Mind map

Cardiovascular System

Olivia Hart English

Map content

Heart
- Generates pressure waves to push blood through blood vessels
- Heart valves ensure one way flow in heart
  - When pressure is greater behind valve, it opens
  - When pressure is greater in front of valve, it closes
- Surrounded by pericardium which protects it
- Conducting system
  - Sequence of excitation:
    - 1. Sinoatrial node (pacemaker) generates impulses
      - 2. Signal propagates from right to left atrium
        3. Atria depolarize, fires action potential, calcium comes in and contracts
        4. Signal reaches atrioventricular node
        5. Signal goes down and spreads through ventricles, depolarizes, calcium comes in for muscles to contract
    - AV node delay - period of time signal waits in atrium before travelling to ventricles
    - AV node - routes electrical signal so heart contracts from apex (bottom) to base (top); this delay is accomplished by slower conductional signals through nodal cells
- Electrocardiogram - graphic record of heart's electrical activity; signals show changes in voltage
  - P wave, PR segment, QRS complex, ST segment, T wave
- Cardiac cycle
  - Comprises all events involved with blood flow through heart during one heart beat
  - Systole - contraction phase
    - End systolic volume - amount of blood left in ventricles at end of systole
  - Diastole - relaxation phase
    - Longer than systole
    - End diastolic volume - volume of blood in ventricles at end of diastole
      - EDV determined by venous return
        Stroke volume increases as EDV increases
        How much the myocardium is stretched by the blood coming in
        The larger the stretch, the more forceful the contraction, and the larger the stroke volume
  - 1. Start at end of diastole
    - 2. AV valve is open, and semilunar valve is closed
      - 3. Ventricle contracts, pressure rises causing AV valve to shut and SL valves are still closed (isovolumetric contraction)
        4. Pressure in left ventricle is higher than aorta (ejection phase)
        5. Pressure in left ventricle lowers below aorta, SL valve shuts (isovolumetric relaxation)
        6. Pressure in ventricles follows below that of the atria, AV opens (filling)
        7. Atrial contraction delivers the final blood to the ventricles
  - Stroke volume - amount of blood ejected from ventricles during systole
    - SV = EDV - ESV
    - Depends on:
      - Change sympathetic input to ventricles, which affects contractility of ventricles
        inotropic agent - chemical that affects contractility
        Negative inotropic effects - decrease contractility
        Positive inotropic effects - increase contractility
        Ejection fraction - contractility; EF = SV/EDV
        Increased ejection fraction leads to increased contractility
      - Afterload - combined load of EDV and arterial resistance during ventricular contraction
      - Preload - amount of myocardial stretch before contraction; this depends on EDV
  - Ascultation - listening to heart through chest wall through stethoscope; closing of AV and semilunar valves produces sounds that can be heard through stethoscope
    - - Lub (first sound) produced by closing of AV valves
    - - Dub (second sound) produced by closing of semilunar valves
- - With every beat the heart pumps about 60% of blood in its chambers or 70 mL
- Innervation of the heart (heart rate)
  - Parasympathetic system:
    - 1. Vagus nerves
      - 2. Acetylcholine connected to muscarinic receptors on atria
  - Sympathetic system: (increases heart rate)
    - 1. thoracic spinal nerves
      - 2. Norepinephrine come from nerves, and epinephrine come from bloodstream
        3. These bind to beta receptors (adrenergic = bind to adrenaline)
  - To increase heart rate:
Blood
- Plasma - blood without cells
- Circulation pathway as drop of blood:
  - 1. Starting as deoxygenated blood that arrives in right atrium
    - 2. Tricuspid valve (AV valve)
      - 3. Right ventricle
        4. Pulmonary valve (SL valve)
        5. Pulmonary artery
        6. Pulmonary capillaries to get oxygenated
        7. Pulmonary vein
        8. Left atrium
        9. Mitral/bicuspid valve (AV valve)
        10. Left ventricle
        11. Aortic valve (SL valve)
        12. Aorta
        13. Systemic arteries
        14. Systemic capillaries to get deoxygenated
        15. Systemic veins
        16. Superior/inferior cava
- Pulse pressure = systolic P - diastolic P
- MAP = diastolic P + 1/3(systolic P - diastolic P)
- Cardiac output - amount of blood moved per unit of time
  - CO = HR x SV
- Ventricles are driving force for blood flow
Blood vessels
- capillaries - blood and nutrient exchanges occur here
  - Velocity of flow is slow because their total cross sectional area is large
  - Nutrient exchange and metabolic end products diffuse across capillary wall
    - Blood delivers oxygen and glucose to muscle cells
      - Muscle cells then produce carbon dioxide and gives to capillary tube which collects and carries wastes away
    - Starts at arteriole, passes through system capillary, and ends at venule
  - Distribution of ECF between blood and interstitial compartments is in state of dynamic equilibrium
  - Tube is made up of endothelial cells that lines it and red blood cell (erythrocyte) inside tube along with plasma
  - Overall fluid movement in capillaries is determined by net filtration pressure and forces opposing it (starling forces)
    - Absence of vascular smooth muscle and elastic tissue reinforcement in capillaries, facilitates exchange
    - Capillary hydrostatic pressure = pressure coming from plasma; pushes out
    - Interstitial fluid hydrostatic pressure = usually negligible
