2.2 Blood circulation and control

Question 1

What are the principle vessels of resistance?

Answer 1

Arterioles

Question 2

What do arterioles respond to?

Answer 2

Blood pressure changes. Local, neural and hormonal factors.

Question 3

Name 2 local factors that result in vasoconstriction.

Answer 3

Endothelin, internal BP.

Question 4

Name 7 local factors that result in vasodilation.

Answer 4

Hypoxia, NO, K+, CO2, H+, adenosine, bradykinin, tissue breakdown products.

Question 5

What neural factors result in vasoconstriction?

Answer 5

Sympathetic nerves that release noradrenaline.

Question 6

What neural factors result in vasodilation?

Answer 6

Parasympathetic innervation.

Question 7

Name hormonal factors that result in vasoconstriction.

Answer 7

Epinephrine (adrenaline)
Angiotensin 2
Vasopressin

Question 8

Name 2 hormonal factors that result in vasodilation.

Answer 8

Atrial natriuretic peptide
Acetylcholine

Question 9

What is myogenic auto-regulation of blood flow?

Answer 9

An intrinsic mechanism in smooth muscle blood vessels. If BP increases the vessel constricts. This is important in regulating blood flow.

Question 10

Describe capillaries

Answer 10

40 000km
large surface area = slow flow

Question 11

What determines the interstitial fluid flow?

Answer 11

The distribution of extra cellular fluid between compartments

Question 12

What is capillary flow determined by?

Answer 12

Arteriolar resistance

Number of open pre-capillary sphincters

Question 13

What is the uni-directional flow of lymphatics aided by?

Answer 13

Smooth muscle in lymphatic vessels

Skeletal muscle pump

Respiratory pump

Question 14

Name 3 effectors in circulation control.

Answer 14

1. Blood vessels - vasoconstrict/dilate and effect TPR.
2. The heart - can affect rate or contractility.
3. Kidneys - regulates blood volume and fluid balance.

Question 15

Where are baroreceptors located?

Answer 15

Aortic arch and carotid sinus.

Question 16

What activates baroreceptors?

Answer 16

They contain stretch receptors which respond to pressure.

Question 17

Are atrial baroreceptors involved in short-term or long-term regulation of BP?

Answer 17

Short-term. (Cardiopulmonary = long-term).

Question 18

Where central chemoreceptors located?

Answer 18

In the medulla oblangata.

Question 19

What do central chemoreceptors respond to?

Answer 19

Changes in pH/(H+).
Increased PaCO2
increases H+ and so decreases pH.

Question 20

What does increased PaCO2 result in?

Answer 20

Vasodilation

Question 21

Short term and long term pathway of BP control:

Answer 21

Short term: Baroreceptors
Long term: Volume of blood

Question 22

Describe the arterial baroreceptor reflex in response to an increase in blood pressure.

Answer 22

High bp,
Increased parasympathetic outflow,
Decreased contractility,
Decreased CO,
Increased vasodilation,
Lowers bp.

Question 23

Describe the arterial baroreceptor reflex in response to a decrease in blood pressure.

Answer 23

Low bp,
Increased sympathetic outflow,
Increased contractility,
Increased CO,
Increased vasoconstriction,
Increases bp.

Question 24

How do central chemoreceptors respond to an increase in PaCO2?

Answer 24

Vasoconstriction to increase blood pressure.

Question 25

Why do central chemoreceptors stimulate vasoconstriction in response to an increase in PaCO2?

Answer 25

They act to counter the affect of CO2 as a vasodilator and so maintain blood flow to tissues.