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Flashcards in Vascular control Deck (62):
1

What tissues make up blood vessels?

Endothelium
Elastic tissues
Smooth muscle
Fibrous (collagenous) tissues

2

What is the layer that all blood vessels have?

Endothelium

3

How is vascular smooth muscle layered?

Circular layers which are capable of vasoconstric/dialtion

4

What is unique of VSM?

Must sustain active tention for prolonged periods or time

5

What is vascular tone?

General contractile state of vessel or vascular region
- used as individual VSM cells activation

6

What are the short term adjustments of VSM?

Regulating contractile activity of VSM cells

7

What is a long term adjustment to VSM?

Adaptations to both active and passive components (Structural CT) of vascular wall

8

What are the differences of VSM and cardiac/skeletal muscle?

1. Contract/relax more slowly
2. Contractile activity as result of either AP or resting membrane potential
3. Can change contractile activity in absence of any changes in membrane potential
4. Can maintain tension for prolonged periods at low energy cost
5. Can be activated by stretch

9

What is the contractile process of VSM like?

Ca2+ dependent
-
1. Ca2+ complexes with calmodulin
2. This complex activates myosin light-chain kinase
3. MLC kinase allows ATP to phosphorylate MLC protein
4. MLC phosphorylation enables cross-bridge formation & cycling, during which energy from ATP is utilized for tension development/shortening

10

What are some characteristics of VSM membrane potentials?

-40-(-65) like most cells
- due to K+ perm (inward rectifiers)
- AP are predominately a result of slow inward Ca2+ (slow type)

11

What is another unique thing about VSM activation?

Stretch-sensitive cation channels involved in cellular response of muscle stretch.

12

What is VSM electromechanical coupling?

SM membrane contains voltage operated Ca channels (VOC's)
- partially activated at low resting MP of VSM. Thus changing resting potential can alter basal contractile state

13

What leads to contraction of VSM?

Membrane depolarize leads to VOCs--> Ca2+ in and contraction

14

What cause VSM relaxation?

Hyperpolarization

15

What is VSM pharmacomechanical coupling?

SM contraction without change in membrane potential
- Receptor operated Ca2= channels (ROC)
- Formation of inositol triphosphate opens CA2+ channels on SR

Need Receptor for GTP binding proteins

16

What do chemical vasodilators target?

G protein couple receptors
-B2 receptors

17

What does binding to B2 receptors cause? What binds to them?

Leads to increase cAMP/cGMP activates protein Kinase A to cause phosphorylation of many proteins
1. stimulate Ca EFFLUX
2. membrane hyperpole
3. decrease contractile machinery sensitivity to Ca

abnormal high levels of epi
Histamine
Vasoactive intestinal peptide

18

What strongly influences control of arterial tone?

local metabolic needs in region their reside

19

What is basal tone?

Arteriole remains in a state of partial constriction after removal of external influences
- intrinsic tone

20

What are some external influences on basal tone?

Local
Neural
Hormonal

21

What does continual internal pressure on arterioles lead too?

Result of tonic production of local vasoconstrictors by endothelial cells that line the inner surface

22

What are the local influences that control arterial tone?

Metabolic
Endothelial cells
Other chemicals
Transmural pressure

23

What is the most important means of local flow control?

VSM being subject to chemical composition of organ/tissue they serve

24

What are some things that simulate vasodilation?

low: o2
high: CO2, H+, K+
*** all because of exercise for example

Release of adenosine

25

What doe endothelial cells produce to influence arterial tone?

Nitric oxide
-Easily diffuses across cell membrane and stimulates cGMP production--> cGMP inhibits Ca2+ entry, activates K+ channels leading to hyperpolarization, activates MLC phosphatase

26

What other factors increase NO production?

acetylcholine, bradykinin, vasoactive intestinal peptide, supstance P

less known Prostacyclin
Endothelial derive hyperpolarizing factor

27

What are some local chemicals that affect arterial tone?

-Prostaglandins and thromboxanes
- leukotrienes
-Histamine
-Bradykinin

28

Can prostaglandins and thrombaxanes be both vasodialtors and constrictors?

yes

29

What is the importance of prostaglandins involved with platelets?

Important vasoconstrictors and platelet aggregating response to vascular injury and hemostatic (flow stopping and antibleeding)

30

What is transmural pressure?

