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Cardiology > Physiology 2 > Flashcards

Physiology 2 Flashcards

1
Q

How and where is SVR regulated?

A

Vascular smooth muscles
Mainly in arterioles
e.g. contraction –> vasoconstriction –> increased SVR and MAP

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2
Q

How are nerves involved in the regulation of systemic vascular resistance? What are the neurotransmitters/receptors involved?

A

Vascular smooth muscle supplied by SYMPATHETIC nerves
- neurotransmitter is noradrenaline acting on alpha receptors

Increased sympathetic discharge –> vasoconstriction
Decreased sympathetic discharge –> vasodilatation

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3
Q

Which hormone is involved in control of vascular smooth muscle and where does it come from?

A

Adrenaline

From adrenal medulla

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4
Q

How does adrenaline effect vascular smooth muscle?

A

Depends on type of receptor:

  • alpha –> vasoconstriction
  • beta-2 –> vasodilatation

Alpha receptors in skin, gut and kidneys

Beta-2 receptors in cardiac and skeletal muscle

Allows strategic distribution of blood during exercise

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5
Q

Which 2 other hormones affect vascular smooth muscle and what is their effect?

A

Angiotensin II
ADH
–> both cause vasoconstriction

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6
Q

Give some examples of chemical factors which cause vasodilatation

A
  • decreased local PO2
  • increased local PCO2
  • increased local H+
  • increased extracellular K+
  • adenosine release (from ATP)
  • histamine
  • bradykinin
  • nitric oxide
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7
Q

Give some examples of chemical factors which cause vasoconstriction

A
  • serotonin
  • thromboxane A2
  • leukotrienes
  • endothelin
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8
Q

What is shock?

A

An abnormality of the circulatory system –> inadequate tissue perfusion and oxygenation

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9
Q

What is hypovolaemic shock? Give some examples

A

Loss of blood volume –> decreased CO and decreased BP

e.g. haemorrhage, D&V, excessive sweating

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10
Q

What is cardiogenic shock? Give an example

A

Sustained hypotension caused by decreased cardiac contractility

e.g. acute MI

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11
Q

What is obstructive shock? Give some examples

A

Obstruction leading to reduced CO

e.g. cardiac tamponade, tension pneumothorax, PE

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12
Q

What is neurogenic shock? Give an example

A

Loss of sympathetic tone to blood vessels and heart

  • -> massive vasodilatation
  • -> decreased HR (unlike other types of shock)

e.g. spinal cord injury

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13
Q

What is vasoactive shock? Give some examples

A

Release of vasoactive mediators –> vasodilatation and increased capillary permeability

e.g. septic shock, anaphylactic shock

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14
Q

How is syncope defined?

A

Transient loss of consciousness due to cerebral hypoperfusion, characterised by:

  • rapid onset
  • short duration
  • spontaneous complete recovery
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15
Q

What are the three different types of syncope?

A
  1. reflex syncope
  2. orthostatic hypotension
  3. cardiac syncope
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16
Q

What is reflex syncope?

A

Neural reflexes –> decreased HR and/or decreased vascular tone (vasodilatation)

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17
Q

What are the three different types of reflex syncope?

A
  1. vasovagal syncope
  2. situational syncope
  3. carotid sinus syncope
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18
Q

What is the most common type of syncope?

A

Vasovagal syncope

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19
Q

What is vasovagal syncope?

A

FAINT triggered by emotional distress (e.g. pain, fear, blood phobia) or orthostatic stress

20
Q

What happens before a vasovagal episode?

A

Typical prodrome of

  • pallor
  • sweating
  • nausea
21
Q

How can a vasovagal episode be averted?

A

Adopting a horizontal position or leg crossing

–> increases venous return

22
Q

What is situational reflex syncope?

A

Faint during or immediately after a specific trigger e.g.

  • cough
  • micturition
  • swallowing
23
Q

What is carotid sinus reflex syncope?

A

Faint triggered by mechanical manipulation of the neck e.g.
- shaving
- tight collar
May occur after head and neck surgery or radiation

24
Q

What causes postural hypotension?

A

Failure of baroreceptor responses to gravitational shifts in blood when going from lying to standing

25
Q

What is the criteria for postural hypotension?

A

Drop, within 3 minutes of standing from lying:

  • in systolic BP of at least 20 mmHg (with or without symptoms) or
  • in diastolic BP of at least 10 mmHg (with symptoms)
26
Q

What is cardiac syncope?

A

Cardiac event –> sudden drop in cardiac output

27
Q

What are some causes of cardiac syncope?

A
  • arrhythmias
  • acute MI
  • structural disease e.g. aortic stenosis, hypertrophic cardiomyopathy
  • other CV disease e.g. PE, aortic dissection
28
Q

What should the initial investigation of a patient with transient loss of consciousness involve?

A
  • careful history
  • full examination
  • lying standing BP
  • 12 lead ECG
29
Q

How does blood arrive at/drain from the cardiac muscle?

A

Comes from left and right coronary arteries (arising from base of aorta)

Drain via coronary sinus into right atrium

30
Q

During which part of the cardiac cycle does blood flow in the coronary arteries?

A

Diastole

31
Q

What effect would increased HR have on coronary blood flow?

A

Reduced –> less time in diastole

32
Q

At which MAP does autoregulation of cerebral blood flow fail?

A

MAP < 60 mmHg or

MAP > 160 mmHg

33
Q

What is the effect of PCO2 on cerebral blood flow?

A

Increased PCO2 –> cerebral vasodilatation

Decreased PCO2 –> cerebral vasoconstriction (this is why hyperventilation can cause fainting)

34
Q

How is cerebral perfusion pressure calculated?

A

CPP = MAP - ICP

35
Q

How does pulmonary capillary pressure compare to systemic capillary pressure?

A

Pulmonary is lower

36
Q

What is the effect of hypoxia on pulmonary arterioles?

A

Vasoconstriction

opposite effect on systemic arterioles

37
Q

What happens if valves in lower limb veins become incompetent?

A

Blood pools in lower limb veins –> varicose veins

38
Q

If blood is gathered in varicose veins, why does this not lead to a reduced CO?

A

Chronic compensatory increase in blood volume

39
Q

What is oedema?

A

Accumulation of fluid in the interstitial space

40
Q

What are the 4 physiological causes of oedema?

A
  1. Raised capillary pressure
  2. Reduced plasma osmotic pressure
  3. Lymphatic insufficiency
  4. Changes in capillary permeability
41
Q

What are the causes of raised capillary pressure as a cause of oedema?

A

Arteriolar dilatation

Raised venous pressure

  • left ventricular failure
  • right ventricular failure
  • prolonged standing (swollen ankles)
42
Q

What type of oedema results from left ventricular failure?

A

Pulmonary oedema

43
Q

What type of oedema results from right ventricular failure?

A

Peripheral oedema (ankle, sacral)

44
Q

What are the causes of reduced plasma osmotic pressure as a cause of oedema?

A

Plasma protein < 30 g/l

  • malnutrition
  • protein malabsorption
  • excessive renal excretion of protein
  • hepatic failure
45
Q

What are the causes of lymphatic insufficiency as a cause of oedema?

A

Lymph node damage

Filariasis - elephantiasis

46
Q

What are the causes of changes in capillary permeability as a cause of oedema?

A

Inflammation

Histamine increases leakage of protein

Cardiology (14 decks)

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