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Human Physiology 2 > Ch. Eight: Vascular Physiology > Flashcards

Ch. Eight: Vascular Physiology Flashcards

1
Q

Flow Rate

A
  • blood through a vessel is directly proportional to the pressure gradient and inversely proportional to vascular resistance
  • can be adjusted according to metabolic needs
  • brain can least tolerate disrupted supply
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2
Q

Reconditioning Organs

A
  • receive more blood than needed for metabolic needs
    ex. kidneys, digestive organs and skin
  • adjust extra blood to achieve homeostasis
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3
Q

Resistance Depends on 3 Things

A
  1. blood viscosity: remains the same
  2. vessel length: does not change
  3. vessel radius: smaller the radius= less blood flow and more resistance
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4
Q

Fluid Properties

A
  • friction between molecules of flowing fluid
  • greater the friction, greater the viscosity
  • blood viscosity determined by number of RBC’s
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5
Q

Vessel Properties

A
  • longer the vessel, greater the resistance but remains constant in the body
  • vessel radius is the major variable; smaller the vessel, greater the resistance
    R is proportional to 1/r^4
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6
Q

Relationship of Resistance and Flow

A
  • doubling radius= decreases resistance x16 and increases flow by x16
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7
Q

Arteries

A
  1. serve as rapid-transit passageways for blood from the heart to organs
    - due to large radius, arteries offer little resistance to blood flow
  2. act as pressure reservoir to provide driving force for blood when heart is relaxing
    - arterial connective tissue contains collagen and elastin fibres
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8
Q

Blood Pressure

A
  • force exerted by blood against a vessel wall

- depends on volume of blood contained within vessel and compliance of vessel walls

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9
Q

Pressure Reservoir

A
  • expand and contract as blood is ejected by heart
  • allows blood flow to be continuous
  • compliance= V/P
  • higher the compliance of a structure, the more easily it can be stretched
  • elastic recoil (not as compliant as veins)
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10
Q

Systolic and Diastolic Pressure

A
  • peak pressure exerted by ejected blood (~120mm Hg)
  • minimum pressure in arteries when blood is draining off into vessels downstream (~80mm Hg)
  • mean pressure: 93mm Hg
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11
Q

Measuring Blood Pressure

A
  • measured indirectly by using sphygomomanometer
  • Korotkoff sounds: heard when determining blood pressure and are distinct from heart sounds associated with valve closure
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12
Q

Pulse Pressure

A
  • pressure difference between systolic and diastolic pressure
    ex. bp is 120/80, pulse pressure is 40 mm Hg
  • pulse that can be felt in artery lying close to surface of skin is due to pulse pressure
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13
Q

Mean Arterial Pressure

A
  • average pressure driving blood forward into tissues throughout cardiac cycle
  • formula for approximating mean arterial pressure: map= diastolic+ 1/3 pulse pressure
    ex. 120/80, mean pressure= 80+1/3(40)= 93mm Hg
  • spend more time in diastolic
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14
Q

Muscular Arteries

A
  • deliver blood to specific organs (mesenteric and renal artery)
  • proportionally thick muscular media (smooth muscle); very active in vasoconstriction
  • can play a large role in the regulation of blood pressure
    ex. mesenteric artery caries 25% of the CO, so alterations in its diameter would have a large effect
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15
Q

Muscular Arteries: Radius Adjustment

A

radius supplying individual organs can be adjusted independently to:

  1. distribute cardiac output among systemic organs, depending on body’s momentary needs
    - if they contract, blood flow is diverted away from their tissues
    - if they dilate, then blood flow to the tissue increases
  2. help regulate arterial blood pressure
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16
Q

Arterioles

A
  • major resistance vessels
  • radius supplying individual organs can be adjusted independently to:
    1. distribute cardiac output among systemic organs depending on body’s momentary needs
    2. help regulate arterial blood pressure
  • mechanisms involved in adjusting arteriolar resistance: vasoconstriction and vasodilation
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17
Q

