Chapter 21 Flashcards

1
Q

Blood Vessel Types

A

Arteries

  • large elastic
  • medium muscular
  • arterioles

Capillaries

Veins

  • venules
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2
Q

Blood Reservoir

A

Systemic veins & venules

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3
Q

Arteries

A

carry blood away from heart

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4
Q

Veins

A

carry blood **toward **heart

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5
Q

Largest arteries

A

**conducting arteries (elastic arteries) **

  • wall are thin compared to overall size
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6
Q

Elastic Arteries

  • function?
A

storing mech E during ventricular systole & then transmitting E to keep blood moving after aortic & pulmonary valves

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7
Q

Muscular (distributing) arteries

A

more smooth muscle in tunica media

  • help maintain **vascular tone **to ensure efficient blood flow to distal tissue beds
  • ***brachial & radial **artery *
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8
Q

Anastomosis

A

union of vessels supplying blood to same body tissue

*should vessel be occluded, **vascular anastomosis **provides **collateral circulation **(alternative route) for blood to reach tissue *

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9
Q

Arterioles

A

deliver blood to capillaries

have greatest collective influence on local blood flow & overall BP

  • **primary adjustable nozzles **across which greatest drop in pressure occurs
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10
Q

Capillaries

A

only site in entire **vasculature **where **gases/water/nutrients **are exchanged

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11
Q

Venule/vein walls vs. artery walls

A

thinner walls

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12
Q

Veins

A

thinner walls, less muscle & elastic tissue, designed to operate at **lower pressure **

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13
Q

Intravenous pressure in venules vs. arterioles

A

intrav P in venules = less than half (16 mmHg) of intrav P in arterioles (**35 mmHg) **

**- **drops to just **1-2 mmHg **in some larger veins

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14
Q

Bc intravenous pressure is **so low, **how does blood keep flowing in one direction?

A

**valves **

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15
Q

What happens when veins are exposed to higher than normal pressure?

A

can become incompetant (varicose veins)

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16
Q

What determines how much fluid leaves arterial end of **capillary **& how much is **reabsorbed **at **venous end **

A

**hydrostatic & osmotic forces **at capillaries

(Starling Forces)

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17
Q

filtration

A

movement of fluid through walls of capillary into interstitial fluid

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18
Q

Reabsorption

A

movement of fluid from interstitial fluid **back into capillary **

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19
Q

Substances enter & leave capillaries by **(3) **basic mechanisms

A

diffusion

transcytosis

bulk flow

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20
Q

Bulk Flow

A

passive process in which **large numbers **of ions/molecules/particles in fluid move together in same direction

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21
Q

(2) pressure promote **filtration **

A

Blood hydrostatic pressure **(BHP) **

Interstitial fluid osmotic pressure **(IFOP) **

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22
Q

Blood hydrostatic pressure (BHP)

A

generated by **pumpinh action of heart **

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23
Q

Interstitial fluid osmotic pressure (IFOP)

A

constant at about 1 mmHg

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24
Q

(2) pressures promote **reabsorption **

A

blood colloid osmotic pressure **(BCOP) **

interstitial fluid** **hydrostatic pressure **(IFHP) **

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25
Q

blood colloid osmotic pressure (BCOP)

A

force caused by colloidal suspension of large proteins in plasma (averages 26 mmHg)

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26
Q

Interstitial fluid osmotic pressure (IFOP)

A

pulls fluid out of capillaries into interstitial fluid

  • very small (.1-5 mmHg)
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27
Q

Pushing Forces

A

Hydrostatic Pressure

28
Q

Pulling forces

A

Osmotic pressure

29
Q

Net filtration pressure **(NFP) **

  • indicates?
  • calculation?
A

indicates **direction of fluid movemnet **

NFP = (BHP + IFOP) - (BCOP + IFHP)

= (35+1) - (26 + 0) = **10 mmHg **(arterial end)

= (16+1) - (26-0) = **-9mmHg **(venous end)

= (filtration pressures - reabsorption pressures)

30
Q

Values of :
a) BHP

b) **IFOP **
c) BCOP
d) **IFHP **

A

a) **35 mmHg **(arterial end), **16 mmHg **(venous end)
b) **1 mmHg **(0.1-5 mmHg)
c) **26 mmHg **
d) **0 mmHg **

31
Q

positive vs. negative value of **NFP **

A

positive = net outward pressure (filtration)

negative = net inward pressure (reabsorption)

32
Q

Normally, there is nearly as much fluid ___ as there is ___

A

reabsorbed

filtered

33
Q

ON AVERAGE, __% of fluid **filtered **is reabsorbed?

A

85%

34
Q

What happens to fluid that is not reabsorbed?

A

enters **lymphatic vessels **to be eventually returned to blood

35
Q

In contrast to **bulk flow of fluids at capillaries, **exchange of gases & small particles is..

A

purely **passive diffusion **process

36
Q

Venous return

A

volume of blood returning through veins to **RA **must be same amount of blood pumped into arteries from **LV **

volume of blood flowing back to heart through systemic veins

37
Q

Besides pressure, venous return is aided by? (3)

A

presence of venous valves

skeletal muscle pump

action of breathing

38
Q

Skeletal muscle pump

A

uses action of muscles to milk blood in one direction (due to valves)

39
Q

Respiratory pump

A

uses negative pressures in **thoracic & abdominal cavities **generated durnig inspiration to pull venous blood toward heart

40
Q

Blood pressure

A

measure of **force **exerted in lumen of blood vessels

41
Q

Blood flow

A

amount of blood actually reaching end organs

42
Q

Resistance

A

sum of many factors which oppose flow of blood

*increased Systemic vascular resistance (SVR) *

by increased: # of RBCs (polycthemia), body size, blood viscosity, total BV length

by decreased: BV radius (vasoconstriction)

43
Q

Cardiovascular homeostasis is mainly dependant on?

