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HAN 202 > Cardiovascular System: Blood Vessels > Flashcards

Cardiovascular System: Blood Vessels Flashcards

1
Q

Blood vessels

A
  • delivery system of dynamic structures that begins and ends at the heart
  • arteries: carry blood away from the heart; oxygenated EXCEPT for pulmonary circulation and umbilical vessels of a fetus (branch)
  • Capillaries: contact tissue cells and directly serve cellular needs
  • veins: carry blood toward the heart (converge)
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2
Q

structure of blood vessel walls

A

arteries and veins:

  • tunica intima (inner coat)
  • tunica media (middle coat)
  • tunica externa (outer coat)

Lumen:
*central blood-containing space

Capillaries:
*endothelium with sparse basal lamina

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3
Q

arterial system

A

3 groups of arteries:
-> Elastic arteries- near heart (stretch). able to withstand high pressure (aorta)

  • > muscular arteries- distributes to organs, thick tunica media
  • > arterioles- smallest of arteries
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4
Q

capillaries

A
  • Microscopic blood vessels
  • Walls of thin tunica intima, one cell thick
  • Size allows only a single RBC to pass at a time
  • Most tissues are rich in capillaries except tendons & ligaments and absent for cartilage
  • Consist of two types of vessels:
    1. Vascular shunt (metarteriole—thoroughfare channel):
  1. True capillaries –
    Branch off the metarteriole or terminal arteriole
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5
Q

blood flow through capillary beds

A
  • Precapillary sphincters regulate blood flow into true capillaries
  • Regulated by local chemical conditions and vasomotor nerves
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6
Q

sphincters open- blood flows thru true capillaries

A

true

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7
Q

sphincters closed- blood flows thru metarteriole thoroughfare channel and bypass true capillaries

A

true

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8
Q

veins

A
  • have thinner walls, larger lumens than arteries
  • lower BP than arteries
  • called capacitance vessels (blood reservoirs); contain up to 65% of the blood supply
  • adaptations that ensure return of blood to the heart:
    1. large-diameter lumens offer little resistance
    2. valves prevent backflow of blood

-venous sinuses: flattened veins with extremely thin walls (e.g., coronary sinus of heart, dural sinus of brain)

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9
Q

varicose veins

A
  • looks clumpy thru skin

- distorted shape

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10
Q

vascular anastomoses

A
  • interconnections of blood vessels
  • arterial anastomoses provide alternate pathways (collateral channels) to a given body region… common at joints in abdominal organs, brain, heart
  • vascular shunts of capillaries are examples of arteriovenous anastomoses
  • venous anastomoses are common (saphenous vein in CABG)
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11
Q

Bloofd flow

A
  • Volume of blood flowing through a vessel, an organ, or the entire circulation in a given period, based on needs
  • Measured as ml/min
  • Equivalent to cardiac output (CO) for entire vascular system
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12
Q

blood pressure (BP)

A
  • Force per unit area exerted on the wall of a blood vessel by the blood
  • Expressed in mm Hg
  • The pressure gradient provides the driving force that keeps blood moving from higher to lower pressure areas
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13
Q

Resistance

A

opposition to flow
-measure of the amount of friction blood encounters

3 important sources of resistance:

  • blood viscosity
  • total blood vessel length
  • blood vessel diameter
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14
Q

Resistance: blood viscosity

A

The “stickiness” of the blood due to formed elements and plasma proteins

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15
Q

resistance: total blood vessel length

A

the longer the vessel, the greater the resistance

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16
Q

resistance: blood vessel diamter

A

arterioles are the major determinants of peripheral resistance

-abrupt changes in diameter or fatty plaques from atherosclerosis dramatically increase resistance

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17
Q

Relationship Between Blood Flow, Blood Pressure, and Resistance (F= ΔP/R)

A
  • Blood flow (F) is directly proportional to the blood pressure gradient (ΔP)
  • If increase in BP, blood flow speeds up
  • Blood flow is inversely proportional to peripheral resistance (R)
  • If R increases, blood flow decreases
  • R is more important in influencing local blood flow because it is easily changed by altering blood vessel diameter
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18
Q

systemic blood pressure

A

-pressure results when flow is opposed by resistance

systemic pressure:

  • highest in the aorta
  • declines throughout the pathway
  • is 0 mm Hg in the right atrium

-steepest drop occurs in arterioles

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19
Q

systolic pressure (arterial blood pressure)

A

pressure exerted during ventricular contraction (120)