Vasoconstriction (Arterioles) Caused By…

A
  • increase in: myogenic activity, oxygen, endothelin, and sympathetic stimulation (except in brain) and NE, alpha receptors
  • decrease in carbon dioxide and other metabolites
  • vasopression; anglotensin II
  • cold
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18
Q

Vasodilation Caused By…

A
  • decrease in myogenic activity, oxygen, and sympathetic stimulation
  • increase in carbon dioxide and nitric acid (causes relaxation)
  • histamine release
  • heat
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19
Q

Pressures Throughout Systemic Circulation

A
  • arterioles have high resistance

- capillaries then are non-pulsatile

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20
Q

Vascular Tone

A
  • smooth muscle displays a state of partial constriction

- 2 factors: myogenic activity of smooth muscle and sympathetic fibres continually release NE

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21
Q

Arterioles

A
  • only blood supply to brain remains constant; myogenic activity
  • changes within other organs; alter radius to vessels to adjust blood flow to organ
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22
Q

Arterioles Local Effect

A
  • local chemical influences on radius: local metabolic changes and histamine release
  • local physical influences on radius: local application of heat or cold, chemical response to shear stress, and myogenic response to stretch
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23
Q

Cardiac Output at Rest and During Moderate Exercise

A
  • increase in skeletal muscle (15%-64%) and skin (9%-14%), and heart
  • decrease digestive tract, bone, and kidneys
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24
Q

Intrinsic and Extrinsic Factors in Vaso-const./dilation

A
  • local environment; oxygen, carbon dioxide, sympathetic stimulation
  • neuronal inputs
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25
Q

Active Hyperemia

A
  • increase in metabolic activity increase local blood flow
  • increase in metabolic activity and decrease in oxygen
  • increase in metabolites in organ interstitial fluid
  • causes dilation and increase blood flow
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26
Q

Local chemical factors the produce relaxation

A
  • decreased O2
  • increases CO2, acid, K+, osmolarity
  • Adenosine release
  • prostaglandin release
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27
Q

Local Vasoactive Mediators: Endothelial Cells

A
  • release chemical mediators that play key role in locally regulating arteriolar caliber
  • release locally acting chemical messenger in response to chemical changes in their environment
  • among best studied local vasoactive mediators is nitric oxide
28
Q

Extrinsic Control

A
  • accomplished primarily by sympathetic nerve influence
  • cause constriction
  • some by hormones
29
Q

Extrinsic Sympathetic Control of Radius

A
  • influence of total peripheral resistance
  • NE influence on smooth muscle
  • local controls overriding sympathetic vasoconstriction
  • NO parasympathetic innervation
30
Q

Total Peripheral Resistance (TPR)

A

Mean Arterial Pressure= Cardiac output x TPR

(delta) P= F x R
* sympathetic nervous system influences TPR

31
Q

How does SNS control TPR

A
  • cardiovascular control centre: medulla of brain stem, and integrating centre for blood pressure regulation
  • hormone that influence radius:
  • SNS stimulation of adrenal medulla (NE and E)
  • vasopression (control fluid balance)
32
Q

Capillaries

A
  • smallest blood vessels
  • thin-walled, small-radius, extensively brached
  • sites of exchange between blood and surrounding tissue cells
  • max surface area and min. diffusion distance
  • velocity of blood flow through is relatively slow (non-pulsatile)
  • provides adequate exchange time
33
Q

2 Types of Passive Exchanges

A
  • diffusion:

- bulk flow:

34
Q

3 Types of Capillaries

A
  1. Continuous:
    - skin, muscle; have tight junctions
  2. Fenestrated:
    - more permeable; intestines, hormone producing tissues, kidneys
  3. Sinusoidal:
    - incomplete basement membrane; liver, bone marrow, lymphoid tissues
35
Q

