Reflex, hormonal and local blood flow regulation

Question 1

how does blood flow

Answer 1

it flows form a high pressure are to a low pressure area

Question 2

overall blood flow in adults

Answer 2

around 5000mL/min (cardiac output)

Question 3

functions of circulatory system

Answer 3

deliver blood to organs
deliver oxygen and nutrients
removal of CO2
maintenance of ion concentrations
delivery of hormones around of body

Question 4

what is the circulatory system consisted of

Answer 4

a pump - the heart, when it contracts it creates the pressure needed
collecting tubes - veins have low pressure and high volume
extensive system thin vessels - capillaries

Question 5

how is the circulatory divided (3)

Answer 5

arterial system - from heart to tissues
venous system - from tissues to heart
microcirculation - exchange between tissues

Question 6

hemodynamics

Answer 6

velocity, pressure, flow, resistance, dimensions of components of systemic circulation
all applied to blood flow
vessels are not rigid tubes
blood changes due to viscosity

Question 7

arterial blood pressure

Answer 7

development and maintenance adequate to perfuse tissues is base requirement for survival

Question 8

formula for mean arterial blood pressure

Answer 8

MABP = Cardiac Output (CO) x Total peripheral resistance (TPR)

Question 9

formula for cardiac output

Answer 9

CO = Heart rate (HR) x Stroke Volume (SV)

Question 10

formula for flow

Answer 10

Q = Velocity (V) x Cross sectional area (A)

measure of volume per unit of time

Question 11

Darcy’s Law

Answer 11

Q = Pressure differential / Resistance (R)

Question 12

Largest cross sectional area

Answer 12

in small capillaries (2500 cm2)
each have a small cross sectional area but there is a lot of them
they decrease the velocity of blood flow

Question 13

how does the velocity of blood change in relationship with the cross sectional area

Answer 13

as area increases, the velocity decreases
this is due to the extensibility of arteries
resistance is greatest in small vessels
velocity lowest in capillaries to promote exchange

Question 14

what is shear stress

Answer 14

as blood flows though a blood vessel, it exerts a force on the vessel wall parallel to the wall
is directly proportional to flow rate and viscosity

Question 15

poiseuille’s law

Answer 15

governs the flow of fluid through cylindrical tubes
steady laminar flow
blood viscosity does not remain constant

Question 16

poiseuille’s law formula

Answer 16

Q = [pi(Pi-Po)r^4]/8nl

Pi-Po - pressure gradient form the inlet (i) of the tube to the outlet (o)
r - radius of the tube
n - viscosity of the fluid
l length of tube

Question 17

resistance to blood flow

Answer 17

it is directly proportional to the length of the vessel and viscosity of blood

R= Ln/r^4

Question 18

Total peripheral resistance (TPR)

Answer 18

sum of all vascular resistance within systemic circulation

Question 19

how are the arteries supplying blood to organs arranged

Answer 19

in parallel

Question 20

what is the advantage of the organs not being downstream from another

Answer 20

changes in resistance in one organ directly affect blood flow in only that organ

Question 21

what alters resistance

Answer 21

contraction of the smooth muscle in the vessel wall

local tissue factors

Question 22

what is functional/active hyperaemia

Answer 22

increase in organ blood flow associated with increased metabolic activity of an organ or tissue
when cells are active they use more oxygen and fuel

Question 23

the by-products of metabolism

Answer 23

vasodilators that increase the blood flow: CO2, H+, K+, lactate, adenosine

Question 24

how does blood flow change in relationship with O2

Answer 24

as O2 consumption increases so does the blood flow

Question 25

why does reactive hyperaemia occur

Answer 25

occurs due to tissue hypoxia and a build up of vasodilator metabolites to dilate arterioles and decrease vascular resistance
flow is elevated as a result

Question 26

when does reactive hyperaemia occur

Answer 26

after cessation of blood flow

e.g. after myocardial infarction or stroke

Question 27

what happens to the tissues in reactive hyperaemia

Answer 27

tissues become reoxygenated and vasodilator metabolites are washed out
the resistance vessels regain normal vascular tone, flow returns to control

Question 28

what happens to blood flow during reactive hyperaemia

Answer 28

blood flow goes beyond the nasal level (the original level), reaches a peak, and then returns to the basal level due to the washing out of vasodilator metabolites

Question 29

period of occlusion

Answer 29

induces greater metabolic stimulus for vasodilation

increases in peak and duration of reactive hyperaemia

Question 30

what controls the innvervation

Answer 30

the autonomic nervous system via the sympathetic and the parasympathetic tone

Question 31

effect of sympathetic and parasympathetic nervous systems in heart

Answer 31

sympathetic: accelerates heart
parasympathetic: inhibits heart
together: balance

Question 32

what fires nerve innervation

Answer 32

changes in body fluid volumes - changes in blood volume

Question 33

the sympathetic innervation consists in

Answer 33

vasoconstriction (alpha-adrenergic stimulation) of vascular smooth muscle
skeletal muscle vasodilation (beta-adrenergic and cholinergic simp. stimulation releasing Ach)

Question 34

why does the heart accelerates in symp. innveration

Answer 34

SA node is accelerated and increases the contractility due to the beta-adrenergic stimulation

Question 35

why does the Mean Arterial Pressure (MAP) increases

Answer 35

increased TPR and CO

Question 36

parasympathetic innervation functions

Answer 36

vasodilator of vascular smooth muscle (few organs)
slows heart rate
less involved in changing TPR

Question 37

the deceleration of the heart rate is due to

Answer 37

the deceleration of SA node and decreased atrial contractility due to action of muscarinic receptors

Question 38

what are muscarinic receptors

Answer 38

where Ach from the parasympathetic nervous systems reacts

Question 39

what can signal the innervation

Answer 39

baroreceptors and chemoreceptors

Question 40

what are baroreceptors

Answer 40

receptors that respond to vascular stretch

Question 41

location of baroreceptors

Answer 41

carotid sinus and aortic arch

Question 42

functions of baroreceptors

Answer 42

vasodilation

restoration of BP to lower level - increased BP leads to parasympathetic stimulation (vagal and glossopharyngeal nerves)

Question 43

what are chemoreceptors

Answer 43

receptors that respond to chemical signals, changes in pO2, pCO2, pH

Question 44

where are chemoreceptors located

Answer 44

carotid sinus and aortic arch

Question 45

where do chemoreceptors act

Answer 45

respiratory centres and vasomotor regions

Question 46

hormones involved in vasoconstriction

Answer 46

adrenalin, angiotensin II, vasopressin

Question 47

hormones involved in vasodilation

Answer 47

atrial natriuretic factor, kallikrein-kinin system

Question 48

action of vasocontriction hormones

Answer 48

increase cardiac output by increasing the heart rate and force heart contractions
cause vasoconstriction of arterioles and veins in the skin and abdominal organs

Question 49

action of vasodilation hormones

Answer 49

lowers blood pressure by causing vasodilation and by promoting the loss of salts and water in the urine, which reduces blood volume

Question 50

paracrine agents

Answer 50

Nitric oxide (NO) and Endothelin (ET-1)

Question 51

action of NO

Answer 51

endothelium derived relaxing factor

• released from endothelium
• vasodilator
• anti-proliferative, anti-thrombotic
• impairment of NO -> thrombus that can lead to stroke

Question 52

action of ET-1

Answer 52

• released from endothelium
• most potent vasoconstrictor
• release stimulated by Ang II, hypoxia, sheer stress, catecholamines