Wake Cv Blood Pressure Control Mechanisms

Front 1

What is the equation for Cardiac Output?

Back 1

Sumation of Regional Blood Flow

Front 2

Global view of circulation

Back 2

- Systemic circulation is a parallel arrangement of regional circulations
- Distribution of CO to regional circulations is determined by the vascular resistance of each regional circulation

Front 3

Local view of circulation

Back 3

- Circulation within an organ arranged as a series of multiple parallel vessels (parallel vessels reduce vascular resistance)
- Each class of vessels are in series with each other

Front 4

Hemodynamics

Back 4

- describes the physical factors that govern blood flow within a system

Front 5

Hemodynamics
In Series Arrangements

Back 5

- resistance is equal to the sum of the individual resistances decrease vascular resistance.

RT = RArtery + Rarterioles + Rcapillaries + Rvenules + RVeins
- The resistance of each segment relative to the total resistance determines what effect changing the resistance of one segment will do to the total resistance

Front 6

Hemodynamics
In Parallel Arrangements

Back 6

- decrease vascular resistance
- Resistance is calculated as the reciprocal of the sum of the reciprocal of each segments resistance
- Total resistance of a network of parallel resistances (vessels) is LESS THAN the resistance of the single lowest resistance
- When many parallel vessels exist, changing the resistance of only a few will have only a small effect on overall resistance of the network

Front 7

What causes a larger effect on the total resistance (if all the resistances are the same values), changing one value in a parallel or in series arrangement?

Back 7

there is a larger effect with the change in resistance in the in series total resistance than with the change of the total resistance in a parallel circuit

Front 8

Systemic Vascular Resistance

Back 8

(a.k.a. total peripheral resistance)
- Calculated by summing the resistances of the arteries, arterioles, capillaries, venules and veins (excluding the pulmonary circulation) throughout the body
- Changing the generalized state of the vasculature (either vasoconstriction or vasodilation) will change SVR

Front 9

How can you calculate Systemic Vascular Resistance?

Back 9

SVR=(MAP-CVP)/CO

- although SVR is determined by vascular diameter, length, anatomic arrangement and blood viscosity

Front 10

Control of Blood Pressure

Back 10

-SVR is regulated by changes in precapillary vessel diameter changes
- these vessels are normally partially constricted, thus having "vascular tone"
- vascular tone is regulated by both extrinsic and intrinsic mechanisms

Front 11

Medulla and BP

Back 11

contains cell bodies for parasympathetic (vagal) and sympathetic efferent nerves

Front 12

Hypothalamus and BP

Back 12

- modulates medulla activity during exercise or temp regulation

Front 13

Cortex (higher centers) and BP

Back 13

- modulate cardiovascular function at times of emotional stress (fear, anxiety)

Front 14

PNS
Preganglionic Fibers

Back 14

- are long
- Preganglionic synapse in or near organ
- Neurotransmitter is ACh
- Receptor is nicotinic

Front 15

PNS
Postganglionic Fibers

Back 15

- are short
- Neurotransmitter is ACh
- Receptors are muscarinic
(located in the heart primarily)

Front 16

SNS
Preganglionic Fibers

Back 16

- are short
- Neurotransmitter is Ach
- Receptors on postganglionic fiber are nicotinic

Front 17

SNS
Postganglionic Fibers

Back 17

- are long
- Neurotransmitter is NE
- Receptor on postganglionic fiber are alpha and beta adrenergics

Front 18

Alpha 1 Receptor
(potency, agonist, antagonist, site)

Back 18

potency: Epi>NE>Isop
agonist: Phenylephrine
antagonist: Prazosin
site: VSM

Front 19

Alpha 2 Receptor
(potency, agonist, antagonist, site)

Back 19

potency: NE>Epi
agonist: Clonidine
antagonist: Yohimbine
site: CNS, Prejunctional

Front 20

Beta 1 Receptor
(potency, agonist, antagonist, site)

Back 20

potency: Isop>Epi>NE
agonist: Dobutamine
antagonist: Atenolol
site: Cardiac

Front 21

Beta 2 Receptor
(potency, agonist, antagonist, site)

Back 21

potency: Isop>Epi>NE
agonist: Terbutaline
antagonist: Propranolol
site: VSM, Glandular

Front 22

What is the relationship between heart rate and atropine?

Back 22

- Atropine blocks the parasympathetic drive
- increases heart rate

Front 23

What is the relationship between heart rate and propranolol?

