Control of blood flow Flashcards
What are the two primary systems involved in the control of blood flow in different organs?
Sympathetic (neuronal) and Endocrine (hormonal) systems.
What are autocoids in the context of blood flow control?
Local hormones that influence blood flow.
What does “active hyperaemia” refer to in local blood flow control?
The increase in blood flow to tissues based on their metabolic activity.
What is “flow autoregulation” in blood flow mechanisms?
The ability of tissues to maintain a consistent blood flow despite changes in perfusion pressure, involving local myogenic and metabolic factors.
What role does the sympathetic nervous system play in blood vessel control?
The sympathetic nervous system, using noradrenaline, regulates blood vessel constriction and dilation via central control.
Which part of the nervous system is responsible for central control of blood vessel tone?
The sympathetic nervous system.
What is the role of sympathetic nerves in the vasculature?
Sympathetic nerves cause vasoconstriction, especially in the spleen, kidneys, skin, and muscles, by releasing noradrenaline that acts on α₁ receptors.
Why is the sympathetic nervous system important for blood flow?
It redistributes blood flow and increases total peripheral resistance (TPR) to raise mean arterial pressure (MAP).
What neurotransmitter and receptor are associated with parasympathetic nerves in vasodilation?
Acetylcholine acting on muscarinic receptors.
Which organs are primarily affected by parasympathetic-induced vasodilation?
Salivary glands, pancreas, intestinal mucosa, and penis.
Does parasympathetic nervous system (PNS) activation affect total peripheral resistance (TPR)?
No, PNS activation has no significant effect on TPR as it affects only a few vascular beds.
In the provided image, what do the red and green structures represent?
Red represents smooth muscle cells, and green represents sympathetic nerve fibers.
What two types of hormonal control regulate blood vessels?
Hormones in the blood and autocoids (local hormones).
What are autocoids, and what role do they play in vascular control?
Autocoids are local hormones that mediate both direct and indirect dilation or constriction of blood vessels.
What layer of the blood vessel is targeted by hormones to regulate vessel tone?
Hormones primarily act on the smooth muscle layer to regulate vasoconstriction or vasodilation.
What is the role of the renin-angiotensin system in blood vessel control?
The kidneys release renin, which converts angiotensinogen into angiotensin II, causing vasoconstriction and raising total peripheral resistance (TPR) in response to reduced blood volume.
How does anti-diuretic hormone (vasopressin) affect blood vessels?
Released by the posterior pituitary in response to dehydration, it causes vasoconstriction to help maintain blood pressure.
What is the effect of adrenaline on blood vessels?
Adrenaline, released from the adrenal glands via SNS activation, can cause vasoconstriction or vasodilation depending on the receptors it acts upon.
How does atrial natriuretic peptide (ANP) influence blood vessel tone?
ANP is released by the atria in response to increased blood volume and promotes vasodilation, lowering TPR.
What are the two opposing effects of vasoactive hormones on TPR?
Angiotensin II: Raises TPR in response to low blood volume.]
ANP: Lowers TPR in response to high blood volume.
Which neurotransmitter is more important at rest in mediating SNS effects on the cardiovascular system?
Noradrenaline
Where is adrenaline secreted from, and under what conditions does its secretion increase?
Adrenaline is secreted by the adrenal medulla, with increased secretion during stressful situations such as fight or flight, hypotension, and hypoglycaemia.
What receptor does noradrenaline primarily act on to cause vasoconstriction?
α₁ receptors, which mediate vasoconstriction via IP₃/DAG signaling.
What receptor does adrenaline act on to increase heart rate and cardiac contractility?
β₁ receptors, which act via cAMP signaling.