Local regulation of blood flow Flashcards
- When is adrenaline released?
released in response to lowered BP
- What two things does adrenaline do?
- Speeds heart rate and force of ventricular contraction
- Dilates skeletal muscle vascular beds and constricts the splanchnic (mesenteric) vascular beds
- What does the things that adrenaline does result in
results in increased cardiac output and systolic BP
What is the main role of ADH
Main role is formation of concentrated urine by retaining water to control plasma osmolarity
- What are 2 other names for anti-diuretic hormone
Arginine vasopressin or vasopressin
- What can slow down the release of ADH
alcohol
- What is the function of the ventricles
pumping chamber
- What is the function of arterioles
resistance vessels
- What is the function of capillaries
Exchange vessels
- What is the function of venules/veins
Capacitance vessels
- What is the function of the atrium
Receiving chamber
- What is a metarteriole continuous with
A metarteriole is continuous with the thoroughfare channel passing between terminal arteriole and postcapillary venule
- What do capillaries enable?
enable the exchange of water, O2, CO2 and many other nutrient and waste chemical substances between blood and surrounding tissues
- What does metarterioles being continuous cause?
This causes blood to be shunted between the two vessels when precapillary sphincters are closed, bypassing the capillary bed
- What does basal flow vary by?
flow varies by tissue
- Where is are examples of basal flow being high and it being low
High: Kidneys
Low: skeletal muscle
- What happens when cells become more active
When cells become more active this increases circulation to the region, at the expense of other tissues.
- what 3 things mediate the regulation of blood flow
The regulation of local flow is mediated by:
- Neural factors (sympathetic nervous system)
- Endocrine factors (hormones)
- Local factors (bi-products signaling metabolic demand)
- what are 2 factors that affect blood flow
- Pressure (driving force) of the flow (Cardiac Output)
- Total peripheral resistance
- what is Total Peripheral resistance (TPR)?
the sum of the resistance of all peripheral vasculature in the systemic circulation
- what are 4 factors that affect TPR
Affected by:
- Mean arterial pressure
- Viscosity/ volume of the blood
- Turbulence
- Length/volume of the conduction system
- what 2 things is varying the resistance of the arterioles used to control?
- flow to a particular organ/organs
- whole-body perfusion pressure
- where does neural input come from
comes via the sympathetic nervous system
- what does sympathetic nervous system release to cause vascoconstriction
releases noradrenaline
- what does noradrenaline bind to on vascular smooth muscle
binds to α1 adrenoreceptors
- where are the effects of neural input the strongest
effects are strongest in the skin, kidney, skeletal muscle and digestive tract vessels
- which 2 instances is blood flow regulation most important
Flow regulation is most important:
1. in organs that require constant perfusion
- where local metabolic conditions may change rapidly and markedly
- what are the 2 primary functions of local mechanism
- autoregulation
- Metabolic vasodilation
- what is autoregulation
adjustment of local resistance over a large range of arterial pressures to provide constant local flow
- what is metabolic vasodilation
upregulation of flow when local metabolic demands increase achieved by dilating muscular vessels to decrease resistance
- outline the mechanism of autoregulation
- Stretch receptors (mechanically gated ion channels) open, leading to constriction in vessels
2.This allows influx of Na+ ions and Ca2+ ions
- Vasodilating metabolites (adenosine, K+ ions) act on smooth muscle cells to cause relaxation
- As flow increases these substances are washed out of the tissue and muscle tone increases again
- what type of vasodilator is nitric oxide?
A potent vasodilator
- What produces nitric oxide
vascular endothelium
- What are the 2 forms of NOS
- endothelial NOS (eNOS)
2.inducible NOS (iNOS)
- How is NO synthesised
NO is synthesised from L-arginine and oxygen by the nitric oxide synthase (NOS) enzyme in response to increased intracellular Ca2+
- outline the mechanism for NO signalling
- NO quickly diffuses out of the endothelium and into vascular smooth muscle
- in vascular smooth muscle, it activates guanylyl cyclase
- This increases cyclic GMP levels, leading to relaxation
- what does sildenafil citrate AKA Viagra cause when it acts on the NO signalling pathway?
it causes the enhancement of the NO signalling pathway
