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Physio > Cardio 6 > Flashcards

Cardio 6 Flashcards

1
Q

Describe the circulatory system.

A

-closed circuit
-blood returning to heart equals blood pumped by LV into aorta
-flow of blood around circuit depends on:
>number & strength of heart contractions
>total volume of blood
>characteristics of vessels

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2
Q

What are the 2 circulations in series in the cardiovascular system?

A
  1. Pulmonary circulation
  2. Systemic circulation
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3
Q

Describe pulmonary circulation.

A

-portion of CVS that carries deoxygenated blood away from heart, to the lungs, & returns oxygenated blood back to the heart

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4
Q

Describe systemic circulation.

A

-part of CVS that carries oxygenated blood away from the heart to the body & returns deoxygenated blood back to the heart

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5
Q

Describe the circulation 3 divisions.

A
  1. Distribution system
    -ventricles, arteries, arterioles
  2. Perfusion/exchange system
    -capillaries
  3. Collecting system
    -venules, veins, atria
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6
Q

Describe arteries.

A

aorta is the largest artery in systemic circulation
-receive blood from heart
-strong vascular walls
-blood flows at high velocity
-elastic tissue
-smooth muscle
-CT
-transport blood under high pressure to tissues
>carry stressed volume
-deliver oxygen & other nutrients to organs

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7
Q

What are the two types of arteries?

A
  1. Elastic (high compliance)
    -more elastin (increased distensibility)
    -more capable to hold lg volume of blood
    EX: aorta & carotid artery
  2. Muscular (high resistance)
    -more smooth muscle
    -more capable to vasoconstriction & dilation
    EX: femoral & mesenteric arteries
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8
Q

Describe compliance.

A

volume of blood the vessel can hold at a pressure
[C = V/P]
C = compliance (mL/mmHg)
V = volume (mL)
P = pressure (mmHg)

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9
Q

Describe vascular resistance.

A

-resistance that must be overcome to push blood through the circulatory system & create flow

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10
Q

Describe arterioles.

A

-last smallest branch of arterial system
-act as control conduits (blood released into capillaries)
-strong muscular walls = allow vasoconstriction/vasodilation
>innervated by sympathetic adrenergic nerve fibers
>alter blood flow in response
site of highest resistance to blood flow

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11
Q

Describe alpha 1 & 2 receptors.

A

-expressed in arterioles of most visceral organs
-alpha 1 = predominant & couple to Gq
-alpha 2 = couple to Gi
>present in nerve terminal to inhibit NE release (feedback)
-norepinephrine = primary endogenous agonist
>released from postganglionic neurons
-found in vascular smooth muscle
-causes vasoconstriction
smooth muscle contraction

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12
Q

Describe beta 2 adrenergic receptors.

A

-expressed in arterioles of coronaries, skeletal muscle, & liver
-GPCR = Gs
-epi is primary endogenous agonist
>released from adrenal gland
-found in vascular smooth muscle
-cause vasodilation
smooth muscle relaxation

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13
Q

Describe the tonic control of arteriolar diameter.

A

-arterioles = site of highest resistance & site where resistance can be changed by sympathetic activity
>by circulating cathecolamines & other vasoactive substances

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14
Q

Describe capillaries.

A

-exchange fluid, nutrients, electrolytes, hormones, & other substances between the blood & interstitial fluid
-thin walled
-single layer of endothelial cells surrounded by basal lamina
-lipid soluble substances cross capillary wall by dissolving in & diffusing across endothelial membrane
-water soluble (ex. Ions) cross capillary wall through:
1. Water filled clefts (spaces) between endothelial cells
2. Large pores in walls (ex. Fenestrated)
not all capillaries perfumed w blood always = depends on metabolic needs

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15
Q

Describe venules.

A

-collect blood from capillaries & coalesce into larger veins
-thin walled
-endothelial layer
-elastic
-smooth muscle
-CT

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16
Q

Describe veins.