Back 23

- Propranolol blocks the sympathetic drive
- decreases heart rate

Front 24

Cardiac Actions of SNS

Back 24

- increase HR = positive chronotropic effect
- increase cardiac contractility = positive inotropic effect

Front 25

Cardiac Actions of PNS

Back 25

- decrease HR = negative chronotropic effect
- Counteracts positive inotropic effect of SNS

Front 26

oxygen extraction

Back 26

- is measured by differences in arterial and venous [oxygen] surrounding an organ

Front 27

What do low versus high oxygen extraction values mean regarding local blood flow?

Back 27

small differences in arterial and venous oxygen suggest that an organ could increase oxygen extraction without greatly increasing blood flow through the organ
- if a tissue has a high extraction rate normally, then you must increase blood flow in order to meet the demands of the tissue during metabolic processes

Front 28

Auto-regulation of Blood Flow

Back 28

… the ability of an organ to MAINTAIN A CONSTANT BLOOD FLOW DESPITE CHANGES IN PERFUSION PRESSURE
- This occurs in the absence of neural and hormonal influences and is, therefore, INTRINSIC to the organ.
- If decrease pressure, increase flow or decrease resistance
- involves metabolic and myogenic mechanisms

Front 29

Hyperemia

Back 29

- is a transient increase in local blood flow (ie. to an organ) in response to metabolic need

Front 30

Active Hyperemia

Back 30

blood flow increase in response to increased metabolic demand (ie. exercise)
- Vascular resistance decreases due to vasodilation and vascular recruitment

Front 31

Reactive Hyperemia

Back 31

blood flow increase in response to brief periods of ischemia
- During ischemia, oxygen is consumed and vasodilator substances have accumulated (metabolites such as ADO)
- Re-establishment of blood flow increases tissue oxygen levels and washes out metabolites

Front 32

Intrinsic Factors that Regulated Blood Flow

Back 32

PHYSICAL and CHEMICAL determinants of a localized circulation
- Tissue derived factors
- Endothelial factors
- Smooth muscle properties
- Physical factors

Front 33

Tissue Factors that Regulate Local Blood Flow

Back 33

- Originate in tissue surrounding vessel, often as metabolic products
- Can act as either constrictors or relaxors; may differ in different vascular beds

Front 34

Examples of Metabolic Tissue Factors involved in Blood Flow Regulation

Back 34

- Carbon dioxide
- H+
- K+
- lactate
- adenosine

Front 35

Examples of Paracrine factors involved in Blood Flow Regulation

Back 35

- histamine
- bradykinin
- prostacyclin
- leukotrienes

Front 36

Endothelial Factors and Regulation of Blood Flow

Back 36

- Can be endocrine, paracrine or autocrine in nature
- Physical factors (shear stress)
- May act either through endothelial receptors or directly on smooth muscle
> Dilators (NO, Prostacyclin)
> Constrictors (Endothelin, Leukotrienes, Thromboxanes)

Front 37

Sodium Nitroprusside
(SNP)

Back 37

- an endothelial cell receptor INDEPENDENT vasodilator
- donates NO despite the lack of endothelium

Front 38

Myogenic Response

Back 38

- Originates within the smooth muscle of arteries and arterioles (innate property) in some vascular beds (ie. Intestinal and renal circulations)
- Occurs in response to a sudden change in pressure
> In response to increase in pressure, the smooth muscle contracts IN ORDER TO PRESERVE VASCULAR RESISTANCE AND VESSEL DIAMETER
> In response to decrease in pressure, the smooth muscle relaxes and the vessel dilates

Front 39

Adenosine and Coronary Circulation

Back 39

- Adenosine (ADO) is a metabolic product of cardiac tissue
- it is also a very strong vasodilator

Front 40

Non-Chemical Factors and Local Control of Skeletal Muscle Vascular Resistance

Back 40

- High myogenic tone
- Strong contraction of muscle can mechanically obstruct or reduce blood flow

Front 41

Chemical Factors and Local Control of Skeletal Muscle Vascular Resistance

Back 41

- Metabolic substances produced in skeletal muscle during exercise or transient ischemia increase muscle BF (+VD)
- Locally produced metabolites can increase muscle BF by 20-30 times
- VD caused by locally produced metabolites competes with sympathetic VC

Front 42

What is the primary function of skin?

