospitable? Some cells are more particular than others when it comes to pH, temp, oxygen, etc. Brain cells – very finicky Muscle cell – more tolerant

Homeostasis “alike-standing” Water Oxygen Carbon Dioxide pH (-log [H+]) Temperature Osmolarity Nutrients Wastes Pathogen-free environment Normal Range Lethal 7.4 7.3-7.5 6.9-8.0 98.60F 98-98.8 65-110 (370C) (36.6-37.40C) (18-430C) (Sodium) 142mM 138-146 115-175 ( for humans )

Hierarchy of Organism Cell (cardiac muscle cell) Tissue (muscle) Epithelial Connective Nervous Muscle Organ (Heart) Organ System (Cardiovascular) Organism (Elephant Seal)

Diffusion is a major concern for multicellular organisms Diffusion is a major concern for multicellular organisms. Bulk Movement for large distances

Surface area : Volume BUT!! surface area of structures like lungs and blood vessels are proportional to volume of animal! S.A. = L2 * 6 Vol. = L3

Surface Area to Volume Ratio (and body temperature) 65 kg human walks from shadow to sun with little effect on body temp 10 mg fly moves from shadow to sun and body temp increases 10 0 C in 10 seconds!

Surface Area to Volume Ratio (for different sized cats) 0.1 square meters of skin on 1 kg cat (0.1/1) 0.46 square meters of skin on 10kg cat (0.046/1) 1.53 square meters of skin on 60kg cat (0.0255/1) This ratio is significant in maintaining proper body temperature (e.g. small animals cool more quickly than large animals.) How can small animals reduce surface area to volume ratio?

Negative Feedback Set point (desired temp) Integrator (desired - current = ? If not = 0 then…) Effector (make current = desired temp)

Heating and Cooling cost energy and resources!

“Warm Blooded” & “Cold Blooded” Endotherms & Ectotherms (heat from within) (heat from outside) Homeotherms & Heterotherms (same temp) (different temp) There are no hard and fast rules here. (e.g. some insects are endotherms and some mammals are ectotherms)

Is the body temp of this very small (~20 grams) mammal under homeostatic control?

Is the body temp of this very small (~20 grams) mammal under homeostatic control during torpor?