Cellular Physiology Flashcards
(69 cards)
1
Q
Elements
A
Definition
- the material or matter fundamental to cells.
Characteristics
- most common elements are oxygen, carbon, hydrogen and nitrogen
- composed of atoms
2
Q
Atoms
A
Definition
- small clusters of protons (positive), electrons (negative) and neutrons (no charge)
Characteristics
- central nucleus and a surrounding field containing protons and neutrons
- electrons circulate at different energy levels
- first level has 2 electrons
- second level has 8 electrons
- do not have a full outer level and are therefore unstable until bonds are formed and the outer levels are full
3
Q
Ionic Bonds
A
Definition
- formed through the gain or loss of an outer electron between one or more electrons
** Characteristics**
- ionic bonds are released when the compound is dissolved in water, resulting in ions which carry an electric charge
- an ion is attracted to another ion of opposite charge
- an atom that gains one or more electrons acquires a negative charge and is called an anion
- an atom that loses one or more electrons acquires a positive charge and is called a cation
4
Q
Covalent Bonds
A
Definition
- formed when electrons are shared and each atom fills its outer electron level
Characteristics
- acids and bases are compounds which share electrons
5
Q
Hydrogen Bonds
A
Definition
- covalent bonds with hydrogen as a component
Example
- water has both covalent and hydrogen bonds, with the oxygen attracting the hydrogen electron more strongly, causing the hydrogen atoms to be slightly positive and the oxygen atom to be slightly negative. This causes a strong attraction between molecules, leading to surface tension.
6
Q
Phosphate Bonds
A
Definition
- unique chemical bonds which store energy
- high phosphate bonds are between phosphate groups and adenosine monophosphate (AMP)
Characteristics
- ADP is formed by the first phosphate bond between AMP and phosphate
- ATP is formed by the second phosphate bond between two phosphates and AMP
7
Q
Carbohydrates
A
Definition
- sugars and starches
Characteristics
- complex carbohydrates are starches, which must first be broken down into simple sugars for cellular uptake
- sugars are primarily used or stored as cellular fuel
8
Q
Proteins
A
Definition
- the structural and communication ingredients of the body made from amino acids
Characteristics
- 20 known amino acids
- diversity of proteins is due to the length and organization of the amino acid chains
- structural proteins provide structure, support, strength, and tension (ex. collagen, keratin, and elastin)
- Functional proteins are mobile and chemically active in biological processes including cellular communication (ex. transmitters, hormones, antibodies, enzymes, and contractile muscle
9
Q
Lipids
A
** Classifications**
- triglycerides
- phospholipids
- steroids
Characteristics of Triglycerides
- comprised of a glycerol and three fatty acid chains
- the major source of stored energy for the body
Characteristics of Phospholipids
- bipolar lipids comprised of two fatty acid chains
- unique in that the phosphorus polar end attracts water and ions
- major component of the cell membrane of most cells
Characteristics of Steroids
- lipids which are structurally related as rings, not chains
- vary greatly in function and structure
- cholesterol is the primary steroid lipid and is the base for steroid hormones such as testosterone, estrogen, aldosterone, and cortisol
10
Q
Nucleic Acids
A
Definition
- the most complex molecules in the body
Classifications
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
Characteristics of DNA
- located in the nucleus
- responsible for cell division and protein synthesis
- genes for identical cell replication and new cell production is stored in DNA
Characteristics of RNA
- located outside of the cell nucleus
- carries out the orders from DNA for protein synthesis
11
Q
Cell Membrane
A
Basic Structure
- double layer of phospholipids with embedded specialized structures
- channels
- carriers
- pumps
- exchangers
- receptors
- effectors
Characteristics
- semipermeable due to the basic structure of phospholipids and embedded proteins
- a barrier to easy movement of water and water soluble substances
- lipids move freely through membrane
Function
- to control or regulate the intracellular environment
12
Q
Bi-Polar Phospholipid Layer
A
Structure
- only two molecules thick
- hydrophilic - water soluble molecules
- hydrophobic - repellant to water
- two hydrophobic molecules face each other
Characteristics
- due to the polarity and lipid structure, the membrane is not normally permeable to numerous substances such as ions, glucose, and urea
13
Q
Protein Channels
A
Structure
- embedded in the lipid layer
- have gates which block the pathway between the intracellular and extracellular environment
Function
- provide pathways through the phospholipid layer
- the gates must open to allow substances or enzymes into the cell
Characteristics