Capillaries (substances that pass)

A
  • narrow, water-filled gaps (pores) lie at junctions between cells; permits passage of water-soluble substances, and size of pores varies from organ to organ
  • lipid soluble substances readily pass through endothelial cells by dissolving in lipid bilayer barrier
  • proteins by vesicular transport; not plasma proteins
36
Q

Capillary Bed

A
  • many capillaries are not open
  • capillaries surrounded by precapillary sphincters
  • contraction of sphincters reduces blood flowing into capillaries in an organ; relaxation of sphincters has opposite effect
  • metarteriole; runs between an arteriole and a venule
37
Q

Passive DIffusion

A
  • down concentration gradients of material between blood and interstitial fluid
  • except plasma proteins
38
Q

Bulk Flow

A
  • movement of fluid from blood to interstitial fluid and back again:
  • via water-filled pores, ultrafiltration (out of capillaries), and reabsorption
  • functions to distribute ECF not metabolite exchange
39
Q

Bulk Flow (influence of Starling Forces)

A
  • capillary blood (hydrostatic) pressure= hydrostatic pressure
  • plasma-colloid osmotic pressure
  • interstitial fluid hydrostatic pressure
  • interstitial fluid-colloid osmotic pressure
40
Q

Bulk Flow (dependent on difference between)

A
  • net hydrostatic pressure:
    is the force exerted by the fluid pressing against a wall = capillary blood pressure
  • net colloid osmotic pressure
41
Q

Bulk Flow (Hydrostatic Pressure)

A
  • forces fluid out (filtration):

- especially on the arterial end where pressure is higher

42
Q

Colloid Osmotic Pressure

A
  • force that opposes the hydrostatic pressure
  • created by large nondiffusible molecules (plasma proteins)
  • does not vary from one end of the capillaries to the other; unlike hydrostatic force
43
Q

Net flitration and Net Reabsorption Along the Vessel Length

A
  • outward pressure is higher= ultrafiltration
  • inward pressure (colloid osmotic) remains constant
  • outward pressure (hydrostatic) decreases along the vessel= reabsorption
  • lack of plasma proteins= swelling
44
Q

Role of Bulk Flow

A
  • important in regulating the distribution of ECF between the plasma and the interstitial fluid
  • keeps plasma volume constant; ensure that the circulatory system functions effectively
  • fluid exchange (not for solute exchange)
  • if BP falls, fluid moves into plasma
  • if BP rises (high blood pressure), fluid moves into interstitial space (edema)
45
Q

Lymphatic System

A
  • extensive network of one-way vessels
  • provides accessory route by which fluid can be returned from interstitial to the blood
  • initial lymphatics:
  • small, blind-ended terminal lymph vessels
  • permeate almost every tissue of the body
46
Q

Lymph and Lymph Vessels

A
  • interstitial fluid that enters a lymphatic vessel
    lymph vessels:
  • formed from convergence of initial lymphatics
  • eventually empty into venous system near where blood enters right atrium
  • one way valves spaced at interval direct flow of lymph toward venous outlet in chest
47
Q

Lymphatic Systems Functions

A
  • return of excess filtered fluid= lymph
  • defense against disease; lymph nodes have phagocytes which destroy bacteria filtered from interstitial fluid
  • transport of absorbed fat
  • return of filtered protein
48
Q

Edema

A
  • swelling of tissues: occurs when too much interstitial fluid accumulates
  • causes of edema:
  • reduced concentration of plasma proteins
  • increased permeability of capillary wall
  • increased venous pressure
  • blockage of lymph vessels
49
Q

Veins

A
  • venous system transports blood back to heart
  • capillaries drain into venules
  • venules converge to form small veins that exit organs
  • smaller veins merge to form larger vessels
  • veins have large radius offers little resistance to blood flow and serve as blood reservoir
50
Q

