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1020: Physiology FM1020 (E) > P: Arterial blood pressure > Flashcards

P: Arterial blood pressure Flashcards

1
Q

How is mean arterial pressure (MAP) (Pa) calculated?

A

Pa = Pd + (Ps - Pd)/3

Ps = Systolic pressure
Pd = Diastolic pressure

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2
Q

What is the normal Pa?

A

Pa = 93 mmHg (120/80) –> rounded up to 100 mmHg

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3
Q

What is the main physical determinant + physiological determinants of MAP?

A
  • Physical determinant = arterial blood volume (Va)
  • Physiological determinants = rate of inflow of blood (Qh) + rate of outflow (Qr)
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4
Q

What happens to MAP if:
- Qh = Qr
- Qh > Qr
- Qh < Qr

A
  • Qh = Qr –> MAP stays constant
  • Qh > Qr –> MAP increases
  • Qh < Qr –> MAP decreases
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5
Q
  • Constriction causes pressure to ___ in the arterioles and downstream vessels.
  • Constriction causes pressure to ___ upstream in the arterial system.
  • Increase in total peripheral resistance (TPR) (vasoconstriction of arterioles) causes blood pressure to ____.
A
  • fall
  • increase
  • increase
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6
Q

Long term increases in either ___ or ___ will result in long term effects on Pa.

A
  • CO
  • TPR
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7
Q

MAP = ____ x ____
and
MAP = ___ x ___ x ___

A
  • CO x TPR
  • SV x HR x TPR (CO = SV x HR)
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8
Q

What determines the rate of change of Pa?

A

Compliance of the arteries
- Rigid arteries attain higher Pa level rapidly
- Elastic arteries: increases in Pa occur at slower rate (pressure absorbed by wall)

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9
Q

What are 2 determinants of pulse pressure?

A
  • SV (major determinant)
  • Compliance
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10
Q

What is the tool used to measure systolic and diastolic pressure and how?

A
  • Sphygmomanometer and inflatable cuff
  • Cuff placed around upper arm over brachial artery –> inflated cuff = pressure on artery
  • Cuff pressure > systolic pressure (120 mmHg) –> artery closed, blood flow stops
  • Cuff pressure slowly dropped: cuff pressure < systolic pressure –> partially opens artery –> blood flow restarts in a turbulent fashion
  • Causes Korotkoff sounds (thumping noise), detected with stethoscope on artery
  • Cuff pressure < diastolic pressure (80 mmHg) –> artery completely open –> sounds stop
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11
Q

Regulation of smooth muscle contraction/relaxation in arterioles controls ____

A

TPR
- Contraction closes lumen of blood –> reduces blood flow
- Relaxation increases lumen diameter (dilation) –> increases blood flow

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12
Q

What is the equivalent of troponin C from skeletal/cardiac muscle in skeletal muscle?

A

Calmodulin: Ca2+ sensor
- Ca2+/calmodulin complex binds and activates MLCK

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13
Q
A
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14
Q

Myogenic regulation of vascular smooth muscle (VSM):
- ____ in blood pressure induces reflex contraction of arterioles
- ____ in blood pressure induces reflex dilation of vessels
- ____ is maintained (autoregulation of blood flow)

A
  • Rapid increase in blood pressure induces reflex contraction of arterioles
  • Rapid reduction in blood pressure induces reflex dilation of vessels
  • Constant blood flow is maintained (autoregulation of blood flow)
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15
Q

Where is resistance to blood flow the greatest?

A

In arterioles and capillaries due to narrow diameter

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16
Q

How does stroke volume determine pulse pressure?

A
  • During ventricular ejection, arterial blood volume increases to V2
  • Blood pressure increases to P2
  • During diastole, peripheral runoff reduces volume to V1 and pressure to P1.

