3.1.2

• circulatory systems


  transport gases and nutrients around an organism in a transport liquid. The liquid is transported in vessels and moved by a pump.
• open circulatory system


  A transport medium is pumped into an open body cavity requiring few transport vessels meaning the medium is at a low pressure and does not contain gases. The medium returns to a pump via open ended vessel
• closed circulatory system


  Transport medium is always inside a transport vessel meaning the molecules must enter or leave the medium via diffusion or high hydrostatic pressure. The medium contains dissolved gases carried by a pigment or other molecule
• single circulatory system


  Blood passes through the heart once per cycle.

  This usually works as there is a counter current exchange occurring at the exchange surface

  Heart -> exchange surface -> respiring tissue

  
• double circulatory system


  blood passes through the heart twice per cycle.

  heart -> exchange surface is the pulmonary circuit

  heart -> tissue is the systemic circuit

  
• capillary function


  form a capillary bed at the exchange surface and respiring tissue
• capillary structure


  narrow diameter and 1 cell thick - slows blood flow meaning cells can only pass single file reducing diffusion distances at the red blood cells are pressed against the wall
• artery function


  transport blood from heart to the respiring tissue
• artery structure


  smooth muscle - can constrict and dilate to control blood flow

  elastic layer - allows maintenance of high pressure and walls can stretch and recoil in response to heart beat

  collagen - provides structural support

  thick wall and small lumen - maintain high pressure
• arteriole function


  transport blood from artery to capillary
• arteriole structure


  smooth muscle - restrict blood flow to capillary

  elastic layer , thick wall , small lumen - maintain pressure

  collagen - structural support

  at a lower pressure than an artery - to control the blood flow more
• venule function


  transport blood from capillary to vein
• venule structure

  thin smooth muscle , large lumen - at low pressure

  thin walls - join together from many venue to form a vein

  valves - move blood against gravity at low pressure stopping backflow
• vein function


  transport blood from respiring tissue to heart
• vein structure


  thin smooth muscle , large lumen , thin elastic layer - low pressure and cannot control blood flow

  lots of collagen - structural support

  thin walls - due to low pressure they will not burst so allows for deformation to move blood against gravity to heart

  valves - movement of blood at low pressure
• tissue fluid


  liquid and molecules forced out of the blood that bathe respiring tissue providing nutrients and removing waste
• hydrostatic pressure


  pressure exerted by a liquid
• oncotic pressure


  the tendency of water to move into the blood via osmosis
• formation of tissue fluid 


  1. blood enters capillaries from arterioles. Small lumen means they have a high hydrostatic pressure
  2. water , dissolved gases and nutrients are forced out of the arterial end of the capillary bed through the small gas in the capillary
  3. tissue fluid has been formed providing nutrients into cells and waste leaving cells into it.
• reformation of blood after the formation of tissue fluid


  1. large molecules have remained in the capillaries reducing the water potential of the blood causing a high oncotic pressure the further along the capillary bed the blood moves
  2. tissue fluid moves back into the capillary at the venule end due to high oncotic pressure , low hydrostatic pressure and low water potential via osmosis
  3. once the water potential gradient has been met no more tissue fluid is reabsorbed
• what happens to tissue fluid that is not reabsorbed 


  it is absorbed into the lymphatic system forming lymph that re enters the blood stream near the heart
• what is lymph


  a liquid containing no proteins and less oxygen
• formation of tissue fluid diagram

  A) oncotic

  B) high hydrostatic pressure

  C) high oncotic pressure

  D) hydrostatic

  
• what is the mammalian heart made from


  cardiac tissue
• what is the heart responsible for


  pumping transport fluid around the vessels
• myogenic


  used to describe the mammalian heart as it automatically contracts and relaxes without getting fatigued
• coronary artery function


  supply cardiac muscle with oxygenated blood for respiration
• pericardial membrane function


  inelastic membrane around the heart that prevents it from filling and swelling with too much blood
• stages of the cardiac cycle


  diastole

  atrial systole

  ventricular systole
• diastole


  atria and ventricles relax increasing volume and decreasing pressure within the heart

  blood moves in via the vena cava and pulmonary vein , the increase in pressure from the blood opens the atrioventricular valves
• atrial systole


  atria contract decreasing volume and increasing pressure within the atria causing blood to move into the ventricle
• ventricle systole


  ventricles contract increasing ventricle pressure

  the atrioventricular valves shut due to the lowered pressure in the atria

  the semilunar valves open letting blood leave the heart
• cardiac cycle

  A) atrial

  B) contract

  C) ventricles

  D) ventricular

  E) out

  F) diastole

  G) into

  
• cardiac output


  the volume of blood that leaves the ventricle in 1 minute
• cardiac output =


  heart rate x stroke volume
• heart rate


  beats per minute min^-1
• stroke volume


  volume of blood that leaves the heart each beat dm^3
• control of the cardiac cycle involves

  Sino atrial nodes -> atrioventricular nodes -> bundle of his -> purkyne fibres
• Sino atrial node function


  releases a wave of depolarisation across the atria causing it to contract
• atrioventricular node function


  triggered by the SAN releases another wave of depolarisation. A non conductive layer stops this wave from reaching the ventricle