Back 42

- Primary function of skin (cutaneous) blood flow is maintenance of a constant body temperature.
- Blood flow to the skin exceeds nutritive needs of this tissue.

Front 43

What is the predominant regulatory pathway of cutaneous blood flow?

Back 43

- predominantly through neural (hypothalamic) pathways
- also through physical factors

Front 44

Myogenic Response

Back 44

- Originates within the smooth muscle of arteries and arterioles (innate property) in some vascular beds (ie. Intestinal and renal circulations)
- Occurs in response to a sudden change in pressure
> In response to increase in pressure, the smooth muscle contracts IN ORDER TO PRESERVE VASCULAR RESISTANCE AND VESSEL DIAMETER
> In response to decrease in pressure, the smooth muscle relaxes and the vessel dilates

Front 45

Examining the reflex effect of core temperature on Cutaneous Vascular Resistance

Back 45

- decrease Tcore --> increase VC SNA to cutaneous arterioles --> increase CutVR
- increase Tcore --> decrease VC SNA to cutaneous arterioles --> decrease CutVR
- increase Tcore --> increase SNA to sweat glands --> +VD --> decrease CutVR

Front 46

Raynaud's Syndrome

Back 46

- excessive sympathetic vasoconstriction
- may even lead to ischemia

Front 47

How much CO and Blood Volume does the splanchnic circulation receive?

Back 47

- Receives ~20% of the CO
- Contains ~15% of the circulating blood volume

Front 48

What is the basic function of the splanchnic circulation?

Back 48

absorption of water, electrolytes and nutrition

Front 49

SPLANCHNIC CIRCULATION
Neural control

Back 49

- Sympathetic innervation of arterioles and veins
- Neurally released NE acts at alpha1 adrenergic receptors on Vascular Smooth Muscle.
- High resting sympathetic VC tone; denervation or alpha1 adrenergic blockade increases splanchnic Blood Flow by ~1.5 times.

Front 50

How does splanchnic circulation contribute to compensatory adjustments in exercise?

Back 50

- Redistribution of CO to exercising muscle and redistribution of blood flow to skin to dissipation of heat
- Increased sympathetic activity results in constriction of both arterial and venous resistance vessels leading to increased venous return from splanchnic circulation

Front 51

What is the cardiac output and renal plasma flow of the kidney?

Back 51

- Kidneys receives ~20% of CO; very high blood flow per gram tissue (400 ml/min/100 gm)
- Renal plasma flow ~1000 L/day; 170 L/day filtered into renal tubules; only 1.5 L/day excreted as urine

Front 52

What is the function of Renal Circulation?

Back 52

- Primary function of renal circulation is to excrete waste products
- pivotal role in salt and water balance (i.e. long term BP control)

Front 53

What is the role of renal anatomy in renal function?

Back 53

- Changes in afferent and efferent arteriole resistances affect blood flow as well as hydrostatic pressure in glomerular and peritubular capillaries
- Glomerular capillaries require high pressure (~50 mmHg to drive filtration)
- Peritubular capillaries have low pressure to facilitate reabsorption

Front 54

How do the kidneys exhibit autoregulation?

Back 54

- Blood flow and filtration are tightly coupled so that filtration occurs over a small range of pressures

- Afferent arteriole become primary location of resistance regulation

- Afferent arteriole autoregulates through myogenic mechanisms and…

- Tubuloglomerular feedback: poorly understood mechanism by which the macula densa senses the osmolarity of fluid in the distal collecting ducts

Front 55

Renal Circulation and Sympathetic Stimulation

Back 55

- Little resting sympathetic tone

- Under strenuous exercise or hemorrhage, sympathetic outflow can almost completely stop renal blood flow

- Because of the large % of CO the kidney receives, this is an important mechanism for maintaining blood pressure in these cases

- Downside: can lead to compromised kidney function

Front 56

Pulmonary Circulation Composition

Back 56

composed of two circulations:
- pulmonary circultion
- bronchial circulation

Front 57

Pulmonary Vasculature

Back 57

- supplies blood to alveoli for gas exchange

- Derived from right ventricle
- Low resistance, low pressure, high compliance
- Hypoxia causes vasoconstriction (different than other organs!) as a means to maintain proper ventilation-perfusion ratios
- Sympathetic activation increases pulmonary vascular resistance and PA pressures; this mobilizes blood to the systemic circulation

Front 58

Bronchial Vasculature

Back 58

- nutritive flow to trachea and bronchial structures
- Derived from aorta (left side)