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Blood pressure and perfusion (Blood vessel regulation (Neural control (SNS…
Blood pressure and perfusion
Heart Circulation
Afterload
Ejection fraction
Perfusion
Circulation of blood within organ or tissue: meet cell's needs for oxygen, nutrients and waste removal
H2O, Glucose, Lipids, AA, vitamins, minerals, O2
Preload
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
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
Lymphatics
Transport clean fluids back to blood
Drains excess fluids from tissue
Removes 'debris' from cells of body
Transports fats from digestive system
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
SNS
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
PSNS
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
Hormones
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
Renin, ADH, and aldosterone
(Epinepherine and thyroxine)
Autoregulation
Medullary CVS control centre
Changes in blood pressure
Carotid and aortic baroreceptors