1. Introduction to Physiology
Physiology is the study of the functions of living things. Specifically, we will focus on how the human body works.

2. Body Systems

4. Homeostasis
Maintenance of a relatively stable environment (homeo means “the same”; stasis means to “ stand or stay”).

5. Homeostasis is essential for the survival of each cell, and each cell, through its specialized activities, contributes as part of a body system to the maintenance of the internal environment shared by all cells

6. Homeostasis: the foundation of Physiology
Homeostasis depend on maintain a balance between the input and output of all constituent present in the internal fluid environmental.
So when the total body input of a particular substance equals its output a stable balance exists.
when the gain via input for substance exceed its output a positive balance exists.
when the losses for a substance exceed its gain a negative balance exists.

7. About 60%of the adult human body is fluid.
Some of this fluid is inside the cell and is called the intracellular fluid (ICF).
The fluid in the space outside the cell is called the extracellular fluid (ECF).
The extracellular fluid is divided into two components:
1.the interstitial fluid
2. blood plasma

9. The major differences between the ECF and ICF are:
1. The presence of cellular proteins in the ICF that are unable to permeate the enveloping membranes to leave the cells and presences of a distinctly different plasma proteins in the ECF that cannot leave the plasma and enter the cells
2. The unequal distribution of Na+ and K+ .

11. The pH of pure water is 7.0, which is considered chemically neutral .
Solutions having a pH less than 7.0 are considered acidic
The solutions having a pH value greater than 7.0 considered alkaline.

13. The Cell Membrane

14. Membrane structure and function
plasma membrane is a thin layer of lipids and proteins that forms the outer boundary of every cell and enclose the intracellular contents.

15. Functions of plasma membrane
1- Acting as a mechanical barrier that traps needed molecules within the cell. 2- The plasma membrane helps determine the cell’s composition by selectively permitting specific substances to pass between the cell and its environment. 3- Controls the entry of nutrient molecules and the exit of secretory and waste products.

16. 4- Maintains differences in ion concentrations inside and outside the cell, which are important in the membrane’s electrical activity. 5- Participates in the joining of cells to form tissues and organs. 6- Plays a key role in enabling a cell to respond to changes, or signals, in the cell’s environment.

17. The plasma membrane of every cell consists mostly of: # lipids
The plasma membrane of every cell consists mostly of: # lipids. # proteins. # small amounts of carbohydrate.

20. Membrane Proteins
Different types of membrane proteins serve the following
specialized functions:
# Channels protein.
# Carriers or transport protein.
# Membrane- bond protein.
# Receptors.
# Cell adhesion molecules.
Glycoprotein serve as cell marker. #

21. Many Functions of Membrane Proteins
Outside
Plasma
membrane
Inside
Transporter
Enzyme activity
Cell surface receptor
Signal transduction - transmitting a signal from outside the cell to the cell nucleus, like receiving a hormone which triggers a receptor on the inside of the cell that then signals to the nucleus that a protein must be made.
Cell surface identity marker
Cell adhesion
Attachment to the cytoskeleton

22. Membrane carbohydrates
The short carbohydrate chains on the outer membrane surface serve as self-identity markers that enable cells to identify and interact with one another in the following ways:
1. Different cell types have different markers.
The unique combination of sugar chains projecting from the surface membrane proteins serves as the “trademark” of a particular cell type, enabling
a cell to recognize others of its own kind.
cell-to-cell interactions

23. 2. Carbohydrate-containing surface markers are also involved in tissue growth, which is normally held within certain limits of cell density.

24. Cell- to- cell adhesion
In multicellular organisms such as humans, the plasma membrane not only serves as the outer boundary of all cells but also participates in cell-to-cell adhesions.

25. Cells are held together by three different means:
1- Cell adhesion molecules in the cells plasma membrane.
2- Extracellular matrix: an intricate meshwork of fibrous proteins embedded in a watery, gel like substance composed of carbohydrate.
3- Specialized cell junctions.

26. Cells are directly linked together by one of three specialized cell junctions: Desmosomes (adhering junctions) filaments extend between the plasma membrane of two closely but not touching cells. Tight junction (impermeable junction) the lateral side of adjacent sells are joined together in tight seal way by direct fusion of proteins on the surface of the interacting plasma membrane. Gap junction (communicating junction)  a gap exit between two cells that are linked by a small connecting tunnels known as connexons.

31. Membrane transport
If a substance can cross the membrane, the membrane is said to be permeable to that substance; if a substance cannot pass, the membrane is impermeable to it. The plasma membrane is selectively permeable in that it permits some particles to pass through while excluding other.

32. Two properties of particles influence whether they can permeate the plasma membrane without assistance: (1) The relative solubility of the particle in lipid. (2) The size of the Particle.

33. Two general types of forces accomplish transport of substances across the membrane: (1) passive forces, which do not require the cell to expend energy to produce movement. (2) active forces, which do require the cell to expend energy (ATP) in transporting a substance across the membrane.