A

-function as conduits to transport blood from the venules back to heart
-low pressure
-thin wall
-carry unstressed volume
-muscular (contract/expand)
-major controllable reservoir for extra blood
valves = prevent backflow of blood

17
Q

Describe compliance VS capacitance.

A

-compliance or capacitance of veins higher than arteries
-capacitance = related w distensibilty
-higher compliance = more volume can hold at a pressure
-veins hold large volumes at low pressure
-arteries have low compliance bc hold less blood at higher pressure

18
Q

What happens if there is a change in compliance/capacitance of veins?

A

-redistribution of blood between veins & arteries
-veins constrict = decrease in volume the veins can hold
-blood shifted from veins to arteries
-smooth muscle in walls of veins (arterioles) is innervated by sympathetic nerve fibers
-A1 adrenergic activation = contraction of veins & reduce capacitance & unstressed volume

19
Q

Describe the velocity of blood flow.

A

-rate of displacement of blood per unit of time
vary in diameter & cross section area
[V = Q/A]
V = velocity of blood flow (cm/sec)
Q = flow (mL/sec)
A = cross sectional area (cm^3)

20
Q

Describe the relationship between cross sectional area & velocity of flow.

A

-cross section area of veins are larger than arteries
>explains lg blood storage capacity of venous system
-as systemic arteries branch to form small arteries, arterioles & capillaries = the total cross sectional area of vessels increase
>forward velocity of blood flow decreases
-blood is collected into venules & veins = total cross sectional area is reduced
>velocity of blood flow increases

21
Q

Describe the total cross sectional area & velocity.

A

-velocity of blood varies inversely with total cross sectional area of blood vessels
-TOTAL = all capillaries/arteries/veins together
-CROSS SECTIONAL AREA = area of circle
although capillaries have a smaller diameter, they are more numerous
>flow of blood slows down when there’s a bigger cross sectional area

22
Q

What is blood flow through a blood vessel determined by?

A
  1. Pressure difference between 2 ends of vessel (inlet/outlet)
    >driving force for blood flow
  2. Resistance of vessel to blood flow
    >impediment to flow
    [Q = deltaP/R]
    Q = flow (mL/min)
    deltaP = pressure difference (mmHg)
    R = resistance (mmHg/mL/min)
23
Q

What is the direction of blood flow determines by?

A

-the direction of pressure gradient
-high to low pressure

24
Q

Describe vascular resistance.

A

-resistance that must be overcome to push blood through circulatory system (creates flow)
-amount of blood flowing through circulation = inversely proportional to resistance
>increasing resistance = decreases flow
(EX: arteriolar vasoconstriction)
vice versa

25
Q

What is the major mechanism for changing blood flow in the cardiovascular system?

A

-changing the resistance of blood vessels
-particularly arterioles

26
Q

What are the 3 factors that interfere with resistance to blood flow?

A
  1. Viscosity of blood
  2. Length of blood vessel
  3. Radius of blood vessel
    relationship between resistance, blood vessel diameter (radius), & blood viscosity = poiseuille equation
27
Q

Describe the poiseuille equation.

A

[R = 8 ηl/πr4]
R = resistance to flow is directly proportional to viscosity (n) of the blood
L = resistance to flow is directly proportional to length
R^4 = resistance is inversely proportional to the fourth power of the radius

28
Q

What does the total resistance of blood vessels depend on?

A

whether the vessels are arranged in series or in parallel
1. Series
-blood flow sequentially from one vessel to the next
-ex: pulmonary circulation
2. Parallel
-total blood flow distributed simultaneously among vessels
-ex: organs of systemic circulation
-if only in series = lose pressure, O2, & nutrients & any damage would interrupt whole circulation

29
Q

Describe series VS parallel arrangement of blood vessels.

A

less resistance of blood flow in parallel rather than in series
-if resistance of one vessel in a parallel increases = total resistance increases
-resistance of systemic circulation = systemic vascular resistance or total peripheral resistance (TPR)
-flow = pressure/resistance
-cardiac output = blood pressure (MAP)/TPR

Physio (35 decks)

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