Control of arterial blood pressure Flashcards
(44 cards)
What is blood pressure?
The pressure blood exerts on the walls of blood vessels
What are the two distinct mechanisms which both provide influence over blood pressure?
Short term- Baroreceptor (neural control)
Long-term- renin-angiotensin aldosterone system (hormonal control)
Short term control of blood pressure is mediated by the baroreceptor reflex. How does it function?
Feedback loop of
- Stretch sensitive baroreceptors acting as the sensors (afferents)
- Cardiovascular control centre in the Medulla Oblongata acting as the integrator
- Autonomic neurons acting as the effectors (efferents)
How long does the baroreceptor take?
seconds
Arterial blood pressure is monitored by peripheral sensors. Describe the anatomy of arterial baroreceptors. Name two examples
Afferent nerve fibres which relay information to brain about blood pressure- achieved because they are ideally located stretch receptors
Carotid sinus
Aortic arch
Describe cardiopulmonary baroreceptors. Give two examples
Afferent fibres of 4 types (myelinated vena-arterial mechanoreceptors, non-myelinated mechanoreceptors, coronary artery baroreceptors and chemosensory)
Heart
Pulmonary artery
What is short-term control of blood pressure achieved by principally?
Arterial baroreceptors
Carotid sinus firing frequency is in response to what?
Mean arterial blood pressure
Describe each step of the process of baroreceptor activation
- Increase in blood pressure actiavtes the stretch receptors in the carotid sinus
- Impulses are transmitted to glossopharyngeal nerve
- Impulses are transmitted to nuclei tracts solitary (NTS)
- Stimulation of NTS
- Inhibition of SNS
- Reduction in smooth muscle contraction
- Vasodilation
- Fall in BP
In what part of the heart are cardiopulmonary baroreceptors located?
-low-pressure regions’ in the heart and vasculature
What does it mean by not all baroreceptors being created equal?
- Carotid sinus baroreceptors are more sensitive
- They cause greater chainges in blood pressure that aortic arch baroreceptors
Both the carotid sinus and aortic arch contain fibres which help deal with normal and high level blood pressure. What are these fibres?
A-fibres- Deal with normal range blood pressure changes
C-fibres- Deal with high level blood pressure changes
What does long term control of blood pressure rely on and involve?
Control of blood pressure
Involves kidneys
In long-term control, blood comprises red blood cells and plasma. These are both influenced on what?
Kidneys
What are red blood cells mass altered by?
Erythropoietin
How is plasma volume altered?
- Altered by salt excretion by renin-angiotensin aldosterone system (RAAS)
- Altered by antidiuretic hormone (ADH)
- Altered by atrial natriuretic peptide (ANP)
In long-term control, how is the state of the circulation (i.e blood volume) communicated to the kidneys?
- Hormones
- Pressure natriuresis
Hormones which control water excretion and renal salts are influenced by what?
Cardiovascular receptors and initiates hormonal control
How does renin-angiotensin-aldosterone (RAAS) function?
- Decreased renal perfusion pressure aka a decrease in effective circulating volume
- Rise in sympathetic nervous system activity to kidneys
- Decreased NaCl concentration in the macula densa
- production increases after fall in BP
In RAAS, recovery of BP is achieved by what?
Angiotensin II stimulating aldosterone, angiotensin II stimulates generalised vasoconstriction, angiotensin II stimnulates thirst
Angiotensin II production is stimulated by the secretion of what?
Secretion of renin
What is renin, where is it stored and what does it begin with?
Proteolytic
Stored in afferent arterioles of kidneys
Renin begins a cleavage cascade whihc results in generation of angiotension II
What does angiotensin II stimulate and where is it stimulated from?
Aldosterone
Adrenal cortex
Aldosterone stimulates Na+ reabsorption. What does this require?
What does this is affect stimulate?
Na+/K+ pump insertion on basal membrane
Na+ channel on apical membrane
Osmosis