- very selective - due in part to diameter and electrical charge
- gates are controlled by either an electrical charge (voltage gating) or activation through cell communication (ligand gating)
14
Q
Protein Carriers
A
Structure
- a solid pathway from the intracellular to extracellular environment
Function
- bind with substances and trasnport them from one side of the cell membrane to the other
Characteristics
- very selective - due in part to the chemical structure of the transported substance
15
Q
Ion Pumps
A
Characteristics
- most important pump is the sodium-potassium pump
- uses energy to move sodium to the outside of the cell in exchange for potassium movement into the cell
16
Q
Receptors
A
Definitions
- carbohydrate protein compounds are receptors for hormones and transmitters
- specialized to receive stimuli and initiate a cellular response, such as an enzyme or an effector withi the membrane
Classifications
- Functional receptors
* extend to the outer surface of of the cell - Provisional receptors
* located within the cell membrane and must surface before they are functional
Characteristics
- type and number of receptors varies greatly depending on the particular cell
- may be activated or blocked
- an agonist effect occurs when the transmitter or chemical interacts with the particular molecular structure of receptors and initiates a response
- an antagonist effect occurs when the transmitter or chemical occupies the receptors but blocks the agonist and response
17
Q
Cytoplasm
A
Components
- Cytosol
- intracellular viscous fluid in which elements are dissolved and suspended
- different than the extracellular fluid - this is maintained by the cellular membrane
- Organelles
- mitochondria
- ribosomes
- endoplasmic reticulum
- golgi apparatus
- lysosomes
- peroxisomes
- cytoskeleton
18
Q
Mitochondria
A
Functions
- manufacture ATP
- enzymes within the mitochondria break down glucose and capture the released energy to form ATP
Characteristics
- supply 95% of the cell’s energy
- density of mitochondria vary depending on the cell
- require oxygen (aerobic cellular respiration)
19
Q
Ribosomes
A
Function
- synthesize proteins for cell function
Structure
- tiny granules of proteins and RNA
Characteristics
- fairly specific, depending on the cell and particular function
20
Q
Endoplasmic Reticulum
A
Structure
- an extensive network of parallel membranes which form cisternae (fluid filled cavities)
- two types: rough and smooth
- Rough ER has proteins on its surface
- Smooth ER contains enzymes
Function
- Rough ER produces proteins which are transported to the Golgi apparatus
- Smooth ER produces lipids, including the cell’s membrane phospholipids and can have specialized functions depending on the cell
- synthesis of steroid-based hormones
- synthesis of enzymes
- absorption and transport of fats
- synthesis and storage of glycogen
- detoxification and metabolism
21
Q
Golgi Apparatus
A
Structure
- a group of membranous sacs near the nucleus
Function
- modifies and transports specific proteins, such as glycoproteins and secretory enzymes
Characteristics
- the presence of the Golgi apparatus is a strong indicator tha tthe cell is currently active
22
Q
Lysosomes
A
Structure
- membranous sacs which contain hydrolytic (digestive) enzymes
Function
- digestion of particles harmful to the cell (bacteria, viruses, toxins)
- digestion of worn-out particles
- metabolism (such as breakdown of glycogen and release of thyroid hormone)
- breakdown of bone
23
Q
Peroxisomes
A
Structure
- membranous sacs which contain enzymes
Function
- enzymes called peroxidases detoxify harmful or toxic substances (such as alcohol and oxygen-free radicals - a waste product of cellular metabolism)
24
Q
Cytoskeleton
A
Structure
- internal scaffolding composed of
- microfilaments
- intermediate filaments
- microtubules
25
Nucleus
**Function**
* contains genetic information to direct and regulate the cell
* cells which have complex activities have more than one nucleus
* provides information for protein synthesis and genetic reproduction
26
Diffusion
**Definition**
* the movement of substances from an area of high concentration to an area of low concentration
**Classifications**
1. simple diffusion - movement of molecules through the cell membrane or protein channels
2. facilitated diffusion - involves carrier proteins which move substances accross the membrane
**Characteristics**
* energy is not requried for either type of diffusion
* diffusion of lipid soluble substances is more rapid than water soluble substances
*
27
Active Transport
**Definition**
* substances that move from a lower to higher concentration gradient - against the concentration gradient
**Characteristics**
* requires ATP
* can be achieved through protein carriers, pumps, and exchangers
28
Sodium-Potassium Pump
**Function**
* maintains the concentration gradients of sodium and potassium
* transports sodium ions out of the cell and potassium ions into the cell
