Vasculature and Blood Pressure

Question 1

1. why do we need blood pressure?

2. what is normal blood pressure considered to be?

Answer 1

1. for adequate perfusion of the tissues, including the brain
2. 120/80

Question 2

1. what is the equation describing the relationship between flow, pressure and vascular resistance?
2. how can this be rearranged to show the determinants of blood pressure?

Answer 2

1. Q̇ = ΔP/R

2. pressure = flow (cardiac output) x resistance

Question 3

1. How is cardiac output controlled?
2. What is tissue flow determined by?
3. How do the tissues determine the amount of blood they receive?
4. What is poiseulle’s law?
5. how do the arterioles control vascular resistance?
6. Name 4 factors that can affect vascular resistance by acting on arterioles

Answer 3

1. by tissue demand - matching venous return to cardiac output
2. tissue demands determining resistance
3. adjusting peripheral resistance
4. flow is directly proportional to the fourth power of the radius
5. bands of smooth muscle called pre-capillary sphincters, just before entry to capillary bed, act as the main site of peripheral resistance
6. metabolic products - H+, adenosine
   increased CO2
   hypoxia
   sheet stress.
   ALL ACT TO RELAX PRE-CAPILLARY SPHINCTERS

Question 4

1. via which receptors do sympathetic fibres mediate their effects on blood pressure?
2. What is the effect of sympathetic innervation on blood pressure?
3. What receptors monitor peripheral pressure and are linked to sympathetic afferents?
4. Describe a baroreflex in respinse to:
   a) increased BP
   b) decreased BP
5. Name 3 other neural mechanisms of blood pressure control

Answer 4

1. alpha1 receptors
2. raises blood pressure by vasoconstriction (and by increasing cardiac output)
3. baroreceptors located in carotid sinus and aortic arch
   4a) increase in firing rate of afferent fibres > medullary centre > decreased sympathetic tone > decrease in BP
   4b) decrease in firing rate of afferent fibres > medullary centre > increased sympathetic tone > increase in BP
4. • atrial stretch - causes renal arteriolar dilation
     - chemoreceptors - decrease in BP > decrease in PO2 > increase in BP
     - CNS ischemia leads to increased BP

Question 5

RENAL MECHANISMS OF BLOOD PRESSURE CONTROL
1. Describe pressure diuresis

2. what is renin secreted by, and under what conditions?
3. describe the renin-angiotensin-aldosterone system
4. what is the effector molecule of the RAA system? What does it induce?

Answer 5

1. increased BP causes an increased in glomerular filtration rate. This leads to diuresis, which reduces blood pressure
2. secreted by the juxtaglomerular apparatus in response to reduced glomerular BP
3. renin converts angiotensiongen to angiotensin 1
   ACE converts angiotensin 1 to angiotensin 2
   Angiotensin 2 promotes aldosterone release
4. Angiotensin 2. It causes vasoconstriction, aldosterone release and sympathetic activation.

Question 6

1. How do diuretics lower blood pressure?
2. how do thiazide diuretics act?
3. how do loop diuretics act?
4. how do potassium sparing diuretics act?
5. how do carbonic anhydrase inhibitors act?
6. How do beta blockers treat hypertension?
7. what is the suffix of beta blockers?
8. how do alpha blockers treat hypertension?
9. name an example of an alpha blocker
10. how do calcium antagonists treat hypertension?
11. what is the suffix of calcium antagonists?
12. What is the suffix given to ACE inhibitors?
13. What is the suffix given to angiotensin II receptor 1 antagonists?

Answer 6

1. promote diuresis therefore decrease blood volume
2. inhibit sodium chloride symporter in the distal convoluted tubule
3. inhibit sodium reabsorption in the thin ascending loop
4. block sodium channels or antagonise aldosterone (spironolactone)
5. affect bicarbonate and sodium reabsorption in the proximal convoluted tubule
6. inhibit beta receptors therefore reduce cardiac output
7. -olol
8. antagonise alpha 1 receptors in vessels therefore promoting vasodilation
9. doxassin
10. inhibit the flow of calcium into smooth muscle therefore promote vasodilation
11. -ipines
12. -iprils
13. -sartans

Question 7

1. what is the inner most, middle and outer layer of the blood vessel wall
2. what is the tunica intima comprised of?
3. what is the tunica media comprised of?
4. what is the tunica externa comprised of?
5. what are the nerves and blood vessels that supply the tissues of the blood vessels called?

Answer 7

1. innermost - tunica intima
   middle - tunica media
   outermost - tunica externa
2. endothelial cells, basement membrane and internal elastic lamina
3. smooth muscle and connective tissue elastic fibres
4. collagenous fibres, nerves and blood vessels

Question 8

what is the structure of:

1. elastic arteries
2. muscular arteries
3. arterioles
4. capillaries
5. post capillary venules
6. muscular venules
7. veins

Answer 8

1. well defined tunica intima, thick tunica media, that is dominated by elastic fibres and thin tunica externa
2. well defined tunica intima, thick tunica media, that is dominated by smooth muscle and thin tunica externa
3. thin intima. one or two layers of smooth muscle in tunica media and loose, collaginous externa
4. endothelial cell layer with no tunica media or externa
5. endothelial cell layer with sparse tunica externa
6. endothelial cell layer with one or 2 layers of smooth muscle in media
7. thin intima, relatively thin media with no elastic lamina. Tunica externa is thickest layer.

Question 9

1. what are vascular shunts?
2. what are true capillaries?
3. what is the metarteriole?
4. what happens when the pre-capillary sphincter is relaxed?
5. what happens when the pre-capillary sphincter is contracted?

Answer 9

1. metarteriole throughfare channel that connects arteriole directly with post-capillary venule
2. capillaries that branch off the merateriole and return to the throughfare channel at the distal end of the capillary bed
3. terminal end of arteriole. Controls flow of blood through the capillaries
4. blood is permitted through true capillaries
5. blood flow through true capillaries is restricted; blood flow is restricted to the metarteriole throughfare channel.