1. INTRODUCTION TO PHYSIOLOGY
And homeostasis

2. PHYSIOLOGY – THE STUDY OF FUNCTION OF THE BODY
From the Greek “physis” which means nature; logos = study
Comparative Physiology – the physiology of invertebrates and different vertebrate groups
Pathophysiology is the study of how physiological processes are altered by disease.

3. YOU SEE SOMETHING INTERESTING AND YOU…
SCIENTIFIC METHOD
OBSERVATION
YOU SEE SOMETHING INTERESTING AND YOU…
2) GATHER DATA
3) ANALYZE THE DATA
4) COME TO A CONCLUSION AS TO HOW YOU THINK SOMETHING WORKS (A WORKING HYPOTHESIS, OR EDUCATED GUESS)
5) TEST THE HYPOTHESIS
6) SET UP A SERIES OF EXPERIMENTS: IF I DO X, THEN Y SHOULD HAPPEN.

4. SCIENTIFIC METHOD (cont.)
7) GATHER DATA
8) REANALYZE THE DATA
9) CONCLUSION, AND COME UP WITH A NEW HYPOTHESIS
10) KEEP REPEATING THIS UNTIL YOU COME UP WITH A HYPOTHESIS THAT EXPLAINS THE PHENOMENON.
11) PUBLISH THE DATA IN A PEER-REVIEWED JOURNAL

5. “PEER-REVIEWED”
A scientist’s peers review the work and accept it or reject it.
Other scientists try to reproduce the results, and if they can’t then the work is not believable

6. Theory
In science, a theory is a proven fact, which is supported by huge amounts of experimentation, results, evidence!
EXAMPLES:
Evolution
Cell theory

7. Brief history of physiology
Aristotle – Greece ( BC) – speculated about body function (thinkers, not doers)
William Harvey – England ( ) – demonstrated that the heart pumps through a closed system of vessels
Claude Bernard – France ( ) – observed that the internal environment (milieu interieur) stays relatively constant although changes are occurring
Walter Cannon – US (1932) – coined the term, homeostasis, to describe the internal consistency of the body

8. Homeostasis
Homeostasis is constancy of the internal environment. (Dynamic constancy).
2. The main purpose of our physiological mechanisms is to maintain homeostasis.
3. Deviation from homeostasis indicates disease.
4. Homeostasis is accomplished most often by negative feedback loops.

9. Negative Feedback Loops
Pathway
Sensors in the body to detect change and send information to the:
Integrating center, which assesses change around a set point. The integrating center then sends instructions to an:
Effector, which can make the appropriate adjustments to counter the change from the set-point

10. Mechanism of negative feedback loops
Moves in the opposite direction from the change
Makes the change from the set-point smaller
Reverses the change in the set-point
This is a continuous process, always making fine adjustments to stay in homeostasis

11. Negative Feedback Loops

12. Negative Feedback Loops

13. Body temperature example of negative feedback loops
Sensors in the brain detect deviation from 37ºC. Another part of the brain assesses this as actionable (integration), and effectors (sweat glands) are stimulated to cool the body.
Once the body is cool, sensors alert the integrating center, and sweat glands are inhibited.
The end result regulates the entire process. Production of the end product shuts off or down-regulates the process. This is why it is called a negative feedback loop.

14. How Body Temperature is Maintained Within the Normal Range
Shivering and sweating are two antagonistic mechanisms

15. Set Points

16. The end product in a process stimulates the process.
Positive Feedback
The end product in a process stimulates the process.
The action amplifies the changes that stimulated the effectors
Positive feedback could not work alone, but it does contribute to many negative feedback loops.
For example, if a blood vessel is damaged, a process is begun to form a clot. Once the damage is fixed, clotting ends (negative feedback). However, the process of forming the clot involves positive feedback.
The strength of uterine contractions during childbirth is also regulated by a positive feedback loop.

17. Intrinsic and Extrinsic Regulation
Regulation of processes within organs can occur in two ways:
Intrinsically: Cells within the organ sense a change and signal to neighboring cells to respond appropriately.
E.g. paracrine regulators of muscle contraction
Extrinsically: The brain (or other organs) regulates an organ using the endocrine or nervous system.
E.g. oxytocin stimulation of uterine contractions

18. Neural and Endocrine Regulation
The nervous system “innervates” organs with nerve fibers.
The endocrine system releases hormones into the blood, which transports them to multiple target organs.

19. Neural Regulation

20. Feedback Control of Hormone Secretions
Hormones are secreted in response to specific stimuli.
Example - An increase in blood sugar results in the release of insulin, which removes sugar from the blood.
Secretion can be inhibited by its own effects.
Example - Decreased blood sugar inhibits the release of insulin.

21. Feedback Control of Hormone Secretions, cont
Negative feedback inhibition usually involves an antagonist to make sure homeostasis is maintained within normal levels.
Example - When blood sugar is low, the hormone glucagon is secreted, which results in a rise in blood sugar.
Insulin and glucagon are “antagonistic” hormones.

22. Feedback Control of Hormone Secretions

23. MULTICELLULAR ORGANISM
THE HUMAN BODY PLAN
CELLS
TISSUES
ORGANS
ORGAN SYSTEMS
MULTICELLULAR ORGANISM

24. Tissue: “A group of cells with a common function.”
4 TYPES
NERVOUS
MUSCLE
EPITHELIAL
CONNECTIVE

25. 3 types of muscle
skeletal
smooth
cardiac

26. An ORGAN is a group of tissues with a specific function. Examples
Heart pumps blood, which transports nutrients
The heart is composed of nervous, connective, epithelial and muscle tissues.
TESTES make sperm
The femur supports the thigh
Pancreas regulates blood sugar; aids digestion
Kidney
filters blood

27. An ORGAN SYSTEM is a group of organs with a common function.
You must memorize the organ systems and their functions
EXAMPLE: The Urinary System filters the blood to remove wastes, makes urine, and regulates water balance in the body
There are 11 organ systems in the human body
Integumentary Excretory (Urinary)
Skeletal Cardiovascular (circulatory)
Muscular Respiratory
Nervous Reproductive (Male/Female)
Endocrine Immune
Digestive

28. Stem Cells
Stem cells are totipotent, which means they can become anything.
Cells of the early embryo are stem cells. Scientists are working to grow stem cells into organs for transplant.
Adult stem cells are pleuripotent. They can become a number of different types of cells, but they cannot become any cell.