foundations 1 revision Flashcards
how is the resistance to blood flow mainly controlled
by vascular smooth muscles through changes in the radius of arterioles
what is the vasomotor tone
when the vascular smooth muscles are partially constricted at rest
what does Adrenaline acting on alpha receptors cause
vasoconstriction
what does Adrenaline acting on beta2 receptors cause
vasodilation
alpha receptors predominant in
skin, gut, kidney arterioles
beta2 receptors predominant in
cardiac and skeletal muscle arterioles
what factors causes relaxation of arteriolar smooth muscles
- Decreased local PO2
- Increased local PCO2
- Increased local [H+] (decreased pH)
- Increased extra-cellular [K+]
- Adenosine release (from ATP)
what do organic nitrates do
Relaxes smooth muscles via their metabolism to nitric oxide
- Increases coronary blood flow
- useful to treat angina
what does Postural Hypotension result from
failure of Baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position
what Hormones Regulate Extracellular Fluid Volume
The Renin-Angiotensin- Aldosterone System - RAAS
Natriuretic Peptides – NPs
Antidiuretic Hormone (Arginine Vasopressin) - ADH
what are Natriuretic Peptides (NPs)
Peptide hormones synthesised by heart
- Released in response to cardiac distension or neurohormonal stimuli
what are arteries
Passageways of blood from heart to tissues. Pressure must be maintained, but not too high
what are arterioles
major Resistance vessels
what are capillaries
site of Exchange of gas, nutrients and water between blood and tissues
what are veins
Capacitance vessels Passageways of blood from tissues to heart.
Venous Return must provide heart with sufficient blood to pump
where does Excitation of the heart normally originate
in the pacemaker cells in the SA node
what initiates the heart beat
The cluster of the specialised pacemaker cells in the SA node
where is the SA node located
in the upper right atrium close to where the Superior Vena Cava enters the right atrium
what normally drives the entire heart
the SA node
what allows cell to cell conduction in the atria
gap junctions
what allows rapid spread of action potential to the ventricles
The Bundle of His and its branches and the network of Purkinje fibers
what is an ECG
a record of depolarisation and repolarisation cycle of cardiac muscle obtained from skin surface
what supplies SA node, AV node and myocardium in sympathetic supply
cardiac sympathetic nerves
what supplies the SA node and AV node In parasympathetic supply
the vagus nerve
