Cardio L7 Tissue blood flow Flashcards Preview

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Flashcards in Cardio L7 Tissue blood flow Deck (54)
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1

• The Key role of the vascular system is to

distribute the cardiac output according to the metabolic needs of the tissues.

2

• The distribution of blood flow is

is not fixed, for example at rest skeletal muscle receives about 20% of the cardiac output. During heavy exercise this may increase to 80%.

3

Arterioles: function

3. Regulate local blood flow according to local metabolic need.
4. Large amount of Smooth muscle
5. Exhibit:
a. Vasoconstriction
b. Vasodilation

4

Vascular Smooth Muscle (VSM briefly allow

constriction dilation

5

VSM cell shape

1. Spindle shaped cells
2. Approx 50 nanometers x 4um
3. Thick (myosin) and thin (actin) filaments.
4. Actin → inserts into dense bands (inner membrane and dense bodies (cytoplasm)
5. Function syncytium: cells are linked by gap junctions

6

VSM Contraction: process

1. Calcium (from SR or calcium channels) forms a complex with calmodulin
2. Ca-calmodulin regulates an enzyme called myosin light chain kinase (MLKC)
3. MLCK regulates action myosin interaction by phosphorylating the light chain of the myosin head.
4. Latch state of prolonged crossbridge formation (energy efficient tone).

7

VSM contraction stimuli:

VSM contraction stimuli:

8

VasoConstriction controlled by 3 and process

Noradrenaline (alpha 1 receptor)
Angiotensin (ATII receptors action)
Endothelin (act via ETA receptors)
Act via phosphplipase C (PLC) to produce vasoconstriction

9

Vasodilation controlled by

Adrenaline (Beta2) acts via a cAMP dependent pathway to inhibits MLCK and cause vasodilation

10

Beta 2 receptors

Found on skeletal muscle e.g. during exercise increase vasodilation to increase blood flow

11

Vasodilation controlled by

Endothelium derived relaxing factor (EDRF) and atrial natriuretic peptide (ANP) act via cGMP to produce vasodilation.

12

ANP acts via

Acts via cGMP = vasodilation

13

Alpha 1 receptor is for

Vasoconstriction

14

NO

Acts via cGMP causing relaxation

15

Control of Blood Vessels:

local and global control

16

local control

a. Mechanical
b. Metabolites
c. Autocoids

17

Global control

SNS
Hormones

18

Mechanical

A high external pressure may impede blood flow
E.g.
→ Left coronary flow pattern.
→ Pressure sores

19

Mechanical Process of action in arterioles

Raising the internal pressure in arterioles would initially distend them before they reacting by contracting i.e. myogenic response.

20

Metabolites: action

Many products of metabolism cause vasodilation and allow local blood flow to be matched to local metabolite rate

21

Metabolites: examples

Carbon dioxide
Lactate
Adenosine
Potassium ions
Hypoxia

22

Metabolites: clinical


COPD → increase of Co2 pathologically
1. Bounding pulse
2. Headaches

23

Active hyperaemia

Skeletal muscle during exercise. Metabolites increases and so vasodilation occurs and more blood flow.

24

Reactive hyperaemia

After a period of ischemia. E.g cuff
Build up of metabolites that has occurined during ischemia

25

Autocoids (local hormone) Function

These are vasoactive chemicals that are produce locally, released locally and act locally

26

Autocoids (local hormone) Examples

Histamine
Serotonin (5-HT)
Bradykinin
Prostaglandins

27

Thromboxane

Predominantly produce by platelets → platelet aggregation and vasoconstriction

28

Prostacyclin

Produce by endothelium. Inhibits platelet aggregation and causes vasodilation

29

Aspirin

Inhibit production of thromboxane. Acute treatment of MI

30

Auto-regulation: function

Over a range of perfusion pressures blood flow remains remarkably constant.
2. Brain, kidney, myocardium, intestine → flow doesn’t obey straight line increase pressure increase flow

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