Arterioles are actively and passively response to changes in transmural pressure

31

What is an example of transmural pressure?

Slight dilation leads to VSM constriction and reverses dilation
- or vice versa

32

How does this response to pressure occur?

Activation of stretch sensitive ion channels on arteriolar VSM cells

33

What is hyperemia?

Flow rate

34

What is active hyperemia?

In organs with highly variable metabolic rate, the blood flow closely follows the tissue’s metabolic rate!`

35

What is reactive hyperemia?

Higher than normal blood flow after removal of restriction (tourniquet)

-Duration dependent on severity of occlusion and metabolic needs

36

What is the most important means of reflex control of vasculature?

Neural influences-Vasoconstrictor nerves

- increase activity leads to increased vasoconstriction

37

What is neurogenic tone?

Continual firing (tonic firing) activity increases the normal contractile tone of arterioles to above basal

38

What does NE do to arterial tone?

-Increase tone after combining with α1-adrenergic receptor on smooth muscle cells

39

What do alpha1-adrenergic receptors bind and what does this cause?

Catacholamines

Lots of these receptors in vasculature, less sensitive to Epi

VASOCONSTRICTION

40

What doe Beta2 adrenergic receptors bind and what is its bind?

Catecholamines but not NE

-Only in arterioles of SOME organs
-Fewer of these in vasculature, more sensitive to Epi than α1

VASODILATION

41

What does vasopressin and angiotensin II do to arterioles?

Vasoconstrictor

42

How does one control the venous tone?

Volume
- not subject to local metabolic needs

43

Differences between VSM in veins compared to arterioles?

-Very little basal tone normally in dilated state (in the absence of any external influences! This is almost never the case in the in tact system though!!!)
-Vasodilator metabolites may accumulate in the tissues and have little effect on veins because of this

-Thin walls = more susceptible to physical influences
-External compressional force is important determinant of venous volume
-Ex: skeletal muscle pump helps return blood to heart during exercise

44

What is the job of arterioles?

to efficiently distribute the CO amount tissues with diff current needs

45

What is the job of veins?

To regulate the distribution of blood volume and cardiac filling

46

What are 2 ways to contract VSM?

1. Increase intracellular Ca2+
2. Ca2+ sensitivity of the contractile machinery
(increasing MLC Phosphatase)

47

What often leads to VSM relaxation and why?

increasing intracellular conc. of cyclic nucleotides.

- NET state of phosphorylation of MLC depends on ratio between Calcium dependent and independent MLC phosphatases.

48

What is a VOC?

Voltage operated channel
- electromechanical coupling
- depolarization leads to contraction

49

What do vasoconstrictors target on VSM?

alpha 1 (a1) adrenergic receptor
- binds NE
- ROCs open and influx of Ca2+ leading to greater contraction of the VSM
- Or via IP3 to stimulate specific channels on SR to release Ca2+

50

When interstitial fluid is low in O2 what does that mean?

Using O2 faster than it is being supplied by the blood.

51

What does high O2 do to vessels?

Vasoconstrictor

52

Cells that are deprived of O2 release what?

Adenosine
- vasodialate

53

What represents the most important means of local blood flow?

local metabolic mechanisms
- increase interstitial vasodilators leads to vasodilation and diffusion of dilators into the blood

54

What does acetylecholine do to endothelial cells and non endothelial cells?

Intact vessels- vasodilator
Vasoconstrict of vessels stripped of endothelial lining

55

What produces NO?

Endothelial cells

Nitric oxide synthetase which is activated by high intracellular levels of Ca2+ (means it has been contracting)

56

Which pathway does histamine use to vasodilate?

cAMP pathway
- makes vasculature porous and leads to edema. Stimulate sensory nerves to cause pain and itching

57

What causes blood flow autoregulation?

local metabolic feedback and myogenic mechanisms

58

What serves as the backbone to system for controlling total peripheral resistance?

Sympathetic vasoconstriction innervation

59

Do vessels have parasympathetic innervation?

no

60

Where are Beta 1 adrenergic receptors found and what is their purpose?

found in the heart to increase HR and contractibility

61

What are the major controllers arterial tone?

Basal tone
Local metobolic vasodilator factors
Sympathetic vasoconstrictor nerves by Alpha 1

62

What are the major controllers of veinous tone/

Internal pressure
Sympathetic vasoconstrictor nerves
External compression from muscles