35. Simple diffusion
Simple diffusion depend on the concentration different between two adjacent areas which is called concentration gradient or (chemical gradient).

36. FICK’S LAW OF DIFFUSION Several factors in addition to the concentration gradient influence the rate of net diffusion across a membrane.

38. Osmosis
The net diffusion of water down its concentration gradient through a selectively permeable membrane.

39. Assisted membrane transport
Movement of substance across the membrane through a carrier protien. carrier-mediated transport

41. Carrier-mediated transport systems display three important characteristics that determine the kind and amount of material that can be transferred across the membrane: Specificity Saturation Competition

43. Active transport
Active transport also involves the use of a carrier protein to transfer a specific substance across the membrane, but in this case the carrier transports the substance uphill against its concentration gradient.

44. Active transport comes in two forms: In primary active transport, energy is directly required to move a substance against its concentration gradient; the carrier splits ATP to power the transport process. In secondary active transport, energy is required in the entire process, but it is not directly used to produce uphill movement

45. PRIMARY ACTIVE TRANSPORT
In primary active transport, energy in the form of ATP is required to vary the affinity of the binding site when it is exposed on opposite sides of the plasma membrane. In contrast, in facilitated diffusion the affinity of the binding site is the same when exposed to either the outside or the inside of the cell.

47. Na+ –K+ ATPase pump
(Na+ –K+ pump) found in the plasma membrane of all cells. This carrier transports Na+ out of the cell, concentrating it in the ECF, and picks up K+ from the outside, concentrating it in the ICF. (Na+ - K+ pump) moves three Na+ out of the cell for every two K+ it pumps in.

48. The Na+ – K+ pump plays three important roles: 1
The Na+ – K+ pump plays three important roles: 1. It establishes Na+ and K+ concentration gradients across the plasma membrane of all cells; these gradients are critically important in the ability of nerve and muscle cells to generate electrical signals essential to their functioning. 2. It helps regulate cell volume by controlling the concentrations of solutes inside the cell and thus minimizing osmotic effects that would induce swelling or shrinking of the cell.

49. 3. The energy used to run the Na+ – K+ pump also indirectly serves as the energy source for secondary active transport.

50. SECONDARY ACTIVE TRANSPORT
With secondary active transport, the carrier does not directly split ATP to move a substance against its concentration gradient. Instead, the movement of Na+ into the cell down its concentration gradient (established by the ATP-splitting Na+ – K+ pump) drives the uphill transport of another solute by a secondary active-transport carrier. This is very efficient, because Na+ must be pumped out anyway to maintain the electrical and osmotic integrity of the cell.

51. Secondary active transport occurs by two :mechanisms Symport Antiport depending on the direction the transported solute moves in relation to Na+ movement.

52. In symport (also called cotransport), the solute and Na+ move through the membrane in the same direction, that is, into the cell (sym means “together;” co means “with”). Glucose and amino acids are examples of molecules transported by symport in intestinal and kidney cells.

53. In antiport (also known as countertransport or exchange), the solute and Na+ move through the membrane in opposite directions, that is Na into and the solute out of the cell. Anti means “opposite” counter means “against”.

55. How about large molecules?
Moving large molecules into & out of cell
* Through vesicles & vacuoles
* Endocytosis
phagocytosis = “cellular eating”
pinocytosis = “cellular drinking”
* Exocytosis

56. Endocytosis

57. Exocytosis Secretion of cellular product
Joining the vesicle with the plasma membrane

58. Membrane Potential
The plasma membranes of all living cells have a membrane potential, or are polarized electrically.

59. Membrane potential is a separation of opposite charges across the plasma membrane
The term membrane potential refers to a separation of opposite charges across the membrane or to a difference in the relative number of cations and anions in the ICF and ECF.

60. A separation of charges across the membrane is called a membrane potential because separated charges have the potential to do work. Potential is measured in volts (the same unit used for the voltage in electrical devices), but because the membrane potential is relatively low, the unitused is the millivolt (mV) (1 mV 1⁄1000 volt).

66. Membrane potential is due to differences in the concentration and permeability of key ions
All cells have membrane potential. The cells of excitable tissues—namely, nerve cells and muscle cells—have the ability to produce rapid, transient changes in their membrane potential when excited. These brief fluctuations in potential serve as electrical signals.

67. The constant membrane potential present in the cells of nonexcitable tissues and those of excitable tissues when they are at rest—that is, when they are not producing electrical signals—is known as the resting membrane potential.

68. The unequal distribution of a few key ions between the ICF and ECF and their selective movement through the plasma membrane are responsible for the electrical properties of the membrane. In the body, electrical charges are carried by ions.

69. The ions primarily responsible for the generation of the resting membrane potential are Na+, K+, and A. The A refers to the large, negatively charged (anionic) intracellular proteins. Other ions (calcium, magnesium, chloride, bicarbonate, and phosphate) do not contribute directly to the resting electrical properties of the plasma membrane in most cells, even though they play other important roles in the body.

71. Thank you