Control Of Blood Pressure Flashcards
1
Q
What is pressure necessary for?
A
- to circulate blood
- facilitates the transport of nutrients, oxygen & hormones
- dispose of metabolites, carbon dioxide and waste
2
Q
Why is regulation of blood pressure important?
A
- to allow proper function of the cardiovascular system
3
Q
Where is the limiting resistance in the system?
A
- the point of the greatest pressure drop, the arterioles
4
Q
Low pressure in cardiovascular system:
A
- lungs
- aorta
5
Q
High pressure in cardiovascular system?
A
- lung
- pulmonary arteries
6
Q
Highest pressure?
A
To body
7
Q
Lowest pressure?
A
To the heart
8
Q
What monitors blood pressure control?
A
- baroreceptors
- chemoreceptors
9
Q
What regulates blood pressure control?
A
Autonomic nervous system:
- sympathetic activity
- parasympathetic activity
- chemical secretion
- the kidneys
10
Q
Arterial baroreceptors - what are they?
A
- pressure sensors
- sensitive to stretching of vessel walls where the nerve endings lie
11
Q
Where are arterial baroreceptors located?
A
- carotid sinus
- aortic arch
12
Q
What pressure do carotid sinus receptors respond to?
A
60-180mmHg
13
Q
What pressure does aortic arch receptors respond to?
A
- they have a higher threshold pressure
- sensitive to the rate of pressure change
- they sense the difference in pulse pressure
14
Q
What is the difference in pulse pressure?
A
- systolic minus diastolic pressure
15
Q
Why is sensing the difference in pulse pressure important?
A
- hemorrhagic shock, when pulse pressure and mean pressure decrease
- this reinforces the baroreceptors reflex
- decrease in arterial pressure = decreased baroreceptors firing
16
Q
How does the cardiovascular centre within the medulla respond when there is a decrease in baroreceptor firing due to a decrease in arterial pressure?
A
- increases sympathetic outflow
- decreases parasympathetic outflow
17
Q
Under normal conditions - how do baroreceptors work:
A
- baroreceptors firing exerts an inhibitory influence on sympathetic outflow
- from the medulla
18
Q
Baroreceptors mechanism:
A
- heart quickens
- carotid sinus baroreceptors & aortic arch baroreceptors fire
-cardiovascular centre = in medulla oblongata - sympathetic nerves = is inhibited
- vasoconstriction occurs
19
Q
What are chemoreceptors?
A
- sense partial pressure of oxygen and carbon dioxide
- sense pH and temperature
20
Q
Where are the peripheral chemoreceptors?
A
- carotid & aortic bodies
- they sense oxygen better than carbon dioxide
21
Q
Where are the central chemoreceptors?
A
- in the medullary neurons
- they sense carbon dioxide better than oxygen
22
Q
What are the function of chemoreceptors?
A
- to regulate respiratory activity
23
Q
How does chemoreceptor activity affect cardiovascular function?
A
- directly
- indirectly
24
Q
How does it affect it directly?
A
Interacting with medullary vasomotor centres
25
How does it affect it indirectly?
- alters the pulmonary stretch receptor activity
26
A drop in oxygen or rise in carbon dioxide leads to….
Heightened receptor firing
27
What does heightened chemoreceptors firing do?
- activates the sympathetic system
- systemic vasoconstriction and increased heart rate.
28
Where are carotid bodies located?
- on external carotid arteries, near the bifurcation
- highest blood flow of any organ
- threshold oxygen pressure = 80mmHg
- normal arterial oxygen pressure = 95mmHg
29
What also causes receptor firing?
- elevation of carbon dioxide pressure above 40mmHg
- or a decrease in pH below 7.4
30
Arterial chemoreceptors mechanism:
- carotid body chemoreceptors
- aortic body chemoreceptors
- vagus nerve = parasympathetic
- cardio regulatory centre
- chemoreceptors in medulla oblongata
31
Sympathetic control of the heart:
- SA & AV nodes
- conduction pathways
- myocytes
- peripheral arteries and veins
- causes vasoconstriction when the heart quickens
32
What do sympathetic nerves do?
