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Flashcards in Control of circulation Deck (22)
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What are baroreceptors and where are they found?

Stretch receptors and are found in the carotid sinus and aortic arch


What happens when the baroreceptors are stimulated by an increased blood pressure

Carotid sinus sends action potentials along the sinus nerve then the glossopharyngeal nerve fibres -
Aortic arch sends APs along vagus nerve fibres to the medulla (nucleus tractus solitarius)
Inhibitory interneurons suppress the sympathetic nervous system activity that would normally be causing tonic vasoconstriction/increased heart rate/CO which are therefore decreased.


What is meant by tonic sympathetic adrenergic constrictor input

Seen in most vessels - in normal conditions sympathetic signalling to these vessels causes consistent levels of constriction - adrenergic


What neurotransmitter causes vasodilation in pre-capillary vessels in skeletal muscle, kidneys, lungs, and heart

Acetylcholine - exception to the rule that sympathetic post-ganglia axons usually release noradrenaline


What autonomic supply does the erectile tissue/glands have and what does it cause

Parasympathetic supply by Ach causes vasodilation


What is the effect of adrenaline at the skin/viscera



What is the effect of adrenaline at the skeletal muscle/liver



What role do kinins have on circulation

Bradykinin - vasodilatory peptide


What role does angiotensin II have on circulation

Vasoconstriction - increases blood pressure - Formed by enzymes (renin) acting on precursors when BP falls (ACE in the lungs)


What effect do prostaglandins have on blood vessels



What effect does histamine have on blood vessels

Released by mast cells - vasodilation, fluid accumulation by making the vessel leaky


What is the action of endothelium-derived relaxing factor

Released after Ach stimulation - Nitric oxide stimulates cGMP in muscle - this causes relaxation of smooth muscle and therefore vasodilation


What effect does viagra have on cGMP

Inhibits the action of cGMP on smooth muscle so maintains contractility - used to maintain an erection


What is the action of nitroglycerin

Increases NO levels, causing vasodilation, causing increased blood flow and increased oxygen supply - used to treat angina (the heart isn't getting enough blood)


What is the action of the sympathetic and parasympathetic nervous systems in the cushing reflex

1. Sympathetic control - due to head injury - swelling within the cranium causes intracranial pressure to rise - when it exceeds mean arterial blood pressure it becomes very hard for the blood to receive blood - compensation for this from the SNS - Causes vasoconstriction and tachycardia
2. parasympathetic - baroreceptors detect the change in BP (stretched) afferent fibres to the medulla (nucleus tractus solitarius) inhibitory interneurons act to inhibit sympathetic NS action on the heart causing bradycardia
Very dangerous - High BP and Low heart rate - death


What areas of the circulatory system detect low pressure in blood vessels

baroreceptors found in the atria, left ventricle and pulmonary veins


What is ANP and what does it do

Atrial natriuretic peptide - Mostly produced in the atria - acts at the level of the kidney to inhibit water re-uptake


What action do chemoreceptors have on control of circulation

Angina - cardiac chemoreceptors detect a fall in pH/rise in CO2 and signal pain - leads to an increase in BP


What is the hypo-defence area of the hypothalamus' role

leads to sympathetic dilation of skeletal muscles and blood vessels


What is the role of the hypo-thermoregulatory centres

When warm - Vasodilation and sweating
When cold - Vasoconstriction and shivering


What is the role of the hypo-medial preoptic area

Sexual response


What is the role of the anterior cingulate gyrus

Bradycardia - hypotension
Drops HR and BP to avoid predation in animals who are playing dead