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CVS > L13 - Control of Circulation > Flashcards

L13 - Control of Circulation Flashcards

1
Q

Vessels have a resting tension (basal tone) created by?

A

Muscle and elastic fibres

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2
Q

Myogenic regulation of basal tone

A

Stretch evokes a contraction to maintain vessel diameter

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3
Q

Metabolite regulation of basal tone

A

By local pCO2, pH, pO2, temperature, lactate, [K+]

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4
Q

What is autoregulation?

A

Low level control designed to give a constant flow

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5
Q

Extrinsic control - sympathetic autonomic - what sort of constrictor input to most vessels have?

A 
Most vessels (not capillaries and venules) have tonic sympathetic adrenergic constrictor input 
- Adrenaline binds to alpha receptors causing constriction
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6
Q

Extrinsic control - sympathetic autonomic -how are pre-capillary vessels in skeletal muscle, heart and kidney controlled?

A

Sympathetic acetylcholine - vasodilation

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7
Q

Extrinsic control - sympathetic autonomic - how is erectile tissue controlled?

A

Parasympathetic acetylcholine – vasodilation

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8
Q

What is the role of sympathetic constrictors?

A

They divert blood

They are tonic and important

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9
Q

Extrinsic control - sympathetic autonomic -density innervation varies depending on?

A

The artery function

  • Cerebral low
  • Cutaneous high
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10
Q

Extrinsic control – humoral - what are the 3 molecules used?

A

Adrenal medullary hormones
Kinins
Angiotensin II

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11
Q

Extrinsic control – humoral - what do adrenal medullary hormones do?

A

Adrenaline causes
- Vasoconstriction in skin and viscera
- Vasodilation in skeletal muscle and liver
Defence reaction
- More venous return to the heart, skeletal muscle and liver
- Nervous system control more important

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12
Q

Extrinsic control – humoral - what do kinins do?

A

Bradykinin – vasodilatory peptide

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13
Q

Extrinsic control – humoral - what does angiotensin II do?

A

Vasoconstrictor – increases blood pressure

Formed by enzymes - e.g. renin acting on precursors when BP falls

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14
Q

Extrinsic control – local agents - what are the 5 molecules used?

A 
Prostaglandins
Serotonin 
Histamine 
Endothelium derived relaxing factor 
Endothelium derived hyperpolarising factors
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15
Q

Extrinsic control – local agents - what does prostaglandin do?

A

Vasodilation

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16
Q

Extrinsic control – local agents - what does serotonin do?

A

Platelets - vasoconstriction

17
Q

Extrinsic control – local agents - what does histamine do?

A

Allergy mast cells – vasodilation

18
Q

Extrinsic control – local agents - what does endothelium derived relaxing factor do?

A

Released after stimulation by acetylcholine
Nitric oxide released from endothelial cells stimulating cGMP in muscle
This leads to vasodilation
Sildenafil citrate (Viagra) - inhibits cGMP breakdown
1. Nitro-glycerine leads to increased Nitric oxide
2. Leads to vasodilation and increased flow and oxygen supply

19
Q

Extrinsic control – local agents - what does endothelium derived hyperpolarising factor do?

A

Released after stimulation by acetylcholine

20
Q

How is circulation controlled centrally?

A

Interlinked CNS centres in the brainstem

Centres receive various inputs from the rest of the body

21
Q

What are the two medullar centres?

A

Cardioexcitation and cardioinhibitory centres

Vasomotor output regulated by neurones in the medulla

22
Q

Local environment medullary neurones respond to changes in?

A

pH, CO2, O2

Raised intracranial pressure – leads to a fall in blood flow to the brain

23
Q

Control of medullary centres -what are the 4 types of peripheral proprioceptors?

A

Baroreceptors
Stretch receptors
Chemoreceptors
Buffer nerves

24
Q

Control of medullary centres - what do stretch receptors detect?

A

Carotid sinus and aortic arch detect high pressure

Atria, left ventricles and pulmonary veins detect low pressure

25
Q

Control of medullary centres - activation of chemoreceptors leads to?

A

Increased blood pressure

26
Q

Control of medullary centres - what are the two types of buffer nerves?

A

Glossopharyngeal and vagus nerve

27
Q

Control of medullary centres - short term

A

Increased arterial pressure leads to increased firing
Leads to decreased vasoconstrictors and increased cardioinhibition
Leads to vasodilation and bradycardia

28
Q

Control of medullary centres - long term

A

By kidney control of blood volume

29
Q

How are the medullary centres controlled by higher brain centres?

A 
Hypothalamus 
Linked to cortex and limbic system 
Defence area 
- Dilation of skeletal muscle 
Thermoregulatory centres 
- Warm – vasodilation and sweating 
Medial preoptic area 
- Sexual responses 
Anterior cingulate gyrus 
- Bradycardia hypotension

CVS (15 decks)

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