    - Osmotic force due to plasma protein concentration = pushes in; bring water into tube
    - Osmotic force due to interstitial fluid protein concentration = pushes in; bring water out of tube and into interstitial tube
- Vein - thin wall but huge lumen (center)
  - Have less smooth muscle and are more elastic than arteries
  - Contain valves that regulate direction of blood flow
    - Open when muscles contract, allowing blood to return to heart
    - Close when muscles relax, and blood can't flow backwards
  - Because they can stretch and expand, they're called capacitance vessels and blood reservoirs
  - Uses pumps because venous pressure itself is not strong enough to push blood back to heart
    - Respiratory pump - pressure changes in the central cavity due to the pressure changes due to breathing; this helps to propel blood back to the heart.
    - Muscular pump - when muscles contract they squeeze the veins, which results in blood moving forward and being prevented from backflow by veins, moving blood into heart
    - Smooth muscle of veins is under SNS control and contract when stimulated
      - This increases venous pressure and venous return
- Artery - thick wall but small lumen
  - Dicrotic notch and arteries as pressure reservoirs
    - Ventricular contraction = contraction of ventricles pushes blood into elastic arteries, causing them to stretch
    - Ventricular relaxation = elastic recoil in arteries maintains driving pressure during ventricular diastole
    - Dicrotic notch - elastic recoil of aorta
- Arteriole - regulates blood pressure
  - Arterial pressure is product of cardiac output and peripheral resistance MAP = CO x PR
  - most important vessels for regulation of peripheral resistance and thus MAP
  - Baroreceptors monitor arterial pressure to ensure adequate perfusion of the brain and heart
  - Blood pressure control includes rapid responses from cardio system and slower responses by kidneys
    - Baroreceptors sense changes in blood pressure
      - Most important of these are localized in aorta and carotic artery
      - Baroreceptor neurons project to the medullary center that regulates/monitors blood pressure
        Neurons in that area are constantly active and their activity and their activity is a measure of blood pressure
        This area will then project to the ANS
- Systemic pressures
  - - Pressure waves created by ventricular contraction travel into the blood vessels
  - - Pressure in arterial side of circulation cycles but pressure waves diminish in amplitude with distance and disappear at capillaries
Cardiac muscle
- Desmosome - prevent cells from tearing apart during contraction
- gap junction - allows for flow of ions between myocytes and autorhythmic cells
- Intercalated disks - border between desmosomes and gap junctions
- 99% of cardiac cells are force making cells (myocytes), which contain striated muscle but can't generate electricity
  - Excitation coupling in contractile heart cells
    - 1. 1. AP sweeps across cardiac muscle cell membrane
      - 2. AP activates DHPRs (L-type calcium channels or LTCCs) - Some calcium from ECF enters cell - Calcium spark
        3. Intracellular calcium activates RyR in SR membrane - More calcium comes into cytosol from ECF - Calcium induced calcium release
        4. Calcium signal causes power strokes and contractions identical to skeletal muscle - Calcium binds to troponin - Tropomyosin moves so myosin heads can bind to actin, etc.
        5. Relaxation when calcium pumped back into SR by SERCA and/or cleared into ECF by sodium calcium exchanger
  - Action potentials of contractile cardiac cells
    - Triggered by entry of ions through gap junctions
      - 1. Brings muscle fiber to threshold so VG sodium channels open (same as neuron)
        2. Then VG sodium channels inactivate, and a new VG potassium channel opens briefly
        3. L-type calcium open, calcium comes in and cause plateau
        4. Transient potassium channels inactivate
        5. L-type calcium channels inactivate, new VG potassium channels open, potassium leaves
- 1% of cells are conducting system, and have no organized sarcomeres
  - Pacemaker action potentials
    - 1. Calcium enters, causing rapid depolarization
      - 2. Small brief calcium plateau; calcium continues to enter but potassium begins to leave
        3. VG potassium channels activate; potassium leaves and we have rapid repolarization
        4. Slow spontaneous depolarization brings membrane to threshold on its own
    - No resting potential
- No summation in heart muscles like in skeletal muscles, so long refractory period lasts almost as long as muscle twitch and prevents tetanus
Autonomous nervous system
- Controls contraction and secretion in internal organs
- Divided into:
  - - Sympathetic system = fight or flight
  - - Parasympathetic system = relaxation/eating
  - Enteric system = regulation of the digestive system
- Parasympathetic pathways uses acetylcholine to slow down heartrate
- Sympathetic pathways use acetylcholine and norepinephrine to increase heartrate
- Actions of SNS and PNS are antagonistic (opposing forces)
Hemorrhage
- - Causes blood volume decrease
  - - Venous return then decreases -
    - EDV decreases
      - - Stroke volume decreases
        - Cardiac output decreases
        - MAP decreases lower than normal
        - Baroreceptor activity decreases lower than normal
        - Cardio control center
        - PNS goes down
        - SNS goes up
        - Vasoconstriction goes to arterioles and veins -
        In the veins, venous pressure goes up -
        This brings PR up
        - Heart rate goes up
        - Contractility goes up
        SV goes up
        CO goes up