Dla Before Lecture 10: Special Circulation

Question 1

How are the following regulated?

1) Coronary
2) Cutaneous
3) Skeletal
4) Cerebral
5) Pulmonary

Answer 1

Metabolic Demand:

1) Coronary
2) Cerebral –> Brain
- Unaffected by parasympathetics and sympathetics
3) Skeletal
4) Pulmonary (Hypoxia-vasocon)

-Can change how much blood flow by how much is needed, metabolites do that (skeletal, heart, brain)

Thermoregulation
1) Cutaneous

Question 2

How Autonomic control effects the blood flow

Answer 2

Sympathetics:

• NE Released
• Activate A1 and A2 –> Vasocon.

Parasympathetic:

• Ach Released
• Vasodil.

Question 3

Coronary Circulation

Factors that affect it

Answer 3

• Receives 5% CO at rest
• O2 to heart depends on flow (Direct relationship)

Factors that effect O2 –> heart:

1) Local control (metabolic hyperemia)
- Release NO and adenosine –.> Vasodilation, increase blood vessels diameter –> increase blood flow

2) Sympathetics
- Vasoconstriction–> decrease flow, overpowered by metabolics

Question 4

What supplies heart O2?

Answer 4

-Coronary arteries on epicardium

Problem/blockage= ischemia

Question 5

Systole and diastole affect on Coronary blood flow?

Answer 5

Increase:
-Diastole

Decrease:
1) Systole

2) Sympathetics
3) Tachycardia -> Increase HR -> decreases diastole –>Vasocon.
4) Exercise (increase O2 demand) –>Vasoconstricts

(All overridden by vasodilation metabolics)

Question 6

Oxygen demand calc

Answer 6

O2 demand = myocardial O2 consumption

Myocardial O2 consumption= Coronary Blood flow X Area-VO2 difference

Pathology:
(Decrease O2/O2 demand = ischemia)

Question 7

Effects of Disease on Coronary circulation

Answer 7

-Disease decreases coronary reserve as arterioles cannot compensate (by dilation) for shortened diastole and increased metabolic demand

(Ex: Atherosclerosis
-Reduces blood flow to mycardial tissue = restricting O2 supply)

Symps:

1) Myocardial ischemia –> can lead to necrosis (complete flow block)
2) Angina Pectoris (chest pain)

Question 8

Coronary artery disease –> ischemic heart disease (IHD)

Answer 8

Cause:
-Atheromatous plaques in coronary vessels (Diet, genes)

Results:

1) Sudden death (coronary occlusion)
2) Progressive weakening of heart (Cardiac failure)

Question 9

Angina Pectoris

Answer 9

-Indicates an underlying insufficiency of coronary vascular reserve

Sym:
-Chest/left arm pain (Triggered when cardiac O2 demand exceeds supply)

(Somatic afferents cause pain to radiate down left arm)

Treatment:

1) Nitroglycerin
- cause vasodilation

2) Beta blockers
- Decrease HR and contractility

Question 10

Skeletal muscle circulation at rest and during exercise

Answer 10

At rest:
-Vasoconstriction

During exercise:
-Vasodilation –> reduction in TPR

Question 11

Phasic and static exercise and skeletal muscle circulation

Answer 11

1) Phasic –> Running
- Active hyperemia
- blood flow is not interrupted
- capillary recruitment → reduced local resistance
- sympathetic control maintains global TPR and MAP

2) Static –> Weightlifting
- Reactive or ischemic hyperemia
- sustained contractions block blood flow → increased local resistance & TPR
- increased TPR and cardiac output can lead to increased MAP
- vasodilation after contraction due to ischemia and build-up of metabolites

Question 12

Intermittent Claudation

Answer 12

-Disease of skeletal muscle blood flow

Sym:
-Pain/cramping in leg during exercise

Cause:
-Peripheral vascular disease –> from atheromatous plaques in arteries supplying legs

Question 13

Cerebral Circulation

Answer 13

-Maintained at all costs

-Circle of Willis –> Collateral blood flow for artery obstructions/cerebral perfusion
(aneurysms common)

• Brain requires glucose for energy
• Increase intracranial pressure, decreases blood flow
• Also has adenosine metabolites

Question 14

Hypertension patient

Answer 14

• Messed up Cerebral circulation
• Chronic high perfusion pressures
• Shifting auto-regulatory curve of blood flow and perfusion pressure to the right –> maintains blood flow at high blood pressure

Question 15

CO2 & O2 in Cerebral Circulation

Answer 15

• PO2

• Large drop in PO2
  (hypoxemia) required for significant increases in blood flow

• PCO2
↑ PCO2 (hypercapnia) →
vasodilation
↓ PCO2 (hypocapnia) → vasoconstriction

Question 16

Cranial Perfusion Pressure (CPP)

Intracranial Pressure (ICP)

Answer 16

CPP:
-Key determinant of cerebral blood flow

Calc:
CPP = MAP - ICP

ICP:
Increased:
1) Intracranial bleeding
2) Cerebral edema
3) Tumor

Decreased:

1) Collapses Veins
2) Decreases effective CPP
3) Reduces blood flow