Chapter 8 Flashcards
Cardiac muscle cells are responsible for
the force of contraction in the ventricles and atria
All muscles cells have the ability to
Propagate an action potential across their surface.
Functional Syncytium
a tissue in which the cytoplasm of different cells can communicate via gap junctions found in intercalated disks
There are no chemical synapses in what kind of cell
cardiac muscle cells
Cardiac conduction system
System which transmits the action potential in the heart from the arterial syncytium to the ventricles
Membrane depolarization lasts longer in
cardiac muscle cells than in neurons, calcium channels stay open longer than the fast sodium channels
Neuronal or hormonal influences
can change the rate and strength of contraction|Do not stimulate the heart to contract
Initiation of each action potential that starts each cardiac cycle occurs in
region of the right atrium called the sinoatrial (SA) node|Under normal circumstance the SA node acts as a pace maker
SA node action potential phases
Phase : (automatic slow depolarization) sodium leak channels start the rhythmic, automatic excitation. Inward flux of sodium = cell potential thresh|Phase O: Voltage gated sodium channels open and cause the upstroke of the pacemaker potential. Ca+ causes depolarization in the SA node.|Phase : Repolarization. Ca+ channels close and K+ channels open, leading to an outward flow of K+ from the cell.
SA cannot spontaneously depolarize because
it has the most Na+ leak channels of all the conduction system. It reaches threshold before any other region of the heart and sets rate of contraction
What happens if the SA node cells are damaged or depolarization pathways are blocked
The AV node (purknjie fibers) will take over as the new pacemaker at a slower rate
Cardiac muscle cell action potential phases
Phase : (depolarization) threshold is reached and Na channels open with sodium rushing into the cell.|Phase : (initial repolarization) Na+ channels inactivate and K+ channels open. Phase : (plateau phase) influx of Ca+ ions balance the K+ efflux|Phase : (repolirization) Ca+ channels close and the K+ channels open, K+ leaves the cell again. Phase : (resting membrane potential) inward=outward
How are the SA and AV nodes connected
AP started by the heart beat in the SA node also spreads down a special conduction pathway that transmits action potentials rapidly w/o contraction|Its called the internodal tract
Why does the impulse travel to the AV node almost instantly but spreads through the atria more slowly?
contracting heat muscle cells pass the impulse more slowly than specialized conduction fibers
Av bundle (bundle of His)
divides into the right and left bundle branches and then into the Purkinje fibers, which allows the impulse to spread rapidly evenly over both ventricles
what role does the autonomic nervous system play with the heart
It regulates the rate of contraction. The intrinsic firing rate of the SA node is bpm reduced to- by the parasympathetic nervous system
The para sympathetic nervous system inhibits depolarization of the SA node using
the vagus nerve, which causes the release of ACh. This constant inhibition is known as the Vargas tone and it reduces the intrinsic firing rate
The parasympathetic system and the vagus are mostly in charge of the heart at rest. When is the sympathetic system used?
during fight or flight responses. The sympathetic postganglionic neurons directly innervate the heart, releasing norepinephrine.|Epinephrine is then secreted by the adrenal medulla and binds to receptors on cardiac muscle cells. The heart rate and force of contraction increases
Systemic arterial pressure
force per unit area exerted by blood upon the walls of arteries
Systolic pressure
the highest pressure that ever occurs in the circulatory system of this paticular person|this is obtained when ventricles contact
Diastolic pressure
as low as the pressure gets between heartbeats
Blood pressure indicates
arterial pressure
In what areas of the heart are the highest pressure in the circulatory system achieved
left ventricle, aorta and other large arteries
Why does diastolic pressure remain so high?
During diastole the arteries exert pressure on the blood and maintains diastolic pressure, providing a driving force for blood
Components of blood
Plasma (%)- liquid portion of the blood. Contains electrolytes, buffers, sugars, blood proteins, lipoproteins, CO, O and metabolic waste products|Formed elements- cellular portion of the blood
Principal sugar of blood
Glucose. Constant concentration is needed to ensure all cells receive proper nutrition.
