Control of circulation Flashcards
Key targets for control
Arteriole resistance and blood storage veins, vascular smooth muscle
What do pre-capillary vessels have and why?
Sympathetic cholinergic control causing vasodilation, in skeletal muscle, heart, lung, kidney
What effect does Endothelium derived relaxing factor have and how?
Released after stimulation by Aah, released from endothelial cells, stimulate cGMP in muscle which causes relaxation
What is the simple loop for short term regulation?
Detector, afferent neural pathways, coordinating centre in CNS, efferent neural pathways, effectors
What are sensors for the short term control of circulation?
Baroreceptors and chemoreceptors
What are the control centres for short term control of circulation?
Mainly medulla but also cortex and hypothalamus
What are the effectors for short term control of circulation?
Pacemaker cells in the heart, vascular smooth muscle in arteries and adrenal medulla
Where are baroreceptors found?
In carotid sinus and aortic arch
What do the negative and positive feedback loops of baroreceptors cause?
negative- decrease BP and bradycardia, positive- increase BP and tachycardia
How do baroreceptors work?
Depolarise the baroreceptor nerve ending, increasing the frequency of firing, signal to the medulla
What nerve does the carotid sinus baroreceptor use?
Glossopharyngeal
What nerve does the aortic arch baroreceptor use?
Vagus
What part of the medulla to the baroreceptors project to?
Nucleus tractus solitarii with glutamate
Sympathetic activity of baroreceptors results in what?
Increase stroke volume, increase blood pressure, decrease vagal activity to increase cardiac output
What is the sympathetic pathway from the medulla?
Cardioaccellatory centre, descending pathway to spinal cord at T1-T4, fibres exit via spinal nerve, enter sympathetic chain (preganglionic and post ganglionic), cardiac nerve, heart, heart rate
What is the parasympathetic pathway from the medulla?
Cardioinhibitory centre, vagus nerve, preganglionic synapses with cardiac plexus, post ganglionic, change heart rate
What is local control to the medulla?
Metabolites that change tone of vessels in the medulla
How can intracranial pressure rise be treated?
Reducing oxygen by increasing ventilation so less oxygen in blood
What do buffer nerves do?
Increase arterial pressure and firing, decrease vasoconstriction and cardioinhibition, vasodilation, bradycardia, reduce output and BP
Vasalva Manouvre
Forced expiration against closed glottis, increase thoracic pressure and BP, reduces venous return so reduces BP, reduces baroreceptors, tachycardia and vasoconstriction, increase venous return increased CO and increase BP, baroreceptors increase firing giving bradycardia and vasodilation, BP briefly drop giving tacchcardia reflex leading to increase CO and increased BP
What does activation of chemoreceptors lead to?
Increase BP
What parts of the hypothalamus are involved with para and sympathetic control?
Anteromedial - para, lateroposterior- symp
Hypothalamus defence area
Sympathetic dilation of skeletal muscle
Hypothalamus thermoregulatory centre
Warm and cold
Hypothalamus median pre optic area
Sexual response
Anterior cingulate gyrus
Bradycardia hypotension
