1. Introduction to Physiology

• Physiology is defined as the study of function of living organism so human physiology attempts to explainhowandwhyhumans function.

Physiology is where we figure out how stuff works.

• • How do muscles contract?

• • How do we run?

• • How does our heart beat?

2. Levels of Structure

In order to understand how something is built and how something works, you must look at all of its components and analyze them both individually and together.

In doing these collective and separate analyses, you must examine things at multiple structural levels, i.e., one must break them down from large to small this is called reductionism

An organism (such as a human being) may be broken down as illustrated on the left.

Organelle Cell Tissue Organ Organ System Organism 3. Levels of Structure

The basic unit of life is the cell.

All living organisms are composed of one or more cells.

The human body contains about 100 trillion cells.

There are about 200 different types of cells in the human body.

The different types of cells have different features but for the most part, all cells are made up of organelles and various macromolecules (e.g., proteins, lipids, carbohydrates and nucleic acids).

Organelles themselves are made of these macromolecules and macromolecules are polymers of smaller molecules which consist of atoms of various chemical elements.

4. A Prototypical Cell 5. Important Organelles

Plasma Membrane-> Separates the cell exterior from the cell interior (cytoplasm).

Nucleus-> Membrane bound structure that contains deoxyribonucleic acid (DNA) which is the set of instructions for the synthesis of all the bodys proteins.

Mitochondria -> Structure bound by a double membrane and the site at which the energy stored in sugars and other organic molecules is transferred to ATP, the chemical which acts as the currency for energy in the cell.

Ribosomes -> Not bound by a membrane. Sites of protein synthesis.May be free floating in the cytoplasm or bound to the endoplasmic reticulum.

6. Important Organelles

Rough Endoplasmic Reticulum -> Membranous set of tubes with ribosomes studded along its surface.Site of the synthesis of proteins that are destined to be exported from the cell.

Smooth Endoplasmic Reticulum -> ER w/o the attached ribosomes.Site of cellular lipid synthesis, among other things.

Golgi Apparatus -> Membrane bound organelle responsible for determining the direction of proteins synthesized in the rough ER.

Lysosomes -> Membrane bound organelle that houses digestive enzymes that can be used to break down ingested toxins or worn out cell parts.

7. More Levels of Structure

Similar cells and cell products come together to formtissues .

A structure made of 2 or more tissue types that perform a particular function is anorgan .

A group of organs with a unique collective function is anorgan system .

8. 9. Integumentary System

Structures:

• - Skin, hair, sweat and oil glands

Functions:

• Forms the external body covering

• Protects deeper tissues from injury

• Involved in vitamin D synthesis

• Prevents desiccation, heat loss, and pathogen entry

• Site of pain and pressure receptors

10. Skeletal System

Structures:

• The 206 bones of the human body

Functions:

• Protects and supports body organs

• Provides a framework that muscles can use to create movement

• Hemopoiesis (synthesis of blood cells)

• Mineral storage

• • Bone contains 99% of the bodys store of what mineral?

11. Muscular System

Structures:

• The 600+ muscles of the body

Functions:

• Locomotion

• Maintaining posture

• Thermogenesis (generation of heat)

12. Nervous System

Structures:

• Brain, spinal cord, and peripheral nerves

Functions:

• Fast-acting control system of the body

• Monitoring of the internal and external environment and responding (when necessary) by initiating muscular or glandular activity

13. Endocrine System

Structures:

• Hormone-secreting glands

• • Pituitary, Thyroid, Thymus, Pineal, Parathyroid, Adrenal, Pancreas, Small Intestine, Stomach, Testes, Ovaries, Kidneys, Heart

Functions:

• Long-term control system of the body

• Regulates growth, reproduction, and nutrient use among other things.

14. Cardiovascular System

Structures:

• Heart, Blood vessels (arteries, veins, and capillaries)

Functions:

• The heart pumps blood thru the blood vessels.

• Blood provides the transport medium for nutrients (glucose, amino acids, lipids), gases (O 2 , CO 2 ), wastes (urea, creatinine), signaling molecules (hormones), and heat.

15. Lymphatic/ImmuneSystem

Structures:

• Lymphatic vessels, Lymph nodes, Spleen, Thymus, Red bone marrow

Functions:

• Disposal of debris

• Attacking and resisting foreign invaders (pathogens i.e., disease-causing organisms)

16. Respiratory System

Structures:

• Nasal cavity, pharynx, trachea, bronchi, lungs

Functions:

• Constantly supply the blood with O 2 , and remove CO 2

• Regulate blood pH

17. Digestive System

Structures:

• Oral cavity, esophagus, stomach, small intestine, large intestine, rectum, salivary glands, pancreas, liver, gallbladder

Functions:

• Ingestion and subsequent breakdown of food into absorbable units that will enter the blood for distribution to the bodys cells

18. Urinary System

Structures:

• Kidneys, ureters, urinary bladder,

• urethra

Functions:

• Removal of nitrogenous wastes

• Regulation of bodys levels of water, electrolytes, and acidity

19. Reproductive System

Structures:

• Male:

• • Testes, scrotum, epididymis, vas deferens, urethra, prostate gland, seminal vesicles, penis

• Female:

• • Ovary, uterine tube, uterus, cervix, vagina, mammary glands

Functions:

• Production of offspring

20. Stayin Alive

Your body has about 100 trillion cells in it.

