Lecture 11 Control of Blood Flow Flashcards Preview

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Flashcards in Lecture 11 Control of Blood Flow Deck (88)
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1

Describe Acute Control

Rapid changes in local vasodilation/vasoconstriction
Occurs in seconds to minutes

2

Describe Long-term Control

Increase in sizes/numbers of vessels
Occurs over a period of days, weeks, or months

3

Basic theories of Acute Control

Vasodilator Theory
Oxygen (nutrient) lack theory

4

Vasodilator theory

Increase Metabolism --> decrease O2 availability --> formation of vasodilators (adenosine, carbon dioxide, adenosine phosphate compounds, histamine, potassium ions, hydrogen ions)

5

Oxygen (nutrient) lack theory

Decrease [O2] --> BV relaxation --> Vasodilation

6

Define Vasomotion

Cyclical opening and closing or precapillary sphincters

7

Number of precapillary sphincters open at any given time is roughly proportional to:

nutritional requirements of tissues

8

Hyperemia - Reactive

Tissue blood flow blocked --(unblocked)--> Blood flow increases 4-7x normal

9

Hyperemia - Active

When any tissue becomes active, rate of blood flow increases

10

Autoregulation

Rapid increase in arterial pressure leads to increased blood flow.
Within minutes, blood flow returns to normal even with elevated pressure.

11

Theories that explain autoregulation

Metabolic theory
Myogenic theory

12

Metabolic theory

Increase in blood flow --> Too much O2 or nutrients --> Washes out vasodilators

13

Myogenic theory

Stretching of vessels --> reactive vasculature constriction

14

Special Acute Blood Flow in the Kidneys

Tubuloglomerular feedback: involves the macula densa/juxtaglomerular apparatus

15

Special Acute Blood Flow in the Brain

Increase [CO2] and/or [H+] --> cerebral vessel dilation --> washing out of excess CO2/H+

16

Special Acute Blood Flow in the Skin

Blood flow linked to body temp.
Sympathetic nerves via CNS
3 ml/min/100 g tissue --> 7-8 L/min for entire body

17

Review endothelial-derived mechanisms for control of tissue blood flow

Slides 16 and 17

18

Vasoconstrictors

Norepinephrine
Epinephrine
Angiotensis II
Vasopressin

19

Vasodilators

Bradykinins
Histamine

20

Angiotensin II normally acts to _______ total peripheral resistance

Increase

21

Vasopressin

aka ADH
Very powerful vasoconstrictor
Major function is to control body fluid volume

22

Bradykinins

Causes both vasodilation and increased capillary permeability

23

Histamine

Powerful vasodilator derived from mast cells and basophils

24

Sympathetic System

Innervates all vessels except capillaries
Primarily results in VASOCONSTRICTION

25

What is the function of the vasoconstrictor area of the brain?

Transmits continuos signals to BVs:
-continual firing results in sympathetic vasoconstrictor tone
-partial state of contraction of BVs = vasomotor tone

26

What is the function of the vasodilator area of the brain?

Inhibits activity in vasoconstrictor area

27

What is the function of the sensory area of the brain?

Receives signals via Vagus Nerves and Glossopharyngeal Nerves & transmits the signals to the motor areas

28

Higher nervous centers that control the vasomotor centers of the brain:

Reticular substance (RAS)
Hypothalamus
Cerebral Cortex

29

Adrenal Medulla Secretes:

Epinephrine and Norepinephrine

30

Neural Rapid Control of Arterial Pressure Simultaneous Changes:

Constriction of most systemic arteries
Constriction of veins
Increased HR