control of arteriolar resistance

Question 1

what does blood pressure depend on?

Answer 1

MAP= C.O. X TPR

Question 2

what happens when you decrease TPR

Answer 2

you decrease MAP

You also increases blood flow

Question 3

What are the extrinsic control systems in the body?

Answer 3

Neural:

• norepinephrine released from sympathetic nerves binds to b1 receptors
• causes arteriolar constriction
• reduced blood flow, increases TPR

Hormonal:

• Epinephrine released from adrenal medulla
• binds to L1 receptors and leads to arteriolar constriction
• in the cardiac muscle and skeletal muscle binds to b2 receptors and leads to arteriolar dilation and therefore increased blood flow and reduced TPR

Question 4

What are the intrinsic control systems in the body?

Answer 4

Active Hyperemia:

• during exercise the concentration of metabolites in the blood increases
• EDFR- endothelium deliberate relaxing factor- is released and diffused into smooth muscle
• contains NO
• Leads to the relaxation of arterioles
• leads to increased blood flow and flushes metabolites away which reduces TPR

Pressure regulation:

• Decrease in MAP- leads to build up of metabolites
• same system as active

Reactive hyperaemia:
-Blockage of a blood system leads to increase in blood flow

Question 5

what does pressure regulation allow?

Answer 5

Allows the blood supply to match pressure requirement

Question 6

What does active hyperaemia allow?

Answer 6

Allows blood supple to match metabolic needs

Question 7

What is injury response

Answer 7

• when damage to the endothelium occurs - factor P is released which leads to the release of histamine
• This leads to arteriole dilation
• increased blood flow and decreased TPR
• increased blood flow to damaged area

Question 8

What are the system specific mechanisms?

Answer 8

• Coronary
• Pulmonary: areas which are poorly ventilated are constricted
• Renal
• Cerebral: shows autoregulation as needs to always be stable

Question 9

define hyperaemia

Answer 9

An increase blood flow to an area of the body in order to meet metabolic demands

Question 10

Coronary regulation

Answer 10

• Coronary blood flow is mainly derived from diastolic Blood flow
• Diastolic blood flow to the coronaries are interrupted during systole
• Very good at active hyperaemia
• Has many beta 2 receptors
• Very sensitive to metabolites especially Adenosine
• When adenosine binds to beta 2 receptors it causes the arterioles to dilate and increase blood flow

Question 11

Renal autoregulation

Answer 11

Filtration highly affected by blood pressure
When there is a high MAP lots of urine is lost:
-less na+ retention and h20 retention

Question 12

Darcy’s Law

Answer 12

Flow= difference in pressure/ Resistance

Question 13

Poiseuille’s law?

Answer 13

Radius controls blood flow

Question 14

What is pressure equal to?

Answer 14

MAP- CVP

CVP: central venous pressure. Very very small so can be omitted

Question 15

How to increase MAP

Answer 15

• Venoconstriction and arteriole constriction- sympathetic release of epinephrine on alpha receotors
• Increase HR
• Increase SV