Human Physiology Welcome to your first day of class!!

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

Function and Process: Teleological vs. Mechanistic Approach to Science What is the purpose or function? Why does something exist? Why does it need to be done? What are the processes involved? What are the processes involved? How does something work? How does something work?

Distinguish between Process & Function Integrate both for complete picture! How do we breathe? How does blood flow? How do RBCs transport O 2 ? Why do we breathe? Why does blood flow? Why do RBC transport O 2 ?

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

The ability of the body to survive in a challenging and changing environment by keeping the internal environment relatively stable The ability of the body to survive in a challenging and changing environment by keeping the internal environment relatively stable

The change in the environment signals a response by the body The change in the environment signals a response by the body The response is to bring the body back to homeostasis 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.

Negative Feedback Negative Feedback Loops are Homeostatic Negative Feedback Loops are Homeostatic Negative feedback loops can restore the normal state but can’t prevent the initial disturbance. Negative feedback loops can restore the normal state but can’t prevent the initial disturbance. Negative Feedback Negative Feedback Refers to the corrective effect produced by the feedback signal. The effect must be to REDUCE the DIFFERENCE BETWEEN the SET POINT and the CONTROLLED VARIABLE Refers to the corrective effect produced by the feedback signal. The effect must be to REDUCE the DIFFERENCE BETWEEN the SET POINT and the CONTROLLED VARIABLE

Negative Feedback The body maintains a set point until there is a perturbation. The body maintains a set point until there is a perturbation. The change in the environment signals a response by the body The change in the environment signals a response by the body The response is to bring the body back to homeostasis The response is to bring the body back to homeostasis If possible! If possible!

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

Positive Feedback Positive Feedback is NOT homeostatic Positive Feedback is NOT homeostatic Positive Feedback reinforces the initial stimulus rather than decreasing or removing it. 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 The response sends the variable being regulated even farther from its normal value This triggers a vicious cycle of ever-increasing response sending the system out of control temporarily 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. Must have a “shut off” switch or it becomes pathological.

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The Science of Physiology is based on the Scientific Method Review 1. Basic steps of scientific method 2. Parameters to consider 3. Experimental design

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

Example: Company has found new artificial sweetener (S) 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 1. Structure – function maps 2. Process maps or Flow charts Follow process in sequence