Blood proteins
Albumin, immunoglobulins (antibodies), fibrinogen and lipoproteins
Albumin
essential for maintain effective of oncotic pressure (osmotic pressure in the caps due only to plasma proteins)
Immunoglobulins
key part of the immune system
Fibrinogen & lipoproteins
essential for blood clotting (hemostasis)|large particles consisting of fats, cholesterol and carrier proteins. Transport lipids in the bloodstream
CO2 & O2
involved in respiration.CO2 is also important in buffering blood
Main waste product
Urea, a break down of amino acids. Bilirubin, a breakdown product of heme.
Hematocrit
Volume occupied by the red blood cells (erythrocytes). Males -%, Females -%|White blood cells (leukocyte) and platelets a count for about %|All the formed elements of the blood develop from special cells in the bone marrow –> bone marrow stem cells
Serum
similar to plasma except it lacks all the proteins involved in clotting
Erythrocytes (RBC)
cell that has no nucleus or other organelles. Uses ATP for ion pumping and cell maintenance. Relies on glycolysis for ATP synthesis.|Purpose is to transport O to the tissues from the lungs and CO from the tissues to the lungs. RBC’s require a large surface area for gas exchange.
universal recipients
Type AB+ and O- individuals do not make antibodies of any of the blood group antigens. Their blood cells posses all three of the antigens.
Leukocytes
The white blood cell’s role is to fight infection and dispose of debris.|White blood cells are large complex cells with all normal eukaryotic cell structures (nucleus, mitochondria, etc.) WBC’s also respond to chemotaxis|Some WBC’s (macrophages & neutrophils) - amoeboid motility. Able to squeeze out of capillary intercellular junctions, roam free & look for pathogens.
Monocytes
monocytes- phagocytosis debris and micro organisms; amoeboid motility; chemotaxis
Lymphoytes
B cell- mature into plasma cell and produce antibodies|T cell- kill virus-infected cells, tumor cells and reject tissue grafts; also control immune responses
Granulocytes
Neutrophil- phagocytose bacteria resulting in pus; amoeboid motility; chemotaxis|Esinophil- destroy parasites; allergic reactions|Basophil- store and release histamine; allergic reactions
What is the function of playlets?
contain no nuclei and a limited lifespan. Aggregate at the site of damage to a blood vessel wall forming a platelet plug.
Fibrin
another component of the hemostatic response. Fibrin is a threadlike protein that forms a mesh which holds the platelet plug together.|Dries and becomes a scab
Thrombin
Converts fibrinogen into fibrin.|A blood clot of thrombus is a scab circulating the blood stream
Several proteins depend on vitamin K for their function. Defects with these proteins cause?
Hemophilia- loving to bleed an X-linked recessive group of diseases involving excessive bleeding
Role of heme (multi ring structure that has a single iron atom bound at its center)
bind O, each hemoglobin has subunits. Heme will bind more oxygen in an area w high oxygen concentration more than in a low concentration area. A lot of oxygen is picked up by the RBC’s in the lungs, and most of it is released as they pass through active tire uses that need oxygen.
Bohr Effect (reduces oxygen affinity)
Decreased pH, increased pCO (level of CO in the blood and increased temperature. This means hemoglobin is ready to release its load of oxygen in region of the body where oxygen is most needed
Carbon dioxide is transported in the blood in ways
Converting it into carbonic acid which is catalyze by the RBC enzyme called carbonic anhydrase. Hitching a ride w hemoglobin. Dissolves into the blood and is carried from the tissues to the lungs
What is the site of exchange between blood and tissues?
Capillaries, they have walls of only a single layer of flattened endothelial cells and spaces (intercellular clefts) which allow substances to pass main types of nutrients|Amino acids and glucose are absorbed from the digestive tract & carried by the hepatic portal vein to the liver -> holds & releases them as needed.|Lipids (fats)- absorbed from the intestine & packaged into chylomicrons,|they enter a tiny lymphatic vessels in the intestinal wall and empty into larger lymphatics which eventually empty into a large vein near the neck.
How does the liver manage waste
it removes waste and converts them into forms which can be excreted in the form of feces, these compounds pass through the gut (bile)|Other wastes are excreted directly by the kidneys
Why does water have a big tendency to flow out of capillaries through the clefts?
