Advance physiology Part 2 Prepared by: A. Riasi Isfahan University of Technology

Cell membrane physiology There are at least six functions for plasma membrane:  Separation  Transport  Regulation  Structural support  Coordination  Fusion

Concentrations of ICF and ECF Figure 3.25b ICFECF Na + : 142 mEq/L……………..…….10 mEq/L K + : 4 mEq/L…………..…….140 mEq/L Ca ++ : 5 mEq/L…………..………..<1 mEq/L Mg ++ : 3 mEq/L…………….………58 mEq/L Cl - : 103 mEq/L…………….………..4 mEq/L HCo3 - : 28 mEq/L…………………….10 mEq/L Posphates 4 mEq/L……………………..75 mEq/L SO4 -- 1mEq/L………………………2 mEq/L Glucose 90 mg………………………0-20 mg Proteins 2 g % …………………….16 g % pH 7.4………………………..7.0

Membrane transport Figure 3.25b Diffusion Osmosis Carrier-mediated transport Vesicular transport Caveolae

 Diffusion using chemical gradient or concentration gradient Diffusion

Osmosis

Figure 3.25b Osmosis

Carrier-mediated transport  Carrier-mediated transport systems display three important characteristics:  Specificity  Saturation  Competition

Carrier-mediated transport

Plasma membranes are permeable FFocus now on Active transport - moving molecules against their concentration gradient TTakes energy – ATP SSodium-Potassium pump is an example of primary active transport: SSodium can “carry” glucose into cell is an example for secondary active transport

The Na + - K + ATPase pump plays three important roles: IIt maintains Na+ and K+ concentration gradients across the plasma membrane of all cells IIt helps regulate cell volume by controlling the concentrations of solutes inside the cell TThe energy used to run the Na + - K + pump also indirectly serves as the energy source for the cotransport of glucose and amino acids across intestinal and kidney cells (Secondary active transport)

Figure 3.25b Plasma membranes are permeable

Vesicular Transport  Exocytosis  Endocytosis  Phagocytosis - cell eating  Pinocytosis – cell drinking

Exocytosis

Endocytosis

Endocytosis (phagocytosis)

Endocytosis (pinocytosis)

Intercellular communication and signal transduction Three type of intercellular (Between cell) communication: 1)Gap junctions 2)Signaling molecules on the surface membrane of some cell 3)Chemical messengers  Paracrines & Autocrines  Neurotransmitters  Hormones  Neurohormones  Pheromones  Cytokines

 Gap junction is the fastest way for cell communication transport.  Gap junctions are important for the cardiac and smooth muscles function.  The gap junctions are closed in high concentration of Ca ++ or H +

 The presence of signaling molecules on the surface membrane of some cell is a way for killing microbes

Figure 3.25b Structural and functional classification of chemical messengers  Eicosanoids  Gases  Purines  Amines  Peptides and proteins  Steroids  Retinoids

Signal transduction Figure 3.25b Extracellular chemical messengers (first messenger) bring about cell responses primarily by signal transduction. There are three ways for the transduction:  Activating an enzyme that phosphorylates a cell protein  Opening or closing specific channels in the membrane to regulate the movement of particular ions into or out of the cell  Transferring the signal to an intracellular chemical messenger (second messenger)

Signal transduction Figure 3.25b An extracellular messenger can alter a chemically gated channel through one of two mechanisms: 1- The receptor binding site on the plasma membrane is part of the channel 2- The receptor is a separate protein located near the channel and the receptor activate membrane-bound known as G protein. The chemically gated channels change ionic movement: 1- A small movement of Na+, K+ across the membrane 2- A transient flow of Ca++ into the cell.

Figure 3.25b There are two major second-messenger pathway: 1- Cyclic adenosine monophosphate (cAMP) pathway 2- Calcium second-messenger pathway