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20
Q

diastolic pressure (arterial blood pressure)

A

lowest level of arterial pressure (70-80), indicates peripheral resistance

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21
Q

pulse pressure (arterial blood pressure)

A

difference between systolic and diastolic pressure

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22
Q

Mean arterial pressure (MAP)

A

pressure that propels the blood to the tissues

-MAP= slightly less than the average btwn systolic and diastolic pressure

bc diastole is longer than systole… if BP=120/80 then MAP= 96

pulse pressure and MAP both decline with increasing distance from the heart

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23
Q

capillary: blood pressure

A
  • Ranges from 15 to 35 mm Hg
  • Low capillary pressure is desirable

High BP would rupture fragile, thin-walled capillaries

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24
Q

veins: BP

A
  • changes little during cardiac cycle

- small pressure gradient, about 15 mm Hg

25
Q

factors aiding venous return

A
  1. Respiratory “pump”: pressure changes created during breathing
  2. Muscular “pump”: contraction of skeletal muscles “milk” blood toward the heart and valves prevent backflow
  3. Vasoconstriction of veins under sympathetic control
26
Q

Maintaining BP

A

The main factors influencing blood pressure:

  • Cardiac output (CO)
  • Peripheral resistance (PR)
  • Blood volume

Important and vital to bring blood to organs

27
Q 
Cardiac Output (CO)
(what determines CO?)
A
  • determined by venous return and neural and hormonal controls
  • Resting heart rate is maintained by the PNS
  • stroke volume is controlled by venous return (EDV)
  • during stress, the cardioacceleratory center increases heart rate and stroke volume via sympathetic stimulation
  • ESV decreases and MAP increases
28
Q

Of the following cardiovascular components, which contains the majority of the body’s blood volume at any one time?

A

systemic veins and venules

29
Q

Of the following blood vessel components, which is the most critical in regulating systemic blood pressure?

A

tunica media

30
Q

What is the major factor controlling stroke volume during resting periods?

A

venous return to the heart

31
Q

control of blood pressure

A

-> F= change Pressure/ Resistance

  • > short-term neural and hormonal controls
  • counteract fluctuations in BP by altering peripheral resistance
  • > long-term renal regulation (kidneys)
  • counteract fluctuations in BP by altering blood volume
32
Q

short term mechanisms: neural controls

A

-neural controls operate via reflex arcs that involve:
*Baroreceptors- mechanoreceptors (stretch) and chemoreceptors (chemicals)
*located in carotid sinuses
and aortic arch

  • vasomotor centers- located in medulla
    * maintains vasomotor tone (moderate constriction of arterioles)

*vascular smooth muscle

33
Q

short term mechanisms: baroreceptor-initiated reflexes

A

increased BP stimulates baroreceptors to increase input to the vasomotor center

  • inhibits the vasomotor center, causing arteriole dilation and venodilation
  • stimulates the cardioinhibitory center
  • used as an emergency brake to avoid abnormally high BP

**Baroreceptors in carotid sinus protect blood supply to brain
Elderly often have blunted baroreceptors – can cause lightheadedness on sit to stand

34
Q

short term mechanisms: chemoreceptor-initiated reflexes

A
  • chemoreceptors respond to rise in CO2, drop in pH or O2
  • increase blood pressure via the vasomotor center and the cardioacceleratory center
  • are more important in the regulation of respiratory rate
  • located in carotid sinus and aortic arch
35
Q

influence of higher brain centers

A

-Impulses from cerebrum pass thru CV centers in medulla

  • Variations in emotional state may affect CV responses (fight/flight)
  • Anticipatory HR
  • White coat phenomena

Voluntary control over HR/BP thru biofeedback/meditation

36
Q

hormonal controls

A
  • > short term regulation thru changes in peripheral resistance
  • > long term regulation thru changes in blood volume
37
Q

short term mechanisms: hormonal control

A
  1. adrenal medulla hormones: NE and E
  2. angiotensin II, generated by kidney release of renin, causes vasoconstriction
  3. atrial natriuretic peptide (ANP) from atria in heart, causes vasodilation
  4. ADH (hypothalmus)- intense vasoconstriction when BP falls dangerously low
38
Q

Long term mechanisms: renal regulation

A

kidneys act directly and indirectly to regulate arterial BP by altering blood volume

  1. direct renal mechanism (at kidney)
  2. indirect renal (renin-angiotensin) mechanism
39
Q

direct renal mechanism (kidney)

