Integration of Cardiovascular Mechanism

Question 1

what is the function of capillaries

Answer 1

Site of gas, nutrient and water between blood and tissues

Question 2

what is the function of veins

Answer 2

capacitance vessels containing most blood volume at rest

venous return must supply heart with sufficient blood to pump

Question 3

what is the main regulator of HR

Answer 3

autonomic nervous system

Question 4

what us the main regulator of Systemic vascular resistance

Answer 4

arterioles (vascular smooth muscle)

Question 5

what effect does vasoconstriction have on SVR and MAP

Answer 5

increases SVR and MAP

Question 6

what effect does vasodilation have on SVR and MAP

Answer 6

decreases SVR and MAP

Question 7

what is resistance to blood flow directionally proportional to

Answer 7

blood viscosity and length of blood vessel

Question 8

what is resistance to blood flow inversely proportional to

Answer 8

radius of the blood vessels

Question 9

what is the most important faction in influencing resistnace/controlling vascular smooth muscle

Answer 9

changes in radius of arterioles

Question 10

when there is a small decrease in the radius what effect is there on resistane

Answer 10

huge increase in resistance

Question 11

what 2 extrinsic mechanisms control vascular smooth muscle

Answer 11

nerves and hormones

Question 12

what nerves supply vascular smooth muscle

Answer 12

sympathetic nerve fibres ONLY (except brain)

baroreceptor reflex

Question 13

what is the neurotransmitter of the sympathetic nerve fibres acting on vascular smooth muscle

Answer 13

noradrenaline

Question 14

what is vasomotor tone and how does it affect SVR

Answer 14

blood vessels are always partially contracted at rest because of tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

Question 15

what effect on vasomotor done does increasing sympathetic discharge have

Answer 15

increased vasomotor tone

VASOCONSTRICTION

Question 16

what effect on vasomotor done does decreasing sympathetic discharge have

Answer 16

decreased vasomotor tone

VASODILATION

Question 17

is there any parasympathetic activity of arterial smooth muscle

Answer 17

no only in penis and clitoris

Question 18

what is the main hormone responsible for control of vascular smooth muscle control

Answer 18

Adrenaline

Question 19

what receptors does adrenaline act on in vascular smooth muscle

Answer 19

A receptors in skin, gut and kidneys

B2 receptors in cardiac muscle and skeletal muscle

Question 20

what effect does adrenaline have on a receptors

Answer 20

induces vasoconstriction of skin, gut, kidneys

Question 21

what effect does adrenenline have on B2 receptors

Answer 21

vasodilation of cardiac and skeletal muscle

Question 22

what hormone is resposnive for strategic redistribution of blood in exercise

Answer 22

Adrenaline

Question 23

what other hormones are responsive for the intermediate control of blood pressure and induce vasoconstriction of arterioles

Answer 23

Angiotensin II

ADH (vasopressin)

Question 24

how does the intrinsic mechanism control systemic vascular resistance and therefore MAP

Answer 24

Local Metabolites can OVER-RIDE extrinsic control

Local control aims to satisfy immediate demands of specific tissue eg. skeletal muscle and heart in exercise

Question 25

give 2 examples of local controls that are responsible for the intrinsic control of SVR

Answer 25

chemical factors and physical factors

Question 26

under what circumstances would local metabolites induce vasodilation and metabolic hyperaemia

Answer 26

``` Decreased local PO2 Increased PCO2 Increased local [H+] decreasesd pH Increased extracellular [K+] Increases osmolarity of ECF Adenosine release from ATP ```

Question 27

what are released in response to tissue injury and inflammation to induce vasodilation to increase blood flow and oxygen to an area

Answer 27

local humoral agents eg. Histamine, Bradykinin, Nitric Oxide

Question 28

where is nitric oxide released from

Answer 28

continuous release by endothelial cells of arteries and arterioles

Question 29

how is nitric oxide formed

Answer 29

from amino acid L-argenine by Nitric Oxide from Synthase (NOS) - an enzyme when FLOW DEPENDANT FORMATION: (increased flow - sheer stress on vascular endothelium causing release of Ca in endothelial cells RECEPTOR STIMULATED FORMATION: activation of NOS or by chemical stimuli

Question 30

what triggers NO to diffuse from vascular endothelium into adjacent smooth muscle to induce vasodilation

Answer 30

when cGMP is activated. signalling for smooth muscle relaxation

Question 31

why is the endothelium so important

Answer 31

maintains vascular health

Question 32

what happens when there is damage to the endothelium

Answer 32

high BP high cholesterol diabetes

Question 33

name 3 endothelial produced vasodilators

Answer 33

o Anti-thrombactic o Anti-inflammatory o Anti-oxidants

Question 34

name 3 endothelial produced vasoconstrictors

Answer 34

o Pro-thrombatic o Pro-inflammatory o Pro-oxidants

Question 35

name 3 physical factors affecting systemic vascular resistance

Answer 35

temperature myogenic response to stretch in Brain and kidneys sheer stress

Question 36

where does the myogenic response only occur

Answer 36

in brain and kindeys

Question 37

how does the myogenic response correct a rise in MAP

Answer 37

resistance vessels either in brain or kidneys constrict to limit the flow to prevent too much blood going to that area and causing swelling

Question 38

how does the myogenic response correct a fall in MAP

Answer 38

resistance vessels either in brain or kidneys dilate to increase blood flow to that area to ensure adequate perfusion

Question 39

how does sheer stress increase blood flow to metabolically active tissue

Answer 39

Dilation of arterioles causes sheer stress in arteries upstream causing dilation

Question 40

give 5 factors that increase venous return

Answer 40

``` increased venomotor tone increased skeletal pump increased respiratory pump increased atrial pressure increased blood volume ```

Question 41

how does increased venomotor tone increase venous return

Answer 41

venous smooth muscle supplied with sympathetic fibres and stimulation causes venous constricition increasing blood to the RA therefore increasing venomotor tone increases venous return, SV and MAP

Question 42

what contains most of the blood at rest

Answer 42

veins

Question 43

how does increasing the skeletal pump increase venous return

Answer 43

contraction of muscles aids venous return as blood is pushed towards the heart valves ensure unidirectional muscle activity increases venous return

Question 44

how does increasing the respiratory pump increase venous return

Answer 44

inspiration, intra-thoracic pressure decreases and intra-abdominal pressure increases pressure gradient for venous return and creates suction moving blood from veins to heart increasing rate and depth increases venous return to heart

Question 45

how does increasing atrial pressure increase venous return

Answer 45

it increases EDV so increased SV (Starling Curve)

Question 46

how does the cardiovascular system respond acutely to exercise

Answer 46

Increased CO increases systolic BP sympathetic vasomotor nerves reduce flow to kidneys and gut by vasoconstriction skeletal and cardiac muscle hyperaemia overcomes vasomotor drive causing vasodilation blood flow to skeletal and cardiac muscle increases in proportion to metabolic activity to increase blood flow and oxygen to tissue Metabolic hyperaemia decreases SVR and DBP so pulse pressure increases

Question 47

what response occurs post exercise

Answer 47

hypotensive response - blood pools in veins

Question 48

what effect on BP does regular exercise ahve

Answer 48

reduces BP

Question 49

what is the chronic CVS response to regular exercise

Answer 49

reduction in sympathetic tone and noradrenaline levels increase parasympathetic tone to heart cardiac remodelling reducing in plasma renin improved endothelial function (increased vasodilators , decreased vasoconstrictors) decreased arterial stiffening