Blood pressure and perfusion

Heart Circulation

Afterload

Ejection fraction

Perfusion

Preload

  • Circulation of blood within organ or tissue: meet cell's needs for oxygen, nutrients and waste removal
    • H2O, Glucose, Lipids, AA, vitamins, minerals, O2

Blood pressure

  • Pulse pressure: strength of pulse wave
    Pulse pressure = Systolic - Diastolic
  • Mean arterial pressure: estimate ventricular pressure
  • Mean arterial pressure = Diastolic + 1/3 pulse p
  • BP measurement of force against walls arteries as heart pumps blood throughout body

Capillaries

  • Interlocking cells
  • One cell thick
  • Nutrients, ions, water + O2 diffuse here
  • Blood moves from capillary to venule, picls up:
    • ions, water, CO2, metabollic wastes + nutreints from intestine

Materials leave capillaries by

  • Diffusion
  • Hydrostatic pressure
  • Pinocytosis

Lymphatics

  • Transport clean fluids back to blood
  • Drains excess fluids from tissue
  • Removes 'debris' from cells of body
  • Transports fats from digestive system

Fluid flow through tube

  • Fluid flows only if there is positive pressure gradient
  • No pressure gradient, no flow
  • Flow depends on delta p, not absolute p
  • Blood vessels create pressure grad by altering diameter size

Blood vessel regulation

Vascular flow

  • Vascular system promote continuous flow of blood to capillaries:
    • Elastic recoil
    • Smooth muscle regulation of diameter of vessels
    • Sphincters/valves
  • Tunica interna
  • Tunica media
  • Tunica externa (adventitia)

Neural control

Hormones

Autoregulation

SNS

PSNS

  • Innervates arteries + arterioles in almost all organs
  • Release NE as neurotransmitter
  • Cause vasoconstriction (except heart and brain)
  • Increased rate spontaneous depolarisation in SA node (AV node): increase heart rate
  • Increased contractility of atria and ventricles: increased stroke volume
  • Innervates some arteries and arterioles
  • Release Ach as neurotransmitter
  • Dilation of arteries and arterioles
  • Decreased rate spontaneous depolarization of Sa node (and AV node), decrease heart rate
  • RAAS
  • Blood volume, arterial pressure, cardiac and vascular function
  • Renin released from kidney, resposnse to decreased kidney perfusion
  • Catalyses first step in formation of angiotensin 2
  • potent vasoconstrictor acts on AT1 receptors
  • Medullary CVS control centre
  • Changes in blood pressure
  • Carotid and aortic baroreceptors

Renin, ADH, and aldosterone
(Epinepherine and thyroxine)