Lecture 19 - Peripheral Vascular Resistance

Question 1

How is blood pressure measured

Answer 1

A sphygmomanometer

Question 2

What are the Kortkoff sounds produced by

Answer 2

Intermittent and turbulent flow through the artery

Question 3

How are the Kortkoff audible

Answer 3

Through a stethoscope

Question 4

When do Kortkoff sounds begin

Answer 4

When the cuff pressure is just below systolic pressure

Question 5

When do the Kortkoff sounds begin to fade

Answer 5

When the cuff pressure is close to diastolic pressure

Question 6

What is the normal systolic pressure at rest for a 20 year old

Answer 6

100-140 mmHg

Question 7

What is the normal diastolic pressure for a 20 year old at rest

Answer 7

50-90 mmHg

Question 8

How is mean arterial blood pressure calculated

Answer 8

By the cardiac output multiplied by the total peripheral resistance

Question 9

What mainly affects systolic pressure

Answer 9

The stroke volume and particularly the ejection velocity

Question 10

What is diastolic pressure mainly affected by

Answer 10

Total peripheral resistance and the time allowed for blood to flow out of the arteries

Question 11

What are the functions of the peripheral vascular system

Answer 11

To convey blood from the heart to the capillaries and then back to the heart, the regulation of arterial tone and peripheral vascular resistance, the regulation of blood flow to muscles and other tissues, to respond to traumatic injury with vasoconstriction and haemostasis, and the response to sustained increase in intraluminal pressure which occurs through growth and hypertrophy

Question 12

What vessels are the main site of resistance

Answer 12

Arterioles

Question 13

Where is the biggest drop in pressure

Answer 13

Between the conduit arteries and the arterial end of the capillaries

Question 14

What controls local blood flow

Answer 14

Local arteriole radius

Question 15

What does doubling the radius of a blood vessel cause

Answer 15

A 16-fold increase in the flow

Question 16

What controls TPR and therefore MABP

Answer 16

The arteriole radius

Question 17

What causes hypertension

Answer 17

The narrowing of the resistance vessels

Question 18

What is the internal radius of arteries

Answer 18

2.5cm to 1mm

Question 19

What is the internal radius of arterioles

Answer 19

0.01-0.2 mm

Question 20

What size of effect does small changes in the radius of the resistance vessels locally cause on blood flow

Answer 20

A relatively large effect

Question 21

What is Raynauld’s disease

Answer 21

Vasoconstriction of the resistance vessels in the hand causing the reduction of blood flow to the point of damage

Question 22

What is causes if all the blood vessels become a little narrower

Answer 22

Hypertension

Question 23

What type of control alters arteriolar radius

Answer 23

Intrinsic or extrinsic

Question 24

What are the intrinsic (local) control mechanisms to alter arteriolar radius

Answer 24

Stretching, production of metabolites and local release of chemicals

Question 25

What are the extrinsic control mechanisms to alter arteriolar radius

Answer 25

Hormones and the autonomic nervous system (mainly sympathetic)

Question 26

What do many organs and tissues have which is caused by sympathetic activity

Answer 26

A resting vasomotor tone

Question 27

What does increased sympathetic activity to arterioles cause

Answer 27

Vasoconstriction

Question 28

What does decreased sympathetic activity to arterioles cause

Answer 28

Vasodilation

Question 29

What is the sympathetic nervous system neurotransmitter

Answer 29

Noradrenaline

Question 30

What receptors does the sympathetic neurotransmitter act on

Answer 30

Alpha 1-adrenoceptors of vascular smooth muscle

Question 31

What are veins stimulated by

Answer 31

Sympathetic venoconstrictor nerves

Question 32

What do the sympathetic venoconstrictor nerves cause

Answer 32

They shift the blood centrally which supports the central venous pressure

Question 33

What causes the sigmoidal shape of the pressure-volume curve in veins

Answer 33

The thin-walled nature of veins

Question 34

If there is less blood on the central veins what happens

Answer 34

The central venous pressure drops causing the stroke volume to decrease

Question 35

What do peripheral veins have in the tunic media

Answer 35

Smooth muscle

Question 36

What do veins serve as

Answer 36

Blood reservoirs

Question 37

Within vascular smooth muscle vasoconstriction occurs through the release of

Answer 37

Adrenaline

Question 38

What activates the alpha 1 vascular receptors

Answer 38

Angiotensin II and endothelin

Question 39

What does the release of angiotensin II and endothelin cause

Answer 39

Vasoconstriction within the endothelium and the opening of calcium channels through depolarisation

Question 40

Within vascular smooth muscle how does vasodilation occur

Answer 40

Through the release of cholinergic and adrenergic molecules

Question 41

What activates the beta 2 vascular receptors

Answer 41

Adenosine and prostacyclin

Question 42

What happens in response to the release of adenosine

Answer 42

The opening of ATP-dependent K+ channels

Question 43

What is the endothelium derived releasing factor

Answer 43

Nitric oxide

Question 44

Why is nitric oxide usually relased

Answer 44

Due to shear stress

Question 45

What does the release of nitric oxide cause

Answer 45

Increased blood velocity and vessel dilation