A

blood flow

44
Q

Why do we check **blood pressure **rather than blood flow, even though **cardiovascular homeostasis **is mainly dependant on blood flow?

A

easier to measure

related to blood flow

45
Q

Relationship between blood flow, blood pressure & peripheral resistance

A

follows Ohm’s law

BP = Flow x Resistance

*flow = CO *

46
Q

To meet physiological demands, we can **increased **blood flow by?

A

**increasing BP **

**decreasing systemic vascular resistance (SVR) **

47
Q

Vascular resistance depends on (3)

A

1) size of lumen (1 / radius/diameter4)
2) blood viscosity (proportional)
3) total bv length

R proportional to (viscosity x length)/(r4)

48
Q

Which factors affecing **resistance **are unchangeable?

A

viscosity

total bv length

  • **diameter **is adjustable
49
Q

hardening of arteries

A

loss of **elasticity **

seriously obstructs body’s ability to **increase blood flow **to meet metabolic demands

50
Q

Autoregulation

A

ability of tissue to automatically adjust its blood flow to match its metabolic demands

51
Q

Autoregulation controlled through?

A

negative feedback loops

  • vascular system senses changes in BP & blood flow
  • signals CV centers in brain
  • **arterioles & precap sphincters of metarterioles **adjust reistance at specific tissue beds
52
Q

(2) types of **stimuli **causing autoregulatory changes in blood flow

A

1) **physical changes - **warming (vasod), cooling (vasoc)
- **myogenic response: **contracts more forcefully when stretches & relaxes when stretching lessens
2) **vasod/vasoc chemicals **

53
Q

During emergencies, ANS will vasodilate? vasoconstrict?

A

**vasodilate - **precap sphincters of metarterioles in skeleteal muscles, lungs, brain

**constrict - **precap sphincters in skin, GI tract & kidneys

- sends majority of CO (blood flow) to organs important inflight-or-flight response **while vasoconstricting **non-essential organs **

54
Q

(autoregulation) NS regulates BP via **negative feedback loops **that occur as (2) types of reflexes

A

1) baroreceptor
2) chemoreceptor

55
Q

(2) of most important control points for **blood pressure regulation **

A

**baroreceptors **in **arch of aorta & carotid sinus **

also in kidney & walls of heart

56
Q

(2) important baroreceptor reflexes

A

carotid sinus reflex

aortic reflex

57
Q

carotid sinus reflex

A

baroreceptors in wall of carotid sinuses initiate this

helps regulate BP in brain

58
Q

aortic reflex

A

baroreceptors in wall of **ascending aorta & arch of aorta **

helps regulate **systemic BP **

59
Q

When BP falls, baroreceptors?

A

stretched less → send AP at slower rate to CV → decreases parasymp stimulation & increases symp stimulation

*baroreceptors stretched less & input sensed by CV whcih respond with decreased para & increased symp stimulation *

60
Q

Chemoreceptors reflexes

detect changes in? (3) →stimulate…

A

**chemoreceptors **(sensory receptors that monitor **chemical composition **of blood)

detect changes in blood O2/CO2/H+ level

(**hypoxia, acidosis **or **hypercapnia **stimulates chemoreceptors to send impulses to CV → increases symp stimulation to arterioles & veins →vasoconstriction →increase in BP

  • also provide input tp respiratory center in brain stem to adjust breathing rate
61
Q

Renin-angiotensin aldosterone (RAA) system

A

important endocrine component of **autoregulation **

when blood volume/flow (to kidneys) **decreases renin **secreted by kidneys into bloodstream → renin & ACE produce **angiotension II **→ raises BP in 2 ways

62
Q

How does **angiotensin II **raise BP? (2)

A

blood volume/flow decreases → **renin & ACE **→ produce **angiotensin II **

1) stimulates aldosterone secretion (from adrenal glands) → **increases reabsorption of Na+ & water by kidneys (increases** blood volume which increases BP)
2) **vasoconstrictor - **raises BP by increasing **SVR **

63
Q

Several hormones help regulate **BP & blood flow **by altering CO, changing SVR or adjusting total blood volume (3)

A

1) Renin-Angiotensin-aldosterone (RAA) system
2) epinephrine & norepinephrine
3) **anti-diuretic hormone (ADH) **

64
Q

Epinephrine & norephinephrine - role in BP regulation (autoregulation)

A

released from **adrenal medulla **as autocrine autoregulatory response to **sympathetic stimulation **

→ **increase CO **by increasind rate/force of heart contraction

→also cause **vasoconstriction **which increases BP

65
Q

**Antidiuretic hormone (ADH) **

A

produced by **hypothalamus **

released by **posterior pituitary **in reponse to **dehydration or decreased blood volume **

  • vasoconstriction

- promotes movement of H2O from kidneys to **bloodstream **(increases blood volume & decreases urine output)

66
Q
A