A
  • alters blood volume independently of hormones
  • increased BP or blood volume causes the kidneys to eliminate more urine, thus reducing BP (rate of which blood filters thru kidney tubules speeds up, faster filtrate flow and kidneys cannot reabsorb fast enough)

*decreased BP or blood volume causes the kidneys to conserve water, and BP rises

40
Q

indirect mechanism

A

the renin angiotensin mechanism:

  • decreased arterial blood pressure-> release of renin
  • renin-> production of angiotensin II

angiotensin II:

    1. adrenals secrete aldosterone which enhances renal reabsorption of Na
      1. causes posterior pituitary to release ADH
      2. triggers sensation of thirst
      3. causes vasoconstriction which increases BP by increasing resistance

-kidneys release renin

41
Q

alterations in BP

A
  • Hypotension: low BP
  • systolic pressure below 100 mm Hg
  • often associated with long life and lack of cardiovascular illness
  • hypertension: high BP
  • sustained elevated arterial pressure of 140/90 or higher
  • may be transient adaptations during fever, physical exertion, and emotional upset
  • often persistent in obese ppl
42
Q

circulatory shock

A

inadequate blood flow to meet tissue needs

43
Q

hypovolemic shock

A

results from large scale blood loss

44
Q

vascular shock

A

results from extreme vasodilation and decreased peripheral resistance, i.e anaphylaxis (allergic response)

45
Q

cardiogenic shock

A

results when an inefficient heart cannot sustain adequate circulation (pump failure)

46
Q

transient vascular shock

A

prolonged exposure to heat, sun stroke

47
Q

velocity of blood flow

A
  • changes as it travels thru the systemic circulation
  • is fastest in the aorta, slowest in the capillaries, increases again in veins
  • slow capillary flow allows enough time for exchange btwn blood and tissues
48
Q

autoregulation of blood flow

A
  • local regulation of blood flow, controlled intrinsically by changing diameter
    1. metabolic: stimulated by shortage of O2 or inflammatory chemicals
  1. myogenic: involves the local response of smooth muscle to passive stretch
    * passive stretch involves vasoconstriction
    * reduced stretch promotes vasodilation
49
Q

intrinsic mechanisms (autoregulation)

A

distribute blood flow to individual organs and tissues as needed

50
Q

extrinsic mechanisms

A

maintain mean arterial pressure (MAP)

-redistribute blood during exercise and thermoregulation

51
Q

long term autoregulation

A

angiogenesis:
-occurs when short term autoregulation cannot meet tissue nutrient requirements

  • the # of vessels to a region increases and existing vessels enlarge
  • common in the heart when a coronary vessel is occluded, or throughout the body in people in high altitude areas
52
Q

blood flow: skeletal muscles

A

during muscle activity:

  • blood flow increases in direct proportion to the metabolic activity
  • local controls override sympathetic vasoconstriction

-muscle blood flow can increase 10x or more during physical activity

53
Q

blood flow and exercise

A

-major portion to working muscles

-shunting of blood:
kidneys practically shut down

-blood flow is not disturbed:
brain and heart

54
Q

blood flow: brain

A

-Blood flow to the brain is constant, as neurons are intolerant of ischemia

  • Metabolic controls
  • Declines in pH, and increased carbon dioxide cause marked vasodilation
  • Myogenic controls
  • Decreases in MAP cause cerebral vessels to dilate

*Increases in MAP cause cerebral vessels to constrict (protects)

55
Q

blood flow: brain

A
  • The brain is vulnerable under extreme systemic pressure changes
  • MAP below 60mm Hg can cause syncope (fainting)
  • MAP above 160 can result in cerebral edema
  • Increases capillary permeability
56
Q

blood flow: lungs

A
  • autoregulatory mechanism is opposite of that in most tissues:
  • low O2 levels cause vasoconstriction; high levels promote vasodilation

*allows for proper O2 loading in the lungs

57
Q

blood flow: heart

A

during ventricular systole

  • coronary vessels are compressed
  • myocardial blood flow ceases
  • stored myoglobin supplies sufficient O2
58
Q

blood flow: heart

A

during strenuous exercise:
*coronary vessels dilate in response to local accumulation of vasodilators

*blood flow many increase 3-4x

59
Q

circulatory pathways

A

Two main circulations:
-> Pulmonary circulation:
short loop that runs from the heart to the lungs and back to the heart

-> Systemic circulation:
long loop to all parts of the body and back to the heart

HAN 202 (13 decks)

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