Lecture 3 - Basic principles and measures

Question 1

Explain local blood flow control

Answer 1

Microvessels monitor demand and dilate or constrict
to control local blood flow;

Nervous control of circulation from central nervous
system and hormones also support control of tissue
blood flow.

Question 2

Explain cardiac output control

Answer 2

Cardiac output controlled by sum of all
local tissue flows;

Upon flowing through tissues blood
returns through veins to the heart;

This increased inflow of blood is
immediately pumped back into the
arteries;

In this way the heart responds immediately
to tissue needs (automaton);

The heart often needs support from
nervous system to make it pump required
amounts of blood flow

Question 3

Why is local blood flow control necessary?

Answer 3

When muscles are active they require 20-30x more O2 and nutrients, but the heart can only increase cardiac output by 4-7x

Question 4

Explain arterial flow control.

Answer 4

Independent of local blood flow control or
cardiac output control;

If pressure goes too low, nervous signals cause raised heartrate and constriction of arterioles to raise pressure.

Question 5

What is pressure measured in?

Answer 5

mmHg (millimetres of mercury) OR Pa (pascals, SI Unit)

1mmHg =133.3 Pa

Question 6

Name the most common methods to measure blood pressure.

Answer 6

Auscultatory (blood pressure cuff). sphygmomanometer used with stethoscope measures pressure in brachial artery

Ultrasonic Doppler Flowmeter

Electromagnetic Flowmeter

Question 7

What are Korotkoff sounds

Answer 7

Sounds believed to be caused by blood jetting
through the partially occluded vessel and
oscillations of vessel wall;

Heard when doing Auscultatory measurements.

Question 8

Describe the Auscultatory method

Answer 8

Cuff placed on upper arm and inflated to occlude
brachial artery;

Stethoscope placed over ante-cubital artery to
hear/monitor sounds;

Pressure in cuff elevated well above systolic pressure
(brachial artery collapse à no sound) (A);

When pressure falls just below systolic sounds are
heard on antecubital artery (B);

When pressure approaches diastolic value (C) sounds
become muffled.

Question 9

How does arterial pressure change with age?

Answer 9

Increases - Caused by effects of aging on pressure control
mechanisms

Increase in systolic pressure after 60 mainly
caused by arterial stiffening or hardening