Venous Circulation

A
  • completes circulatory system

- slowed down, low pressure

51
Q

Vein Anatomy

A
  • walls are thinner than arteries and appear collapsed in histological slides
  • little smooth muscle, little elasticity; more collagen than elastin
  • veins are highly distensible; capacitance vessels that act as blood reservoirs
52
Q

Factors which Enhance Venous Return

A
  • driving pressure from cardiac contraction (~15mmHg)
  • sympathetically induced venous vasoconstriction
  • skeletal muscle activity
  • effect of venous valves
  • respiratory activity
  • effect of cardiac suction
53
Q

Regulation of Blood Pressure

A
  • ensure adequate blood flow through capillaries
  • requires adequate pressure difference; not too little (lack of supply to brain- fainting) or too much
  • blood pressure is monitored and regulated in the body
  • primary determinants: cardiac output x total peripheral resistance = mean arterial pressure
54
Q

Pressure, Flow, and Resistance

A
  • P= is the force exerted (MAP)
  • F= volume moved and it is measured in L/min (CO; stroke volume)
  • R= how difficult it is for blood to flow between two points at any given pressure difference; resistance is the measure of the friction that impedes flow (TPR- arterial pressure)
55
Q

Mechanisms of Blood Pressure

A
  • arterial pressure sensors; baroreceptors (constantly monitors arterial blood pressure)
  • carotid sinus baroreceptor
  • aortic arch baroreceptor
  • baroreceptor reflex
56
Q

Baroreceptors

A
  • number of action potential increases when MAP increases
  • number of action potential decreases when MAP decreases
  • consider a fall in BP, body responds by increasing CO or TPR through vasocontriction, sympathetic stimulation
57
Q

Sympathetic NS on Blood Vessels

A
  • sympathetic drive regulates arteriolar (TPR) and venular diameter (CO)
  • activation of alpha1-adrenoceptors = constriction of arterioles (more SNS)
58
Q

Baroreceptor Reflex

A

short-term control adjustments:

  • occur within seconds
  • adjustments made by alterations in cardiac output and TPR
  • mediated by autonomic nervous system influences on heart, veins, and arterioles
  • rapid response to return blood pressure to normal (set-point)
  • if pressure deviated for more than a few days- new set-point
59
Q

Long-term Regulation of Arterial BP

A
  • baroreceptors adapt to long term changes in BP
  • Barorecptors cannot set long-term arterial pressure
  • Blood Volume is a major determinant:
  • via venous side of circulation, influences stroke volume, therefore CO, and renin-angiotensin system
  • requires minutes to days
  • involves adjusting total blood volume by restoring normal salt and water balance through mechanisms that regulate urine output and thirst
  • blood volume:
    via venous side of circulation and influenced stroke volume and CO
  • renin-angiotensin system
60
Q

Blood Pressure Abnormalities

A

Hypertension: blood pressure above 140/90mmHg

  • two broad classes: primary and secondary hypertension
    hypotensoin: blood pressure below 100/60mmHg
61
Q

Hypertension

A
  • complication of hypertension:

- congestive heart failure, stroke, heart attack, spontaneous hemorrhage, renal failure, retinal damage

62
Q

Hypotension

A
  • occurs when there is too little blood to fill the vessels and heart is too weak to drive the blood
  • orthostatic (postural) hypotension: transient hypotensive condition resulting from insufficient compensatory responses to gravitational shifts in blood when person moves from horizontal to vertical position
63
Q

Circulatory Shock

A
  • occurs when blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained
  • four main types:
  • hypovolemic “low volume” shock
  • cardiogenic “heart produced” shock
  • vasogenic “vessel produced” shock
  • neurogenic “nerve produced” shock
64
Q

Skeletal Muscle Pump

A
  • enhances venous return
  • squeeze on veins
  • counteracts the effects of gravity
65
Q

Venous Valves

A
  • permit the flow of blood only toward the heart

Human Physiology 2 (10 decks)

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