Human Physiology

Human Physiology Welcome to your first day of class!!

You Can Contact Me • lisa.harvey@vvc.edu • 760-245-4271, ext. 2658

Physiology is… • The study of the functionof all plants and animals in their normal state. • An integrative science

Distinguish betweenProcess & Function Why do we breathe? Why does blood flow? Why do RBC transport O2? How do we breathe? How does blood flow? How do RBCs transport O2?

Key Concept in Physiology: Homeostasis • Homeostasis refers to maintaining relative constancy in a system.

Homeostasis Homeostasis is a dynamic, not a static, process. Physiological variables can change dramatically over a 24-hr. period, but the system is still in overall balance. When homeostasis is maintained, we refer to physiology; when it is not, we refer to pathophysiology.

Homeostasis Through: Negative Feedback • The ability of the body to survive in a challenging and changing environment by keeping the internal environment relatively stable

Negative Feedback • The change in the environment signals a response by the body • The response is to bring the body back to homeostasis • If possible!

Homeostasis • A given system tends to stay in equilibrium or balance despite influences that cause disequilibrium.

Interpret the arrows in textbook's flow charts as “leads to” or “causes.” (e.g., decreased room temperature causes increased heat loss from the body, which leads to a decrease in body temperature, etc.)

Blood glucose levels increase after eating. Levels return to their set point via homeostasis. This is an example of dynamic constancy. Levels change over short periods of time, but remain relatively constant over long periods of time.

Positive Feedback • Positive Feedback is NOT homeostatic • Positive Feedback reinforces the initial stimulus rather than decreasing or removing it. • The response sends the variable being regulated even farther from its normal value

Positive Feedback • This triggers a vicious cycle of ever-increasing response sending the system out of control temporarily • Must have a “shut off”switch or it becomes pathological.

http://www.youtube.com/watch?v=Vae5CcaPN_8&feature=related

Clinical Case Study A 64-year-old, fair-skinned man in good overall health spent a very hot, humid summer day gardening in his backyard. After several hours in the sun, he began to feel dizzy and confused as he knelt over his vegetable garden. Although he had earlier been perspiring profusely, his sweating had eventually stopped. Because he also felt confused and disoriented, he could not recall for how long he had not been perspiring, or even how long it had been since he had taken a drink of water. He called to his wife, who was alarmed to see that his skin had turned a pale blue color. She asked her husband to come indoors, but he fainted as soon as he tried to stand. The wife called for an ambulance, and the man was taken to a hospital and diagnosed with a condition called heat stroke. What happened to this man that would explain his condition, and how does it relate to homeostasis?

the end

The Science of Physiologyis based on the Scientific Method Review • Basic steps of scientific method • Parameters to consider • Experimental design

Basic Steps of Scientific Method: Observation (and/or study of prior knowledge)/Question Hypothesis Experimentation Collection and analysis of data (can you replicate results?) Conclusion: reject or accepthypothesis theory

Example: Company has found new artificial sweetener (S) Prior knowledge: Some food additives are not safe. Hypothesis: ? Experiments: ? Collect and analyze data Conclusion

Animal vs. Human Experimentation • In Physiology most knowledge is derived from _______ experimentation. • Sometime human experimentation is necessary. • Difficulties of Human Experimentation: • Very dissimilar test subjects • Psychological aspects (placebo and nocebo effects) • Ethical questions (is it o.k. to withhold potential drug from seriously ill?)

Focus on . . . . (Concept) Mapping • Structure – function maps • Process maps or Flow charts Follow process in sequence

Human Physiology