**Characteristics**
* the pump is activated when sodium and potassium ions bind to the receptors
* both ions are moved against their concentration gradient
* affects cellular ion concentrations and electrical charge
* more sodium than potassium is transported out, therefore there is a net loss of positive charge within the cell - with each exchange through the pump, 3 positive ions move out and only 2 positive ions move into the cell
29
Filtration
**Definition**
* movement of water and solutes across the cell membrane
* dependent on hydrostatic and osmotic pressures
* water moves accross the membrane to achieve equilibrium between these pressures
30
Metabolism
**Definition**
* reactions which change the complexity and size of molecules
**Classifications**
1. Anabolism - larger molecules and structures are created
2. Catabolism - conversion of complex, larger molecules to simple, building blocks
* vitamin dependent
* aerobic
3. Cellular Respiration - the group of reactions in which glucose, fatty avids, and amino acids are broken down and the energy released is captured to form ATP
**Characteristics**
* nutrients are taken into the body primarily through digestion and the intestinal tract, are broken down into organic compounds and then transported to tissue cells
* within the cells, nutrients are either build into cellular molecules or broken down by catabolic pathways to acetyl CoA for energy
* glucose is initially broken down into pyruvic acid and then acetyl CoA before they can enter the citric acid or Krebs cycle
* Acetyl CoA enters the mitochondria for catabolism
31
\*Formation of ATP
diagram from page 44
32
Action Potential
**Definition**
* electrical activity which enable cells to intiate, transmit, and/or respond to messages
* a sudden chnge in the resting membrane potential, followed by a return to the resting membrane potential
**Characteristics**
* vary in shape, duration, and currents depending on the cell type
* initiated by any event which causes teh resting potential to rise toward zero and reach threshold
* move from cell to cell by electric or chemical transmission
**Process**
1. Resting membrane potential
2. Threshold
3. Depolarization
4. Repolarization
33
Resting Membrane Potential
**Definition**
* negatively charged intracellular membrane in relation to the extracellular environment
**Characteristics**
* expressed in millivolts
* nerve cells -90mv
* smooth muscles -60 mv
* three main factors which cause the intracellular negative charge 1) sodium-potassium ATPase pump, 2) potassium diffusion, 3) protein charge
34
Threshold
**Definition**
* the value which must be attained before the cell can achieve an action potential
* positive ions move into the cell and cause the cell to move towards zero - becoming less negative
**Characteristics**
* the threshold potential of the neuron is about -70mv
35
Depolarization
**Definition**
* primarily due to the rapid influx of sodium
**Process**
* sodium channels open
* sodium pours into cell due to concentration and electrical gradients
* sodium is positively charged and causes the resting membrane potential to move towards zero
36
Repolarization
**Definition**
* when the membrane becomes impermeable to sodium
* potassium gates open and potassium ions diffuse out of the cell making the cell increasingly negative
* when the cell is depolarized it cannot be depolarized again
**Characteristics**
* when the cell reaches resting membrane potential the sodium-potassium pump gets very active to re-establish the sodium and potassium concentrations
37
Absolute Refractory Period
**Definition**
* sodium channels cannot be reopened until the cell membrane is repolarized
* it doesn't matter how strong the impulse is, it will not be able to initiate a second action potential
38
Alpha 1 Receptors
**Tissue Location**
* vascular smooth muscle
* heart
* liver
**Response**
* contraction (vasoconstriction)
* slow, prolonged increase in force of contraction
* glycogenesis; glucogenesis
39
Alpha 2 Receptors
**Tissue Location**
* pancreatic islets
* platelets
* nerve terminals
* vascular smooth muscle
**Response**
* decreased insulin secretion
* aggregation
* decreased release of NE
* contraction and relaxation
40
Beta 1 Receptors
**Tissue Location**
* heart
* juxtaglomerular cells
**Response**
* increased force and rate of contraction (sinus node)
* increased atrioventricular node conduction velocity
* increased force of contraction
* increased renin secretion
41
Beta 2 Receptors
**Tissue Location**
* heart
* smooth muscle (vascular, bronchial, GI, and GU)
* skeletal muscle
* liver
**Response**
* increased force and rate of contraction
* smooth muscle relaxation
* glycogenolysis: potassium uptake by skeletal muscle
* glycogenolysis: gluconeogenesis by the liver
42
Beta 3 Receptors
**Tissue Location**
* adipose tissue
**Response**
* lipolysis
43
Dopamine Adrenergic Receptor 1
**Tissue Location**
* smooth vascular muscle (renal, splanchnic, coronary, cerebral)
* proximal tubule
**Response**
* relaxation of smooth muscle, vasodilation
