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Physiology > Blood Pressure > Flashcards

Blood Pressure Flashcards

1
Q

Which 2 factors is MABP dependant on

A

Cardiac output (volume per min)

And total peripheral resistance

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2
Q

What is total peripheral resistance

A

Sum of resistance to flow in all vessels

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3
Q

How do you work out MABP

A

CO x TOtal peripheral resistance

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4
Q

What would happen to blood pressure if CO or TPR increased

A

It would also increase

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5
Q

What 3 things affects TPR

A

1- blood viscosity

2- vessel length

3- vessel diameter

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6
Q

SV x HR = CO

Which factors affect HR

A

Control of HR by the autonomic NS (efferent)

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7
Q

How does the PNS have effect on heart rate

A

PNS sends signal down the vagus X nerve

This causes release of acH which then later binds to the muscarinic receptors

This binding causes decrease in HR

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8
Q

What 2 things does muscarinic binding via Ach do to decrease HR in SAN

A

Slows depolarisation in the pacemaker potential

Makes more negative RMP so that threshold is reached slower

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9
Q

What effect on channels does ach have which reduces HR at san

A

Increases K permeability which allows repolarisation instead

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10
Q

What is lowered HR called

A

Bradycardia

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11
Q

The SNS allows release of Nadr and adr from adrenal medulla, what does this allow

A

Increase HR

By binding at the B1 receptor which causes increased HR

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12
Q

As well as increased HR, what does SNS adr/nadr binding to B1 do

A

Increases contraction at heart muscles

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13
Q

What stimulation effects on the SAN does the SNS adr/nadr release have

A

Increases rapid depolarisation in pacemaker potential

Also causes a less negative RMP

Threshold reached quicker

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14
Q

What is increased HR called

A

Tachycardia

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15
Q

What is a change in HR called

A

Chronotopic effects

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16
Q

To control stroke volume (factor of CO) what 2 mechanisms are there

A

Intrinsic and extrinsic mechanisms

17
Q

What is the intrinsic control of stroke volume about

A

Suggests stroke volume is dependant on muscle fibre length when in diastole

18
Q

How can an increased VR cause an increase in SV/force

A

Increased VR will mean cardiac muscle stretches more in late diastole (when filling)

This increased stretch/EDV will increase the force so increases volume out of the heart(SV)

19
Q

Why is less ca2+ needed to cause tension in stretched muscle fibres

A

Increased sensitivity of proteins to calcium when muscle fibre is stretched due to increased VR which causes increased EDV

20
Q

Why is the intrinsic law to regulating SV important

A

It allows CO to be equal to VR

If VR increases so does SV which increases CO

21
Q

What would happen if VR and CO weren’t equal eg if Right ventricle was higher output

A

More blood would be going to the lungs(VR) than to the body(CO)

This causes oedema (flooding of the lungs)

22
Q

What 5 things maintain VR which allows to maintain CO by affecting SV intrinsically

A

Venous- atria pressure gradient

Venous valves - stop back flow

Respiratory pump

Skeletal muscle pump

Venomotor tone

23
Q

What is the venomotor tone which maintains VR

A

It’s the fact that veins smooth muscle is supplied with SNS which allows contraction

24
Q

What is the extrinsic mechanism to controlling SV

A

Contractility of muscle dependant in the SNS (B1 adr/nadr binding)

25
Q

Which system is activated when adr/nadr binds to B1 to increase contraction

A

Adenylate cyclase

Causes production of camp

26
Q

Which 2 proteins does cAMP phosphorylate

A

Ca2+ channels

Phospholamban

27
Q

What happens when ca2+ channels are phosphorylated by pka system (SNS)

A

Increases opening of Ca2+ channels which increases trigger calcium

Increased trigger calcium causes increased release of calcium via ryanodine channels on SR

This increases amount which binds to troponin = contraction

28
Q

How does phospholamban increase contraction

A

It increases Ca2+ ATPase activity to increase calcium in SR so more is released

29
Q

Why does phospholamban cause shorter contractions of heart muscle

A

Increased Ca2 ATPase activity causes more ca to be removed from the troponin site, which means contraction occurs shorter

30
Q

What is change in muscle relaxation called

A

Lusitropic effects

31
Q

What is increased contractility via SNS called

A

Positive ionotropic effects

Physiology (31 decks)

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