(V2- V1) proportional to (P2-P1) = pulse pressure

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17
Q

Explain endothelial-mediated regulation

A
  • Increased blood flow causes shear stress to endothelium and induces release of nitric oxide (NO) (synthesised from L-arginine)
  • NO diffuses to VSM cells and activates guanylyl cyclase –> increases [cGMP]i –> decreases [Ca2+]i in VSM –> dilation of blood vessels
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18
Q

How can metabolic activity of a tissue regulate capillary blood flow? What is the name given to rise in blood flow caused by increased tissue activity?

A
  • If O2 levels are inadequate, metabolites with vasodilator activity are produced –> diffuse to VSM –> relaxation –> increases capillary blood flow
  • Active hyperemia = rise in blood flow caused by increased tissue activity
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19
Q

Explain extrinsic control of peripheral blood flow

A
  • Post-ganglionic sympathetic nerves innervate VSM of arterioles and veins
  • Noradrenaline binds to alpha1-adrenergic receptors on VSM cells = vasoconstriction (activate phospholipase C –> produces 2nd messengers –> increase [Ca2+]i)
  • Adrenaline binds to B2-adrenergic receptors on VSM cells in skeletal blood vessels = vasodilation (activate adenylate cyclase –> increase [cAMP]i –> inhibits MLCK)
  • NA binds to alpha 1 = activate PLC = 2nd messengers = increase in Ca2+ = vasoconstriction
  • Adrenaline binds to Beta2 in skeletal blood vessels = activate adenylyl cyclase = increase cAMP = inhibit MLCK = vasodilation
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20
Q

In arterioles:
- At rest, SNs constantly release ___ inducing a degree of ___ (tonically active or ___ tone)

A
  • noradrenaline
  • vasoconstriction
  • vasoconstrictor tone
21
Q

Sympathetic nerve stimulation:
- Reduces ____ into tissues by ____ of arterioles
- Decreases tissue ____ by ____ of venules
- Reduces capillary ____ pressure –> absorption of ____ into capillaries increases

A
  • blood flow, constriction
  • blood volume, constriction
  • hydrostatic, interstitial fluid
22
Q

Vasoconstriction mobilizes blood from ____ and returns it to ___. During exercise:
- Increased ____
- Increased ____
- Increased ____
- Increased ____

A
  • capacitance vessels, heart
  • venous return
  • EDV
  • SV
  • CO
23
Q

Regulation of peripheral resistance is mediated by ____

A

sympathetic nerves

24
Q

What’s another word for cardiovascular control centre in the brain and where is it located?

A
  • Vasomotor Centre: in reticular substance of medulla + lower third of Pons
25
Q

The Vasomotor Centre transmits impulses via ____ to the heart, sympathetic impulses via ____ and peripheral ____ nerves to the heart and arteries, arterioles and veins.

A
  • vagus nerves
  • spinal cord
  • sympathetic
26
Q

Stimulation of rostral ventrolateral medulla (RVLM) increases ___ and ___

A

BP and HR (very important in maintaining normal BP –> vasoconstrictor area)

27
Q

Caudal ventrolateral medulla (CVLM) function

A

Inhibit RVLM activity –> vasodilation

28
Q

What is the origin of vagal projection to the heart?

A

Nucleus ambiguus (NA, AMB) and dorsal motor nucleus of vagus (DMV)

29
Q
  • Nucleus of the tractus solitarius (NTS) receives sensory nerve signals from circulatory system mainly through ____ and ____ nerves.
  • These nerves are stimulated by ____ and ____.
  • NTS sends the output to the ____ and ____.
  • Stimulation of NTS reduces ____ and increases ____.
A
  • Vagus and glossopharyngeal
  • Baroreceptors and cardiopulmonary receptors
  • NA and CVLM
  • Sympathetic outflow, vagal outflow
30
Q
A
31
Q

NTS in the medulla receives sensory impulses from:

A
  • Baroreceptors
  • Cardiopulmonary receptors
  • Chemoreceptors
  • Other brain regions
32
Q

How are sudden changes in blood pressure detected?