* inhibition of sodium reabsorption
44
Dopamine Adrenergic Receptor 2
**Tissue Location**
* adrenal cortex
* nerve terminals and autonomic ganglia
* anterior pituitary gland
* carotid body
**Response**
* inhibition of aldosterone synthesis and release
* decreased release of norepinephrine and inhibition of sympathetic nerve activity
* decreased thyroid and prolactin release
* inhibit ventilartory response to hypoxia
45
Leukocytes
**Function**
* protect against injury/invasion as well as remove cellular debris
* phagocytosis
* antigen processing and presenting
* release of mediators
* antibody production
**Classifications**
* neutrophils
* eosinophils
* basophils
* monocytes/macrophages
* lymphocutes (t-cells and b-cells)
**Characteristics**
* commonly known as white blood cells
* mobile unit of the body's defence mechanism
* independent movement
* self/non-self recognition
* normally quiescent until they are activated
* circulate in the blood stream but act primarily in the tissues
* normally circulate in the central stream (axial zone) rarely interacting with the blood vessels
46
Bone Marrow
**Structure**
* a collection of blood vessels, nerves, fatty tissue, stem cells, and stored blood cells
**Functions**
* leukocytes, erythrocytes, and platelets originate as hematopoietic stem cells in the bone marrow
* produces immature, undifferentiated cells called hematopoietic stem cells in active marrow
* mature neutrophils, basophils, and eosinophils preior to releasing them into the blood stream
47
Granulocytes
**Definition**
* the cytoplasm contains granules which contain enzymes and mediators which are important in distinguishing functional characteristics of granulocytes
* develop from myeloid stem cell in the bone marrow
**Characteristics**
* stored in three pools strategically located throughout the body to hold a reserve of leukocytes to meet an increase in demand
1. storage pool - located in bone marry and lymphoid tissue. Holds the greatest amount and represents a large reserve which can be rapidly mobilized when the need arises
2. marginal pool - lies along the capillary walls; granulocytes are able to move into tissues when needed
3. circulating pool - in the blood stream; cells from the circulating pool replace cells which migrated into tissue from the marginal pool
* phagocytes
48
Monocytes/Macrophages Development
**Function**
* scavenging and degrading dead tissue, cellular debris, and foreign cells
* attaching and presenting antigen in order for the antigen to be recognized by the lymphocytes
* synthesizing lysozymes for lysis of microorganisms and cellular debris
* releaseing mediators, which regulate the inflammation and immune responses (such as colony-stimulating factors which stimulate growth and differentiation of granulocytes and monocytes in the bone marrow)
**Structure**
* differ from granulocytes in that they have fewer and larger granules in their cytoplasm and have a single, unsegmented nuclei
**Characteristics**
* monocytes are precursors for macrophages
* ingest activated clotting factors, thus limiting the coagulation process
* ingest some antigen-antibody complexes
* more powerful phagocytes than neutrophils
* capable of destroying as many as 100 bacteria
* can engult larger substances than neutrophils
* tissue macrophages are known as histiocytes
**Development**
* develop from the myeloid stem cell maturational pathway
* develop into the monoblast stage to mature into monoblasts which enter the circulation for 1-2 days before entering the tissues to mature into macrphages
* macrophages do not re-enter the blood but live for months to years in the tissues and will migrate to the site when needed
* monocyte production and release from the bone marrow is increased when needed
* body sites at greatest risk for injury/invasion have the highest concentration of tissue macrophages to provide protection such as the alveoli, liver, and peritoneal cavity
49
Lymphocyte Development
**Natural Killer Cells**
* resemble lymphocytes and cause direct cell lysis of non-specific antigens such as tumour cells
* development and maturation not clearly understood
**Lymphocytes**
* originate as lymphoid stem cells in the bone marrow but are released before they mature
* to become immunocompetent these stem cells migrate to specific lymphoid tissue to mature and differentiate
* b-lymphocytes
* mature in tonsils, lymph nodes, and spleen
* a percentage are released after maturation while the rest remain in the lymphoid tissue
* during development in the bone marrow, lymphoid stem cells develop antigen-specific surface antibody
* t-lymphocytes
* migrate to the thymus gland to mature
* immunocompetent t-cells are released into the circulation and are also stored in lymphoid tissue
* develop memory
50
HLA
**Definition**
* a unique sequence of proteins which is genetically determined
* Human Leukocyte Antigen
**Characteristics**
* unique to each individual
