L45 - blood pressure regulation Flashcards
What is mean arterial pressure regulated by?
- baroreceptors (short term)
- blood volume (kidney - long term)
what do baroreceptor neurons functions as?
- sensors in homeostatic maintenance of mean arterial pressure
- nerve endings are sensitive to stretch and pressure in artery
where are baroreceptors located?
- located in aortic arch, carotid sinuses where they monitor pressure
- in thinner walls that can be stretched by pressure
what is rate of baroreceptor never firing like?
- proportional magnitude and changes in MAP
- response is lost in minutes (short term sensors of BP)
what do arterial baroreceptors act as?
- part of neg feedback pathway, regulate MAP via brain (central control)
- actions are coordinated by medulla oblongata (medullary cardiovascular centre)
what is the hormonal regulation of MAP?
- adrenaline - inc MAP
- angiotensin II and vasopressin - inc MAP
what is the ANS regulation of MAP?
- sympathetic - inc MAP
- parasympathetic - dec MAP
how are sympathetic nerves involved in central control?
- mediated by noradrenaline via B-adrenergic receptors
- a1-adrenergic receptors in arterioles
- inc cardiac output and peripheral resistance
how are parasympathetic nerves involved in central control?
- mediated by ACh via muscarinic receptors
- inhibit heart rate
What parts of the heart inc B1-AR in sympathetic?
- SA - heart rate
- AV - conduction
- atrial muscle contraction - inc stroke vol
- ventricular muscle contraction - inc stroke vol
what parts of blood vessels inc B1-AR in symptathetic?
- arteriole vasoconstriction - peripheral resistance
- venous vasoconstriction - inc stroke vol
what parts of the heart dec m2-AR in parasympathetic?
SA node - heart rate
What is central control like in ANS?
- dec parasympathetic discharge to heart
- inc sympathetic discharge to heart - inc heart rate
- inc sympathetic discharge to veins - inc constriction
- inc sympathetic discharge to arterioles - inc constriction
What are the causes of hypotension (reduction in arterial pressure)?
- loss of blood (hemorrhage)
- loss of salts - burns, sweating, diarrhoea/vomiting
- stress or emotions (fainting)
what does standing up do?
- orthostasis
- drop in mean BP
Why does mean BP drop when you stand, how does cardiovascular sys. compensate?
- blood pools in legs due to gravity
- red blood vol, lowers central venous pressure
- red venous return, red end-diastolic pressure, red stroke vol
- baroreceptor reflex compensates
what is vol of blood primarily determine by venous vol?
venous volume
what is the blood reservoir?
most of blood distributed in veins and venules
what is responsible for long-term regulation of BP?
changes in blood vol regulated by the kidneys (renin-angiotensin system)
what is local flow regulated by?
- local
- neural
- hormonal factors
what are local factors that control arteriole vasodilation and vasoconstriction?
- myogenic response
- vasodilation induced by metabolites
- autocoids
what is the myogenic response?
- vasoconstriction caused by stretch smooth muscle
- brain, kidney and heart
what is the vasodilation induced by metabolites?
- dec O2, inc CO2
- inc H+, inc adenosine, inc K+, inc osmolarity
what are autocoids?
- released as a result of inflammation and bleeding
- histamine, bradykinin, prostaglandins