A

Stretch-sensitive mechanoreceptors (baroreceptors) in walls of carotid artery (carotid sinus) and aortic arch become more active in response to stretched walls from raise in BP

33
Q

What are the afferent pathways of arterial baroreceptors?

A
  • Carotid sinus nerve, glossopharyngeal nerve, NTS
  • Vagus nerve, NTS
34
Q

BP > ___ mmHg –> rapid inhibition of sympathetic nerve activity + increase in vagal activity (and vice versa)

A

100 mmHg

35
Q

Firing of baroreceptor terminals is enhanced by increases in ____ and diminished by reductions in ____

A

Arterial pressure for both

36
Q

Which baroreceptors are quantitatively more important for regulating arterial blood pressure?

A

Carotid sinus baroreceptors (aortic are less sensitive)

37
Q

What is responsible for short term vs long term changes in arterial pressure?

A
  • Short term = baroreceptors
  • Long term = kidney
38
Q

Consequences of sudden reduction in blood pressure
Increased sympathetic nerve activity will:
- Increase ____ by increasing ___ and ___
- Contract ____ muscle promoting ____
- Stimulate contraction of ____ muscle to increase ____
- ____ in kidney arterioles also minimizes urine formation

Reduction in ____ nerve –> diminish inhibitory effect on HR

A

Increased sympathetic nerve activity will
- Increase CO by increasing HR and SV
- Contract venous smooth muscle promoting venous return
- Stimulate contraction of arterial smooth muscle to increase peripheral resistance
- Vasoconstriction in kidney arterioles also minimises urine formation

Reduction in vagus nerve –> diminish inhibitory effect on HR

39
Q

Consequences of sudden elevation blood pressure

A
  • Stimulation off vagus nerve activity will reduce CO by slowing HR
  • Inhibition of sympathetic nerve activity will: reduce CO by slowing HR and SV + cause relaxation of arterial smooth muscle (vasodilation) –> decrease peripheral resistance
  • Kidneys are stimulated –> excrete more water as urine –> reducing total blood volume (long term control)
40
Q
A
41
Q
A
42
Q

Where are cardiopulmonary receptors located and what is their function?

A
  • Atria, ventricles and pulmonary vessels
  • Reflex that lowers arterial BP in response to changes in blood volume
  • Acts mainly on kidneys to reduce blood volume by increasing urine output
43
Q

What’s the Bainbridge Reflex?

A
  • Increased blood volume increases atrial pressure –> rapid increase in HR
  • Mediated by atrial stretch receptors that transmit afferent signals via vagus nerves to the NTS
  • Efferent signals are transmitted back through vagal and sympathetic nerves to increase HR and contractility
44
Q
  • Bainbridge and baroreceptor reflexes are ____.
  • Higher blood volume –> ____ predominates
A
  • antagonistic
  • Bainbridge reflex
45
Q

Where are chemoreceptors located and what do they do?

A
  • Medulla, carotid sinus and aortic arch
  • Respond to changes in arterial PO2, PCO2 and pH
  • Set appropriate rate and depth of ventilation (breathing)
  • Chemoreceptor reflex: increase BP and HR (secondary effect of increase in ventilation)
46
Q

Anterior hypothalamus function

A

decreases BP and HR

47
Q

Posterior and lateral hypothalamus function:

A
  • Alerting reaction
  • Increased BP + HR, vasodilation in skeletal muscle
  • Vasoconstriction in skin and splanchnic organs
48
Q

Cerebral cortex functions:
- Involved in ___ functions
- Cause ____ of skin, splanchnic and renal vessels
- ____ in skeletal muscles

A
  • Involved in motor functions
  • Cause vasoconstriction of skin, splanchnic and renal vessels
  • Vasodilation in skeletal muscles
49
Q

Equation of pulse pressure

A

Pulse pressure = Systolic (Ps) - Diastolic pressure (Pd) = 40 mmHg at rest

1020: Physiology FM1020 (E) (12 decks)

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