- release noradrenaline
- binds to specific receptors in target tissue
33
What does noradrenaline do in the heart?
- binds to beta-1 adreno-receptors
- positive chronotropy & dromotropy
- also binds to alpha-1 adrenoreceptors on the myocytes
- small increases in inotropy
- noradrenaline & adrenaline from the adrenal medulla
- can also bind to these adrenoreceptors
34
What does noradrenaline do in the peripheral arteries and veins?
- binds to alpha-1 adrenoreceptors
- causes vasoconstriction
35
What does sympathetic outflow also do?
- stimulates the secretion of adrenaline & renin
36
How is parasympathetic activity carried out?
- parasympathetic cholinergic nerves
37
What do parasympathetic nerves do in the heart? To the SA & AV nodes:
- binds to muscarinic receptors in the heart
- negative chronotropy & dromotropy
- minimal negative inotropy
- the nerve is also known as = vagus nerve
- BLOOD PRESSURE RISES
38
Autonomic control of blood pressure summary:
- rate
- contractility
- conduction velocity
- vasoconstriction
- venous volume
39
What does the sympathetic nervous system effect?
Rate = chronotropy = +++
Contractility = inotropy = +++
Conduction velocity = dromotropy = ++
Vasoconstriction = +++
Venous volume = +++
40
What does the parasympathetic nervous system effect?
Chronotropy = rate = ———-
Inotropy = contractility = -
Conduction velocity = dromotropy = ————
Vasoconstriction = 0
Venous volume = 0
41
Chemical regulation =
- sympathetic activity results in adrenaline being secreted
42
How does adrenaline regulate the heart?
- binds to beta-1 adrenoreceptors
- positive inotropy, chronotropy & dromotropy
- binds to alpha-1 adrenoreceptors on myocytes
- small increases in inotropy
43
Adrenaline can also cause vasodilation in the skeletal muscle:
- exercise
- causes blood redirection
44
The kidney regulates the production of:
- renin
- angiotensin II
- aldosterone
45
Where is angiotensinogen secreted from?
- the liver
46
What does renin and angiotensin II control?
Total peripheral resistance
47
What does aldosterone control?
- urine output, blood volume & venous return
48
What does renin cleave?
Angiotensin to angiotensin I
49
Renin is secreted from the kidney in response to;
- low blood pressure
- low blood volume
- sodium ion depletion
50
ACE cleaving angiotensin I to angiotensin II mechanism:
- pulmonary and renal endothelium produce ACE
- angiotensin II binds to angiotensin receptors
- angiotensin receptor binding = vascular smooth muscle
- causes vasoconstriction
- increases systemic vascular resistance & arterial pressure
- angiotensin receptor binding in adrenal cortex causes aldosterone secretion
51
Where does aldosterone act upon?
- distal tubes & collecting ducts of the nephron
- causes retention of sodium ions and water
- causes secretion of potassium ions
- results in an increase in blood volume & pressure
52
What does angiotensin II do?
- stimulates the release of ADH from the posterior pituitary
- ADH makes kidneys increase fluid retention
- stimulates thirst centres in brain
- allows noradrenaline release from sympathetic nerve endings, inhibits re-uptake
- enhances sympathetic adrenergic function
53
Renin-angiotensin aldosterone system:
- sodium ion depletion
- blood volume decreases
- blood pressure decreases
- renin is released
- angiotensinogen
- angiotensin 1
- ACE converting enzyme
- angiotensin II
- aldosterone is released
- NA+ retention
- blood volume increases
- blood pressure increases
54
High blood pressure summary:
- more common in those over 35
- heavy drinkers, women on birth control
- no symptoms
- damages tissue & puts a strain on cardiovascular system
- many drugs used to control it
- many counteract the multiple systems discussed
55
Diuretics =
Cause the body to excrete water and salt
56
ACE inhibitors =
Reduce the production of angiotensin II
57
Beta-blockers =
- block effects of noradrenaline and adrenaline
- slow the heart beat, lessens the force needed to
58
Vasodilators
- dilate blood vessels
59
Calcium-channel blockers =
- cause vasodilation
- decrease the force and rate of heart contractions