* the component of the cell membrane that the WBCs use to identify self and non-self cells
51
Diapedesis
**Definition**
* movement or migration of cells across the vascular wall from the blood into the tissue
**Process**
1. activation
2. margination (pavementing) - movement of leukocytes out of the axial (central) stream of flowing blood towards the periphery to interact and adhere to the blood vessel wall
3. adhesion - promoted by adhesion receptors on both leukocytes and endothelial cells
4. diapedesis - movement of leukocytes from the blood vessel to the site of injury/invasion
52
Ameboid Motion
**Definition**
* a slow, crawling like, and random movement of a cell
53
Chemotaxis
**Definition**
* the directed or controlled movement of leukocytes toward the chemotactants formed in response to injury/invasion
* chemotactants form a chemical gradient for the leukocyte to follow with its ameboid motion
54
Neutrophils
**Characteristics**
* most numerous
* highly mobile
* first leukocytes to arrive at the site of injury/invasion
* major phagocytes (mature cells only)
* immature neutrophils called bands
* short lifespan due to their:
* inability to reproduce
* limited energy supply
* inability to synthesize more proteolytic enzymes - a predetermined amount of granules and when those are used up, the neutrophil dies
**Structure**
* granules contain enzymes which have bactericidal/antimicrobial action
* nucleus may have two to five lobes making it look polymorphous and giving it a segmented appearance
55
Eosinophils
**Characteristics**
* more responsive in parasitic invasions and allergic reactions
* unique enzymes capable of dissolving cell membranes of parasites
* do not phagocytize parasites, rather they bind tightly to the parasite, then the granules migrate to the surface for degranulation into the outer membrane of the parasite which destroys it
* appear 48-72 hours after neutrophils
* move slower and are slower to react to chemotactants
* longer lifespan
**Structure**
* large granules
* contain unique mediators which control/limit the response to injury/invasion
* contain unique enzymes capable of dissolving cell membranes of parasites
56
Basophils
**Characteristics**
* least common
* significant role in allergic reactions mediated by IgE
* attachment of IgE to the basophil initiates degranulation of the basophil which consequently releases mediators to promotes the signs and symptoms seen with allergies
**Structure**
* larger in size than neutrophils
* granules contain different mediators, such as histamine, serotonin, heparin and chemotactic factors for neutrophils and eosinophils
57
Lymphocytes
**Structure**
* agranulocyte
* mononuclear
**Function**
* main cellular components of the immune response
* production of immunoglobulins
* tumour/cancer protection
* graft/transplant rejection
* control and regulation of the immune and inflammation responses
**Characteristics**
* have memory (developed after the first exposure to the antigen) and specificity (each B or T-cell recognizes only one specific type of antigen) which can produce permanent protection and immunity
**Classifications**
* t-lymphocytes
* cell mediated immunity
* b-lymphocytes
* humoral immunity
58
Neutralization
**Definition**
* binding with an antibody which interferes or prevents the antigen binding to receptors of host cells
* this renders the antigen harmless as its receptor sites are bound with antibody
59
Precipitation
**Definition**
* formation of a large, insoluble complex which is unable to remain suspended in blood and precipitates out of blood
* non-moving precipitates are easy targets for phagocytes
* usually associated with agglutination
60
Agglutination
**Definition**
* binding of more than one antigen to each antibody causing clumping and slowing the movement of the antigen
* this increases the change of the complex being phagocytized
61
Erythrocytes
**Structure**
* does not have a nucleus
* a biconcave sphere (increases the surface area to enable oxygen exchange)
* numerous aquaporins to help it change shape and move through capillaries and organelles (reverse deformability - requires ATP)
* hemoglobin consists of four globin molecules (protein) and four heme (iron) complexes
**Function**
* transport oxygen via hemoglobin
* hemoglobin increases oxygen transport by 100 times
**Development**
* stem cells originate in the bone marrow
* stimulated by erythropoetin
* cells differentiate and mature within the active marrow
* erythroblasts are the precursors to erythrocytes
* synthesis of hemoglobin occurs in the nucleus and cytoplasm
* nucleus decreases in size until it is lost
* the remaining cell is called a reticulocyte
* contains ribosomes and mitochodria for metabolism and additional hemoglobin synthesis
* released into the blood stream where they mature into erythrocytes in about 1 to 2 days
**Characteristics**
* factors contributing to the amount of erythrocytes:
* oxygen availability (high altitude, hemorrhage, pulmonary disease, low blow volume, poor blood flow).
