Components of Cardiovascular System

Question 1

Components of CVS

Answer 1

Heart
Arteries
Veins
Arterioles
Capillaries

Question 2

Arteries

Answer 2

Passageway of blood from heart to tissue

pressure must be maintained

Question 3

Arterioles

Answer 3

Major resistance Vessels

Question 4

Capillaries

Answer 4

Site of exchange of gas, nutrients and water between blood and tissue

Question 5

Veins

Answer 5

contain most blood volume at rest- capacitance vessels

blood from tissue to heart

Question 6

Regulation of SVR

Answer 6

Vascular smooth muscles

• contraction increases SVR and MAP
• controlled by intrinsic and extrinsic mechanisms

Question 7

Relationship between blood flow and resistance

Answer 7

R is directly proportional to blood viscosity and blood vessel length and inversely proportional to the radius of blood vessel^4

Question 8

Which nerve fibres control vsm? Which nt is involved?

Answer 8

sympathetic nerve fibre

noradrenaline acting on alpha receptors

Question 9

Vasomotor tone

Answer 9

vascular smooth muscle is partially constricted at rest

Question 10

What causes vasomotor tone?

Answer 10

tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline
* increasing sympathetic discharge increases vasomotor tone-> vasoconstriction

Question 11

Hormones involved in control of VSM

Answer 11

Mainly adrenaline

also angiotensin II, andiuretic hormone (vasopressin)

Question 12

What effect does adrenaline acting on alpha receptors have?

Answer 12

Vasoconstriction

Question 13

What effect does adrenaline acting on beta-2 receptors have?

Answer 13

Vasodilation

Question 14

Where are alpha receptors predominantly found?

Answer 14

skin, gut, kidney arterioles

Question 15

Where are beta-2 receptors predominantly found?

Answer 15

cardiac and skeletal muscle arterioles

Question 16

Effect of angiotensin II on VSM

Answer 16

vasoconstriction

Question 17

Effect of vasopressin on VSM

Answer 17

vasoconstriction

Question 18

Intrinsic control of VSM

Answer 18

matches blood flow of different tissue to their metabolic needs
can override extrinsic mechanisms
includes chemical and physical factors

Question 19

Local metabolites

Answer 19

these chemical changes influence contraction of arteriolar smooth muscle

Question 20

Factors causing vasodilation and metabolic hyperaemia

Answer 20

• Decreased local PO2
• Increased local PCO2
• Increase local [H+]/ decreased pH
• Increased ec [K+]
• Increased ECF osmolality
• ATP release of adenosine

Question 21

Influence of local humoral agents

Answer 21

contraction of arterial and arteriolar smooth muscle

Question 22

When are local humoral agents released?

Answer 22

Response to injury or inflammation

Question 23

Humoral agents which cause vasodilation

Answer 23

Histamine
Bradykinin
NO (constantly released by endothelial cells in arteries and arterioles)

Question 24

Production of NO

Answer 24

constantly produced from L-argenine in vascular endothelium through action of Nitric Oxide Synthase

Question 25

Is NO a vasodilator or constrictor

Answer 25

Potent vasodilator | Has life of only a few seconds

Question 26

Flow dependent NO formation

Answer 26

Stress, due to increased flow, on vascular endothelium causes vascular endothelial cells to release calcium. This activates NOS

Question 27

Receptor stimulated NO formation

Answer 27

Chemical stimulation allows vasoactive substances to act

Question 28

Activation of formation of cGMP

Answer 28

NO diffuses from vascular endothelium to surrounding smooth muscle cells, activating formation of cGMP

Question 29

Role of cGMP

Answer 29

second messenger for signalling smooth muscle relaxation

Question 30

Humoral agents which cause vasoconstriction

Answer 30

Serotonin Thromboxane A2 Leukotrienes Endothelin

Question 31

Endothelin

Answer 31

potent vasoconstrictor released from endothelial cells

Question 32

Characteristics of endothelial produced vasodilators

Answer 32

anti-thrombotic anti-inflammatory anti-oxidants

Question 33

Characteristics of endothelial produced vasoconstrictors

Answer 33

pro-thrombotic pro-inflammatory pro-oxidants

Question 34

Effect of temp of VSM

Answer 34

cold- vasoconstriction; warm- vasodilation

Question 35

Myogenic response to stress

Answer 35

MAP rises= automatic constriction of resistance vessels | Important in tissue like brain and kidneys

Question 36

Sheer stress in terms intrinsic control of vascular smooth muscle

Answer 36

Dilation of arterioles causes stress in arteries upstream, making them dilate also - increases blood flow to metabolically active tissue

Question 37

Autoregulation of Cerebral blood flow

Answer 37

Myogenic response keeps cerebral blood flow constant over wide range of MAPs

Question 38

Sympathetic nervous system role

Answer 38

primarily role of the control of arteriolar radius and SVR (the brain is an exception)

Question 39

Factors which cause an increase in venous return

Answer 39

Increase in venomotor tone increase in blood volume increase in respiratory pump increase in skeletal muscle pump

Question 40

Impact of increased venous return on stroke volume

Answer 40

causes increase on arterial pressure-> increased EDV-> increased SV

Question 41

Increased Venomotor Tone

Answer 41

Increased venous return, SV and MAP

Question 42

What happens to intrathoracic and intraabdominal pressure during inspiration? What impact does this have on venous return?

Answer 42

ITP decreases IAP increases increases pressure gradient for venous return and creates suction effect, moving blood from veins to heart

Question 43

Effect of increasing rate and depth of breathing on venous return?

Answer 43

Increases venous return

Question 44

Impact of increased muscle activity on venous return

Answer 44

increases venous return to heart | large veins limbs lie between skeletal muscles

Question 45

Acute CVS responses to exercise

Answer 45

increase in sympathetic nerve activity ->increase in HR, SV and hence CO, causing increased SBP ->reduced flow to kidneys and gut metabolic hyperaemia overcomes vasomotor drive in skeletal and cardiac muscle -> vasodilation in proportion to metabolic activity -> decreased SVR and DBP (PP increases)

Question 46

Effect of sympathetic stimulation on heart

Answer 46

increases HR by increasing firing rate of SAN and decreasing AVN delay Increases force of contraction

Question 47

Effect of noradrenaline on pacemaker cells

Answer 47

increase in slope of pacemaker potential, causing pacemaker potential to reach threshold quicker and frequency of action potential to increase (+ve chronotropic effect)

Question 48

Effect of sympathetic stimulation on ventricular contraction

Answer 48

Peak ventricular pressure rises, causing contractility of heart at given EDV to rise FS curve shifts to left

Question 49

Chronic CVS responses to exercise

Answer 49

reduced sympathetic tone and noradrenaline levels increased parasympathetic tone to heart cardiac remodelling Reduced plasma renin levels Improved endothelial function (increase in vasodilators; decrease in vasoconstrictors) Decrease in arterial stiffening