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The Circulatory system 1-5, Going down Aortic pouch pulmonary trunk …

- - - - membrane junctions:
        
        Desmosomes: cell to cell junctions
        
        Gap junctions: cell to cell communicaton junctions
  - - - Troponin and tropomyosin are major regulatory proteins in muscle tissue
    - - Process of excitation
        
        Action potential arrives at cell
        
        Voltage-gated Ca2+ channels open and Ca2+ enters cell
        
        Entry of Ca2+ causes release of Ca2+ through RyR causes a Ca2+ spark creating a signal
        
        Ca2+ ions bind to troponin initates contraction
        
        Relaxation occurs when Ca2+ unbinds from troponn
        
        Ca2+ pumped back into sacroplasmic reticulum for storage
        
        Ca2+ exchanged with Na+
        
        Na+ gradient is maintained by the Sodium potassium - ATPase
      - Sliding filament theory
        
        Action potentual reaches muscle travels down T tubules
        
        Ca2+ released from sacroplasmic reticulum and enters
        
        Ca2+ causes tropomyosin which blocks binding site on myosin head of actin, to move uncovering binding site
        
        ADP is attached to myosin head and myosin attaches to binding sites
        
        forms a cross-bridge
        
        Thin filaments slide inward between thick filament --> contraction
- - - - Transportation:
        
        Respiratory ( Transports O2 and CO2 )
        
        Nutritive ( Carries absorbed products of digestion to liver and to organs and tissues )
        
        Excretory ( Carries metabolic wastes to kidneys fore excretion)
      - Regulation
        
        Hormonal ( Carries hormones to target tissues to produce their effects )
        
        Homeostasis ( Helps maintain their internal environment )
        
        Temperature (Diverts blood to cool/warm the body )
      - Protection
        
        Hemostasis: ( Mediates blood clotting to prevent bleeding )
        
        Immunity: ( Carries leukocytes, cytokines to protect against invading pathogens
    - - Total volume varies with body size , changes in fluids and electrolyte concentration
        amount of adipose tissue
        Constituites ~8% body weight
        5-6 l in male
        4-5 l in females
      - Blood consists of blood cells suspended in liquid plasma
        Plasma: straw-coloured liquid consists of 92% water and dissolved solutes
        
        7% specialised proteins
        
        electrolytes - Ions
        
        nutrients, hormones and metabolic wastes
        
        Cellular elements 45%
        
        Red blood cells - erythrocytes
        
        White blood cells - leukocytes
        
        Platelets - thrombocytes
        
        Plasma
        
        Components
        
        Fibrinogen: For coagulation process -> converted to fibrin which forms stable blood clot. Found in Liver
        
        Organic nutrients: Lipids, cholesterol, carbohydrates and amino acids
        
        Electrolytes: Ions needed for cell function
        Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, SO4-
        
        Albumins: protein constitute of plasma composed of 60% plasma protein: found in liver helps maintain colloid osmotic pressure
        
        Other proteins: Enzymes, co-enzymes, hormones
        
        Globulins: Antibodies - carries water-insoluble hormones lipids and vitamins
        
        Organic waste products: Urea, uric acid, creatinine, bilirubin and ammonium ions
      - Cellular elements
        
        Erythrocytes RBC
        Contains Hb and transports O2 to cells
        
        Structure:
        1) smooth round with biconcave discs
        2) no nuclei, mitochondria/ most organelles
        3) contains alot of Hb for transport of CO2 and O2 - most amount found in infants
        4) formed in bone marrow stimulated by erythroprotein
        
        Haemoglobin: Fe containig molecule that binds loosley and reversibly to oxygen which is syntheisied and packed into RBCs during cell development
        4 chains 2 alpha and 2 beta polypeptide chains, 4 Fe containing haem prosthetic groups each Hb molecule carries 4 O2 molecules
        
        Platelets Thrombocytes
        
        Important in hemostasis - initiates process
        
        Granule-rich packages
        
        key role in circulatory system - blood flow
        
        Granules contain serotonin, calcium ions, enymes, ADP and PDGF - growth factor for platletes
        
        Leukocytes WBC
        
        Immune defence system
        
        transported in blood to sites of injury/ invasion by pathogens
        
        2 main Types 1) Granulocytes (70%) and 2) Agranulocyte (30%) ANKI
- - - - During resting: the inside of the membrane is negative and polarised
  - - - Aorta: accepts output of first left ventricle sustains high systolic pressure
        Pulmonary artery: accepts output of the right ventricle **sustains peak pressure
        Superior / inferior vena cava: largest vessel returning deoxygenated blood to heart through R atrium from systemic circulation
        Pulmonary veins: Largest vessel returning *oxygenated **blood to heart from pulmonary circulation*
        Coronary arteries and veins: supply blood to cardiac muscle tissue
        
        Coronary circulation:
        Myocardinal O2 and Nutrient demand
        
        Heart beats constantly requires constant + adequate supply of O2 and nutrients
        Myocardinal O2 and nutrient supply
        
        supplied via special network of blood vessels
        consists of L and R coronary arteries
- - - - stroke volume is the volume of blood ejected by the left ventricle with each heart beat (ml/beat)
    - - Determinants of HR
        
        ANS (autonomic tone on heart)
        
        increasing the SNS increases HR
        
        increasing PNS decreases HR
      - Determinants of SV
        
        preload
        
        afterload
        
        cardiac contractility
        
        Preload; The work placed on the heat before the contraction begins = EDV/P
        End-diastolic volume or pressure (EDV/P) is volume of blood/ pressure in the ventricle prior to contraction
        Relates to frank starling Law of the Heart
        SV is directy proportional to Preload/ VR -> venous return
        
        An increase in Preload
        
        increase stretch of cardiac muscle fibres
        
        increase contraction
        
        increased stroke volume
        
        Afterload; The load against which the heart must contract to push blood into aorta and the amount of pressure the heart must generate to eject the blood to aorta
        aortic pressure = systemic arterial Blood pressure
        Determined by systemic or total peripheral resistance
        
        SV is inversely proportional to afterload
        
        Increase in afterload
        
        Decrease in SV
        
        Contractility; Ability of the heart to change its force of contraction without chnging its resting muscle length
        = the strength of contraction at any given EDV
        Depends on availability of intracellular Ca2+ (free calcium)
        SV is directly proportional to cardiac contractility
        
        Increase in CA2+
        
        Increase actin and myosin cross-bridge formation
        
        Increased contractility
        
        Increased Stroke volume
  - - - BP determined by:
        
        Cardiac output
        
        Total peripheral resistance
      - Cardiac output is determined by:
        
        heart rate
        
        stroke volume
    - - Homeostatic BP
        Short term control mechanisms via Baroreceptors (ANS)
        Long term control mechaniss via the kidney