* adequate amounts of folic acid, vitamin B12 or iron required
* gender - males have greater RBC production due to muscle mass and testosterone
* age - decreases normal RBC production due to the replacement of active red marrow with fatty yellow marrow
62
Thrombocytes
| (Platelets)
**Structure**
* fragments of very large cells called megakaryoctyes
* have no nucleus
* contain granules that release biochemical markers in response to injury
**Characteristics**
* life span of about 10 days
* one third are kept in reserve in the spleen
* normally smooth spheres until activated - they then change shape and develop protrusions, aggregate, and degranulate forming a plug
63
Vascular Endothelium
**Function**
* regulation of vascular smooth muscle tone
* regulation of vascular permeability to large molecules
* adhestion of leukocytes and platelets
* relsease of pro-thrombotic and anti-thrombotic substances
* release of mediators
**Structure**
* a layer of single (unicellular) cells which lines the entire vascular system
* form tight junctions
* three layers
* tunica intima
* the inner most layer
* composed of endothelium, connective tissue, and a basement membrane
* tunical media
* the middle layer
* a bulky layer composed of smooth (involuntary) muscle and elastic connective tissue
* tunica adventitia
* the outer layer
* composed of a thin, supporting connective tissue containing elastic and collagenous fibres which run lengthwise
64
Arachidonic Acid Cascade
Tissue Injury
* cell membrane distruption
* phospholipid availability
* arachidonic acid
* lipoxygenase pathway
* leukotrienes
* cyclooxygenase pathway
* prostaglandins and thromboxane
65
Nitric Oxide
* synthesized and released from endothelial cells following stimulation by a number of mediators such as bradykinin and/or histamine
* once released, appears to mediate enzyme activity required for vascular smooth muscle relaxation, inhibition of platelet aggregation, and prevention of leukocyte adhesion
* believed to play a major role in maintaining blood fluidity and vessel patency of microvasculature in health
* causes smooth muscle relaxation by increasing intracellular cyclic guanosine monophosphate (cGMP)
* continuously released by the endothelium
* half life less than 10 seconds
* more potent vasodilator than prostacyclin
* used in ICU for critically ill patients as a bronchodilator (ARDS, Severe Lung Injury)
66
Endoperoxide and Thormboxane
* mediators synthesized from the arachidonic acid cascade
* in direct opposition of prostacyclin and nitric oxide
* mediate vascular smooth muscle contraction and enhanced platelet aggregation
67
Endothelin
* extremely potent vasoconstrictor
* synthesized and released from endothelial cells when stimulated by such triggers as hypoxia, epinephrine, norepinephrine, endotoxin, IL-1, thrombin, antidiuretic hormone, and/or angiotensin II
* following stmiulation, endothlin is released casuing vasoconstriction believed to be due to decreases in intracellular cAMP
68
How does the vascular endothelium promote fluid blood flow?
* maintenance of a smooth, continuous blood vessel lining to prevent adherence/aggregation of cells, such as platelets
* generation of mediators, such as protacyclin and nitric oxide, which inhibit platelet and leukocyte aggregation
* synthesis and release of tissue plasminogen activator (t-PA) and urokinase to promote clot lysis
* synthesis and release of antithrombin II which inhibits thrombin formation (thrombin is required to form a stable clot by promoting the converstion of fibrinogen to fibrin
69
Mediators for Endothelium Functions
**Selective permeability**
* normally well-approximated and semi-permeable
* increased in response to mediators released during injury/invasion
**Vasoregulation**
* vasodilation or relaxation (EDRFs)
* nitric oxide
* prostaglandin
* PAF
* vasoconstriction or contracting (EDCFs)
* endothelin
* endoperoxide
* thromboxane
* angiotensin II
**Coagulation Process**
* anticoagulant properties
* inhibition of platelet aggregation
* nitric oxide
* prostacyclin
* prevention of clot formation
* antithrombin II
* clot lysis
* t-PA
* urokinase
* promote or enhance platelet aggregation (prothrombic)
* PAF
* endoperoxide
* thromboxane
**Cell Adhesion/Aggregation**
* platelets, leukocytes
* anti-adhesive
* nitric oxide
* prostacyclin
