Lecture 32 - Cardiovascular System: Control of Blood Flow Within Tissue Flashcards

1
Q

Where are the 2 key points where blood flow through capillary beds can be controlled. What are their characteristics?

A

Arterioles and pre-capillary sphincters

Key characteristics:
- Smooth muscle
- Relatively narrow lumen = larger proportional changes in diameter

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2
Q

What is the function of vasoconstriction and vasodilation in smooth muscle?

A

They related to the amount of tension produced in the smooth muscle of the tunica media

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3
Q

How does intrinsic regulation (autoregulation) affect blood flow?

A

Through regulation by factors occurring within the local environment of that vessel. Can be direct or indirect

Ex. Metabolic regulation, immune regulation, myogenic regulation

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4
Q

How does extrinsic regulation affect blood flow?

A

Regulation by mechanisms involving integrative organ systems (outside the local environment)

Ex. Neuronal regulation (ANS), hormonal regulation

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5
Q

How can vasodilation through autoregulation occur DIRECTLY?

A

It occurs directly through changes in gases, ions, or metabolites in the surrounding tissue

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6
Q

Name 4 stimuli that would directly trigger muscle relaxation in peripheral tissue

A
  1. Dec. O2
  2. Inc. CO2
  3. Inc. H+
  4. Inc. K+
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7
Q

How can vasodilation through autoregulation occur INDIRECTLY?

A

Paracrine signalling pathways

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8
Q

Name 3 paracrine signalling pathways

A
  1. Paracrine factors - chemical messengers that remain within their local environment
  2. Vasoactive paracrine factors - can be generated in surrounding tissues or by endothelial cells
  3. Nitric oxide (NO) - soluble gas; causes smooth muscle relaxation by reducing Ca2+ entry into smooth muscle
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9
Q

How can vasoconstriction through autoregulation occur?

A

It can occur through:

Myogenic mechanism - stretching vascular smooth muscle triggers increases in its contraction, returning vessel diameter to original value

Paracrine mechanism - endothelins are paracrine factors which are constantly secreted at low levels, helping to maintain a baseline state of slight vasoconstriction

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10
Q

Role of a1 adrenergic receptors in changes to vessel diameter

A

They elevate intracellular calcium, enhancing smooth muscle contraction (vasoconstriction)

Very sensitive to NE (ie. ANS activity)

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11
Q

Role of b adrenergic receptors in changes to vessel diameter

A

They elevate intracellular cAMP, reducing smooth muscle contraction (vasodilation)

Very sensitive to E (ie. hormonal release)

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12
Q

How does epinephrine and other hormones affect blood vessel diameter?

A

It can lead to vasoconstriction or dilation depending on the type of intracellular biochemistry triggered by its receptors and its location

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13
Q

What reflexes are triggered during exercise when metabolic activity increases?

A

Global chemoreceptor reflexes are triggered, including general vasoconstriction across all peripheral arterioles

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