INTRODUCTION TO PHYSIOLOGY And homeostasis

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.

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.

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

“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

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

Brief history of physiology Aristotle – Greece (384-322 BC) – speculated about body function (thinkers, not doers) William Harvey – England (1578-1657) – demonstrated that the heart pumps through a closed system of vessels Claude Bernard – France (1813-1878) – 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

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.

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

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

Negative Feedback Loops

Negative Feedback Loops

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.

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

Set Points

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.

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

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.

Neural Regulation

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.

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.

Feedback Control of Hormone Secretions

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

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

3 types of muscle skeletal smooth cardiac

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

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

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.