For your life toNOTend abruptly, these cells need to have the correct amount of:

• • Oxygen

• • Nutrients

• • Waste removal

• • Heat

• • Ions (sodium, calcium, etc.)

• • Lots of other stuff

21. The Cells Environment

In order to keep the right amount of stuff in the cell, weve got to make sure that all the fluid surrounding our cells (i.e., theextracellular fluid ) has the right assortment of nutrients, ions, etc.

We keep both our cells and the fluid surrounding our cells in a dynamically stable environment via a process calledHOMEOSTASIS.

22. Homeostasis

Defined as the bodys ability to maintain stable internal conditions in spite of the changing external conditions.

Our body needs to have the right amount of stuff (i.e., temperature, blood glucose, pH etc.)at all times in order to function properly.

First, lets refer to all this stuff as different variables

23. Lets use a thermostat as an example

In order to keep the temperature in my house at the right level, the thermostat must first measure the current temperature in the house.

After the thermostat measures the temperature, it compares the current value to a preset standard value.

• If there is no difference then theres nothing to do.

• However, if its too hot or too cold, the thermostat has to send a signal to the furnace or air conditioner to change the temperature of the house so that it equals the standard value.

24. Lets clarify some stuff.

In the previous example we had a:

• • Variabletemperature

• • Measuring implementthermostat

• • Control centeralso the thermostat

• • A preset or standard value for the variable

• • Effectorsthe air conditioner and furnace

Similar situations arise in the human body where there are lots of variables that we want to maintain at certain precise levels

25. Blood Pressure

BP is avariablethat weve got to maintain at a certain level

We havesensory receptorsthat measure the BP in the body.Theyre located in the aorta (the big blood vessel coming out of the heart) and in the carotid arteries (the large vessels that bring blood to the brain).

These pressure receptors measure BP and then send the info (we can call thisinput ) to acontrol centerin the brain the particular BP control center is in themedulla oblongataof the brain

26. Blood Pressure

We call the connection btwn the receptor and the control center theafferent pathway .

In the control center, the input BP is compared with a set value.

If there is a difference between the current BP value and the reference BP value then weve got an error.

And weve got to fix that error!

27. Blood Pressure

The control center will signaleffector organs such as the heart in this case to alter their activity.This process is calledoutput .

The connection between the control center and the effector organ is called theefferent pathway.

28. Blood Pressure

Suppose the current BP is too high.

The effector must act in a way to decrease it so the medulla oblongata (the control center) would signal the heart to decrease the force and rate of its contractions;this would decrease BP.

Notice that the original stimulus was anIncreasein BP and the bodys response was to act so as toDecreaseBP.

The stimulus is opposite the response!

29. Negative Feedback

The movement of a variable in one direction causes the body to enact processes that cause the variable to move in the opposite direction (so as to return the value to the correct level) we call itnegative feedback

Lets look at BP again:

30. Increased BP Sensed by pressure receptors in aortic arch and carotid sinus Input sent via afferent pathwayto medulla oblongataCurrent BP compared with set point and error signal generated Output sent along efferent pathway to heart and blood vessels Heart rate & force of contractiondecrease Blood vessel diameter increases BP DECREASES 31. Why isNegative Feedbackso common in the body?

Every time a variable starts changing too much, weve got to bring it back to normal.Weve got to counteract its change.

• • THATS NEGATIVE FEEDBACK

Other examples you will encounter:

• Maintenance of blood [Ca 2+ ], blood [Glucose], blood pH, and many others

32. When does a negative feedback process end?

A negative feedback process begins when a particular variable leaves its homeostatic range.

The process ends when that variable is back within its normal range.

Negative feedback processes (or loops) are self-terminating.

33. Homeostasis is Important!

Most of the physiological processes that occur in your body are designed to maintain homeostasis.

34. 35. 36. What this means is that the homeostatic variables are NOT kept rigidly fixed upon a single value.They are kept within a certain range, and when they exit that range thats when negative feedback loops turn on to bring them back. 37. What about Positive Feedback?

Positive feedback occurs when the responsemagnifiesthe stimulus that produced it.

In other words, a variable is altered and then the bodys response alters that variable even moreinthe same direction .

38. PositiveFeedback in Blood Clotting 39. Dangerous Positive Feedback Rise in body temperature Increase in body metabolism Increase in bodyheat production 40. What stops a positive feedback loop? 41. Water, water everywhere!

About 60% of the human body is water

2/3 of this water is found within your cells so we refer to it asintracellular fluid (ICF)

The other 1/3 is outside your cells so we call itextracellular fluid (ECF)

The 2 main types of ECF are:

• The fluid that surrounds the cells thetissue fluidorinterstitial fluid

• Blood!

Minor types of ECF include cerebrospinal fluid and intraocular fluid