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ACCN Physiology > Cellular Physiology > Flashcards

Cellular Physiology Flashcards

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
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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
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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
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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
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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.
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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
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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
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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
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9
Q

Lipids

A

** Classifications**

  1. triglycerides
  2. phospholipids
  3. 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
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10
Q

Nucleic Acids

A

Definition

  • the most complex molecules in the body

​Classifications

  1. deoxyribonucleic acid (DNA)
  2. 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
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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
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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
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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)
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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
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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
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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

  1. Functional receptors
    * extend to the outer surface of of the cell
  2. 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
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17
Q

Cytoplasm

A

Components

  1. Cytosol
  • intracellular viscous fluid in which elements are dissolved and suspended
  • different than the extracellular fluid - this is maintained by the cellular membrane
  1. Organelles
  • mitochondria
  • ribosomes
  • endoplasmic reticulum
  • golgi apparatus
  • lysosomes
  • peroxisomes
  • cytoskeleton
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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)
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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
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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
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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
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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
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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)
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24
Q

Cytoskeleton

A

Structure

  • internal scaffolding composed of
    • microfilaments
    • intermediate filaments
    • microtubules
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25
Q

Nucleus

A

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
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26
Q

Diffusion

A

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
    *
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27
Q

Active Transport

A

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
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28
Q

Sodium-Potassium Pump

A

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
Q

Filtration

A

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
Q

Metabolism

A

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
Q

*Formation of ATP

A

diagram from page 44

32
Q

Action Potential

A

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
Q

Resting Membrane Potential

A

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
Q

Threshold

A

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
Q

Depolarization

A

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
Q

Repolarization

A

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
Q

Absolute Refractory Period

A

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
Q

Alpha 1 Receptors

A

Tissue Location

  • vascular smooth muscle
  • heart
  • liver

Response

  • contraction (vasoconstriction)
  • slow, prolonged increase in force of contraction
  • glycogenesis; glucogenesis
39
Q

Alpha 2 Receptors

A

Tissue Location

  • pancreatic islets
  • platelets
  • nerve terminals
  • vascular smooth muscle

Response

  • decreased insulin secretion
  • aggregation
  • decreased release of NE
  • contraction and relaxation
40
Q

Beta 1 Receptors

A

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
Q

Beta 2 Receptors

A

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
Q

Beta 3 Receptors

A

Tissue Location

  • adipose tissue

Response

  • lipolysis
43
Q

Dopamine Adrenergic Receptor 1

A

Tissue Location

  • smooth vascular muscle (renal, splanchnic, coronary, cerebral)
  • proximal tubule

Response

  • relaxation of smooth muscle, vasodilation
  • inhibition of sodium reabsorption
44
Q

Dopamine Adrenergic Receptor 2

A

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
Q

Leukocytes

A

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
Q

Bone Marrow

A

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
Q

Granulocytes

A

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
Q

Monocytes/Macrophages Development

A

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
Q

Lymphocyte Development

A

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
Q

HLA

A

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
Q

Diapedesis

A

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
Q

Ameboid Motion

A

Definition

  • a slow, crawling like, and random movement of a cell
53
Q

Chemotaxis

A

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
Q

Neutrophils

A

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
Q

Eosinophils

A

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
Q

Basophils

A

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
Q

Lymphocytes

A

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
Q

Neutralization

A

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
Q

Precipitation

A

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
Q

Agglutination

A

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
Q

Erythrocytes

A

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
Q

Thrombocytes

(Platelets)

A

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
Q

Vascular Endothelium

A

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
Q

Arachidonic Acid Cascade

A

Tissue Injury

  • cell membrane distruption
    • phospholipid availability
      • arachidonic acid
        • lipoxygenase pathway
          • leukotrienes
        • cyclooxygenase pathway
          • prostaglandins and thromboxane
65
Q

Nitric Oxide

A
  • 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
Q

Endoperoxide and Thormboxane

A
  • 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
Q

Endothelin

A
  • 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
Q

How does the vascular endothelium promote fluid blood flow?

A
  • 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
Q

Mediators for Endothelium Functions

A

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

ACCN Physiology (3 decks)

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