() hydrostatic pressure (fluid pressure) created by the heart tends to squeeze water our of the capillaries|() High osmolarity of the tissues tends to draw water out of the blood stream
Effects of plasmas high osmolarity
relative concentration of plasma proteins increases which causes water to flow back into the tissues
Edema
water in tissues, or swelling. Small amounts of albumin in alcoholics cause water to be lost to the tissues.
The lymphatic system
one-way flow system which starts with tiny lymphatic capillaries in all the tissues of the body –>larger lymphatic vessels –> lymphatic ducts|Acts like a suction pump to retrieve water, proteins, and WBC’s from the tissues
Lymphatic nodes
contain many white blood cells that can initiate an immune response
Large lymphatic ducts merge to form
the thoracic duct, located in the chest. It emptiness into a large vein near the neck.
Lymphatic vessels from the intestines are in charge of
dumping dietary fats in the form of chylomicrons into the thoracic duct types of immunity. Innate, humoral and cell-mediated
Innate immunity
general nonspecific protection the body provides against various invaders (skin, tears, saliva, macrophages and neutrophils, complement system)
Complement system
group of about blood proteins that can no specifically bind to the surface of foreign cells, leading to their destruction
Hummoral Immunity
specific protection by proteins in the plasma called antibodies (Ab) or immunoglobulins (Ig)|Antibodies- specifically recognize and bind to microorganism leading to their destruction and removal from the body|Immunoglobins- IgG, IgA, IgM, IgD and IgE.
Antibody molecules are composes of two copies of two different polypeptides
Light chains and heavy chains joined by disulfide bonds.
Antibody molecules also contain two different regions
Variable region- responsible for specificity of antibodies in recognizing foreign particles|Constant region- same for all antibodies in a given class. ( most are in the IgG)
Epitope
Small site that an antibody recognizes within a larger molecule
Hapten
when a small molecule does not elicit the production of antibodies on their own so they will bind to a protein and become the antigenic
Removal of the antigen from the body can occur by
binding of an antibody may directly inactivate the antigen|Binding of an antibody can induce phagocytosis of a particle by macrophages and neutrophils|Presence of antibodies on the surface of a cell can activate the complement system to form holes in the cell membrane and lyse the ceLil
B cells are responsible for producing
Antibodies. Antibodies procured by an individual B cell can recognize only one specific antigen.
Plasma and Memory cells roles in antibody production
Plasma cells actively produce and secrete antibody protein into the plasma.|Memory cells are produced from the same cline and have the same variable regions, but do not secret antibodies. They are pre-activated, dormant B cell
Colonal selection
method of selecting B cells with specific antigen binding
Primary immune response
the st time an antigen is encountered during an infection it takes a week or more for B cells to proliferate and secrete significant levels of Ab
Secondary immune response
swifter and stronger. Symptoms never develop.
Cell
mediated immunity: types of T cells - T helper cells (CD cells) and T killers (CD cells)
T helper
activate B cells, T killer cells and other cells of the immune system.|Central controller of the immune response|releases special hormones (lymphokines & interleuukins) to communicate with other cells
Role of the T killer cells
destroy abnormal host cells (virus infected host cells, cancer cells, foreign cells such as the cells from a skin graft from an incompatible donor)
In what gland is the T cell developed during childhood?
the thymus; the thymus destroys all self-specific T cells in order to avoid an autoimmune response
Major histocompatibility complex (MHC) I
proteins are found on the surface of every uncleared cell in the body.|Their role is to randomly pick up peptides from inside cells and display them on the surface
MHC II
antigen-presenting cells (APC’s). Role is to phagocytize particles or cells, chip them up and display fragments using the MCH II display system
Bone marrow
site of synthesis of all cells of the blood from a common progenitor
Bone marrow stem cell
cells that gives rise to all the various blood cells
Spleen
filters blood and is the site of immune cell interactions|destroys aged RBC’s
Tonsils
masses of lymphatic tissue in the back of the throat that help catch pathogens that enter the body through respiration or ingestion
Appendix
similar to tonsils, both in structure and function and is found near the beginning of the large intestines
